pvri review 2:2&3 2010

Pulmonary VascularResearch Institute

PVRI is proud to announce

at the Riu Panama Plaza hotel in

The 5 Annual General Meetingand Workshops & Debates 2011,

th

Panama City

This year’s program will focus on the following themes:

• Chronic thromboembolic pulmonary hypertension (CTEPH)

• Pulmonary arterial hypertension – molecular dissection of a heterogeneousdisease

• Classification of pulmonary hypertension in paediatric patients

WEDNESDAY, FEBRUARY 2, 3 PM - SATURDAY, FEBRUARY 5, 2 PM

For more information and the full program, please see www.pvri.info

PVRI ReviewISSN 0974-6013

E-ISSN 0975-1602

Editorial Board......

CHIEF EDITOR

Harikrishnan S.Additional Professor in Cardiology,

Sree Chitra Tirunal Institute for Medical Sciences and Technology,Trivandrum, India - 695011

EXECUTIVE EDITORS

Ghazwan Butrous

R. Oudiz

Ioana Preston

Mardi Gomberg-Maitland

Andrew Peacock

Alexi Crosby

Saleh Aldammas (Arabic Edition)Majdy Idrees (Arabic Edition)Jun Wang (Chinese Edition)

Maria Virginia Tavares Santana (Portuguese Edition)

Katia Stewart (Portuguese Edition)Julio Sandoval (Spanish Edition)

EDITORIAL TEAM

Sheila Glennis Haworth Sastry Bhagavathulla R. Krishna Kumar Shyam Sunder Kothari Goverdhan Dutt Puri Anita Saxena Qadar Pasha Sivasankaran Sivasubramonian Chandrasekharan Cheranellore Kartha

EDITORIAL TEAM FOR PORTUGUESE EDITION

Maria Virginia Tavares SantanaAntonio Augusto Lopes

Ângela Bandeira Vera Demarchi Aiello Maria Angélica Binoto

Daniel Waetge Jaquelina Ota Renato Maciel

Veronica Amado Frederico Thadeu Campos

Maria Ilma AraújoKátia Stewart

EDITORIAL BOARD/ REVIEWERS

PVRI Faculty

PVRI ReviewThe JournalPVRI Review (ISSN: Print - 0974-6013, Online - 0975-1602) is peer-reviewed journal published on behalf of the Pulmonary Vascular Research Institute, supported by the Indian (South-East Asia region) task force. The journal publishes articles on the subject of Pulmonary circulation and pulmonary vascular diseases. The Journal is published quarterly (in the last week of January, April, July and October).

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The copies of the journal to the members of the association are sent by ordinary post. The editorial board, association or publisher will not be responsible for non receipt of copies. If any member/subscriber wishes to receive the copies by registered post or courier, kindly contact the publisher’s offi ce. If a copy returns due to incomplete, incorrect or changed address of a member/subscriber on two consecutive occasions, the names of such members will be deleted from the mailing list of the journal. Providing complete, correct and up-to-date address is the responsibility of the member/subscriber.

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CopyrightThe entire contents of the PVRI Review are protected under Indian and international copyrights. The Journal, however, grants to all users a free, irrevocable, worldwide, perpetual right of access to, and a license to copy, use, distribute, perform and display the work publicly and to make and distribute derivative works in any digital medium for any reasonable non-commercial purpose, subject to proper attribution of authorship and ownership of the rights. The journal also grants the right to make small numbers of printed copies for their personal non-commercial use.

PermissionsFor information on how to request permissions to reproduce articles/information from this journal, please visit www.pvrireview.org Disclaimer The information and opinions presented in the Journal refl ect the views of the authors and not of the Journal or its Editorial Board or the Publisher. Publication does not constitute endorsement by the journal. Neither the PVRI Review nor its publishers nor anyone else involved in creating, producing or delivering the PVRI Review or the materials contained therein, assumes any liability or responsibility for the accuracy, completeness, or usefulness of any information provided in the PVRI Review, nor shall they be liable for any direct, indirect, incidental, special, consequential or punitive damages arising out of the use of the PVRI Review. The PVRI Review, nor its publishers, nor any other party involved in the preparation of material contained in the PVRI Review represents or warrants that the information contained herein is in every respect accurate or complete, and they are not responsible for any errors or omissions or for the results obtained from the use of such material. Readers are encouraged to confi rm the information contained herein with other sources.

AddressesEditorial Offi ce

Dr. S. Harikrishnan Associate Professor in Cardiology,Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India-695011.Tel. 91-471-2551692, FAX- 91-471-2446433E-mail: [email protected] site: www.pvrireview.org

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Printed atDhote Offset Technokraft Pvt. Ltd., Satyam Ind. Estate, Jogeshwari, Mumbai, India

GENERAL INFORMATION

PVRI ReviewApril - June 2010 | Volume 2 | Issue 2

Contents.....

EDITORIAL

The New Face of PVRI ReviewS. Harikrishnan ...................................................................................................................................................................................61

MINI REVIEW

Angiogenesis in Lung Development, Injury, and RepairBernard Thébaud ...............................................................................................................................................................................62

REVIEW ARTICLE

Pulmonary Arterial Hypertension in Adults with Congenital Heart Disease: The Eisenmenger SyndromeAntonio Augusto Lopes, André Cogo Dalmaschio ...........................................................................................................................69

PVRI WEBINAR

Pulmonary Hypertension with Chronic Obstructive Pulmonary DiseaseSerge Adnot, Ari Chaouat ..................................................................................................................................................................75

CASE REPORT

Pulmonary Hypertension in Chronic Obstructive Pulmonary Disease: Three Case ReportsAri Chaouat, Emmanuel Gomez, François Chabot ..........................................................................................................................80

MANAGEMENT OF PULMONARY VASCULAR DISEASES

The Clinical Utility of Brain Natriuretic Peptide in Pulmonary Arterial HypertensionBrian Casserly, James R. Klinger .....................................................................................................................................................85

JOURNAL SCAN

Commentary − Distinct Patterns of Circulating Endothelial Cells in Pulmonary HypertensionSwapna Menon ..................................................................................................................................................................................91

PVRI TASKFORCE ACTIVITIES - REPORT

Inaugural meeting of the PVRI Sub-Saharan African Task Force - Report Karen Sliwa ........................................................................................................................................................................................93

Pulmonary Hypertension in NigeriaOkechukwu Samuel Ogah .................................................................................................................................................................95

Pulmonary Hypertension in The Young AfricanAna Olga Mocumbi ............................................................................................................................................................................96

HIV-associated Pulmonary Hypertension: A South African PerspectiveRosie Burton .......................................................................................................................................................................................97

PVRI ReviewJuly - December 2010 | Volume 2 | Issue 3

Contents.....

EDITORIAL

From the Editor’s DeskS. Harikrishnan ...................................................................................................................................................................................99

REVIEW ARTICLE

Review of Management Guidelines of Pulmonary Arterial Hypertension in the Pediatric PopulationHanaa Hasan Banjar........................................................................................................................................................................100

WEBINAR

Pulmonary Arterial Hypertension Associated with HIV Infection – Transcription of the WebinarSonia C. Flores ................................................................................................................................................................................114

MINI REVIEW

Disease Genes and Pathways Exploration: A Listing of Basic Bioinformatics ResourcesSwapna Menon ................................................................................................................................................................................123

CASE REPORT

Persistent Pulmonary Artery Hypertension Following Supracardiac Total Anomalous Pulmonary Venous Connection RepairKumar B., Mutu R., Puri G. D., Singh Anju, Rana S. S. ..............................................................................................................126

JOURNAL SCAN

Autophagy in Pulmonary Arterial Hypertension: CommentarySwapna Menon ................................................................................................................................................................................128

ORIGINAL RESEARCH ARTICLE

Does High Altitude Protect Against Irreversible Pulmonary Hypertension?Alexandra Heath, Stewart K., Mendes J., Ramirez M., Freudenthal F. ........................................................................................131

AUTHOR INDEX, 2010 .............................................................................................................................................................134

TITLE INDEX, 2010 ..................................................................................................................................................................135

Apr - Jun 2010 • Volume 2 • Issue 2 61 PVRI REVIEW

The New Face of PVRI Review

Following the decisions in the last AGM held at Lisbon in January 2010, PVRI Review is getting a new face. Since PVRI is coming out with its peer-reviewed journal Pulmonary Circulation, the role of PVRI Review had to be redefined. It will be the official newsletter of PVRI, publishing all the activities going on in different PVRI regions. It will publish reports on the activities of the regional PVRI task forces and on various meetings held under the auspices of PVRI.

In addition to its function as a newsletter, it will also publish view points, case studies, commentaries on interesting articles published in major journals, and compilation of all articles published elswhere on PH (Journal Scan). PVRI Review will become a forum to express the personal viewpoints and opinion as well as observations in the field of pulmonary vascular diseases. The articles will be not representing the views of editorial board of PVRI or PVRI, but it will be sole opinion of the authors. Also, it was decided to have PVRI Review published thrice a year, in July, October and January.

In this issue of PVRI Review, we have a special report on the very successful inaugural meeting conducted by the sub-Saharan region task force. Professor Karen Sliwa has written an introduction and also an overview of the meeting. Following this, the articles written by the presenters at the meeting are included.

Bernard Thébaud, in a review article, observes that the old notion that the development of blood vessels in the lung passively follows that of the airways is challenged with new evidences. We have new data to show that lung blood vessels actively promote alveolar growth during development and contribute to the maintenance of alveolar structures throughout postnatal life. These observations are relevant in pulmonary hypertension which is characterized by arrested alveolar growth/loss of alveoli. This short review summarizes the recently recognized role of angiogenic growth factors during normal alveolar development, injury and repair.

Antonio Augusto Lopes and André Cogo Dalmaschio have written an excellent review article on Eisenmenger syndrome. Eisenmenger syndrome (reversed right-to-left shunting caused by heightened pulmonary vascular resistance) is not uncommon in the developing world, where the corrective intervention for left-to-right shunt lesions is usually not undertaken at the right time. Eisenmenger syndrome is a multisystemic disorder associated with progressive right heart failure and hypoxemia. The authors conclude that even

in the era of the “new drugs” for treatment of pulmonary hypertension, general therapeutic measures remain central in the management of patients with Eisenmenger syndrome.

Brain natriuretic peptide (BNP) is a marker which is utilized in the diagnosis and assessing the prognosis in patients with ventricular failure. Brian Casserly and James R. Klinger review the utility of BNP in the management of patients with PH. They conclude that BNP may be a useful marker for right ventricular dysfunction and shows great promise in estimating the efficacy of therapy in patients with PAH.

You all may be aware about the webinars which are aired by pahforum.com, the webcasts site for the PVRI. We are planning to transcribe the webcasts and publish in our journal. The first of its kind is done by Serge Adenot et al. on pulmonary vascular diseases and COPD. We are publishing this transcription of the webinar along with three case reports on the same topic by Ari Chaouat et al. The combination of these two looks very informative and interesting.

The use of CEC and/or CPC counts as surrogate markers of endothelial status has been investigated in various pathological conditions including pulmonary arterial hypertension (PAH). Swapna Menon in her usual column – Commentary – has reviewed an article by Smadja et al. on the patterns of CEC in PH. She mentions that the current study corroborates observations on CEC count in PAH, i.e. the CEC count appears to be a more reliable marker in PH, with increase in numbers associated with severe disease.

Dear readers, we, in the editorial board, request you to send your suggestions and comments about PVRI Review. Please send your contributions which will suit the new face of PVRI Review.

S. HarikrishnanEditor in Chief, PVRI Review,

Fellow, Pulmonary Vascular Research Institute, Co-leader, PVRI Publication Taskforce.

E-mail: [email protected]

DOI: 10.4103/0974-6013.68483

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PVRI REVIEW 62 Apr - Jun 2010 • Volume 2 • Issue 2

Address for correspondence: Dr. Bernard Thébaud, Department of Pediatrics, University of Alberta, HMRC 407, Edmonton, Canada - T6G 2S2. E-mail: [email protected]

DOI: 10.4103/0974-6013.68484

Angiogenesis in Lung Development, Injury, and Repair

Bernard ThébaudDepartment of Pediatrics, Division of Neonatology, Women and Children Health Research Institute, Cardiovascular Research Group, University of Alberta, Edmonton, Canada

MIN

I R

EV

IEW

Recent evidence has challenged old notions that the development of blood vessels in the lung passively follows that of the airways. Rather, lung blood vessels actively promote alveolar growth during development and contribute to the maintenance of alveolar structures throughout postnatal life. These observations may be relevant for lung diseases characterized by arrested alveolar growth/loss of alveoli and pulmonary hypertension. This short review summarizes the recently recognized role of angiogenic growth factors during normal alveolar development, injury, and repair.

Key words: Aging, angiogenesis, injury, lung, oxygen repair

THE CHALLENGE TO PREVENT/CURE LUNG DISEASES CHARACTERIZED BY ARRESTED ALVEOLAR DEVELOPMENT/LOSS OF ALVEOLI: IMPLICATIONS FOR LUNG ANGIOGENESIS

Advances in perinatal medicine—including major breakthroughs, such as antenatal steroids and postnatal surfactant—have allowed the survival of infants that are more and more immature. As a consequence, the challenge to prevent lung injury in this patient population has increased. Indeed, 40 years after the first description, bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, has not disappeared, but now affects babies born at <28 weeks gestation when they are just beginning the parallel processes of alveolarization of the distal lung saccules and development of the alveolar capillary bed.[1] Perinatal lung injury in neonates born during the late canalicular stage arrests the normal sequence of lung development, resulting in the histologic pattern of alveolar simplification (larger but fewer alveoli with decreased septation).[2,3] At the other extreme of life, lung emphysema is characterized by the disappearance of alveoli. In both BPD and emphysema, arrested alveolar development/loss of alveoli is accompanied by a marked rarefaction of lung capillaries, suggesting a potential role for angiogenesis during normal alveolar development, injury, and repair. Similarly, promoting angiogenesis may be of benefit in pulmonary hypertension associated with distal pruning of lung capillaries. This review summarizes evidence that has challenged old notions that the development of the blood vessels in the lung passively follows that of the airways. Rather, lung blood vessels actively promote alveolar growth during development and contribute to the maintenance of alveolar structures throughout postnatal life, opening new

therapeutic avenues for lung diseases characterized by alveolar damage by modulation of angiogenesis.

NORMAL LUNG DEVELOPMENT IN BRIEF

The classical stages of lung developmentLung development is classically subdivided into 5 overlapping stages in human and rodents, on the basis of gross histologic features. The first 4 stages, termed the embryonic, pseudoglandular, canalicular, and the saccular stages, occur during gestation. At the end of the saccular stage at about 36 weeks, lungs have formed alveolar ducts and air sacs. Alveolarization, the final stage of lung development, begins in the near-term lung prior to birth but primarily occurs postnatally, during the first 2–3 years of life, and may continue at a slower rate beyond childhood.[4,5] The formation of alveoli occurs by the outgrowth of secondary septae that subdivide terminal saccules into anatomic alveoli. Premature infants at greatest risk for BPD in the postsurfactant era are born at 24–28 weeks, during the late canalicular or saccular stage of lung development just as the airways become juxtaposed to pulmonary vessels.

Lung angiogenesisFormation of the pulmonary circulation has been primarily described as dependent on 2 basic processes: vasculogenesis and angiogenesis. Vasculogenesis is the de novo formation of blood vessels from angioblasts or endothelial precursor cells that migrate and differentiate in response to local cues (growth factors, extracellular matrix) to form vascular tubes. Angiogenesis is the formation of new blood vessels from preexisting ones. It has generally been accepted that the distal vasculature arises by vasculogenesis, and the proximal vasculature by angiogenesis, but this remains controversial.[6] Vasculogenesis results in the de novo formation of blood vessels from blood islands present within the mesenchyme of the embryonic lung (embryonic day 9, E9 in the mouse).[7] Angiogenesis starts around E12 when arteries and veins begin to sprout from the central pulmonary vascular trunks. Around

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E14, peripheral sinusoids and central vessel sprouts connect and establish a vascular network. This union of peripheral and central vascular structures is accompanied by extensive branching of the arteries, which follow the branching pattern of the airways. Again, the relative contributions of vasculogenesis and angiogenesis to lung vascular growth during each stage of lung development are controversial, and additional studies with appropriate experimental models are required to better define these underlying mechanisms. Studies in human fetal lung suggest that airways act as a template for pulmonary artery development, and that endothelial tubes form around the terminal buds of distal airspaces, suggesting an inductive influence of the epithelium.[8] More recently, Parera et al. suggested distal angiogenesis as a new mechanism for lung vascular morphogenesis, based on morphologic analysis from the onset of lung development (E9.5) until the pseudoglandular stage (E13.5) in Tie2–LacZ transgenic mice.[6] In their model, capillary networks surrounding the terminal buds exist from the first morphologic sign of lung development and then expand by the formation of new capillaries from preexisting vessels as the lung bud grows.[6] Clearly, new tools, routinely used in developmental biology, need to be applied to deepen our understanding about the formation of the pulmonary circulation.

The final important step of microvascular maturation overlaps the alveolar stage of lung development.[9] Capillaries, which are organized as double capillary layers in the immature gas-exchange region, later remodel to form a single capillary layer. This process is completed in the rat by about the third postnatal week. The alveolar wall thins and its cellular composition changes. In the rat, the thickness of the alveolar wall and the air–gas barrier (the distance between alveolar gas and capillary blood) decrease by 20%–25%. Between birth and adulthood, the alveolar and capillary surface areas expand nearly 20-fold and the capillary volume by 35-fold. Further expansion of the capillary network subsequently occurs via 2 angiogenic mechanisms: sprouting angiogenesis from preexisting vessels and intussusceptive growth.[10] Little is known about intussusceptive microvascular growth in the lung. This novel mode of blood vessel formation and remodeling occurs by internal division of the preexisting capillary plexus (insertion of transcapillary tissue pillars) without sprouting, which may underlie alveolar growth and remodeling throughout adult life and thus be amenable to therapeutic modulation for lung regeneration. Much more needs to be learnt about the anatomic events underlying lung vascular development and time-specific mechanisms that regulate growth and function at each stage. Nonetheless, current knowledge gained mostly from developmental biology and cancer literature about key angiogenic growth factors, has been exploited to investigate the role of lung angiogenesis during normal alveolar development.

EVIDENCE THAT ANGIOGENIC GROWTH FACTOR–DRIVEN ANGIOGENESIS PROMOTES NORMAL ALVEOLAR DEVELOPMENT

Vascular endothelial growth factor is pivotal for the proper formation of blood vesselsVascular endothelial growth factor (VEGF) is a highly specific mitogen and survival factor for vascular endothelial cells. VEGF binds to transmembrane tyrosine kinase receptors,

VEGFR-1 (flt-1) and VEGFR-2 (flk-1/KDR), which are expressed on vascular endothelium.[11] The absolute requirement of VEGF for the development of the embryonic vasculature in mice has been demonstrated by inactivation studies of VEGF alleles[12,13] and knockouts of VEGFR-1[14] and VEGFR-2.[15] In each of these studies, inactivation of the target genes resulted in lethal phenotypes characterized by deficient organization of endothelial cells. Inducible Cre-loxP-mediated gene targeting or administration of a soluble VEGF receptor chimeric protein (mFlt (1-3)-IgG) to inactivate VEGF in early postnatal life results in increased mortality, stunted body growth, and impaired organ development.[16] VEGF inhibition resulted in less significant alterations as the animal matured, and the dependence on VEGF is lost around the fourth postnatal week. Interestingly, this period coincides with the end of alveolarization and microvasculature maturation in the lung.

VEGF promotes normal alveolar developmentThe spatial relationship between receptor and ligand suggests that VEGF plays a role in the development of the alveolar capillary bed. In addition, pharmacologic and genetic inactivation of VEGF arrests alveolar development. VEGF mRNA and protein are localized to distal airway epithelial cells and the basement membrane subjacent to the airway epithelial cells.[17] This suggests that translocation of VEGF protein occurs after its synthesis in the epithelium. VEGFR-1 and VEGFR-2 mRNA expression also increases during normal mouse lung development[18,19] and is localized to the pulmonary endothelial cells closely apposed to the developing epithelium.[20] VEGF120, VEGF164, and VEGF188 are present in alveolar type II cells in the developing mouse lung, and their expression peaks during the canalicular stage, when most of the vessel growth occurs in the lung, then decreases toward until day 10 postnatal (P10) when it increases to levels that are maintained throughout adulthood.[20]

Targeted exon deletion of the VEGF gene reveals that mice that lack the heparin-binding isoforms VEGF164 and VEGF188 display a variety of vascular defects, including a significant reduction in the formation of air spaces and capillaries, resulting in distended and underdeveloped alveoli.[21] Similarly, pharmacologic and genetic VEGF inhibition during alveolar development decreases alveolarization and pulmonary arterial density, features encountered in clinical BPD.[21-24] Chronic treatment of adult rats with the VEGFR-1 and VEGFR-2 blocker SU5416 leads to enlargement of the air spaces, indicative of emphysema,[25] suggesting that VEGF is required not only for the formation but also for the maintenance of the pulmonary vasculature and alveolar structures throughout adulthood. Conversely, lung overexpression of VEGF during normal lung development, disrupts the lung architecture suggesting a tight regulation of VEGF-driven angiogenesis to insure proper lung development.[26,27] In a series of elegant experiments, Dr. Vu’s group used pharmacologic VEGF inhibition in lung renal capsule grafts[24] and genetic VEGF inactivation[28] to show that selective inactivation of VEGF in respiratory epithelium results in an almost complete absence of pulmonary capillaries, demonstrating the dependence of pulmonary capillary development on epithelium-derived Vegf-A. Deficient capillary formation in Vegf-A deficient lungs was associated with a defect in primary septae formation, coupled with suppression of epithelial cell proliferation and decreased hepatocyte growth factor (HGF) expression. Lung

Thébaud: Angiogenesis in lung


endothelial cells express HGF, and selective deletion of the HGF receptor gene in respiratory epithelium phenocopies the malformation of septae, confirming the requirement for epithelial HGF signaling in normal septae formation and suggesting that HGF serves as an endothelium-derived factor that signals to the epithelium. In summary, these observations suggest that inhibition of vascular growth itself may directly impair alveolarization.

Perturbation of nitric oxide is associated with arrested alveolar and lung vascular growthThe role of the endothelium-derived relaxing factor nitric oxide (NO) in the regulation of the pulmonary vascular tone in the perinatal period is well established;[29] however, little was known about its potential role in the structural development of the pulmonary vasculature. Recent studies suggest that VEGF-induced lung angiogenesis is in part mediated by NO. SU5416 (VEGF inhibitor)-induced arrested alveolar and vascular growth in newborn rats is associated with decreased lung endothelial nitric oxide synthase (eNOS) protein expression and NO production; treatment with inhaled NO improves vascular and alveolar growth in this model.[30] Lungs of late fetal and neonatal eNOS-deficient mice have a paucity of distal arteries and reduced alveolarization,[31] and are more susceptible for failed vascular and alveolar growth after exposure to mild hypoxia and hyperoxia.[32]

Platelet endothelial cellular adhesion molecule-1Administration of an anti–platelet endothelial cellular adhesion molecule-1 (PECAM-1) antibody that inhibits endothelial cell migration, but not proliferation or survival in vitro, also impairs alveolarization in neonatal rats, without reducing endothelial cell content.[33] These data suggest that the loss of PECAM-1 function compromises postnatal lung development and provides evidence that inhibition of endothelial cell function, in contrast to loss of viable endothelial cells, inhibits alveolarization.

EVIDENCE THAT ANGIOGENESIS IS DISRUPTED IN EXPERIMENTAL MODELS OF ARRESTED ALVEOLARIZATION AND IN HUMAN BPD AND EMPHYSEMA

Link between angiogenesis and arrested alveolar growth/loss of alveoliThe proposed link between alveolarization and angiogenesis is suggested by the secondary abnormalities that occur in one process when the other is primarily affected. Alveolar hypoplasia and dysmorphic changes of the lung vasculature are consistent findings in experimental and human BPD. Earlier in 1959, Liebow had made similar observations in adult patients with centrilobular emphysema: alveolar septa were thin and nearly avascular, suggesting that a reduction in the blood supply of the small precapillary blood vessels might induce the disappearance of alveolar septa.[34] The first evidence that abnormal vascular development may contribute to neonatal lung disease came from autopsy studies showing reduced pulmonary microvascularization in infants dying from BPD.[35] A more recent postmortem study of newborns dying after short and prolonged durations of mechanical ventilation also quantified lung microvascular growth.[36] This study confirmed

the reduction in vascular branching arteries, but interestingly lung PECAM-1 protein content (a marker of endothelial cells) was decreased in infants dying after brief ventilation, but was increased after prolonged ventilation.[36] These findings suggest a transient decrease in endothelial proliferation, followed by a brisk proliferative response, despite a reduction in vessel number. This observation suggests that dysmorphic lung vascular growth in BPD may not necessarily result simply from a reduction in the number of endothelial cells, emphasizing the need for more extensive studies in animal models of BPD to better define the mechanisms that underlie early and the time-dependent sequence of events that precede the development of impaired distal lung structure.

Decreased VEGF signaling in BPDVarious animal models of impaired alveolar development also display abnormal lung vascular development.[37-41] Accordingly, animal and human studies show decreased expression of VEGF and its receptors in chronic newborn lung injury. Decreased VEGF expression is found in alveolar type II cells of newborn rabbits[42] or in newborn rat lungs[23] exposed to 100% O2. In the preterm baboon model of BPD, arrested PECAM-1, a distal lung endothelial cell marker, expression and reduced capillary density are associated with lower VEGF and VEGFR-1 mRNA and protein expression seen at 125-day vs 140-day term animals.[43] Similar observations exist in chronically ventilated premature sheep[44] and in term mice.[45] Premature sheep with antenatal endotoxin exposure (mimicking chorioamnionitis, another risk factor for BPD) also display decreased lung VEGF expression.[46] In humans, similar observations have been made in some,[47-49] but not all,[50] studies. Infants developing BPD have lower VEGF levels than those surviving without BPD.[49] VEGF may participate in pulmonary repair after acute lung injury. In lung tissue from infants who died from BPD, the typical patterns of alveolar simplification with “dysmorphic” microvasculature is associated with reduced lung VEGF and VEGFR-1 mRNA and protein expression.[47] Likewise, there are lower VEGF levels in the tracheal aspirates of preterm infants dying from severe respiratory distress syndrome than survivors and in infants subsequently developing BPD, as compared with premature infants surviving without pulmonary complications.[47]

Hypoxia is a major stimulus of VEGF expression.[51] Premature exposure of the developing lung to a hyperoxic environment may downregulate VEGF expression. Even ambient O2 levels (21%), that is, premature birth per se, may interfere with normal lung vascular development.[52] Interestingly, hypoxia-inducible factor (HIF)—a master transcription factor modulating O2-sensitive gene expression (including VEGF and angiopoietins [Ang]) and vessel growth[51]—is activated in hypoxia and inhibited by increased O2 levels.[53,54] Accordingly, HIF-1a- and HIF-2a mRNA is significantly decreased in the lung of hyperoxic newborn rats.[55] However, because HIF deficiency is embryonically or immediately postnatally lethal, the role of HIF during alveolarization remains unknown.

Perturbation of other angiogenic growth factors provides further evidence for a link between disrupted angiogenesis and BPDDespite its central role in vascular formation, VEGF works in concert with other factors, notably Ang to stabilize the vascular



wall. Unlike mouse embryos lacking VEGF or VEGFR-2, embryos lacking Ang1 or its receptor Tie2 develop a rather normal primary vasculature.[56-58] However, endothelial cells fail to associate appropriately with underlying support cells, which are the cells that provide the Ang1 protein that acts on endothelial Tie2 receptors.[59] Whereas VEGF leads to immature, leaky, and hemorrhagic vessels, Ang1 generates vessels that are resistant to leak suggesting that Ang1 maximizes interactions between endothelial cells and their surrounding support cells and matrix.[60] These findings indicate that Ang1 is complementary to VEGF during vessel formation, acting at a later stage of angiogenesis to elicit vessel maturation and integrity. However, little is known about the role of Ang during normal alveolarization. In the baboon lung, Ang1 is mainly expressed in the septal mesenchymal cells and Ang1 and its receptor Tie2 increases during lung development. Conversely, Tie2 expression is decreased in lungs of ventilated baboons[43] and humans with BPD.[61] The role of Ang2 during angiogenesis is less clear. Ang2 displays similarly high affinity for Tie2 and may act as a Tie2 antagonist. In lung epithelial cells, Ang2 expression is induced during hyperoxia.[62] Hyperoxia-induced oxidant injury, cell death, inflammation, permeability, and mortality are ameliorated

in Ang2 knockout mice and in Ang2 siRNA–treated mice. Finally, Ang2 tracheal aspirate levels are increased in newborns that develop BPD.

Likewise, chronically ventilated preterm lambs[63] and baboons[64] have decreased lung eNOS expression, suggesting that NO deficiency may contribute to the decreased alveolarization seen in these models of BPD.

Antiangiogenic factorsEndothelial monocyte activating polypeptide II (EMAP-II) and endostatin are potent natural angiogenesis inhibitors. The role of EMAP-II has been explored only at the earlier stages of lung development, but its activation decreases neovascularization, interrupts lung branching morphogenesis, and decreases lung surfactant.[65] Endostatin was recently measured in tracheal aspirate fluid, and higher endostatin concentrations correlated with parameters reflecting lower lung maturity.[66] It is very likely that other pro- and antiangiogenic growth factors play a role during lung angiogenesis and the balance between these growth factors is crucial for the coordinated assembly and remodeling of blood vessels during alveolar development [Figure 1].

Figure 1: (a) Normal lung development is interrupted in bronchopulmonary dysplasia (BPD). Preterm infants at risk of developing BPD are born at the late canalicular–early saccular stage of lung development. Factors contributing to BPD, such as preterm birth, infl ammation, oxygen, mechanical ventilation, and steroids, interfere with the formation of alveoli resulting in large, simplifi ed, and fewer distal airspaces. (b) Arrested alveolar development in BPD is associated with decreased angiogenesis. In experimental and human BPD, arrested alveolarization is associated with decreased lung angiogenesis and decreased vascular endothelial growth factor (VEGF) signaling. (c) Inhibition of angiogenesis impairs alveolarization. Conversely, during normal lung development, nonspecifi c and specifi c pharmacologic and genetic VEGF inhibition results in arrested alveolar development reminiscent of BPD. (d) VEGF-driven angiogenesis preserves and restores normal alveolarization in experimental BPD. Intratracheal adenovirus-mediated VEGF gene therapy or intraperitoneal VEGF peptide preserve and restore normal alveolar and lung vascular growth in oxygen-induced arrested alveolar development in newborn rats. Similar fi ndings have been made with inhaled nitric oxide and pharmacologic hypoxia-inducible factor activation in preterm ventilated lambs or baboons


¯VEGF signaling

Preterm birth Inflammation

OxygenVentilation

Postnatal steroids

Saccular stage Alveolar stage

Normal alveoli

Simplified alveoli in BPD


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FumagillinThalidomide

VEGF inhibition-Genetic or Pharmacologic (Su-

5416, VEGF trap)


VEGF

Impaired alveolar development

Preterm birth Inflammation

OxygenVentilation

Postnatal steroids

Oxygen

Established oxygen-induced lung injury

Saccular stage lung

Prevention

Restoration


Endoglin (CD105) is a hypoxia-inducible transforming growth factor-beta (TGF-b) coreceptor. Excessive lung TGF-b expression contributes to arrested alveolarization.[67] High levels of endoglin expression have been described in vascular endothelial cells in tissues undergoing active angiogenesis, such as regenerating and inflamed tissues or tumors.[68] Lungs of short-term ventilated preterm infants showed significant upregulation of endoglin mRNA and protein levels, immunolocalized to the microvasculature compared with age-matched nonventilated control lungs.[69] Similar but more variable endoglin upregulation was noted in lungs of long-term ventilated infants with BPD. This was associated with decreased mRNA levels of VEGF, Ang1, and their respective receptors.[69]

In summary, these data provide strong evidence that angiogenesis is necessary for alveolarization during normal lung development, and that an imbalance in angiogenic growth factors during a critical period of growth contributes to the late sequelae of BPD. These observations also provide the rationale for testing the therapeutic potential of proangiogenic growth factors to promote alveolar development.

PROOF OF PRINCIPLE EXPERIMENTS INDICATING A THERAPEUTIC POTENTIAL OF ANGIOGENIC GROWTH FACTORS TO PREVENT ARRESTED ALVEOLAR GROWTH

Recombinant human VEGF treatment of newborn rats during or after exposure to hyperoxia enhances vessel growth and improves alveolarization.[70,71] Likewise, postnatal intratracheal adenovirus-mediated VEGF gene therapy improves survival, promotes lung capillary formation, preserves alveolar development and regenerates new alveoli in this same model of irreversible lung injury.[23] In both animal studies, VEGF induced immature and leaky capillaries and lung edema. However, combining lung VEGF and Ang1 (which promotes vascular maturation) gene transfer preserves alveolarization and enhances angiogenesis with more mature capillaries that are less permeable, reducing the vascular leakage seen in VEGF-induced capillaries.[23]

These observations highlight the tightly orchestrated process of angiogenesis and points toward the need to closely recapitulate this process to warrant efficient and safe angiogenesis. The transcription factor HIF regulates several angiogenic growth factors. HIF activation via inhibition of prolyl hydroxylase domain–containing proteins prevents lung injury in the premature baboon model of BPD and supports further a potential role for angiogenic growth factor in promoting alveolar development.[72]

Given that VEGF-induced angiogenesis is in part mediated by NO, some of these findings may explain the beneficial effects of early and prolonged low-dose inhaled NO seen in 3 recent randomized controlled trials to prevent BPD.[73-75] Factors acting downstream of NO may exert similar beneficial effects.

CONCLUSIONS AND FUTURE DIRECTIONS

These observations provide proof of concept for the crucial role of the lung vasculature in what is traditionally thought of as an airspace disease and open new therapeutic avenues to protect

or regenerate new alveoli. However, much more needs to be learned about the morphologic changes and the mechanisms that regulate lung vascular development and saccular and alveolar growth. For example, intussusceptive microvascular growth, the internal division of the preexisting capillary plexus (insertion of transcapillary tissue pillars) without sprouting, is a relatively recently described mode of blood vessel formation in the lung.[10] Intussusceptive microvascular growth may promote alveolar development and remodeling throughout adult life and thus be amenable to therapeutic modulation for lung regeneration if we can unravel its regulatory mechanisms. Likewise, it will be crucial to recapitulate the tightly orchestrated process of angiogenesis (appropriate factor or combination of factors, dosing, and timing) if this mechanism is to be exploited therapeutically. Finally, the recent excitement in stem cell biology has sparked the interest in the reparative potential of endothelial progenitor cells. If angiogenic growth factors contribute to alveolar homeostasis, then vascular progenitor cells are appealing candidate cells likely to be involved in the same mechanisms. Recent observations, including the developing lung,[76] suggest that endothelial progenitor cells migrate from the bone marrow to the peripheral circulation and the lung where they contribute to the repair of injured endothelium and help restore lung integrity. Endothelial progenitor cells improve experimental pulmonary hypertension, and clinical pilot studies are underway.[77] These are exciting perspectives unraveling the therapeutic potential of promoting angiogenesis to treat lung diseases characterized by alveolar damage and pulmonary hypertension.

ACKNOWLEDGMENTS

Supported by the Canadian Institutes for Health Research (CIHR), the Canada Foundation for Innovation (CFI), the Alberta Heritage Foundation for Medical Research (AHFMR), the Heart and Stroke Foundation of Alberta and Nunawut, the Alberta Lung Association, the Stollery Children’s Hospital Foundation and a Canada Research Chair in Translational Lung and Vascular Developmental Biology.

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Source of Support: Nil, Confl ict of Interest: None declared.



Address for correspondence: Dr. Antonio Augusto Lopes, Department of Paediatric Cardiology and Adult Congenital Heart Disease - The Heart Institute (InCor) - HC.FMUSP - Av. Dr. Eneas de Carvalho Aguiar, 44 - 05403-900 - São Paulo – Brazil. E-mail: [email protected]

DOI: 10.4103/0974-6013.68486

Pulmonary Arterial Hypertension in Adults with Congenital Heart Disease: The Eisenmenger Syndrome

Antonio Augusto Lopes, André Cogo Dalmaschio1

Department of Pediatric Cardiology and Adult Congenital Heart Disease, 1Heart Institute, University of São Paulo School of Medicine, São Paulo, Brazil

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Despite the early surgical repair of congenital cardiac defects in most institutions of developed countries, advanced pulmonary vasculopathy associated with unrepaired shunts remains a major problem, particularly in underserved areas of developing nations. The so called Eisenmenger syndrome (reversed right-to-left shunting caused by heightened pulmonary vascular resistance, sometimes above the systemic level) is a multisystemic disorder associated with progressive right cardiac failure and hypoxemia. Management of this disorder is far beyond the simple administration of vasodilators. Rather, in the era of the “new drugs” for treatment of pulmonary hypertension, general therapeutic measures remain central in patient care. These include monitoring of blood viscosity and prevention of hyperviscosity states, prophylaxis against pulmonary and systemic infections and thrombotic events, monitoring of renal function and systemic blood pressure, contraception in females, and management of specifi c cardiac complications such as myocardial ischemia and arrhythmias.

Key words: Pulmonary hypertension, Eisenmenger syndrome, thrombosis, hypoxemia, blood hyperviscosity

DEFINITION AND EPIDEMIOLOGY

After the initial description of a 32-year-old cyanotic patient who died of massive hemoptysis, with postmortem examination showing a ventricular septal defect (1897, Viktor Eisenmenger), in 1958, Paul Wood [Figure 1] coined the term Eisenmenger complex to define the condition of a large ventricular septal defect associated with heightened pulmonary artery pressure and vascular resistance causing bidirectional or reversed (right-to-left) shunting and systemic oxygen desaturation. Subsequently, the term Eisenmenger syndrome has been used to describe any congenital cardiac septal defect or shunt between the great arteries (persistent ductus arteriosus or aortopulmonary window) associated with advanced pulmonary vascular disease and reversed shunting.[1] There has been some debate whether the condition of a cyanotic anomaly (eg., transposition of the great arteries or univentricular hearts) causing severe pulmonary arterial hypertension (PAH) should be referred to as Eisenmenger syndrome.

According to the report of the Joint Study on the Natural History of Congenital Heart Defects,[2] approximately 13% of unoperated patients with a nonrestrictive ventricular septal defect develop the Eisenmenger syndrome. More recently, a 5-year survey on adult congenital heart disease in the European Community revealed that the syndrome

was present in 1.6% and 11.7% of all adults with an atrial or ventricular septal defect, respectively.[3] Thus, despite the general agreement that patients with congenital cardiac defects should be assigned to operation early in life, the Eisenmenger syndrome is still prevalent even in developed countries.

NATURAL HISTORY

Compared with idiopathic pulmonary arterial hypertension (IPAH), the natural history of patients with the Eisenmenger syndrome is considerably better, with survival curves showing that more than 40% of the subjects are expected to be alive 25 years following the diagnosis[2,4] [Figure 2]. This

Figure 1: Paul Hamilton Wood (1907–1962), who coined the term “Eisenmenger complex”

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Figure 4: Vascular lesions that may be found in patients with pulmonary arterial hypertension associated with congenital heart disease. (a) Medial hypertrophy only; (b) medial hypertrophy associated with abnormalities of the internal elastic lamina (arrow) and intimal proliferation leading to a marked reduction of the lumen; (c) medial hypertrophy and intimal fi brocellular proliferation with an excentric residual lumen (thrombotic lesion). (Courtesy, Dr. Vera D. Aiello, Heart Institute, São Paulo, Brazil)

a b ca b c

associated with pulmonary arterial thrombosis and pulmonary infarction (thrombotic diathesis) as well. On the other hand, hypoxemia and blood hyperviscosity may account for a number of systemic abnormalities, including myalgia, subtle neurologic events (headache, dizziness, and visual disturbances), cerebrovascular accidents, and cerebral abscess.[7] Systemic hypertension associated with decreased renal function and uremia is occasionally seen.

Pulmonary vasculopathy that occurs in the Eisenmenger syndrome is not different from IPAH[8] or pulmonary hypertension (PH) associated with congenital cardiac defects in general,[9] except that large-vessel disease is probably more prevalent, particularly in adults, due to the chronic character of the disorder. Small-vessel abnormalities include medial hypertrophy of the pulmonary arteries and intimal fibrocellular proliferation leading to progressive narrowing of the vascular lumen [Figure 4]. Increased elastolytic activity has been described in association with the whole process of cellular migration into the intima and proliferation.[10] Vascular dilatation may be seen, with

Figure 2: Survival curves for patients with Eisenmenger syndrome (from diagnosis) compared with idiopathic pulmonary arterial hypertension (PPH). Data correspond to patients not receiving prostacyclin analogs, endothelin receptor antagonists, or phosphodiesterase inhibitors. Unpublished data from the Heart Institute, São Paulo, Brazil

Figure 3: Short-term (1-year) survival in patients with idiopathic pulmonary arterial hypertension (PPH) and the Eisenmenger syndrome (congenital heart disease-associated pulmonary hypertension [CHD-PH]) as a function of the circulating (plasma) levels of von Willebrand factor (vWF:Ag). For any given level of vWF:Ag, the probability of survival is considerably higher for patients with CHD-PH. Reproduced from Ref. 6, with permission

Lopes and Dalmaschio: PAH in adults with congenital heart disease

is important while planning the therapeutic strategies, because outcomes must be analyzed on a long-term basis. Variables that have been demonstrated to be associated with poor outcome are syncope, elevated right atrial pressure and right ventricular filling pressure (8mmHg or above), and peripheral (systemic) oxygen saturation < 85%.[4]

In our institution, we have observed that heightened circulating levels of von Willebrand factor (vWF:Ag) are associated with decreased life expectancy in these patients [Figure 3]. For unknown reasons, some subjects in very stable conditions have low plasma endothelial dysfunction marker levels.[5,6]

PATHOPHYSIOLOGY AND PATHOLOGY

The Eisenmenger syndrome is a multisystemic disorder that includes chronic hypoxemia, erythrocytosis with increased blood viscosity, vascular abnormalities not only in the pulmonary but also in the systemic circulation, and increased risk of thrombotic events. Hemoptysis, which was interpreted for many years as the result of bleeding diathesis and/or rupture of thin-walled (abnormally dilated) pulmonary vessels, is now known to be


angiomatoid structures or plexiform lesions (thin-walled lesions with capillary-like proliferation inside). Finally, necrotizing arteritis may be observed, with reactive inflammatory exudate throughout the vascular layers.[11]

Large-vessel abnormalities (extrapulmonary and intrapulmonary) are easily detected by chest computed tomography and include enlargement of the proximal pulmonary arteries (which are sometimes aneurismal), mild-to-massive pulmonary arterial thrombosis, and mild-to-extensive mural calcific deposits.[12] In a study of ours, patient age, peripheral oxygen desaturation, and plasma level of D-dimer were associated with increased likelihood of in situ pulmonary arterial thrombosis, but in multivariate analysis, only the age was found to be an independent predictor of this complication.[13] Occasionally, an enlarged pulmonary trunk may cause extrinsic compression of the left main coronary artery leading to myocardial ischemia.[14]

CLINICAL PRESENTATION

The typical patient with Eisenmenger syndrome is an adult with chronic cyanosis and progressive exercise intolerance. Symptoms (in general, class II or III, New York Heart Association) tend to be more prominent during the winter, and include breathlessness, palpitations, chest pain, and syncope (which is associated with poor outcome). Myalgia and arthralgia are frequent complaints, as are headaches, dizziness, and transient visual disturbances. On physical examination, central cyanosis with clubbing is evident [Figure 5]. Right ventricular heave and a loud pulmonary component of the second heart sound are typically present. Abdominal tenderness and peripheral edema may be present as well.[1,7]

Occasionally, patients are seen in the emergency room with serious complications, such as cerebral abscess or cerebrovascular accidents, causing neurologic disturbances, bleeding diathesis, rupture of thin-walled pulmonary vessels or lung infarction causing massive hemoptysis, bacterial endocarditis leading to systemic infection, or severe myocardial dysfunction presenting as low systemic output. Less severe complications include epistaxis or gingival bleeding, calcium bilirubinate gallstones, and hyperuricemia associated with gout arthritis.[1,7]

DIAGNOSTIC PROCEDURES

The tests that are routinely performed in patients with the Eisenmenger syndrome are summarized in Table 1. Additional tests that are performed in patients with PAH in general may be considered in particular instances and include pulmonary function tests, ventilation–perfusion lung scintigraphy, blood screening for connective tissue disease, and screening for schistosomiasis, portal hypertension, and HIV infection.

Either the 6-min walk test or the cardiopulmonary exercise test can be used to assess the physical capacity in these patients.[15,16] These tests provide useful information on the behavior of arterial oxygen saturation during exercise. Termination of exercise depends largely on the severity of hypoxemia. Because the prognostic value of peak oxygen consumption deserves further scrutiny in cyanotic patients, the measurement of the 6-min walk distance represents the preferred method in practice.

Transthoracic echocardiography may be used not only to determine the intracardiac anatomy, but also to estimate the hemodynamic parameters, such as pulmonary pressures and vascular resistance.[17,18] Magnetic resonance imaging is useful to determine intracardiac anatomy in patients with inadequate echocardiographic window, and provides additional information or right (and left) ventricular volumes and function. Neither of these tests can be used as a substitute for cardiac catheterization, but they are useful for repeated patient evaluations on a long-term basis. High-resolution computed tomography is particularly useful to determine the existence and extent of pulmonary arterial thrombosis.[12,13,19] It can be used in association with the circulating levels of D-dimer to evaluate subjects presenting with breathlessness, worsening of hypoxemia, chest pain, and hemoptysis.

There is no current substitute for cardiac catheterization when accurate analysis of pulmonary hemodynamics is in order (eg, in

Figure 5: Central cyanosis and clubbing in an adult with Eisenmenger syndrome

Table 1: Tests routinely performed in patients with Eisenmenger syndromeECGChest radiography*Transthoracic echocardiography*Cardiac magnetic resonanceChest high-resolution computed tomography*Exercise testing

6-min walk distanceCardiopulmonary exercise testing

Cardiac catheterizationRoutine laboratory testing

Full blood count (especially platelet count)*Urea and creatinine*Liver function testsUric acid*Iron status/transferring saturation/serum ferritin*Coagulation tests/factors*Plasma D-dimer level*/thrombin–antithrombin complexes

(*)Frequently performed in the emergency room



clinical trials aimed at determining the efficacy of vasodilators). In these instances, direct measurement of pulmonary vascular resistance is mandatory. It should be emphasized that pulmonary artery pressures are not expected to decrease substantially in the course of vasodilator therapy, because increased pulmonary flow may compensate for decreased pulmonary vascular resistance, with no changes in pressures. An association between acute pulmonary vascular response to vasodilators and prognosis has been demonstrated in adults with Eisenmenger syndrome.[20] However, criteria for a positive response to acute vasodilator administration has not been defined in this syndrome. Those adopted for patients with IPAH (eg, a 10 mmHg drop in the mean pulmonary artery pressure with a final value of <40 mmHg) are definitely not appropriate.

Routine laboratory testing is important in patients with Eisenmenger syndrome, and is summarized in Table 1. Attention should be given to coagulation abnormalities (either hypo- or hypercoagulable/prothrombotic states)[21-23] and altered blood viscosity particularly associated with depletion of iron reserves. Iron deficiency, a common finding in these patients, influences erythrocyte deformability,[24] resulting in increased blood viscosity, clinical deterioration, and heightened risk of thrombotic events. Chronic intravascular coagulation may be present in some patients. Frequent monitoring of D-dimer levels, circulating thrombin–antithrombin complexes, and platelet count is therefore recommended.

GENERAL THERAPEUTIC MEASURES

For many decades before the era of the so-called new drugs for treatment of PAH, patients with Eisenmenger syndrome were managed conventionally. Those who were adequately assisted had a reasonable quality of life and much better life expectancy compared, for example, with subjects with IPAH. Thus, conventional therapeutic measures remain absolutely important in the management of these patients, even in the era of the “new drugs.” General therapeutic measures [Table 2] have not been supported by evidence, and are largely based on personal/institutional expertise. There has been a general agreement that the most important principle in the management of patients with Eisenmenger syndrome is “primum non nocere.”

Monitoring of blood viscosity and avoidance of critical

hyperviscosity states is mandatory. In this way, monitoring and replenishment of iron reserves is considerably more efficacious than repeated phlebotomies.[25] When absolutely necessary to control hyperviscosity-related symptoms (breathlessness, headaches, dizziness, arthralgia, and visual disturbances associated with a hematocrit > 65%), hemodilution is planned to produce mild reductions in the hematocrit level, not to achieve normal levels. In order to avoid significant changes in circulating blood volumes, hemodilution should be planned so that extracted blood is simultaneously replaced by hyperoncotic solutions. Low–molecular weight dextran may be useful in these instances, even in the presence of decreased platelet counts.[26]

In contrast to IPAH, long-term beneficial effects of chronic oral anticoagulation have not been definitely demonstrated. Arguments against the use of anticoagulants are based on the observation of altered coagulation in some of these pa-tients. Arguments in favor of chronic anticoagulation are based on the age-dependent occurrence of in situ pulmo-nary arterial thrombosis, which becomes massive in some individuals.[12,13,27] Furthermore, it is not known whether anticoagulation prevents extension of the thrombotic lesions once large-vessel intrapulmonary thrombosis is detected by computed tomography. Thus, unless clearly contraindicated, it is our policy to keep patients with Eisenmenger syndrome on chronic oral anticoagulant therapy (warfarin) with careful monitoring of the “international normalized ratio” (INR, which is generally main-tained between 2.0 and 3.0 in these subjects).

Other measures seem to be equally relevant. Although there has been a debate about the beneficial effects of chronic oxygen administration in adults with Eisenmenger syndrome,[28] it may be useful for relief of symptoms in selected patients presenting with severe hypoxemia, particularly if lung disease is present in association. Prevention and early treatment of infectious diseases are crucial, in particular taking into account the increased risk of serious complications, such as bacterial endocarditis and cerebral abscess. Annual pneumococcal and influenza vaccination is recommended. Because chronic hypoxemia and blood hyperviscosity may lead to progressive impairment or renal function and systemic hypertension, monitoring of these abnormalities is mandatory.

TARGETED THERAPIES

Pro tano ids , endo the l in - recep to r an tagon i s t s and phosphodiesterase inhibitors have been used as an attempt to improve hemodynamics and the physical capacity in patients with Eisenmenger syndrome. Prostacyclin analogs (intravenous administration) have been shown to improve the functional capacity and pulmonary hemodynamics in patients with PH associated with congenital heart disease.[29] Bosentan (oral administration) is probably the most extensively used drug in intention-to-treat open-label studies.[30-32] A recent randomized placebo-controlled study has become available.[33] Sildenafil (oral administration) has been successfully used in patients with PAH, including subjects with congenital heart disease,[34] but further studies are required to demonstrate its benefits specifically in the Eisenmenger syndrome.

It must be emphasized that treatments with drugs capable of

Table 2: General therapeutic measuresManagement of hyperviscosity syndrome

Avoidance of dehydrationMonitoring of hematocritMonitoring of iron levels/storesHemodilution if absolutely necessary (hematocrit > 65%)

Chronic anticoagulation (international normalized ratio between 2.0 and 3.0)Chronic oxygen administrationMonitoring/treatment of systemic disturbances

Systemic arterial hypertensionRenal dysfunction/failure

Avoidance of infectionEarly diagnosis and treatment of infectionsPneumococcal and influenza vaccination



inducing pulmonary vasodilatation and/or improving vascular remodeling is totally palliative in these patients. In contrast to young patients (infants and young children) who might theoretically benefit from a combination of drug therapy (to reduce pulmonary vascular resistance) and surgical procedures planned to limit the increase in pulmonary flow (partial or total closure of septal defects, pulmonary arterial banding), patients with Eisenmenger syndrome who respond favorably to drug therapy are expected to have a modest decrease in pulmonary vascular resistance, not sufficiently impressive to allow for correction of the cardiac defects. Therefore, in these patients, only short- to mid-term improvement of hemodynamics, peripheral oxygen saturation, and physical capacity is expected to occur as a result of successful vasodilator therapy. There is no evidence that such effects can be sustained on a long-term basis. Furthermore, it is not known whether increased flow at sites of drug-induced vasodilatation could provoke further endothelial damage and vascular remodeling. Thus, the long-term effects of the “new drugs” on patient’s quality of life and survival remain to be demonstrated. Increased time to lung or heart–lung transplantation would theoretically represent a relevant benefit. But this remains to be demonstrated as well.

SPECIAL SITUATIONS – PREGNANCY

In view of the considerable risk of serious maternal and fetal complications, pregnancy is strongly discouraged in women with Eisenmenger syndrome. More than that, termination of pregnancy is usually recommended in these instances. There have been reports of a >25% maternal mortality in relation to pregnancy and ~20% prevalence of cardiac abnormalities in the offspring.[35] On the other hand, there are restrictions for the use of hormonal contraceptives in view of the potential risk of thromboembolic complications.[36] Contraception protocols that involve progesterone-only pills or devices may be useful, although controlled studies are needed to evaluate the risk/benefit ratios with their use. Despite these risks and recommendations, some women decide to carry on with their pregnancy. In these instances, hospitalization from the end of the second trimester to delivery, the use of heparin (20,000–40,000 units per day) and supplemental oxygen during the third trimester, and cesarean section may be of help to decrease mortality.[37]

SUMMARY

The Eisenmenger syndrome is a multisystemic disorder that affects patients at all ages. Although its prevalence tends to be higher in underserved areas/countries, many patients have now been diagnosed and treated in developed countries. Correction of congenital cardiac shunts in the presence of advanced pulmonary vascular disease involves unacceptable risk of poor outcomes and therefore, should be strongly discouraged. Once adequately diagnosed and treated, patients with Eisenmenger syndrome have survival curves considerably better than those with IPAH or PH associated with connective tissue disease. With the development of the so-called new drugs for treatment of PAH, namely prostacyclin analogs, endothelin receptor antagonists, and phosphodiesterase inhibitors, substantial short- and mid-term improvements in terms of physical capacity and quality of life have been reported. Until results of further studies become available for a better understanding of the long-term benefits of

these treatments, general therapeutic measures remain important in the management of these patients.

REFERENCES

1. Vongpatanasin W, Brickner ME, Hillis LD, Lange RA. The Eisenmenger syndrome in adults. Ann Intern Med 1998;128:745-55.

2. Kidd L, Driscoll DJ, Gersony WM, Hayes CJ, Keane JF, O'Fallon WM, et al. Second natural history study of congenital heart defects. Results of treatment of patients with ventricular septal defects. Circulation 1993;87:I38-51.

3. Engelfriet PM, Duff els MG, Möller T, Boersma E, Tĳ ssen JG, Thaulow E, et al. Pulmonary arterial hypertension in adults born with a heart septal defect: the Euro Heart Survey on adult congenital heart disease. Heart 2007;93:682-687.

4. Saha A, Balakrishnan KG, Jaiswal PK, Venkitachalam CG, Tharakan J, Titus T, et al. Prognosis for patients with Eisenmenger syndrome of various aetiology. Int J Cardiol 1994l;45:199-207.

5. Lopes AA, Maeda NY, Bydlowski SP. Abnormalities in circulating von Willebrand factor and survival in pulmonary hypertension. Am J Med. 1998;105:21-6.

6. Lopes AA, Maeda NY, Gonçalves RC, Bydlowski SP. Endothelial cell dysfunction correlates diff erentially with survival in primary and secondary pulmonary hypertension. Am Heart J 2000;139:618-23.

7. Diller GP, Gatzoulis MA. Pulmonary vascular disease in adults with congenital heart disease. Circulation 2007;115:1039-50.

8. Pietra GG. The pathology of primary pulmonary hypertension. In: Rubin LJ, Rich S, editors. Primary pulmonary hypertension. New York: Marcel Dekker, Inc.; 1997. p. 19-61.

9. Heath D, Edwards JE. The pathology of hypertensive pulmonary vascular disease; a description of six grades of structural changes in the pulmonary arteries with special reference to congenital cardiac septal defects. Circulation 1958;18:533-47.

10. Rabinovitch M. Elastase and the pathobiology of unexplained pulmonary hypertension. Chest 1998;114:213S-24S.

11. Wagernvoort CA, Heath D, Edwards JE. The Pathology of the pulmonary vasculature. Springfi eld, IL: Charles Thomas; 1964. p. 224-54.

12. Perloff JK, Hart EM, Greaves SM, Miner PD, Child JS. Proximal pulmonary arterial and intrapulmonary radiologic features of Eisenmenger syndrome and primary pulmonary hypertension. Am J Cardiol 2003;92:182-7.

13. Caramuru LH, Maeda NY, Bydlowski SP, Lopes AA. Age-dependent likelihood of in situ thrombosis in secondary pulmonary hypertension. Clin Appl Thromb Hemost 2004;10:217-23.

14. Mesquita SM, Castro CR, Ikari NM, Oliveira SA, Lopes AA. Likelihood of left main coronary artery compression based on pulmonary trunk diameter in patients with pulmonary hypertension. Am J Med 2004;116:369-74.

15. Diller GP, Dimopoulos K, Okonko D, Li W, Babu-Narayan SV, Broberg CS, Johansson B, Bouzas B, Mullen MJ, Poole-Wilson PA, Francis DP, Gatzoulis MA. Exercise intolerance in adult congenital heart disease: comparative severity, correlates, and prognostic implication. Circulation 2005;112:828-35.

16. Dimopoulos K, Okonko DO, Diller GP, Broberg CS, Salukhe TV, Babu-Narayan SV, et al. Abnormal ventilatory response to exercise in adults with congenital heart disease relates to cyanosis and predicts survival. Circulation 2006;113:2796-802.

17. Hirschfeld S, Meyer R, Schwartz DC, Kofh agen J, Kaplan S. The echocardiographic assessment of pulmonary artery pressure and pulmonary vascular resistance. Circulation 1975;52:642-50.

18. Kitabatake A, Inoue M, Asao M, Masuyama T, Tanouchi J, Morita T, et al. Noninvasive evaluation of pulmonary hypertension by a



pulsed Doppler technique. Circulation 1983;68:302-9.19. Pruszczyk P, Torbicki A, Pacho R, Chlebus M, Kuch-Wocial A,

Pruszynski B, et al. Noninvasive diagnosis of suspected severe pulmonary embolism: transesophageal echocardiography vs spiral CT. Chest 1997;112:722-8.

20. Post MC, Janssens S, Van de Werf F, Budts W. Responsiveness to inhaled nitric oxide is a predictor for mid-term survival in adult patients with congenital heart defects and pulmonary arterial hypertension. Eur Heart J 2004;25:1651-6.

21. Perloff JK, Rosove MH, Child JS, Wright GB. Adults with cyanotic congenital heart disease: hematologic management. Ann Intern Med 1988;109:406-13.

22. Perloff JK. Systemic complications of cyanosis in adults with congenital heart disease. Hematologic derangements, renal function, and urate metabolism. Cardiol Clin 1993;11:689-99.

23. Lopes AA. Pathophysiological basis for anticoagulant and antithrombotic therapy in pulmonary hypertension. Cardiovasc Hematol Agents Med Chem 2006;4:53-9.

24. Reinhart WH. The infl uence of iron defi ciency on erythrocyte deformability. Br J Haematol 1992;80:550-5.

25. Broberg CS, Bax BE, Okonko DO, Rampling MW, Bayne S, Harries C, et al. Blood viscosity and its relationship to iron defi ciency, symptoms, and exercise capacity in adults with cyanotic congenital heart disease. J Am Coll Cardiol 2006;48:356-65.

26. Lopes AA, Maeda NY, Ebaid M, Chamone DF, Pileggi F. Eff ect of intentional hemodilution on platelet survival in secondary pulmonary hypertension. Chest 1989;95:1207-10.

27. Lopes AA, Caramurú LH, Maeda NY. Endothelial dysfunction associated with chronic intravascular coagulation in secondary pulmonary hypertension. Clin Appl Thromb Hemost 2002;8:353-8.

28. Sandoval J, Aguirre JS, Pulido T, Martinez-Guerra ML, Santos E, Alvarado P, et al. Nocturnal oxygen therapy in patients with the Eisenmenger syndrome. Am J Respir Crit Care Med 2001;164:

1682-7.29. Rosenzweig EB, Kerstein D, Barst RJ. Long-term prostacyclin for

pulmonary hypertension with associated congenital heart defects. Circulation 1999;99:1858-65.

30. Apostolopoulou SC, Manginas A, Cokkinos DV, Rammos S. Long-term oral bosentan treatment in patients with pulmonary arterial hypertension related to congenital heart disease: a 2-year study. Heart 2007;93:350-4.

31. Gatzoulis MA, Rogers P, Li W, Harries C, Cramer D, Ward S, et al. Safety and tolerability of bosentan in adults with Eisenmenger physiology. Int J Cardiol 2005;98:147-51.

32. Schulze-Neick I, Gilbert N, Ewert R, Witt C, Gruenig E, Enke B, et al. Adult patients with congenital heart disease and pulmonary arterial hypertension: fi rst open prospective multicenter study of bosentan therapy. Am Heart J 2005;150:716.

33. Galiè N, Beghett i M, Gatzoulis MA, Granton J, Berger RM, Lauer A, et al. Bosentan therapy in patients with Eisenmenger syndrome: A multicenter, double-blind, randomized, placebo-controlled study. Circulation 2006;114:48-54.

34. Galiè N, Ghofrani HA, Torbicki A, Barst RJ, Rubin LJ, Badesch D, et al. Sildenafi l citrate therapy for pulmonary arterial hypertension. N Engl J Med 2005;353:2148-57.

35. Daliento L, Somerville J, Presbitero P, Menti L, Brach-Prever S, Rizzoli G, et al. Eisenmenger syndrome. Factors relating to deterioration and death. Eur Heart J 1998;19:1845-55.

36. Schmaltz AA, Neudorf U, Winkler UH. Outcome of pregnancy in women with congenital heart disease. Cardiol Young 1999;9:88-96.

37. Avila WS, Grinberg M, Snitcowsky R, Faccioli R, Da Luz PL, Bellott i G, et al. Maternal and fetal outcome in pregnant women with Eisenmenger's syndrome. Eur Heart J 1995;16:460-4.




Address for correspondence: Prof. S Adnot, Service de Physiologie Explorations Fonctionnelles, Hôpital Henri Mondor, 94010, Créteil and INSERM U955, Faculté de Médecine de Créteil, 94010, Créteil, France. E-mail: [email protected]

DOI: 10.4103/0974-6013.68493

“disproportionate to the degree of lung disease.” A. Chaouat studied 27 patients with disproportionate PH: 16 had COPD associated with a pathological condition including restrictive lung disease, sleep apnea syndrome, thromboembolic disease, left heart disease, obesity, portal hypertension, or dexfenfluramine intake; so it was not clear whether PH was due only to COPD or was aggravated by these associated alterations. Eleven other patients with COPD had severe PH without other diseases; these patients were characterized by severe dyspnea on exertion and exhibited pulmonary hemodynamics similar to patients with PAH. These patients were also characterized by a short life expectancy. So there are really two levels of PH severity in patients with COPD. Because severe PH in patients with COPD is clinically very close to PAH, it is likely that the pathophysiological mechanisms of severe PH in patients with COPD are distinct from those at the origin of the mild PH found in the large majority of patients with COPD.[4,5]

DIAGNOSIS OF PH IN COPD

Echocardiography with Doppler imaging can provide an estimated right ventricular systolic pressure (RVSP), which is felt to reflect pulmonary artery systolic pressure in the absence of RV outflow tract obstruction. Echocardiography has been shown to have twice the sensitivity of clinical assessment in detecting PH in patients with COPD. However, TTE has low sensitivity, specificity, and predictive values in patients with COPD when compared to RHC. This is largely due to technical difficulties in obtaining good windows in even half the patients because of air trapping. This is illustrated by Arcasoy et al. study showing that Echocardiography can be inaccurate to assess really precisely the level of PH in patients with COPD [Figure 4].[6]

Another way to assess the severity of PH in patients with COPD is to measure circulating BNP, which can be a good marker of the level of the PAP and also of the level of survival if patients are classified according to their BNP values.[7]

Therefore BNP level, Doppler echocardiography is simple and noninvasive and can detect cardiac comorbidities, but it is frequently inaccurate. Right heart catheterization remains the gold standard but it is invasive. It is still useful, especially when severe PH is suspected [Figure 4].

INTRODUCTION

In contrast to many vascular diseases, chronic obstructive pulmonary disease (COPD) is becoming increasingly prevalent in many countries and is expected to become the third cause of death worldwide in 2020. Therefore we may expect pulmonary hypertension (PH) from COPD to become the most frequent cause of PH in future [Figure 1][1] (also see PVRI Review literature scan[2]).

Levine et al. published in 1967 a study showing that PH may be very severe in patients with COPD.[3] One characteristic of this type of PH is that it is very responsive to oxygen since in most patients, it could be reversed by supplemental oxygen. Now, at the time of supplemental oxygen therapy, PH in COPD is often much less severe, and it is very unusual to have such a high level of pulmonary arterial pressure.

CHARACTERISTICS OF PH IN COPD

Figure 2 illustrates the level of pulmonary arterial pressure (PAP) usually reported now in patients with COPD. The range of pulmonary arterial pressure is usually close to 22–26 mm Hg, usually associated with a normal cardiac output and hypoxemia. Thus, at the time of oxygen therapy, PH is usually mild to moderate in patients with COPD.[4]

Figure 3 shows the range of PAP measured here in a wide study population of 998 patients with COPD reported by the team of E. Weitzenblum and A. Chaouat in France in 2005. Most of patients have PAP values between 10 to 25 mm Hg. A few patients have PAP values close to 30–35 mm Hg; only rare patients have PAP values above 40 mm Hg and close to 50 mm Hg. In the same study population, it is interesting to look at the characteristics of those with moderate PH and those with severe PH. As compared to patients with values ranging from 20 to 40 mm Hg, patients with severe PH (above 40 mm Hg) were characterized by a lesser degree of airway obstruction, lower DLCO, they were more hypoxemic, and were also hypocapnic [Figure 3].

Thus, in some patients with COPD, PH is unexpectedly severe and that does not seem proportionate to the severity of the disease. So this kind of pulmonary hypertension is termed

Pulmonary Hypertension with Chronic Obstructive Pulmonary DiseaseSerge Adnot, Ari Chaouat1

Service de Physiologie - Explorations Fonctionnelles, Hôpital Henri Mondor, INSERM U.651, Faculté de Médecine, Créteil, 1Services des Maladies Respiratoires et Réanimation Respiratoire, CHU de Nancy, Vandoeuvre-lès-Nancy, France

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This article is a summary of the Pulmonary Vascular Research Institute Webinar presented by Dr. Serge Adenot and was followed by case presentation by Dr. Ari Chaouat (PVRI Review Vol. 2: 80-83). The webinar was broadcasted live on 22nd April 2009 and the full recording can be found on the web http://www.pahforum.com/.

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Figure 4: Diagnosis of PH in COPD

Diagnosis of PH in COPDBNP

– Further studies are necessary

Doppler echocardiography– Non invasive, can detect cardiac co - morbidities but frequently inaccurate

Right heart catheterization– Gold standard, but invasive– Useful when severe PH is suspected

Figure 6: Pathogenesis of PH in patients with COPD

Adnot and Chaouat: Pulmonary hypertension in COPD

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Figure 1: Percent change in age-adjusted death rates, U.S., 1965-1998 Figure 2: Characteristics of PH in COPD

Figure 3: Clinical characteristics of COPD patients classifi ed according to their mean PAP levels (Chaouat et al. Am J Respir Crit Care Med 2005)

SIGNIFICANCE OF PH IN PATIENTS WITH COPD

In light of evidence that, in the chronic stable state, patients with COPD-associated PH typically have mildly elevated pressures with preserved cardiac function, the question may reasonably be

asked: is PH in the setting of COPD of clinical relevance? Several lines of evidence indicate that PH associated with COPD has significant clinical implications.

Presently it is clearly known that PH is associated with a bad prognosis in patients with COPD. Many studies have

Figure 5: Signifi cance of PH in patients with COPD (Chaouat et al. AJRCCM 2005)



demonstrated that it is associated with an increased risk of severe exacerbation and a shorter life expectancy.

In the paper published recently by A. Chaouat [Figure 5], PH still appears to be an important predictor of the survival of patients with COPD. Patients with pulmonary pressure above 40 mm Hg have a shorter life expectancy than the others. The study showed no significant differences between patients with pulmonary pressure less or higher than 20 mm Hg. However, if patients were classified according to a PAP above or lower than 25 mm Hg, there would have been a great difference in terms of life expectancy.

So pulmonary hypertension is associated with bad prognosis and can be diagnosed easily as mentioned earlier. There is really an incentive to prevent the development of PH in these patients and, therefore, to better understand the mechanisms at the origin of PH complicating COPD.

THE PATHOGENESIS OF PH IN COPD

The mechanisms underlying PH development in COPD are still not clearly understood. The increase in PAP is usually related to an increase in pulmonary vascular resistance (PVR). Several factors may play a role including anatomical or mechanical factors, such as destruction of lung parenchyma leading to a reduction

of the pulmonary vascular bed, and lung hyperinflation leading to the compression of pulmonary vessels. Hypoxic pulmonary vasoconstriction may also play a role although failure of oxygen therapy to reverse PH points to structural changes in pulmonary vessels as the major factor in established PH complicating COPD. Extensive pulmonary vessel remodeling with prominent intimal thickening, medial hypertrophy, and muscularization of small arterioles is usually observed in patients with COPD although the mechanisms responsible for these structural changes remain incompletely understood [Figure 6].

At the present time, it is not clear to which extent each of these factors contributes to PH. Hence the authors would like to present recent results obtained from a study performed in their centers [Figure 6].

We investigated 148 patients with COPD with right heart catheterization. We first questioned whether anatomical or mechanical factors could be associated with the severity of PH [Figure 4]. Using DLCO and the CT score index as surrogates of pulmonary vascular bed reduction, we found no relationship between these variables and the PAP values, although the two variables correlated with one another, suggesting that the anatomical status of the lungs in patients with COPD is not or weakly related to the presence or severity of PH. FEV1 and the BODE index also did not correlate with PAP [Figure 7].

Figure 7: Correlation between emphysema CT Score and DLCO/VA (Creteil, Strasbourg) Figure 8: Correlation between Pap and PaO2

Figure 9: Correlation between Pap and hemoglobin Figure 10: PH in patients with COPD: Role of infl ammation (Chaouat A et al., Chest 2009)



Figure 14: COPD - Effects and effectors

Figure 11: PH in patients with COPD: Role of infl ammation (Chaouat A et al., Chest 2009)

Figure 12: IL6 gene polymorphism and pulmonary hypertension in COPD (Chaouat A et al., Chest 2009)

Figure 13: 5-HTT and IL6 gene polymorphisms and pulmonary hypertension in COPD (Chaouat A et al., Chest 2009)

In contrast, we found a close relationship between severity of hypoxemia and PAP or PVR, supporting a major role for alveolar hypoxia in PH complicating COPD [Figure 8].

Another finding is that patients with polycythemia are more prone to have PH than those with normal levels of hemoglobin. The mechanisms at the origin of this relationship are not very clear and could be interpreted as a secondary effect of hypoxemia mediated by increased blood viscosity [Figure 9].

In addition to hypoxia, inflammation may contribute to PH in COPD. Such a possibility is suggested by the fact that pulmonary vascular remodeling is observed in lung specimens from patients with mild-to-moderate COPD, who did not have chronic hypoxemia.

Compared to control smokers, we found that patients with COPD had higher values of various cytokines including plasma TGFβ, MCP-1, and IL-6 [Figure 10]. In particular, PAP correlated with plasma IL-6 but not with other cytokines [Figure 11].[8,9]

PH severity was also related to the IL-6 GG genotype (which affected IL-6 levels in controls). MCP-1 or IL1-β polymorphisms did not affect PH severity.

It is interesting to see that patients with GG or CC genotype do not differ with respect to most of the physiological parameters, only the PAP value was higher in patients with the IL-6 GG genotype compared to those with the CG or CC genotypes, supporting the concept that this polymorphism contributes to the genetic susceptibility of patients with COPD for developing PH [Figure 12].

In a study published a few years ago, we found in this study that the serotonin transporter polymorphism was associated with PH and that patients with the LL genotype who exhibit a higher level of 5-HTT expression also had higher levels of PAP values. The role of the LL genotype was again found in this new study. Homozygosity for both the IL-6 and 5-HTT variants had an additive effect on the PH risk with an OR of 6.23 [Figure 13].

So in conclusion, PAP values vary greatly among individuals and do not correlate with the severity of the underlying disease.

PH severity is related mainly to individual genetic susceptibility. We have to check many genes and many variants which may favor the development of PH.

Both hypoxemia and inflammation appear to trigger development



of PH in patients with COPD [Figure 14].

CONCLUSION

COPD is a disease associated with lung and systemic inflammation. Inflammation is supposed to lead to many comorbidities and also to PH. It is, therefore, possible that these cardiovascular complications of COPD share some similarities [Figure 14].

REFERENCES

1. Weitzenblum E, Chaouat A, Canuet M, Kessler R. Pulmonary hypertension in chronic obstructive pulmonary disease and interstitial lung diseases. Semin Respir Crit Care Med 2009;30:458-70.

2. Minai OA. Pulmonary Hypertension In COPD: A review of the literature. PVRI Review 2009;1:20.

3. Levine BE, Bigelow D, Hamstra RD, Beckwitt HJ, Mitchell RS, Nett LM, et al. The role of Long-term continuous oxygen administration in patients with chronic airway obstruction with hypoxemia. Ann Intern Med 1967;66:639-50.

4. Weitzenblum E, Chaouat A. Severe Pulmonary Hypertension In

COPD Is It A Distinct Disease? Chest 2005;127:1480-2.5. Chaouat A, Bugnet AS, Kadaoui N, Schott R, Enache I, Ducolone A,

et al. Severe pulmonary hypertension and chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2005;172:189-94.

6. Arcasoy SM, Christie JD, Ferrari VA, Sutt on MS, Zisman DA, Blumenthal NP, et al. Echocardiographic assessment of pulmonary hypertension in patients with advanced lung disease supported by the craig and elaine dobbin pulmonary research fund. Am J Respir Crit Care Med 2003;167:735-40.

7. Leuchte HH, Baumgartner RA, Nounou ME, Vogeser M, Neurohr C, Trautnitz M, et al. Brain natriuretic peptide is a prognostic parameter in chronic lung disease. Am J Respir Crit Care Med 2006;173:744-50.

8. Eddahibi S, Chaouat A, Tu L, Chouaid C, Weitzenblum E, Housset B, et al. Interleukin-6 gene polymorphism confers susceptibility to pulmonary hypertension in chronic obstructive pulmonary disease. Proc Am Thorac Soc 2006;3:475-6.

9. Chaouat A, Savale L, Chouaid C, Tu L, Sztrymf B, Canuet M, et al. Role for interleukin-6 in COPD-related pulmonary hypertension. Chest 2009;136:678-87.



Address for correspondence: Dr. Ari Chaouat, Service des Maladies Respiratoires et Réanimation Respiratoire, Hôpital de Brabois, Allée du Morvan, 54511, Vandoeuvre-lès-Nancy Cedex, France. E-mail: [email protected]

DOI: 10.4103/0974-6013.68497

ventricular dysfunction or severe pulmonary hypertension (PH). A Doppler echocardiographic examination showed a mild enlargement of the right ventricle; however, tricuspid regurgitation was of an insufficient quality to estimate systolic pulmonary artery pressure (PAP) due to poor echocardiographic window.

Right heart catheterization revealed normal pulmonary pressures and cardiac output (CO) at rest (mean PAP 18 mmHg and CO 3.3 l min-1 m-2); however, 10 min of exercise of 30 W showed a significant increase in PAP to 56 mmHg with a normal wedge pressure [Table 1].

CASE REPORT 1

A 67-year-old man was admitted to the hospital because of progressive dyspnea on exertion with significant worsening over 1 year. He had 45-pack-year history of cigarette smoking. Chronic obstructive pulmonary disease (COPD) was diagnosed 5 years ago and treated with long-acting beta-2 agonist. An adjustment disorder with depressed mood was treated for 3 years with escitalopram.

At admission, the patient was in New York Heart Association (NYHA) functional class III. The blood pressure was 125/80 mmHg, the pulse rate was 82 beats per minute, the temperature 36.8°C, the respiration rate 16 breaths per minute, and the oxygen saturation 91%. The breath sounds were diminished, as well as cardiac sounds. There was no peripheral edema. The remainder of the examination was normal.

The results of arterial blood gases while the patient was breathing ambient air revealed a pH of 7.40, a partial pressure of carbon dioxide (PaCO2) of 38 mmHg (reference range, 31–44 mmHg), a partial pressure of oxygen (PaO2) of 67 mmHg (reference range, 75–100 mmHg), and bicarbonates of 22 mmol/l (reference range, 22–26 mmol/l). Other laboratory-test results were normal. An electrocardiogram revealed a left bundle branch block.

Spirometry showed the following: forced vital capacity (FVC), 3.50 l (94% of predicted value [pred]); forced expiratory volume in one second (FEV1), 1.40 l (49% of pred), and FEV1/FVC, 40%. Lung volumes measured by body plethysmograph revealed residual volume of 4.40 l (178% of pred) and total lung capacity of 8.10 l (125% of pred). Diffusion capacity of the lung for carbon monoxide (DLCO) was 40% of pred. His 6-min walk test distance was 340 m.

A chest radiograph and then a CT pulmonary angiography revealed emphysematous changes in superior lobes and in upper portion of inferior lobes without evidence of pulmonary embolism [Figures 1 and 2].

Due to worsening of dyspnea on exertion over 1 year without substantial change of FEV1, we suspected left

Pulmonary Hypertension in Chronic Obstructive Pulmonary Disease: Three Case ReportsAri Chaouat, Emmanuel Gomez, François ChabotService des Maladies Respiratoires et Réanimation Respiratoire, Hôpital de Brabois, Vandoeuvre-lès-Nancy, France

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Figure 1: Chest x-ray in case report 1 showing thoracic distension

Figure 2: High-resolution computed tomography (CT) in case report 1 revealing emphysema in both lungs

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Since the patient did not qualify for LTOT and did not accept for participation in a pulmonary rehabilitation program, treatments remained unchanged.

CASE REPORT 2

A 56-year-old man was hospitalized for evaluation of severe PH. The patient had been well until approximately 3 years earlier when dyspnea on exertion developed with fatigue. The patient had smoked 50 pack-years. At that time, NYHA functional class was II and lung function tests showed a moderate airflow limitation and a mild hypoxemia. Subsequently, he stopped smoking and started inhaled bronchodilator, which partially improved the symptoms.

Twelve months before admission in our department, the patient complained of worsening of dyspnea on exertion. A new respiratory evaluation was performed and showed an FVC of 3.43 l (83% of pred), an FEV1 of 1.65 l (50% of pred), an FEV1/FVC ratio of 48%, and PaO2 and PaCO2 under room air were 52 and

31 mmHg, respectively. In addition to inhaled bronchodilator, LTOT was prescribed at 4 l/min.

Four days before admission, the patient had visited a cardiologist. A Doppler echocardiography revealed an estimated right ventricular systolic pressure of 75 mmHg.

On examination there, the patient had dyspnea on trivial exertion (NYHA functional class IV), he was alert and afebrile, the blood pressure was 105/65 mmHg, pulse was 96 bpm, and respiratory rate was 20 breaths per minute. The breath sounds were diminished. A loud pulmonary component of the second heart sound and a pansystolic murmur due to tricuspid regurgitation were perceived. The jugular venous pressure was elevated and there was moderate peripheral edema. The remainder of the physical examination was unremarkable. Pulse oximetry showed an oxygen saturation of 76% while he was breathing ambient air. Spirometric measurements were unchanged, arterial blood gases revealed a pH of 7.46, a PaCO2 of 29 mmHg, a PaO2 of 39 mmHg, and bicarbonates of 22 mmol/l. Total lung capacity was slightly increased. DLCO was very low: 3.52 ml min-1 mmHg-1 (29% pred). A ventilation–perfusion lung scan [Figure 3] and a CT pulmonary angiography [Figure 4] excluded a thromboembolic disease. Doppler echocardiography allowed ruling out a left heart disease as well as an intracardiac shunting.

The 6-min walk distance under oxygen therapy was 160 m with a Borg index of dyspnea of 6. A right heart catheterization was performed [Figure 5] and showed severe precapillary PH: right atrial pressure 8 mmHg; mean PAP 52 mmHg, pulmonary wedge pressure (PWP) 9 mmHg; CO 2.4 l min-1 m-2 m2, and pulmonary vascular resistance (PVR) 748 dyn s cm-5. There were no changes of mean PAP and PVR under 10 ppm of inhaled nitric oxide and oxygen during 10 minutes [Table 2]. An endothelin-1 receptor antagonist was started, associated with a prostacyclin analogue 16 weeks later. The patient remained stable during 24 months. Three years after the beginning of these drugs dedicated

Table 1: Results of the right heart catheterization in case report 1

Rest Exercise: 40 WF (bpm) 72 112RAP (mmHg) 0 10PAP (mmHg) 18 56PWP (mmHg) 3 15CO (l min-1 m-2) 3.3 5.1PVR (dyn s cm-5) 230 405SvO2 (%) 70 25

F: Cardiac frequency; RAP: Right atrial pressure; PAP: Mean pulmonary artery pressure; PWP: Pulmonary wedge pressure; CO: Cardiac output; PVR: Pulmonary vascular resistance; SvO2: Mixed venous oxygen saturation

Chaouat, et al.: PHT in COPD case reports

Figure 3: Ventilation/perfusion scan from case report 2 with abnormal ventilation (lower part of the fi gure) due to emphysema and normal perfusion ruling out chronic thromboembolic pulmonary hypertension

Figure 4: CT pulmonary angiography in case report 2 showed dilatation of proximal pulmonary arteries and of the right ventricle. There was no sign of venous thromboembolic disease


to pulmonary arterial hypertension (PAH), the patient died of refractory right heart failure on the lung transplant waiting list of our institution.

CASE REPORT 3

A 42-year-old woman was seen in the ICU because of acute respiratory failure. She had been treated with long-acting beta-2 agonist and inhaled corticosteroid for 1 year. Three days earlier, the patient went to her primary care doctor, and then amoxicillin was prescribed for a presumptive acute bronchitis. On examination at the entry in the ICU, she was unconscious and afebrile with a respiratory rate of 41 breaths per minute and somewhat labored breathing. Pulse oximetry showed an oxygen saturation of 49%. The blood pressure was 82/38 mmHg and the pulse 96 bpm. Bilateral rales were heard on examination of the lungs. There was peripheral edema and examination of abdomen revealed a hepatomegaly.

Arterial blood gases showed a pH of 7.10, a PaCO2 of 85 mmHg, a PaO2 of 23 mmHg, and bicarbonates of 28 mmol/l. Immediately after her admission to ICU, tracheal intubation was performed and adequate oxygenation was maintained thereafter with mechanical ventilatory support, and oxygen therapy.

A chest radiograph showed thoracic distension, cardiomegaly,

and dilated pulmonary outflow compatible with PH [Figure 6]. An electrocardiogram revealed atrial tachycardia and right bundle branch block. Results of laboratory tests are shown in Table 3.

Treatment with dopamine (5–7.5 µg per kilogram of body weight per minute) and aggressive fluid resuscitation to maintain mean systemic blood pressure from 65 to 75 mmHg were started.

An echocardiography showed severe left ventricular dysfunction and evidence of PH. A pulmonary arterial catheter was inserted under treatment with dopamine at the dose of 7.5 µg per kilogram of body weight per minute and revealed the following: right atrial pressure 18 mmHg; mean PAP 49 mmHg; PWP 25 mmHg; and CO 2.2 l min-1 m2.

It was concluded that she had severe acute exacerbation of COPD and left heart failure. The patient was shifted out from the ICU after 15 days and could be discharged from the hospital 12 days later. Treatments prescribed at home were LTOT, noninvasive ventilation, bronchodilators, and angiotensin-converting enzyme inhibitor.

On admission in the respiratory medicine department 3 months later, the patient was in NYHA class III. Spirometry showed the following: FVC 1.50 l (50% of pred); FEV1 0.53 l

Table 3: Results of the laboratory tests in case report 3Reference range ICU admission

Hematocrit (%) 36–46 (women) 38Hemoglobin (g/dl) 11.5–15.5 (women) 13.5White-cell count (per mm3) 4 500–11 000 13 000Platelets (per mm3) 150 000–350 000 78 000Prothrombine time (%) 70–100 31Factor V (%) 70–100 41Sodium (mmol/l) 135–145 133Potassium (mmol/l) 3.5–5.0 3.2Creatinine (mg/dl) 0.6–1.2 1.7C-reactive protein (mg/l) <2 55ASAT (U/l) 9–32 3250ALAT (U/l) 7–30 2820ASAT: Aspartate aminotransferase; ALAT: Alanine aminotransferase


Figure 5: Curves of right atrial, right ventricle, and pulmonary artery pressures in case report 2. The right heart catheterization confi rmed the diagnosis of severe pulmonary hypertension and allowed to exclude left ventricular dysfunction

Table 2: Results of the right heart catheterization in case report 2

Room air O2 O2 O2 + NOrest exercise rest rest

F (bpm) 76 107 77 77RAP (mmHg) 8 16 6 7PAP (mmHg) 52 70 49 45PWP (mmHg) 9 17 9 10CO (l min-1 m-2) 2.4 3.3 2.3 2.4PVR (dyn s cm-5) 748 679 744 622SvO2 (%) 58 42 73 74

F: Cardiac frequency; RAP: Right atrial pressure; PAP: Mean pulmonary artery pressure; PWP: Pulmonary wedge pressure; CO: Cardiac output; PVR: Pulmonary vascular resistance; SvO2: Mixed venous oxygen saturation

Figure 6: Chest x-ray in case report 3 at the admission in ICU showed cardiomegaly and enlargement of proximal pulmonary arteries


(20% of pred); and FEV1/FVC, 31%. Lung volumes measured by body plethysmograph revealed residual volume of 5.00 l (332% of pred) and total lung capacity of 6.7 l (145% of pred). Arterial blood gases under ambient air showed the following: pH 7.41, PaCO2 51 mmHg, and PaO2 45 mmHg. A pulmonary hemodynamic reevaluation revealed under LTOT and angiotensin-converting enzyme inhibitor for 3 months: right atrial pressure 2 mmHg; mean PAP 36 mmHg; PWP 4 mmHg, and cardiac index 3.4 l min-1 m-2. It was concluded that the patient had severe COPD complicated with chronic respiratory failure and PH associated with compensated left heart failure. Due to a progressive worsening of the disease, she was listed for lung transplantation. Four years after her hospitalization in ICU, double lung transplantation was performed.

DISCUSSION

PH is a frequent complication of COPD. A recent study has shown that mean PAP at rest is 14.0 ± 3.3 mmHg in normal subjects and the upper limit of the normal is approximately 20 mmHg.[1] Unlike idiopathic PAH, PH due to lung diseases and/or hypoxia is defined as mean PAP > 20 mmHg. This definition is consistent with several reports showing that patients with lung diseases and a mean PAP > 20 mmHg have a worse prognosis compared to patients with a mean PAP ≤ 20 mmHg.[2] Cor pulmonale is defined as right ventricular hypertrophy and dilatation or both, secondary to PH caused by respiratory disorders. Knowing that the prevalence of COPD is approximately 5% among the adult population and that 50% of patients with severe or very severe COPD (GOLD III or IV, respectively) have PH, it would appear that COPD is one of the most frequent causes of PH.

A number of key issues arise from the current knowledge of PH and cor pulmonale in COPD. Some of these issues have been illustrated by the case reports presented here.

Exercise intolerance in COPD is mainly due to the consequences of expiratory airflow limitation, whereas exercise limitation in PAH is mainly the consequences of pulmonary hemodynamic abnormalities. In the latter case, there is an inability of the overloaded right ventricle to perfuse the lung and, therefore, to adapt systemic oxygen delivery to peripheral tissue oxygen demand during exercise. Thus causes and mechanisms leading to exercise limitation are completely different in these two conditions. In patients with COPD having a moderate to severe airflow limitation, several studies have shown a marked increase in mean PAP during moderate exercise load (30–40 W).[3] This is explained by the fact that PVR does not decrease during exercise, whereas it does in healthy subjects. However, cardiopulmonary exercise test performed in COPD showed that most patients have a reduced ventilatory reserve at maximal exercise, as defined by maximum ventilation reaching maximum voluntary capacity (estimated as 40 × FEV1) demonstrating that exercise limitation is mainly due to the impairment of lung mechanism in COPD.

Case report 1 showed a large rise in mean PAP from 18 to 56 mmHg after 10 min of an exercise load of 30 W. In such a case, one can wonder whether exercise induced increase in PAP is a contributing factor of exercise limitation. It is not confirmed whether lowering PAP during exercise in COPD can significantly

improve exercise performance or not.[4] This issue justifies further clinical research.

During stable disease state, most patients with advanced COPD have mildly or moderately increased mean PAP at rest.[2] However, due to the high prevalence of COPD, it can be observed in combination with COPD an associated disease that could impact the pulmonary circulation in an additive manner.[5] Therefore, frequent comorbidities observed in COPD such as left heart disease (see Case report 3) or obstructive sleep apnea syndrome should be investigated in COPD patients with severe PH since treatable associated conditions covered up by COPD could be found. On the other hand, it is observable that very few patients with COPD, as a unique cause of increase in PAP, develop severe PH (mean PAP > 35–40 mmHg). As illustrated in Case report 2, patients with COPD and severe PH with no associated condition exhibit a distinctive pattern with a moderate airway obstruction, severe hypoxemia, hypocapnia, a considerable decrease in the diffusing capacity of the lung for carbon monoxide, and a rapidly progressive disease. This latter condition has been termed “out-of-proportion” PH.[2,5,6] The estimated prevalence of this condition is probably low and similar to the one of idiopathic PAH.

The only recommended treatment for PH due to COPD is LTOT.[7] Most patients with severe COPD and chronic hypoxemia are under LTOT; therefore, when severe PH in COPD occurs without associated condition, one can wonder whether drugs devoted to PAH may improve exercise limitation and increase the life-expectancy of these patients. Currently, there is no recommendation concerning the use of synthetic prostacyclin (epoprostenol), prostacyclin analogues, endothelin-1 antagonists, and phosphodiesterase-5 inhibitors in COPD-related PH. We suggest that COPD patients with “out-of-proportion” PH should be sent to an experience center and, as far as possible, included in registries and in clinical trials.

Case report 3 raises one further issue: whether or not a postcapillary component can participate in the increase in PAP in COPD. According to a relatively large series,[8] roughly 20% of subjects with moderate to severe COPD have an increase in PWP; however, most of the patients presenting an increase in PWP had an associated left heart disease. In a selected group of 168 patients with end-stage COPD evaluated for lung transplantation, left ventricular dysfunction was present in only 3.6%.[9] In addition, CO at rest in COPD is usually in the normal range. Therefore, PH due to COPD is of the precapillary type and due to an increase in PVR. A postcapillary involvement can participate in the increase in PAP during acute exacerbations as shown in Case report 3. In this patient, the second pulmonary hemodynamic study performed in a stable state of the disease showed a persistent PH despite a striking decrease in PWP from 25 to 4 mmHg under ACE inhibitor. This case report illustrates the participating role of an increase in PWP in the development of PH in COPD patients.

CONCLUSIONS

COPD is a heterogeneous disorder characterized by dysfunction of the airways, destruction of the lung parenchyma, and its vasculature in highly variable combinations. Therefore, the



spectrum of pulmonary vasculopathy in COPD is wide as illustrated in three case reports presented here. It is important to emphasize that PH in COPD is usually mild to moderate; however, PH could be severe during acute exacerbation of the disease and in very few patients in stable state of the disease, in spite of LTOT. Some patients with severe PH have an associated condition explaining the large increase in PAP, while others do not have associated disease. This latter condition is termed “out-of-proportion” PH, in which new drugs dedicated to PAH need to be tested in randomized controlled trials.

REFERENCES

1. Kovacs G, Berghold A, Scheidl S, Olschewski H. Pulmonary arterial pressure during rest and exercise in healthy subjects: A systematic review. Eur Respir J 2009;34:888-94.

2. Chaouat A, Naeĳ e R, Weitzenblum E. Pulmonary hypertension in COPD. Eur Respir J 2008;32:1371-85.

3. Kessler R, Faller M, Weitzenblum E, Chaouat A, Aykut A, Ducoloné A, et al. “Natural history” of pulmonary hypertension in a series of 131 patients with chronic obstructive lung disease. Am J Respir Crit Care Med 2001;164:219-24.

4. Vonbank K, Ziesche R, Higenbottam TW, Stiebellehner L,

Petkov V, Schenk P, et al. Controlled prospective randomised trial on the eff ects on pulmonary haemodynamics of the ambulatory long term use of nitric oxide and oxygen in patients with severe COPD. Thorax 2003;58:289-93.

5. Chaouat A, Bugnet AS, Kadaoui N, Schott R, Enache I, Ducoloné A, et al. Severe pulmonary hypertension and chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2005;172:189-94.

6. Thabut G, Dauriat G, Stern JB, Logeart D, Lévy A, Marrash-Chahla R, et al. Pulmonary hemodynamics in advanced COPD candidates for lung volume reduction surgery or lung transplantation. Chest 2005;127:1531-6.

7. Celli BR, MacNee W. Standards for the diagnosis and treatment of patients with COPD: A summary of the ATS/ERS position paper. Eur Respir J 2004;23:932-46.

8. Chabot F, Schrĳ en F, Poincelot F, Polu JM. Interpretation of high wedge pressure on exercise in patients with chronic obstructive pulmonary disease. Cardiology 2001;95:139-45.

9. Vizza CD, Lynch JP, Ochoa LL, Richardson G, Trulock EP. Right and left ventricular dysfunction in patients with severe pulmonary disease. Chest 1998;113:576-83.




Address for correspondence: Dr. James R. Klinger, Division of Pulmonary Sleep and Critical Care Medicine, Respiratory Care Unit, Brown Medical School, Rhode Island Hospital, 593 Eddy Street, Providence, RI – 029 03. E-mail: [email protected]

DOI: 10.4103/0974-6013.68494

The Clinical Utility of Brain Natriuretic Peptide in Pulmonary Arterial HypertensionBrian Casserly, James R. KlingerDivision of Pulmonary and Critical Care Medicine, The Memorial Hospital of Rhode Island, Pawtucket, RI, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, RI, USA

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INTRODUCTION

The diagnosis and treatment of pulmonary arterial hypertension (PAH) is hampered by difficulty in obtaining accurate measurements of pulmonary arterial pressure (PAP). Unlike the systemic circulation where intravascular pressure is easily measured by syphgmomanometry, there is no accurate, readily available noninvasive test for measuring PAP. Furthermore, PAP is not the best measurement of right ventricular afterload nor the best indicator of disease regression or survival. The PAP will often fall as the right ventricle fails. Right heart catheterization (RHC) provides a direct measurement of PAP, right-sided filling pressures, and cardiac output, and it is a vital part of the proper diagnosis and evaluation of unexplained pulmonary hypertension (PH). However, it is invasive and expensive and not amenable to repeated measurements that are necessary to monitor disease progression. As a result, the clinician must rely on a combination of indirect assessments of PAP and cardiac output, such as transthoracic echocardiography (TTE), 6-min walk test (6MWT), and World Health Organization (WHO) functional class. A simple noninvasive, but objective measure of the right ventricular workload would contribute significantly to the management of PAH patients. Biomarkers that correlate with PAP and/or right-sided filling pressures would allow the practitioner to have an insight into how a patient’s disease is progressing and to evaluate the effect of pulmonary vasodilator therapy. Plasma BNP levels rise in response to right as well as left atrial or ventricular overload and may be important tools for assessing right ventricular performance in PAH.[1]

BRAIN NATRIURETIC PEPTIDE

BNP is one of several members of the natriuretic peptide family that are widely distributed, but evolutionarily conserved throughout the animal kingdom. The natriuretic peptides play important roles in cardiovascular homeostasis, including regulation of vascular tone, blood volume, endothelial permeability, and cardiac hypertrophy. BNP is produced and released by both atrial and ventricular cardiac myocytes,[2] its synthesis and secretion are regulated at the gene level, and the hormone is not stored within the cell.[3,4] Increased cardiac filling pressure is a potent stimulus for the release of BNP[5]; and in the failing heart, BNP production increases and becomes more generalized

throughout the myocardium.[4,6] The precursor preproBNP is cleaved during translation to form the prohormone proBNP [Figure 1], the processing of which releases C-terminal BNP and the N-terminal fragment (NT-proBNP) in the plasma. The C-terminal end represents the mature BNP molecule and contains a disulfide bond-formed ring, which is essential for receptor binding and biological activity.[7] After release into the circulation, BNP binds to natriuretic peptide receptor-A (NPR-A) and stimulates the intrinsic guanylyl cyclase activity of the surface receptor in target cells.[8] Elevated intracellular cyclic guanosine monophosphate (cGMP) modulates a cascade of downstream messengers, which controls cellular and ultimately physiologic functions.[9]

Clinical interpretation of BNP levelsThere is increasing evidence that BNP may be a useful marker for right ventricular dysfunction and predict outcome in patients with PAH. As such, plasma BNP may help guide clinical decision-making in patients with newly diagnosed PAH and help gauge response to treatment.

The circulating BNP level measured at any given time point is the result of the balance between BNP secretion and degradation. BNP has a plasma half-life of about 20 min.[5] Healthy individuals have plasma BNP concentrations around 1 fmol/mL (3.5 pg/mL).[10] However, plasma BNP levels in congestive heart failure patients can be 200- to 300-fold higher. The enormous range of plasma BNP concentrations between healthy subjects and patients with heart failure and the rapid induction of BNP expression in response to acute overload or ischemia make it well suited to serve as an indicator of elevated myocardial loading and cardiac stress.[11,12] Of note, a number of factors have been associated with higher BNP levels in addition to ventricular wall stress. BNP increases with age independent of the increased incidence of diastolic dysfunction.[13] BNP levels are also higher in women than men at any age.[14] The association between BNP and renal function is complex. Patients with chronic renal disease tend to have higher atrial pressure, systemic pressure, and ventricular mass, all of which would be expected to increase BNP synthesis and secretion.[15] Renal excretion of BNP has been described, but alterations in circulating levels in patients with renal disease are more likely related to decreased clearance by natriuretic peptide receptor-C (NPR-C) and neutral endopeptidases (NEPs).

Interestingly, NT-proBNP is less susceptible to degradation by NEP and is not cleared by NPR-C. As such, it may represent a more reliable indicator of cardiac BNP expression and secretion than circulating BNP levels. In fact, some studies

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suggest that plasma NT-proBNP level may be a more sensitive and specific marker of cardiovascular disease than BNP.[16,17] In patients with left ventricular dysfunction, NT-proBNP levels are up to 10 times higher than BNP.[18] NT-proBNP, in contrast to BNP, is predominantly excreted by the kidney, although plasma NT-proBNP appears to maintain its clinical utility even in the presence of renal dysfunction.[15,19] Unfortunately, NT-proBNP assays are not readily available in most clinical laboratories.

Use of BNP as a Biomarker in PHCirculating levels of atrial natriuretic peptide and BNP correlate with mean PAP (mPAP),[20] but elevation in BNP levels are usually not seen until PAP is high enough to cause right ventricular strain.

In addition to PAP, plasma BNP levels are a reliable marker of right heart strain, which is a significant predictor of morbidity and mortality in PAH.[21] Elevated BNP is not specific for right- or left-sided heart disease, but in the absence of left-sided heart disease, may prove to be a useful adjunct to echocardiography in evaluating right heart stress. In patients with right ventricular pressure overload associated with idiopathic pulmonary arterial hypertension (IPAH) or chronic thromboembolic PH (CTEPH), BNP levels were significantly higher than in controls (294 ± 72 pg/mL vs 48 ± 14 pg/mL (P < 0.05).[21] In this study, BNP levels correlated with right ventricular end-diastolic pressure (r = 0.76), mPAP (r = 0.73), and total pulmonary resistance (TPR) (r = 0.79). Long-term treatment with either

prostacyclin or prostaglandin E reduced TPR (from 23 to 15 Wood Units) and reduced plasma BNP levels by more than half (315 ± 120 pg/mL to 144 ± 54 pg/mL). The BNP levels have also been shown to be higher in acute pulmonary embolism and to fall following thromboendarterectomy in patients with CTEPH.[21,22] Conversely, right ventricular dilation is exceedingly uncommon in acute PE when plasma troponin and BNP levels are normal.[23] Souza et al. demonstrated a close correlation between PVR and NT-proBNP (r = 0.80, P < 0.001) in 42 patients with IPAH.[24] BNP levels also correlate with functional capacity in PAH. In one study, BNP levels were inversely correlated with 6MWT (r = −0.70; P< 0.001) and peak VO2 (r = −0.61; P < 0.01), and positively correlated with WHO class (r = 0.79; P 0.001) in 42 patients with IPAH.[25]

The BNP has limited diagnostic value as a screening tool for excluding PAH in populations at low risk for the disease. In select patient groups, however, where the risk of PAH is substantially increased, such as those with connective tissue disease, portal hypertension, congenital systemic to pulmonary shunts, or a family history of IPAH, elevated BNP may help identify patients in whom further testing is warranted. For example, BNP may prove useful as a screening test for PAH in systemic sclerosis (SSc), where the prevalence of PH has been reported to be 12%–35% and where PAH treatment has been shown to be beneficial.[26-30] In 2003, Allanore et al. obtained plasma NT-proBNP levels and echocardiographic estimates of peak PAP in 40 consecutive

Figure 1: Structure of the gene and the biosynthetic pathway of human brain natriuretic peptide (BNP). The major storage form of BNP in the heart is the cleaved mature peptide, although in atrial tissue the prohormone may also be stored.[43]

Casserly and Klinger: Utility of BNP in PAH


patients hospitalized for follow-up care of scleroderma (limited or diffuse disease).[31] All the patients were without symptoms of heart failure, had normal left ventricular ejection fraction, and a creatinine clearance > 58 mL/min. At baseline, 10 patients (25%) were found to have PAH as defined by a peak right ventricular systolic pressure (RVSP) > 40 mmHg. Thirteen patients had high NT-proBNP values (adjusted for age), including all 10 patients classified as PAH by TTE. There was a moderate correlation between peak RVSP and NT-proBNP level (r = 0.44, P = 0.006). A high NT-proBNP concentration (cutoff values supplied by the manufacturer and defined as above the 97th percentile) identified PH with a sensitivity of 90%, specificity of 90%, positive predictive value of 69%, and negative predictive value of 96%. Although the sensitivity and specificity of TTE for detecting PH is only about 90% and 75%, respectively, subsequent studies using RHC to define PAH have obtained similar results.[32] Mukerjee et al. identified PAH by RHC in 23 of 49 patients with SSc.[33] The mean value of NT-proBNP in patients with PAH was 3365 ± 1095) pg/mL compared with 347 ± 174 pg/mL for patients without PAH. There was a statistically significant correlation (P < 0.05) between NT-proBNP values and (i) mPAP (r = 0.53), (ii) right ventricular end-diastolic pressure (r = 0.59), and (iii) PVR (r = 0.49). Receiver–operator characteristic curve analysis showed that a cutoff value of 395.34 pg/mL had a sensitivity of 0.69 and specificity of 1.0. The same group performed a larger study to assess prospectively the specificity of 395 pg/mL in a larger population and to evaluate the prognostic value of NT-proBNP in a homogenous group of patients with systemic scleroderma–associated PAH (SSc-PAH).[32] The study population included 68 individuals with PAH [mPAP > 25 mmHg and PCWP < 15 mmHg] and 41 individuals without PAH. The patients without

PAH had a lower mean NT-proBNP level than those with SSc-PAH. The baseline NT-proBNP levels were correlated positively with mPAP (r = 0.62; P < 0.0001), PVR (r = 0.81; P < 0.0001), and inversely with 6MWT (r = −0.46; P < 0.0001). At an NT-proBNP level of 395 pg/mL, the sensitivity and specificity for predicting the presence of SSc-PAH were 56% and 95%, respectively. Thus NT-proBNP estimation in systemic sclerosis–related PAH is a potentially useful diagnostic tool. Similarly, subjects with lung fibrosis and elevated BNP levels (n = 20) had significantly higher PAP than those with normal BNP levels (mPAP(40.85 ± 3.2 mmHg vs 23.42 ± 1.44 mmHg (P < 0.001).[34]

SURVIVAL AND RESPONSE TO THERAPY

Plasma BNP levels have been shown to have significant prognostic capabilities in patients with PAH.[35] One study measured plasma BNP levels in 60 patients with IPAH at initial RHC and compared the prognostic significance of baseline and follow-up BNP levels with clinical, echocardiographic, and hemodynamic variables.[35] Patients with renal insufficiency were excluded. Measurements were repeated in 53 patients at 3 months. Plasma BNP was increased at baseline and correlated positively with New York Heart Association (NYHA) functional class [Figure 2], mPAP, mean right atrial pressure, and TPR, and correlated negatively with cardiac output. Mean follow-up averaged 24 months, during which time 18 patients died of cardiopulmonary causes. Among the noninvasive baseline parameters studied, only plasma BNP was an independent predictor of mortality by multivariate analysis. Kaplan–Meier analysis demonstrated that follow-up BNP provided a more distinct separation of survival curves than did baseline BNP


Figure 2: (a and b) Correlation between plasma brain natriuretic peptide (BNP) and atrial natriuretic peptide and New York Heart Association (NYHA) functional class in patients with pulmonary arterial hypertension (PAH). (c) Effect of plasma BNP levels at the time of diagnosis on survival in patients with PAH. (d) Effect of plasma BNP levels after treatment on survival in the same patients.[35]


Figure 3: Effect of plasma N-terminal pro-brain natriuretic peptide levels on survival in patients with various forms of precapillary pulmonary hypertension[44]


measurement [Figure 2]. Survival was markedly improved in those patients with a follow-up BNP level below 180 pg/mL. In fact, receiver–operating characteristic analysis suggested that baseline BNP was at least equal to mPAP and superior to CO in predicting mortality. These findings were substantiated by Fijalkowska et al. who demonstrated in their 36 IPAH patients that a serum NT-proBNP level of ≥1400 pg/mL identified patients with a poor long-term prognosis estimated by Kaplan–Meier cumulative survival curves.[36]

Plasma NT-proBNP levels have also been shown to predict survival in patients with other types of PAH [Figure 3]. The use of NT-proBNP to predict survival was assessed in 68 patients with[32] over a mean duration of 10 months (range, 1–18 months). The mean NT-proBNP level in patients without PAH was significantly lower than in those with SSc-PAH (P = 0.0002). For every order of magnitude increase in the NT-proBNP level in patients with PAH, the risk of death increased 4-fold (P = 0.002 for baseline level and P = 0.006 for follow-up level). Baseline NT-proBNP levels correlated directly with mPAP (r = 0.62; P < 0.0001), PVR (r = 0.81; P < 0.0001), and inversely with 6MWT (r = −0.46; P < 0.0001). Plasma NT-proBNP levels also identified differences in functional class among patients with SSc-PAH. The 13 patients (19%) in WHO functional class II had mean NT-proBNP levels of 325 ± 388 pg/mL, whereas the 53 patients (78%) in WHO classes III and IV had mean NT-proBNP levels that were 5-fold higher (1677 ± 2835 pg/mL, P = 0.02).

The correlation of circulating BNP levels with pulmonary hemodynamics, right heart strain, and survival has generated interest in using it as a noninvasive assessment of response to therapy. In an early study of 9 patients with IPAH who underwent prostaglandin therapy,[20] plasma BNP levels fell in conjunction with TPR after a mean follow-up of 35 days (TPR 23 ± 4 Wood Units to 15 ± 3 Wood Units, P < 0.05, plasma BNP (315 ± 120 pg/mL to 144 ± 54 pg/mL (P < 0.05). In a larger follow-up study by Nagaya and colleagues, BNP measurements were repeated after 3 months of vasodilator therapy in 49 patients with IPAH.[35] Changes in plasma BNP were associated with changes in right ventricular end-diastolic pressure and TPR but not with mPAP or right ventricular dimension. During prostacyclin therapy, plasma BNP significantly decreased in survivors but increased in nonsurvivors. Park and colleagues studied 20 patients with PAH

on epoprostenol and similarly found that BNP may help predict those who are refractory to treatment.[37] Leuchte et al. found that BNP levels parallel changes in pulmonary hemodynamics and functional parameters, including 6MWT, in 30 patients with PAH.[38] Progression of the disease was accompanied by an increase in BNP levels, whereas improvement of pulmonary hemodynamics and functional status was accompanied by a significant decline in plasma BNP concentrations. Findings from studies such as these suggest that serial plasma BNP could be useful in monitoring the efficacy of therapy in PAH patients, and this approach is reflected in recent guidelines from the American College of Cardiology that suggest the use of plasma BNP levels in assessing the risk of deterioration in patients with PAH.[39] Although one-time measures of circulating BNP may be difficult to interpret, serial BNP testing may provide a noninvasive measure to help identify patients who are failing their current therapeutic regime and predict right ventricular decompensation before it becomes clinically apparent. This is supported by the finding that higher BNP levels at presentation with pulmonary embolism is associated with increased mortality in 2 recent studies with large cohorts of patients.[40,41] These findings suggest that in pulmonary embolism at least, BNP can help identify patients with increased right ventricular strain at higher risk for acute decompensation.

CONCLUSION

The ability of BNP to be secreted from the heart in response to neurohormonal as well as hemodynamic stimuli and the rapid induction of BNP gene expression in response to ventricular strain make it a robust biomarker of cardiac stress and facilitates its use as a clinical tool. BNP may be a useful marker for right ventricular dysfunction and shows promise in estimating the efficacy of therapy and, therefore, may help inform clinical decision-making in patients with PAH. Recently, it has been recommended that BNP measurement be considered as a secondary end point in clinical trials on patients with advanced PAH.[42] However, it should be noted that elevations of BNP are nonspecific for PAH and cannot distinguish between right- or left-sided heart disease. The current level of clinical data suggest that BNP measurements should presently best be viewed as adjunctive measures to complement the standard assessment of patients with suspected or diagnosed PAH.

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5. Espiner EA, Richards AM, Yandle TG, Nicholls MG. Natriuretic hormones. Endocrinol Metab Clin North Am 1995;24:481-509.


6. Luchner A, Stevens TL, Borgeson DD, Redfi eld M, Wei CM, Porter JG, et al. Am J Physiol 1998;274:H1684-9.

7. Goetze JP. Biochemistry of pro-B-type natriuretic peptide-derived peptides: the endocrine heart revisited. Clin Chem 2004;50:1503-10.

8. Lohmann SM, Fischmeister R, Walter U. Signal transduction by cGMP in heart. Basic Res Cardiol 1991;86:503-14.

9. Lucas KA, Pitari GM, Kazerounian S, Ruiz-Stewart I, Park J, Schulz S, et al. Guanylyl cyclases and signaling by cyclic GMP. Pharmacol Rev 2000;52:375-414.

10. Pott er LR. Domain analysis of human transmembrane guanylyl cyclase receptors: implications for regulation. Front Biosci 2005;10:1205-20.

11. Mukoyama M, Nakao K, Obata K, Jougasaki M, Yoshimura M, Morita E, et al. Augmented secretion of brain natriuretic peptide in acute myocardial infarction. Biochem Biophys Res Commun 1991;180:431-6.

12. Tokola H, Hautala N, Martt ila M, Magga J, Pikkarainen S, Kerkelä R, et al. Mechanical load-induced alterations in B-type natriuretic peptide gene expression. Can J Physiol Pharmacol 2001;79:646-53.

13. Redfi eld MM, Rodeheff er RJ, Jacobsen SJ, Mahoney DW, Bailey KR, Burnett JC Jr. Plasma brain natriuretic peptide concentration: impact of age and gender. J Am Coll Cardiol 2002;40:976-82.

14. Wang TJ, Larson MG, Levy D, Leip EP, Benjamin EJ, Wilson PW, et al. Impact of age and sex on plasma natriuretic peptide levels in healthy adults. Am J Cardiol 2002;90:254-8.

15. Daniels LB, Maisel AS. Natriuretic peptides. J Am Coll Cardiol 2007;50:2357-68.

16. O'Donoghue M, Chen A, Baggish AL, Anwaruddin S, Krauser DG, Tung R, et al. The eff ects of ejection fraction on N-terminal ProBNP and BNP levels in patients with acute CHF: analysis from the ProBNP Investigation of Dyspnea in the Emergency Department (PRIDE) study. J Card Fail 2005;11:S9-14.

17. Seino Y, Ogawa A, Yamashita T, Fukushima M, Ogata K, Fukumoto H, et al. Application of NT-proBNP and BNP measurements in cardiac care: a more discerning marker for the detection and evaluation of heart failure. Eur J Heart Fail 2004;6:295-300.

18. Bionda C, Bergerot C, Ardail D, Rodriguez-Lafrasse C, Rousson R. Plasma BNP and NT-proBNP assays by automated immunoanalyzers: analytical and clinical study. Ann Clin Lab Sci 2006;36:299-306.

19. Leuchte HH, El Nounou M, Tuerpe JC, Hartmann B, Baumgartner RA, Vogeser M, et al. J Chest 2007;131:402-9.

20. Nagaya N, Nishikimi T, Okano Y, Uematsu M, Satoh T, Kyotani S, et al. Plasma brain natriuretic peptide levels increase in proportion to the extent of right ventricular dysfunction in pulmonary hypertension. J Am Coll Cardiol 1998;31:202-8.

21. Nagaya N, Ando M, Oya H, Ohkita Y, Kyotani S, Sakamaki F, et al. Plasma brain natriuretic peptide as a noninvasive marker for effi cacy of pulmonary thromboendarterectomy. Ann Thorac Surg 2002;74:180-4.

22. Tulevski II, Hirsch A, Sanson BJ, Romkes H, van der Wall EE, van Veldhuisen DJ, et al. Increased brain natriuretic peptide as a marker for right ventricular dysfunction in acute pulmonary embolism. Thromb Haemost 2001;86:1193-6.

23. Binder L, Pieske B, Olschewski M, Geibel A, Klostermann B, Reiner C, et al. Circulation 2005;112:1573-9.

24. Souza R, Jardim C, Julio Cesar Fernandes C, Silveira Lapa M, Rabelo R, Humbert M. NT-proBNP as a tool to stratify disease severity in pulmonary arterial hypertension. Respir Med 2007;101:69-75.

25. Leuchte HH, Holzapfel M, Baumgartner RA, Ding I, Neurohr C, Vogeser M, et al. Clinical significance of brain natriuretic peptide in primary pulmonary hypertension. J Am Coll Cardiol 2004;43:764-70.

26. Badesch DB, Tapson VF, McGoon MD, Brundage BH, Rubin LJ, Wigley FM, et al. Continuous intravenous epoprostenol for pulmonary hypertension due to the scleroderma spectrum of disease. A randomized, controlled trial. Ann Intern Med 2000;132:425-34.

27. Batt le RW, Davitt MA, Cooper SM, Buckley LM, Leib ES, Beglin PA, et al. Prevalence of pulmonary hypertension in limited and diff use scleroderma. Chest 1996;110:1515-9.

28. MacGregor AJ, Canavan R, Knight C, Denton CP, Davar J, Coghlan J, et al. Pulmonary hypertension in systemic sclerosis: risk factors for progression and consequences for survival. Rheumatology (Oxford) 2001;40:453-9.

29. Mukerjee D, Yap LB, Holmes AM, Nair D, Ayrton P, Black CM, et al. Signifi cance of plasma N-terminal pro-brain natriuretic peptide in patients with systemic sclerosis-related pulmonary arterial hypertension. Respir Med 2003;97:1230-6.

30. Oudiz RJ, Schilz RJ, Barst RJ, Galié N, Rich S, Rubin LJ, et al. Treprostinil, a prostacyclin analogue, in pulmonary arterial hypertension associated with connective tissue disease. Chest 2004;126:420-7.

31. Allanore Y, Borderie D, Meune C, Cabanes L, Weber S, Ekindjian OG, et al. N-terminal pro-brain natriuretic peptide as a diagnostic marker of early pulmonary artery hypertension in patients with systemic sclerosis and eff ects of calcium-channel blockers. Arthritis Rheum 2003;48:3503-8.

32. Williams MH, Handler CE, Akram R, Smith CJ, Das C, Smee J, et al. Eur Heart J 2006;27:1485-94.

33. Mukerjee D, St George D, Knight C, Davar J, Wells AU, Du Bois RM, et al. Rheumatology (Oxford) 2004;43:461-6.

34. Leuchte HH, Neurohr C, Baumgartner R, Holzapfel M, Giehrl W, Vogeser M, et al. Brain natriuretic peptide and exercise capacity in lung fi brosis and pulmonary hypertension. Am J Respir Crit Care Med 2004;170:360-5.

35. Nagaya N, Nishikimi T, Uematsu M, Satoh T, Kyotani S, Sakamaki F, et al. Plasma brain natriuretic peptide as a prognostic indicator in patients with primary pulmonary hypertension. Circulation 2000;102:865-70.

36. Fĳ alkowska A, Kurzyna M, Torbicki A, Szewczyk G, Florczyk M, Pruszczyk P, et al. Serum N-terminal brain natriuretic peptide as a prognostic parameter in patients with pulmonary hypertension. Chest 2006;129:1313-21.

37. Park MH, Scott RL, Uber PA, Ventura HO, Mehra MR. Usefulness of B-type natriuretic peptide as a predictor of treatment outcome in pulmonary arterial hypertension. Congest Heart Fail 2004;10:221-5.

38. Leuchte HH, Holzapfel M, Baumgartner RA, Neurohr C, Vogeser M, Behr J. Characterization of brain natriuretic peptide in long-term follow-up of pulmonary arterial hypertension. Chest 2005;128:2368-74.

39. McLaughlin VV, Archer SL, Badesch DB, Barst RJ, Farber HW, Lindner JR, et al. ACCF/AHA 2009 expert consensus document on pulmonary hypertension a report of the American College of Cardiology Foundation Task Force on Expert Consensus Documents and the American Heart Association developed in collaboration with the American College of Chest Physicians; American Thoracic Society, Inc.; and the Pulmonary Hypertension Association. J Am Coll Cardiol 2009;53:1573-619.

40. Kucher N, Printzen G, Goldhaber SZ. Prognostic role of brain natriuretic peptide in acute pulmonary embolism. Circulation 2003;107:2545-7.

41. ten Wolde M, Tulevski II, Mulder JW, Söhne M, Boomsma F, Mulder BJ, et al. Brain natriuretic peptide as a predictor of adverse outcome in patients with pulmonary embolism. Circulation 2003;107:2082-4.

42. Hoeper MM, Oudiz RJ, Peacock A, Tapson VF, Haworth SG,



Frost AE, et al. End points and clinical trial designs in pulmonary arterial hypertension: clinical and regulatory perspectives. J Am Coll Cardiol 2004;43:48S-55S.

43. Nakao K, Ogawa Y, Suga S, Imura H. Molecular biology and biochemistry of the natriuretic peptide system. I: Natriuretic peptides. J Hypertens 1992;10:907-12.

44. Andreassen AK, Wergeland R, Simonsen S, Geiran O,

Guevara C, Ueland T. N-terminal pro-B-type natriuretic peptide as an indicator of disease severity in a heterogeneous group of patients with chronic precapillary pulmonary hypertension. Am J Cardiol 2006;98:525-9.



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Address for correspondence: Swapna Menon, PVRI India Offi ce, Seven Hills Hospital, Marol Maroshi Road, Andheri East, Mumbai 400059, India. Email : [email protected].

DOI: 10.4103/0974-6013.68491

Commentary − Distinct Patterns of Circulating Endothelial Cells in Pulmonary HypertensionSwapna MenonPVRI India Offi ce, Seven Hills Hospital, Marol Maroshi Road, Andheri East, Mumbai - 400059, India

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The list of citations related to pulmonary circulation is available at http://pvri.info/pulmonary-hypertension

This section “Pulmonary Hypertension” is placed in E-books under Discussions tab.

The list was obtained using the following search strategy in PubMed:

Keywords: “pulmonary hypertension” OR “pulmonary arterial hypertension”

BACKGROUND

The endothelium is a dynamic monolayer, exposed to the circulation on the one hand and, in contact with the vessel wall on the other. It is central to vascular health, being involved in vessel tone, cellular growth, and angiogenesis, as well as, inflammation and clotting.[1] The circulating compartments of the endothelium include endothelial progenitors, mature endothelial cells, and endothelial microparticles (EMPs). Circulating progenitor cells (CPCs) are derived from the bone marrow. Progenitor cells displaying endothelial markers are called endothelial progenitor cells (EPCs). The progenitors contribute to postnatal vasculogenesis and endothelial repair during injury. Circulating endothelial cells (CECs) are mature endothelial cells dislodged from the vessel wall. EMPs are fragments of the membranes of endothelial cells. Increased CECs and EMPs are considered as indicators of an activated or injured endothelium. The use of CEC and/or CPC counts as surrogate markers of endothelial status has been investigated in various pathologic conditions,[2]

such as atherosclerosis, acute coronary syndrome, coronary artery disease, heart failure, chronic renal failure, diabetes, infectious disease, hematologic and immune disease, various types of cancer, and transplantation. These markers have also been explored in the context of pulmonary arterial hypertension (PAH).

SUMMARY

In this study, the markers of endothelial activation and injury were quantified in 9 idiopathic pulmonary arterial hypertension (IPAH) patients, 9 chronic thromboembolic pulmonary hypertension (CTEPH) patients, and 7 patients who showed normal pulmonary arterial pressures, all of whom had undergone cardiac catheterization for suspected pulmonary hypertension (PH). Among the endothelial compartments examined, only the mean CEC count differed in PH patients. CEC counts were significantly raised among the IPAH patients compared with normal controls and CTEPH

patients. There was no correlation between CEC counts and hemodynamic parameters evaluated. CPC counts as measured did not vary significantly between the 3 groups.

Among the soluble markers examined, vascular endothelial growth factor (VEGF), associated with vascular remodeling was unchanged among the 3 groups. Soluble markers of endothelial activation, sE-selectin and soluble Vascular Cell Adhesion Molecule (sVCAM), were both raised only in IPAH patients and not in CTEPH patients or normal controls.

In line with an earlier study by the same group, equivalent endothelial cell counts were obtained from both peripheral and pulmonary blood. This suggested that endothelial cell population from the peripheral vein closely corresponds to that in the pulmonary artery and, the former is a good, less invasive surrogate site for such analyses.

COMMENTARY

Immunologic markers are used to characterize and distinguish CECs, CPCs, and EPCs by flow cytometry.[3-5] CD34 and CD133 are markers of immaturity. CD34 is a nonspecific marker expressed on early hematopoietic cells and, also, on megakaryocytes and several tumor cells. Progenitors expressing CD34 have angiogenic potential. Selecting for CD34 will, however, also select angiogenic macrophage and monocyte progenitors. CD133 is selectively expressed on hematopoietic and progenitor stem cells. The combination of CD34+ and CD133+ screening is used to count proangiogenic progenitors. Endothelial-specific markers, such as VEGFR2 (also called KDR or Flk1), vWF, and others, are used, in addition, to identify endothelial progenitors.

CD45 is a common leukocyte antigen, whereas CD14 is a monocyte antigen. These markers are present in early progenitors and absent in late EPCs and mature CECs.

Thus, screening for the presence (shown as + in Table 1) and sometimes, absence (shown as − in Table 1), of a combination of markers is used in various studies to identify, differentiate, and count endothelial cell populations. Currently, a unique, standard combination of markers to be used to define each of the endothelial populations, especially

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CPCs and EPCs, is lacking. Thus, identifying the latter tends to be more challenging than identifying CECs. CD146 is a marker specific for mature CECs and is used for affinity capture of these cells. Subsequently, the expression of endothelial-specific markers, such as the lectin UEA1, is used to confirm identity.

Endothelial cells and progenitors in other etiologies leading to PAH have also been studied. Raised CECs are associated with systemic sclerosis–associated PAH (SSc-PAH);[6] furthermore, a reduction in the EPC count has been associated with progression of SSc-PAH.[7] A study on the effect of exposure to high altitude showed that these endothelial populations were reduced after high altitude exposure for 12 days in 15 mountain trekkers.[8] On the other hand, both CECs and CPCs are reportedly unchanged in obstructive sleep apnea without manifestations of PAH.[9] Furthermore, in the study on EPCs in SSc-PAH,[7] it was suggested that there is an increase in EPCs in the initial stage of PAH, when EPCs contribute to pathologic vascular remodeling. In the more severe stages, the EPC count is reduced compared with the controls.

The current study on IPAH patients is consistent with the observations on CEC increase in PAH due to other etiologies. However, there appears to be no change in numbers of CPCs (CD34+/CD133+) in this study. Similar observation of no change in similarly identified progenitor cells was made in a cohort of congenital heart disease–associated PAH patients.[10] In contrast, another study[11] on CD34+/CD133+ cells from IPAH patients showed increase in these circulating bone marrow–derived proangiogenic precursors, compared with normal controls.

CEC count appears to be a more reliable marker in the literature, in general, with the increase in numbers associated with severe disease. The current study corroborates the observations on CEC count in PAH patients. However, there are differences in results

of CPC counts among studies, including the current one. This could be, partially, due to the fact that defining CPCs in vitro is less standardized and, more challenging than that for CECs. In studies using similar definitions of cell types, inherent differences in the study population that affect the pathologic status, such as the duration of disease, drugs, or therapy undergone, individual variability, and so on, could contribute to contrasting results.

REFERENCES

1. Stevens T, Rosenberg R, Aird W, Quertermous T, Johnson FL, Garcia JG, et al. NHLBI workshop report: endothelial cell phenotypes in heart, lung, and blood diseases. Am J Physiol Cell Physiol 2001;281:C1422-33.

2. Siddique A, Shantsila E, Lip GY, Varma C. Endothelial progenitor cells: what use for the cardiologist? J Angiogenes Res 2010;2:6.

3. Mohandas R, Segal MS. Endothelial progenitor cells and endothelial vesicles - what is the signifi cance for patients with chronic kidney disease? Blood Purif 2010;29:158-62.

4. Jacques N, Vimond N, Conforti R, Griscelli F, Lecluse Y, Laplanche A, et al. Quantifi cation of circulating mature endothelial cells using a whole blood four-color fl ow cytometric assay. J Immunol Methods 2008;337:132-43.

5. Mariucci S, Rovati B, Bencardino K, Manzoni M, Danova M. Flow cytometric detection of circulating endothelial cells and endothelial progenitor cells in healthy subjects. Int J Lab Hematol 2010;32:e40-8.

6. Del Papa N, Colombo G, Fracchiolla N, Moronett i LM, Ingegnoli F, Maglione W, et al. Circulating endothelial cells as a marker of ongoing vascular disease in systemic sclerosis. Arthritis Rheum 2004;50:1296-304.

7. Nevskaya T, Bykovskaia S, Lyssuk E, Shakhov I, Zaprjagaeva M, Mach E, et al. Circulating endothelial progenitor cells in systemic sclerosis: relation to impaired angiogenesis and cardiovascular manifestations. Clin Exp Rheumatol 2008;26:421-9.

8. Mancuso P, Peccatori F, Rocca A, Calleri A, Antoniott i P, Rabascio C, et al. Circulating endothelial cell number and viability are reduced by exposure to high altitude. Endothelium 2008;15:53-8.

9. Martin K, Stanchina M, Koutt ab N, Harrington EO, Rounds S. Circulating endothelial cells and endothelial progenitor cells in obstructive sleep apnea. Lung 2008;186:145-50.

10. Smadja DM, Gaussem P, Mauge L, Israël-Biet D, Dignat-George F, Peyrard S, et al. Circulating endothelial cells: a new candidate biomarker of irreversible pulmonary hypertension secondary to congenital heart disease. Circulation 2009;119:374-81.

11. Asosingh K, Aldred MA, Vasanji A, Drazba J, Sharp J, Farver C, et al. Circulating angiogenic precursors in idiopathic pulmonary arterial hypertension. Am J Pathol 2008;172:615-27.

Table 1: Immunologic markers characteristic of endothelial cell populations

CD146 CD45 CD3 CD34 CD14 CD133

Circulating endothelial cells

+ − − + −

T cells, activated + + + −Early progenitor cells/CFU (colony forming unit-Hill)

+ +

Late/outgrowth endothelial progenitor cells

− + +


Menon, et al.: CECs in PAH


Inaugural meeting of the PVRI Sub-Saharan African Task Force - Report Karen SliwaHatter Cardiovascular Research Institute, University of Cape Town and leader of the SSA Region taskforce on the PVRI

Address for correspondence: Prof. Karen Sliwa, Hatter Cardiovascular Research Institute, Cape Heart Centre, 4th fl oor, Chris Barnard Building, Faculty of Health Sciences, Karen. E-mail: [email protected]

DOI: 10.4103/0974-6013.68485

The Sub-Saharan Task Force, under the leadership of Dr. Ana Olga Mocumbi and myself, was established in January 2010. The primary aim of this Task Force was to establish a Sub-Saharan African Registry of Pulmonary Hypertension (PHT) and, subsequently, other research and educational awareness projects.

PHT is a devastating, progressive disease, with increasingly debilitating symptoms and, usually, with a shortened overall life expectancy. The epidemiology of PHT in sub-Saharan Africa has not yet been determined, but limited reports suggest that the incidence is higher than that reported from developing countries, owing to the pattern of diseases prevalent in the region.[1-3] Many known factors for PHT are hyperendemic in this part of the world, including Human Immunodeficiency Virus/Acquired Immune Deficiency Syndrome, Schistosomiasis, chronic hepatitis B and C, and Sickle-Cell Disease. On the other hand, a high prevalence of tuberculosis, poorly treated asthma, high levels of pollution in the urban areas, and exposure to mining, subsequently lead to various forms of PHT and, often, to right heart failure with premature death. The lack of adequate pediatric services to deal with congenital heart disease that leads to PHT, and secondary PHT, is commonly seen, due to the high prevalence of rheumatic heart disease and endomyocardial fibrosis.[4-7]

However, more detailed information is currently not available, thus also leading to poor awareness of these devastating problems, not only in the sub-Saharan Africa, but worldwide. There is, therefore, an urgent need for research into the demographics, natural history, and survival of patients with PHT.

Filling these gaps in knowledge is needed to effectively detect, manage, and prevent PHT in this region.

However, important lessons for the developing world can be learned by understanding the pathophysiologic basis of rarer conditions, which might be applicable to mechanisms of understanding in other diseases. An interesting example is the recent understanding of the importance of increased oxidative stress leading, via the activation of cardiac signaling pathways, to an abnormal breast-feeding hormone (16 kDa prolactin), possibly contributing in a major way to Peripartum cardiomyopathy, a disease particularly common in African women, but prevalent in all other ethnic groups.[8,9]

The first Sub-Saharan Pulmonary Vascular Hypertension Workshop took place on Friday 23rd and Saturday 24th April 2010, at the Hatter Cardiovascular Research Institute, Chris Barnard Building, Faculty of Health Sciences, University of Cape Town.

We had colleagues from South Africa, Africa (Zimbabwe, Mozambique, Nigeria, Kenya, Sudan, Tanzania), United Kingdom (Prof Butrous), Australia (Prof Simon Stewart), and United States (Dr Lori Blauwet) participating in the workshop. The areas of discipline of the participating members ranged from basic scientists, adult and pediatric cardiologists, pulmonologists to cardiothoracic surgeons.

Although a few colleagues were not able to participate in the workshop, they expressed keen interest in participating in the registry and case–control studies.

Others, namely, Prof. Sheila Haworth (PVRI, UK), Prof. Denise Hilfiker-Kleiner from Hannover University, Germany, and Dr. Dirk Otto from Bayer-Schering, Germany, could not travel to the meeting due to the after-effects of the volcanic ash from Iceland. We were, however, pleased to have Tanja Steenekamp and her colleagues from Bayer-Schering, South Africa, in attendance.

We used the workshop to plan a PHT registry in Africa, under the auspices of the Pulmonary Vascular Research Institute–Sub-Saharan Taskforce.

The main objective of this research is to describe the epidemiology of PHT among patients attending referral units for cardiovascular and pulmonary diseases in African countries. This information will be crucial to the development of effective and resource-sensitive strategies to tackle PHT in sub-Saharan Africa. The first step in this direction will be to build a registry of patients with PHT, attending a range of hospitals in several countries from this region.

Prof. Ghazwan Butrous, Professor of Cardiopulmonary Science, University of Kent, Canterbury, gave an overview on the PVRI Institute and its global role. His talk was followed by a Skype presentation, given by Prof Sheila Haworth, on her work with the PVRI India group.

This session was followed by presentations on PHT with a focus on Sub-Saharan Africa.

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Prof Simon Stewart, from the Baker IDI Heart and Diabetes Institute presented unpublished data on our collaborative project from the Heart of Soweto Study (University of the Witwatersrand). As presented recently at the European Cardiac Society Heart Failure meeting in Berlin, Germany, from a tertiary hospital registry at CH Baragwanath Hospital in Soweto, South Africa, 2505 cases presented overall with de novo heart failure among more than 5000 cases diagnosed with new cardiac disease, between 2006 and 2008. Of those 2505 cases, almost 700 cases had right heart failure. The majority presented with dyspnea (New York Heart Association Class II–IV), with a mean right ventricular systolic pressure of more than 50%. Right heart failure was independently associated with being black African, having a lower body mass index, a history of smoking, and having no history of cardiovascular disease. Among those cases with right heart failure, pulmonary arterial hypertension due to idiopathic form HIV, connective tissue disease, and congenital heart disease caused 28% of right heart failure in women and 15% in men.

Dr. Rosie Burton, Consultant in Medicine, University of Cape Town, presented an excellent overview on HIV as an independent risk factor for PHT, highlighting the lack of association of onset and progression of PHT with the CD4 count, viral load and clinical stage of HIV presentation. She describes, in the attached report, that HIV-associated PHT has almost exclusively been studied in the United States and European populations, with only isolated reports from African countries.

Dr. Ana Olga Mocumbi, my Co-Chair Task Force Leader of the Sub-Saharan Task Force of the PVRI, describes, in the attached summary, the broad range of PHT in the young African, highlighting the high incidence of untreated congenital heart disease with left-to-right shunt, schistosomiasis, HIV/AIDS, rheumatic heart valve disease, endomyocardial fibrosis, sickle-cell disease, and tuberculosis.

Dr. O. Ogah gave an excellent overview on the available data on PHT published from Nigeria.

Dr. Friedrich Thienemann, from the University of Cape Town,

Institute of Infectious Diseases and Molecular Medicine, presented a Web-based data collection system, AIDSS-ORG, that could, possibly, be used for the PVRI registry, if funding could be secured.

After lunch the group agreed on the format of the registry, number of cases to be studied (n = 1000), and substudies. The infrastructure of the centers was summarized by Dr. Ana Mocumbi, and the format for possible blood collection was presented by Prof. Sliwa and Prof. Sandrine Lecour.

The importance of securing research funding was highlighted.

A dedicated echocardiography group (Drs. Riaz Garda, Ahmed Suliman, Neil Hendricks, Lori Blauwet, and others), who will design the one-page echo assessment, was formed.

We ended the day with a group photograph being taken and later met for an interactive buffet dinner continuing our discussions.

We ended the meeting by agreeing to have a follow-up meeting in Cape Town in March 2011 or, alternatively, to coincide with the Pan African Cardiac Society meeting in Uganda in May 2011.

REFERENCES

1. Sliwa K, Wilkinson D, Hansen C, Ntyinyane L, Tibazarwa K, Becker A, et al. A broad spectrum of heart disease and risk factors in a black urban population in South Africa: results from The Heart of Soweto study clinical registry. Lancet 2008;371:915-22.

2. Stewart S, Wilkinson D, Hansen C, Vaghela J, Mvungi R, McMurray J, et al. A predominance of heart failure in The Heart of Soweto cohort: emerging challenges for an African cohort. Circulation 2008;118:2360-74.

3. Buist AS, McBurnie MA, Vollmer WM, Gillespie S, Burney P, Mannino DM, et al. International variation in the prevalence of COPD (The Bold Study): a population-based prevalence study. Lancet 2007;370:741-50.

Figure: Adriano Tivane, Kemi Tibazarwa, Riaz Garda, Lori Blauwet, San drine Lecour, Neil Hen dricks, Dike Ojji, Jonathan Matenga, Okechukwu Ogah, Albertino Damasceno, Ana Mocumbi, Ibrahim Ahmed, Karen Silwa, Gill Ainslie, Nowshaad Alam, Akinytemi Aje, Joy McCathy, Rosie Burton, Lydia Lacerda, Rossy Matshela, Ghazwan Butrous, Mark Josh, Abel Makubi

PVRI sub-saharan Africa inaugural meeting



4. Sliwa K, Carrington M, Mayosi BM, Zigriadis E, Mvungi R, Stewart S. Incidence and characteristics of newly diagnosed rheumatic heart disease in urban African adults: Insights from the Heart of Soweto Study. Eur Heart J 2010;31:719-27.

5. Mocumbi AO, Lameira E, Yaksh A, Paul L, Ferreira MB, Sidi D. Challenges on the Management of Congenital Heart Disease in developing countries. Int J Cardiol 2010.

6. Marĳ on E, Ou P, Celermajer DS, Ferreira B, Mocumbi AO, Jani D, et al. Prevalence of Rheumatic Heart Disease detected by

echocardiographic screening. N Engl J Med 2007;357:470-6.7. Sliwa K, Mocumbi AO. Forgott en cardiovascular diseases in

Africa. Clin Res Cardiol 2010;99:65-74.8. Hilfi ker-Kleiner D, Kaminski K, Podewski E, Bonda T, Schaefer

A, Sliwa K, et al. A cathepsin D-cleaved 16 kDA form of prolactin mediates postpartum cardiomyopathy. Cell 2007;128:589-600.

9. Sliwa K, Blauwet L, Tibazarwa K, Libhaber E, Smedema JP, Becker A, et al. Evaluation of bromocriptine in the treatment of acute severe Peripartum Cardiomyopathy: a proof of concept pilot study. Circulation 2010;121:1465-73.

Pulmonary Hypertension in NigeriaOkechukwu Samuel OgahDepartment of Medicine, Division of Cardiology, University College Hospital Ibadan, PMB 5116, Ibadan, Oyo State, Nigeria

Address for correspondence: Dr. Okechukwu Samuel Ogah, Division of Cardiology, Department of Medicine, University College Hospital, Ibadan, PMB 5116, Ibadan, Oyo state, Nigeria, E-mail: [email protected]; [email protected]

DOI: 10.4103/0974-6013.68487

Sir,The article is an attempt to review the available data on the prevalence, etiology, and outcome of pulmonary hypertension/pulmonary heart disease in Nigeria.

All publications on heart disease/pulmonary heart disease in Medline indexed literatures were reviewed from January 1955 to December 2009. Seventeen clinical studies, 7 echocardiographic databases, and 4 autopsy/mortality studies were retrieved. In addition, 4 studies (3 clinical and 1 autopsy based), specifically looked at the etiology of pulmonary heart disease in Nigeria.

Pulmonary hypertension–related heart disease accounts for 0.6-28% of heart diseases, 1.4-10.1% of echo registries, and 0.9-17% of autopsy/mortality studies.

There is no population-based study on the prevalence of pulmonary hypertension in the country.

The common causes of pulmonary hypertension/pulmonary heart disease includes the following: chronic obstructive airway disease,[1-4] pulmonary tuberculosis,[1-4] chronic suppurative lung disease,[1-4] connective tissue disease,[1,2,5,6] and sickle cell disease.[7] Others include pulmonary atherosclerosis,[4] kyphoscoliotic heart disease,[1,2] pulmonary fibrosis,[1,2] schistosomiasis,[8] and primary pulmonary hypertension.[1,2,4]

Mortality associated with the disease is high. Over 70% die in less than 6 months after the onset of symptoms.[4]

REFERENCES

1. Sofowora EO. Pulmonary heart disease in Ibadan. Thorax 1971;26:339-42.

2. Femi-Pearse D, Chronic Cor Pulmonale in Lagos. Nigerian Med J 1973;3:85-8.

3. Adesanya CO. Clinical patt ern of chronic cor pulmonale in Zaria, Nigeria: A ten-year review. Trop Doct 1985;15:166-9.

4. Adetuyibi A. Chronic Cor Pulmonale in Nigerians: A 5-year retrospective study of autopsy proven cases. Trop Cardiol 1976;2:71-5.

5. Awotedu AA, Oluboyo PO, Onadeko BO, Okubanjo A. Pulmonary manifestations of connective tissue diseases in Nigeria. Nigeria Med J 1987;9:121-5.

6. Onadeko BO, Kolawole TM, Sofowora EO. Pulmonary Maifestations of systemic sclerosis in Nigerians. Ghana Med J 1976;15:16-9.

7. Aliyu ZY, Gordeuk V, Sachdev V, Babadoko A, Mamman AI, Akpanpe P, et al. Prevalence and risk factors for pulmonary artery systolic hypertension among sickle cell disease patients in Nigeria. Am J Hematol 2008;83:485-90.

8. Ogunlesi TO. Schistosomiasis and cor-pulmonale in West Africa. Trans R Soc Trop Med Hyg 1962;56:302-4.


Pulmonary Hypertension in The Young AfricanAna Olga MocumbiInstituto do Coração, Moçambique, Cardiologist and Co-leader of the SSA Region Task Force of the PVRI

Address for correspondence: Dr. Ana Olga Mocumbi, Instituto do Coração, Moçambique, Mozambique. E-mail: [email protected]

DOI: 10.4103/0974-6013.68488

INTRODUCTION

Pulmonary hypertension (PH) in children contributes significantly to the morbidity and mortality in diverse pediatric cardiac, lung, hematologic, and other diseases. Without therapy, high pulmonary vascular resistance contributes to progressive right ventricular failure, low cardiac output, and death. The recent advances in basic pulmonary vascular biology have led to several novel therapies, which have significantly expanded therapeutic choices and have led to improved survival and quality of life of many children with pulmonary arterial hypertension in the developed countries, but these improvements have not reached Africa where long-term outcomes remain guarded, and substantial challenges persist particularly with regard to diagnosis, management, and prevention. Epidemiologic data on PH in the young Africans are lacking; however, a high incidence is estimated considering the high prevalence of many risk factors, namely untreated congenital heart disease with left-to-right shunt, schistosomiasis, HIV/AIDS, rheumatic heart valve disease, endomyocardial fibrosis, sickle-cell disease (SCD), and tuberculosis (TB).

PARTICULAR FORMS OF PULMONARY HYPERTEN-SION IN SUB-SAHARAN AFRICAN CHILDREN

Congenital heart diseaseWhile in developed countries prenatal diagnosis is currently used to detect CHD before birth, in developing countries only a minority of children with CHD are detected and very few benefit from a surgical treatment. Due to lack of expertise and lack of services adequately equipped for diagnosis and management of CHD in most sub-Saharan African (SSA) countries, the diagnosis of abnormalities that cause relevant systemic-to-pulmonary shunt early in life is done in late stages, frequently at the time of shunt reversal. Irreversible PH is a common complication at presentation of CHD in SSA, where a prevalence of around 10% has been reported.[1,2]

Rheumatic heart diseaseAlthough preventable, rheumatic heart disease (RHD) has not been targeted by control programs in most countries in SSA, a region that has half of the 2.4 million children affected by RHD worldwide.[3] Rheumatic heart valve disease is highly prevalent in school children[4,5] and PH is the most common complication seen in mitral valve disease.[3,6]

Endomyocardial fi brosisEndomyocardial fibrosis, a restrictive cardiomyopathy

affecting children from certain regions of Africa, causes PH related to recurrent thromboembolism from the right side of the heart and/or diastolic restriction of the left ventricle associated with mitral valve disease.[7]

Sickle cell diseaseThe importance of PH in sickle-cell disease (SCD) is not clear, but may be frequent in the endemic areas of Africa, where children have higher prevalence of PH compared with their counterparts from other parts of the world for reasons that may be related to the interactions between prevalent infectious complications and exaggerated SCD-related hemolysis.[8]

Infectious diseasesSSA is the most endemic area for schis tosomiasis worldwide.[9] This parasitic disease is probably a leading cause of PH in the continent, since children in some regions are easily infested owing to the pattern of their daily activities that include spending long periods in water containing cercaria.

Another important risk factor for PH in children from SSA is the vertical transmission of HIV due to the high prevalence of the infection in women. Also, the incidence of pulmonary tuberculosis and cor pulmonale has been increasing in African children with the pandemics of HIV. This is because the high number of young adults with HIV and HIV-associated TB results in increased rates of TB transmission to children, and HIV-infected children are at an increased risk for TB and more severe forms of TB compared with immunocompetent children.[10]

Other causesMost households in the rural areas of Africa depend on biomass for cooking and heating, and the importance of chronic lung disease associated with indoor wood-smoke exposure in children might be high, considering that they are heavily exposed since early age. Some traditional medications based on plant extracts used by a large proportion of the population in SSA may also contribute to the pathogenesis of unexplained PH.[11] Finally, Takayasu disease, which affects essentially young people, may also lead to arterial PH.[12]

DISCUSSION AND CONCLUSIONS

Information systems in Africa are devoted to the surveillance of highly prevalent transmissible diseases, leading to a lack of systematic information on the prevalence of PH in the pediatric population. However, the number of children with



PH is likely to be much greater than that found in developed countries, considering the disease pattern, the lack of expertise for diagnosis, unavailability of open heart surgery, and the medical therapies currently used for control of infectious diseases. Therefore, the African research community faces a major challenge to reduce the burden of this condition since most causes are preventable or manageable.

REFERENCES

1. Mocumbi AO, Lameira E, Yaksh A, Paul L, Ferreira MB, Sidi D. Challenges on the Management of Congenital Heart Disease in developing countries. Int J Cardiol 2010. [In Press].

2. Sani MU, Karaye KM, Borodo MM. Prevalence and pattern of rheumatic heart disease in the Nigerian savannah: an echocardiographic study. Cardiovasc J Afr 2007;8:295-9.

3. Tantchou Tchoumi JC, Butera G. Rheumatic valvulopathies occurrence, patt ern and follow-up in rural area: the experience of the Shisong Hospital, Cameroon. Bull Soc Pathol Exot 2009;102:155-8.

4. Marijon E, Ou P, Celermajer DS, Ferreira B, Mocumbi AO, Jani D, et al. Prevalence of Rheumatic Heart Disease detected by echocardiographic screening. N Engl J Med 2007;357:470-6.

5. Longo-Mbenza B, Nayekula M, Ngilulu R, Kintoki VE, Bikangi NF, Seghers KV, et al. Survey of rheumatic heart disease in school children of Kinshasa Town. Int J Cardiol 1998;63;287-94.

6. Yuko-Jowi C, Bakari M. Echocardiographic patt erns of juvenile rheumatic heart disease at the Kenyatta National Hospital, Nairobi. East Afr Med 2005;82:514-9.

7. Mocumbi AO, Yacoub S, Yacoub M. Neglected tropical cardiomyopathies: II. endomyocardial fibrosis. Heart 2008;94:384-90.

8. Aliyu ZY, Kato GJ, Taylor J 6th, Babadoko A, Mamman AI, Gordeuk VR, et al. Sickle cell disease and pulmonary hypertension in Africa: a global perspective and review of epidemiology, pathophysiology, and management. Am J Hematol 2008;83:63-70.

9. Doumenge JP, Mott KE, Cheung C, Atlas de la Répartition Mondiale des Schistosomiases. Talence, CEGET-CNRS. Geneve: WHO; 1987. p. 400.

10. Rekha B, Swaminathan S. Childhood tuberculosis – global epidemiology and the impact of HIV. Pediatr Respir Rev 2007;8:99-106.

11. Heath D, Shaba J, Williams A, Smith P, Kombe A. A pulmonary hypertension-producing plant from Tanzania. Thorax 1975;30:399-404.

12. Cakar N, Yalcinkaya F, Duzova A, Caliskan S, Sirin A, Oner A, et al. Takayasu arteritis in children. J Rheumatol 2008;35:913-9.


HIV-associated Pulmonary Hypertension: A South African PerspectiveRosie BurtonDepartment of Medicine, GF Jooste Hospital, Manenberg, Sub-specialist Trainee in Infectious Diseases, University of Cape Town, Cape Town

Address for correspondence: Dr. Rosie Burton, E-mail: [email protected]

DOI: 10.4103/0974-6013.68489

HIV is an independent risk factor for pulmonary artery hypertension(PAH). In the pre–highly active antiretroviral therapy (HAART) era, the prevalence in the US and European populations was reported as 0.5%, which is 2500 times the prevalence of primary pulmonary hypertension in the general population. Although the prognosis for people living with HIV has markedly improved in recent years with the wide availability of HAART, HIV-associated PAH remains a disease with a very poor prognosis.

The onset and progression of PAH in patients with HIV has no association with CD4 count, viral load, or clinical stage of HIV infection. The impact of HAART on pulmonary hypertension remains unclear. Histopathologic studies have shown plexiform arteriopathy and obliteration of small pulmonary arteries, as described in primary pulmonary hypertension. The underlying pathophysiology is considered to be a consequence of immune activation and dysregulation, with a disordered cytokine response to HIV infection resulting in endothelial cell activation. Viral proteins,

such as tat, nef, and gp120, have been shown to promote secretion of endothelin-1 from endothelial cells and macrophages. Direct infection of pulmonary endothelial cells by HIV has never been demonstrated.

On theoretic grounds, it would seem reasonable to assume that HAART would decrease the incidence of HIV-associated PAH and improve prognosis. However, published evidence is conflicting, and no studies have been designed or powered to directly address these issues. There is insufficient data to state whether HAART improves hemodynamics, symptoms, or survival. Published data consist of retrospective studies and case series, and many confounding factors have not been addressed. Antiretroviral regimes have varied over time, patients with symptom onset pre- or post-HAART are not distinguished, and data on virologic suppression−the means of assessing efficacy of treatment−is often lacking. In countries with well-established antiretroviral programs, the prevalence of HIV-associated PAH


has not declined over time. However, as more people infected with HIV are living longer due to HAART, the fact that there has been no decline in the prevalence does not necessarily imply no reduction in the incidence. In order to directly answer this question, a randomized controlled trial of HAART vs placebo needs to be performed. As HAART has many health benefits for patients beyond any proposed effect on pulmonary hypertension, and the indications for starting HAART progressively widen, it is unlikely on ethical grounds that such a trial could be performed. Of note, there is no evidence that HAART causes harm to patients with pulmonary hypertension.

Disease-targeted therapy has also been studied in patients with HIV-associated PAH. Evidence consists of small randomized and nonrandomized trials and case reports, and suggests a similar response with epoprostanol and endothelin receptor antagonists in patients with primary pulmonary hypertension. Outcome was improved in patients treated with HAART plus disease-targeted therapy compared with HAART alone. No randomized controlled trials involving phosphodiesterase-5 inhibitors have yet been reported, however, some case reports suggest that there may be a benefit.

HIV-associated PAH has almost exclusively been studied in the US and European populations, with only isolated reports from African countries. Our experience is that pulmonary hypertension is underdiagnosed, with patients extensively investigated for other conditions, particularly tuberculosis. A diagnosis of pulmonary hypertension is therefore made late in the course of their disease. Whereas HAART has become increasingly available in developed countries, disease-targeted therapy is largely unaffordable; there is no access to this treatment in the state sector in South Africa. However, early diagnosis, supportive treatment, and HAART to optimize general health are measures that can considerably improve the quality of life of patients with HIV-associated PAH will enable assessment of the burden of HIV-associated disease

in the region, and enable optimization of locally available treatments, and to plan future studies.

FOR FURTHER READING

1. Aguilar RV, Farber HW. Epoprostenol (prostacyclin) therapy in HIV-associated pulmonary hypertension. Am J Respir Crit Care Med 2000;162:1846-50.

2. Barbaro G, Lucchini A, Pellicelli AM, Grisorio B, Giancaspro G, Barbarini G. Highly active antiretroviral therapy compared with HAART and bosentan in combination in patients with HIV-associated pulmonary hypertension. Heart 2006;92:1164-6.

3. Carlsen J, Kjeldsen K, Gerstoft J. Sildenafi l as a successful treatment of otherwise fatal HIV-related pulmonary hypertension. AIDS 2002;16:1568-9.

4. Degano B, Guillaume M, Savale L, Montani D, Jaïs X, Yaici A, et al. HIV-associated pulmonary arterial hypertension: survival and prognostic factors in the modern therapeutic era. AIDS 2010;24:67-75.

5. Degano B, Sitbon O, Simonneau G. Pulmonary arterial hypertension and HIV infection. Semin Resp Crit Care Med 2009;30:440-9.

6. Opravil M, Sereni D. Natural history of HIV-associated pulmonary arterial hypertension: trends in the HAART era. AIDS 2008;22:S35-40.

7. Sitbon O, Lascoux-Combe C, Delfraissy JF, Yeni PG, Raffi F, De Zutt ere D, et al. Prevalence of HIV-related pulmonary artery hypertension in the current antiretroviral therapy era. Am J Respir Crit Care Med 2008;177:108-11.

8. Voelkel NF, Cool Cd, Flores S. From viral infection to pulmonary arterial hypertension: a role for viral proteins? AIDS 2008;22:S49-53.

9. Zuber JP, Calmy A, Evison JM, Hasse B, Schiff er V, Wagels T, et al. Pulmonary artery hypertension related to HIV infection: improved haemodynamics and survival associated with antiretroviral therapy. Clin Infect Dis 2004;38:1178-85.


Jul - Dec 2010 • Volume 2 • Issue 3 99 PVRI REVIEW

From the Editor’s Desk

Dear PVRI fellows and members,

This is the third and last issue of PVRI Review in this year. Last GBM that was held in Lisbon, decided to have three issues of PVRI Review in 2010. Due to technical difficulties, we are printing the last two issues in 2010 together, which will reach you in December.

In this issue, we have many interesting articles covering various aspects of pulmonary vascular disease. Hanaa Banjar have done a wonderful job in contributing an article – “Review of Management Guidelines of Pulmonary Arterial Hypertension in the Pediatric Population”. This article serves a longstanding need since most of the existing guidelines for the management of pulmonary hypertension are directed to adult patients and there are no specific guidelines for the pediatric population. Professor Banjar discusses the differences between pediatric and adult pulmonary arterial hypertension in regards to etiology, diagnostic workup and response to treatments. From the classification through to the follow-up, she informs of the differences between the two populations. I am sure this will be useful to many people, who help children with PH.

Alexandra Heath et al., has contributed a thought-provoking article from the “heights” – Bolivia. She presents her observations regarding the pulmonary pressure characteristics of children and young adults with congenital heart defects who were born and live in high altitude. She analyzes the data before and after correction of the defects. She finally concludes that high altitude seems to confer to this group of patients some form of protection against irreversible changes in the pulmonary circulation. Although this observation needs to be validated in larger studies, it is a good piece of data for our High Altitude Task Force to work with.

Progress in various areas in life sciences and the overwhelming development in technology has contributed to greater appreciation of human disease processes. This has led to generation of enormous data which the researcher or clinician might find difficult to navigate. This is true in all fields of life science research, but it is more relevant in the field of genomics as it is a field which is developing at a very rapid pace. Swapna Menon has contributed a review article on data mining in the field of disease related genes. This review briefly lists some of the databases and tools that can be used to explore disease-related genes. While primary bioinformatic databases store the raw molecular data, secondary or derived

databases organize and annotate the data from the primary databases. These databases help the researcher to mine the information easily.

Puri et al. have reported a case of non-regression of pulmonary hypertension in a baby with complex cyanotic heart disease. After surgical correction in this patient, a number of problems arise which are discussed in the case report. It is an eye opener to those dealing with such children.

As you are all aware, we have transcribed the webcasts, which are conducted by PVRI and PAHforum, for publication in PVRI Review. This initiative was started in the last PVRI issue. This issue, we present the webcast on HIV being transcribed: Pulmonary arterial hypertension associated with HIV infection. Professor Sonia Flores discusses the role of HIV-1Nef in the pathogenesis of PH in a simian model of PH. She reports that it was surprising to find the lesions of PH only in the test model monkey lungs infected with a chimeric virus called SHIV-nef. It is a very interesting basic science article, presented in an alternative format.

In addition to the above articles, we have the usual section – Journal Scan – to which Swapna is contributing. She has written a commentary, and the links to the list of citations are available to those who want to go through the literature of the last 3 months.

Dear readers, we, at PVRI REVIEW, are always open to suggestions and opinion regarding the content of this journal and appreciate your valuable feedback. Please send us your articles or viewpoints in order to contribute PVRI’s intention of knowledge sharing and education in the field of pulmonary vascular disease.

S. HarikrishnanEditor in Chief, PVRI Review,

Fellow, Pulmonary Vascular Research Institute, Co-leader, PVRI Publication Taskforce.

E-mail: [email protected]

DOI: 10.4103/0974-6013.73628

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PVRI REVIEW 100 Jul - Dec 2010 • Volume 2 • Issue 3

Address for correspondence: Dr. Hanaa Hasan Banjar, Department of Pediatrics, King Faisal Specialist Hospital and Research Centre (KFSH&RC), P.O.Box. 3354, MBC-58, Riyadh 11211, Saudi Arabia. E-mail: [email protected]

DOI: 10.4103/0974-6013.73629

Review of Management Guidelines of Pulmonary Arterial Hypertension in the Pediatric Population

Hanaa Hasan BanjarDepartment of Pediatrics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia

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The management of paediatric patients with pulmonary hypertension are mostly based on reports on adult patients. There is a long felt need to establish guidelines which are relevant to the pediatric population. In this report, we attempt to summarize the diagnostic and the management guidelines that have been reported in the literature in the pediatric age group.

Key words: Congenital heart disease, guidelines, pediatrics, children, pulmonary hypertension

INTRODUCTION

The management of paediatric patients with pulmonary hypertension are mostly based on reports on adult patients. There is a long felt need to establish guidelines which are relevant to the pediatric population. In this report, we attempt to summarize the diagnostic and the management guidelines that have been reported in the literature in the pediatric age group.

DEFINITION OF PULMONARY HYPERTENSION

The definition of PH is derived from adult patients and includes all individuals with mean pulmonary arterial pressures >25 mmHg at rest or >30 mmHg with exercise regardless of age (British Cardiac Society Guidelines and Medical Practice Committee, 2001). Since most of these measurements are performed by echocardiography, tricuspid regurgitation with a Doppler velocity of >2.5 m/sec has been used for the screening of PH.[1] Most pediatric cardiologists would agree on a definition of PH where systolic pulmonary artery pressure exceeds 50% of systolic systemic pressure.[2] These measurements are usually taken from either tricuspid regurgitation or from any known connection between systemic and pulmonary circulation (i.e., patent ductus arteriosus, ventricular septal defect.[1,2]

IncidenceConflicting data has been published concerning the incidence of persistent pulmonary hypertension in the newborn (PPHN). The incidence is 0.2% of live-born term infants while others gave a higher range of 0.43–6.8 per 1000. The associated mortality rate of PPHN at the beginning of the 21st century was given at 10–20%, whereas earlier

investigations reported mortality rates of up to 50%.

Classifi cationThe WHO classification of PAH was revised in Dana Point 2008, which is shown in Table 1.[2] The same etiologies and classifications can be applied in the paeditric population except in class 4 ( Chronic thrombolic PH) as it is uncommon in this age group. Another difference in group 3, with the chronic lung disease due to prematurity and chronic hypoxia replaces the chronic obstructive pulmonary disease (COPD).

PAH in association with congenital heart disease is more common in the pediatric population [Table 2] according to its type and severity whereas PAH secondary to connective tissue disease, sickle cell disease and HIV are more common in the adult population.[3-9]

Physiological factors that infl uence pulmonary artery pressure[1-12]

Carbon dioxide and hydrogen ion concentrationAlkalosis produces pulmonary vasodilatation and acidosis results in pulmonary vasoconstriction. In an elegant study of children with Trisomy 21 with congenital heart disease and increased propensity to PH following the atrioventricular valve repair, pulmonary vascular resistance (PVR) decreased in spite of a high PaCO2, confirming hydrogen ion concentration to be the primary determinant of PVR.[12]

OxygenAn increase in PVR occurs only below an alveolar oxygen tension of about 60 mmHg. Similarly, the low PO2 environment favors in-utero pulmonary vasoconstriction, whereas increased alveolar PO2 secondary to the first few breathes instantaneously vasorelaxes the pulmonary circulation.[1-12]

Lung volumeDuring anesthesia or resuscitation at low lung volumes, PVR increases because of the surrounding uninflated lungs compressing intrapulmonary blood vessels. As the lungs

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Table 1: Updated clinical classifi cation of pulmonary hypertension, Dana Point 2008[2]

1. PAH1.1 Idiopathic1.2 Heritable

1.2.1 BMPR21.2.2 ALK1, endoglin (with or without hereditary hemorrhagic

telangiectasia)1.2.3 Unknown

1.3 Drugs and toxins induced1.4 Associated with APAH

1.4.1 Connective tissue diseases1.4.2 HIV infection1.4.3 Portal hypertension1.4.4 Congenital heart disease1.4.5 Schistosomiasis1.4.6 Chronic hemolytic anemia

1.5 Persistent pulmonary hypertension of the newborn1’ Pulmonary veno-occlusive disease and/or pulmonary capillary hemangiomatosis2. Pulmonary hypertension due to left heart disease

2.1 Systolic dysfunction2.2 Diastolic dysfunction2.3 Valvular disease

3. Pulmonary hypertension due to lung diseases and/or hypoxia 3.1 Chronic obstructive pulmonary disease3.2 Interstitial lung disease3.3 Other pulmonary diseases with mixed restrictive and

obstructive pattern3.4 Sleep-disordered breathing3.5 Alveolar hypoventilation disorders

3.6 Chronic exposure to high altitude3.7 Developmental abnormalities

4. Chronic thromboembolic pulmonary hypertension5. PH with unclear and/or multifactorial mechanisms

5.1 Hematological disorders: myeloproliferative disorders, splenectomy

5.2 Systemic disorders: sarcoidosis, pulmonary Langerhans cell histiocytosis, lymphangioleiomyomatosis, neurofibromatosis, vasculitis

5.3 Metabolic disorders: glycogen storage disease, Gaucher disease, thyroid disorders

5.4 Others: tumoral obstruction, fibrosing mediastinitis, chronic renal failure on dialysis

ALK-1 = Activin receptor-like kinase 1 gene; APAH = Associated pulmonary arterial hypertension; BMPR2 = Bone morphogenetic protein receptor, type 2; HIV = Human immunodeficiency virus; PAH = Pulmonary arterial hypertension.

Table 2: Cardiac lesions associated with pulmonary hypertension[10]

Increased pulmonary blood flow at increased pulmonary artery pressure

Ventricular septal defect (VSD) Atrioventricular septal (canal) defects Patent ductus arteriosus (PDA) Aortopulmonary window Surgical aortopulmonary connections (modified Blalock-Taussig shunt, Waterson anastomosis, Potts anastomosis)

Increased pulmonary blood flow Atrial septal defect (ASD) Partial anomalous pulmonary venous return

Cyanotic heart disease with or without increased pulmonary blood flow

Transposition of the great arteries Truncus arteriosus Single ventricle hearts Tetralogy of Fallot (pulmonary atresia/VSD)

Pulmonary venous obstructionTotal anomalous pulmonary venous return Pulmonary vein stenosis Cor triatriatum Mitral stenosis Hypoplastic left heart syndrome

are expanded, PVR falls and is lowest at the functional residual capacity. However, with overdistension, PVR increases again as a result of stretching the intrapulmonary vessels.[1-12]

Nitric oxideNitric Oxide (NO) is synthesized in the vascular endothelium by nitric oxide synthase (NOS) via the oxidation of the terminal guanidino nitrogen atom of the amino acid L-arginine (LA). NO relaxes the SMC by activating the soluble enzyme guanylate cyclase, increasing the intracellular cyclic guanosine 3’-5’ monophosphate concentrations initiating a cascade that results in the relaxation of the arterial smooth muscle. It relaxes the smooth

muscle under normal conditions. It also causes relaxation under hypoxic and hypercapnic conditions.[1-12]

EndothelinsEndothelins (ET) are a family of potent vasoactive modulators, which also mediate SMC proliferation in the vascular wall. ET1 is found in the highest concentration and acts on both Endothelin A (ET-A) and Endothelin B (ET-B) receptors. ET-A receptors are responsible for vasoconstriction, whereas ET-B receptors are responsible for vasodilatation and clearance of ET1. Increased concentrations of ET1 have been demonstrated in children with PH. Studies have demonstrated that ET1 concentrations correlated with pulmonary reactivity in response to hypoxia. Endothelin antagonists, both non-specific blockers of ET-A and ET-B receptors, and specific ET-A antagonists reduce PVR and improve symptoms.[1,12]

It appears that an “imbalance” takes place between vasoconstrictor and vasodilator mediators (increased thromboxane and reduced prostacyclins, increased endothelin and reduced NO). Other factors which may also be involved are serotonin, growth factor-derived platelets, angiotensin and loss of vascular NO, and prostacyclin due to synthesis genetic expression. The initial endothelial damage results in the recruitment of local vasoactive mediators provoking a procoagulatory state, leading to consequent vascular obstruction. Furthermore, defects in pulmonary circulation smooth muscle potassium channels also appear to be involved in onset and/or progression of PH.[13]

PathologyStructural changes in persistent pulmonary hypertension PPH of the newborn/pulmonary hypertension.

The severity of pulmonary vascular disease was classified in patient with congenital heart disease from I to VI as it is found in congenital heart disease patients:[13]

Banjar: Review PAH guidelines 2010


• Grade I: medial hypertrophy• Grade II: cellular intimal thickening• Grade III: occlusive intimal thickening• Grade IV: injuries with vascular dilatation• Grade V: plexiform injuries• Grade VI: acute necrotizing arteritis

Grade I to III abnormalities are considered plexogenic (reversible) whereas Grades IV to VI are plexiform (irreversible). Plexiform abnormalities encompass hypertrophy of the tunica media of preacinar arteries, muscularization of intra-acinar arteries, concentric thickening of the preacinar arteries, complex alterations, and dilatations with arteritis and ferrugination.[13]

Although the pathobiological mechanisms involved appear to be the same as in adults, there are some subtle histopathological and functional differences in pediatric patients and adults with PAH.[14,15] In contrast to adults, who frequently present with fixed PAH, severe intimal fibrosis, and plexiform lesions, the pulmonary vasculature may remain more reactive in children with a predominance of medial hypertrophy.[15,16] However, more recent data appear to reveal that even if a greater percentage of pediatric IPAH patients respond to vasoreactivity testing compared with adults, it is not as high as previously reported and is in the range of 10–20%.[17] As a consequence, the sustained vasoreactivity of the pulmonary circulation in children bears the risk of hypertensive crises in conditions associated with alveolar hypoxia and subsequent ventilation/perfusion mismatch, like respiratory tract infections. On the other hand, persistent pulmonary vasoreactivity authorizes the use of calcium channel-blockers (CCBs) as vasodilators, an inexpensive therapy for pediatric patients more than adults.

Signs and symptoms[Table 3].[18]

Functional classifi cation[13]

Patients with PH can be classified according to their functional capacity (degree of functional limitation)

Class IPatients with PH and no limitation of physical activity: Physical activity does not cause dyspnea, chest pain, tiredness, or syncope

Class IIPatients with PH and mild limitation of physical activity: Patient is comfortable at rest. Everyday physical activity causes dyspnea, chest pain, tiredness, or near syncope.

Class IIIPatients with PH and marked limitation of physical activity: Patient is comfortable at rest. All and any physical activity causes dyspnea, chest pain, tiredness, or near syncope.

Class IVPatients with PH incapable of any physical activity whatsoever without causing symptomatology. Patients with signs of DHF, dyspnea and/or fatigue may be present at rest, and distress is increased by any physical activity.

DiagnosisGeneral historyDiagnosis of PH is by exclusion, but there maybe a high degree of clinical suspicion. Family history should be thoroughly investigated for connective tissue disorders, relatives with PH, congenital heart disease, other congenital malformations, and any history of sudden death in the family. Drug use should also be investigated (especially psychotropics and appetite suppressants) as should exposure to altitude, repeated respiratory infections, obstructive sleep apnea (not so rare in children), thromboembolic events (rare in pediatrics), and neonatal antecedents [Tables 3 and 4].[15,18,19]

The routine for diagnostic evaluation may include a series of supplementary tests adapted to the individual clinical requirements of each patient.[13]

ElectrocardiographyElectrocardiography (ECG) is often the first test to suggest PAH by demonstrating right ventricular hypertrophy and right atrial enlargement. Evidence of right ventricular hypertrophy on ECG is present in 87% of patients with IPAH and right axis deviation in 79%.[20] ECG parameters reflective of physiologic and anatomic


Table 3: History and examinationHistory Family history of pulmonary hypertension

Birth and neonatal history (prior cardiac or other surgeries)History of frequent respiratory tract infectionsExposure to high altitudeHigh-altitude pulmonary edemaIngestion of toxic cooking oil, anorexigens, use of psychotropic drugsHIV, hepatitis C infectionPortal hypertension

Symptoms PAH:Infants: Poor appetite, failure to thrive, lethargy, diaphoresis, tachypnea, tachycardia, irritability, possible cyanosis with exertionChildren: exertional dyspnea, fatigue, reduced exercise, tolerance, chest pain, syncopeAssociated disease:Connective tissue disease: Rashes, nail-fold capillary abnormalities, arthritisLeft-sided heart disease: Systemic hypertension, orthopnea, paroxysmal nocturnal dyspneaRight-to-left shunting: CyanosisLung disease: Difficult/abnormal breathing patternsHypoventilatory disorder: Systemic hypertension, snoring, apnea, obesity, kyphoscoliosis, enlarged tonsilsChronic thromboembolic disease: Peripheralvenous insufficiency

Physical examination

Loud second heart sound, right ventricular heaveSystolic murmur of tricuspid regurgitation or diastolic murmur of pulmonary insufficiencyJugular venous distensionHepatomegaly, right ventricular third heart sound, peripheral edemaCold extremities

HIV = Human immunodeficiency virus; PAH = Pulmonary arterial hypertension.


abnormalities in the right atria and right ventricle (a large P-wave amplitude (≥ 0.25 mV) in lead II, qR complex in lead V1 or V3R) have been associated with decreased survival in patients with an established diagnosis of IPAH.[21] In children, a qR pattern in V1 or V3R is indicative of right ventricular hypertrophy regardless of voltage. An upright T-wave in V1 is indicative of right ventricular hypertrophy from seven days to seven years. However, owing to low specificity (0.7) and sensitivity (0.55), ECG is an inadequate screening tool to rule out the presence of clinically relevant pulmonary hypertension.[22]

EchocardiographyEchocardiography is the most useful noninvasive screening tool to evaluate patients with a clinical suspicion of PAH.[23] The echocardiogram documents right ventricular size and function, left ventricular systolic and diastolic function, morphology and function of cardiac valves, and the presence of pericardial effusion or a patent foramen ovale. An acceleration time to ejection time ratio less than 0.30 suggests the presence but not the degree of pulmonary hypertension.[23] Transthoracic Doppler

echocardiography can provide an estimate of the systolic pulmonary arterial pressures (sPAP). In the absence of pulmonary outflow obstruction, sPAP is equivalent to the right ventricular systolic pressure (RVSP), which can be approximated by the formula: RVSP = 4 v2 + RAP. The systolic regurgitant tricuspid flow velocity (V) is measured and the right atrial pressure (RAP) is either a standardized value or an estimated value from characteristics of the inferior vena cava or from jugular venous distension.[23] Tricuspid regurgitation of measurable quality has been reported in as many as 86% of cardiovascular patients.[24,25] Many studies report a correlation between Doppler echocardiography and right heart catheterization measurements of sPAP.[25-27] However, Doppler echocardiography may underestimate sPAP in patients with severe PAH[28] and overestimate sPAP in populations with mild or asymptomatic PAH.[29] When using Doppler echocardiography-estimated sPAP for detecting PAH, the sensitivity ranges from 0.63 to 1.00 and the specificity from 0.68 to 0.98.[29-32] Despite recent advances that have improved the estimation of sPAP, Doppler echocardiography remains less accurate in most patients than


Table 4: Diagnostic evaluation of pulmonary hypertensionPAH detection

Electrocardiography Right ventricular hypertrophy (ST-segment depressions, T-wave inversions)Chest radiography Signs of cardiomegaly and enlarged pulmonary arteriesEchocardiography Right ventricular hypertrophy, quantify right ventricular systolic pressure.

Exclude left heart or congenital heart diseasePAH characterization

Cardiac catheterization with acute vasodilator testing

Evaluated pulmonary artery pressure, resistance, and degree of pulmonary reactivity

Complete blood count with platelet count, urinalysis

Thyroid function testsHypercoagulable evaluation Disseminated intravascular coagulation screen

Antithrombin IIIProtein CProtein SLupus anticoagulant Factor V LeidenAnticardiolipin IgG/IgMPronthrombin gene mutation 20210 G / A

Autoimmune disease evaluation Antinuclear antibodies (DNA, Smith, ribonucleoprotein, SSA, SSB, anticentromere antibody, anti-SCL70)Rheumatoid factorComplementErythrocyte sedimentation rate

HIV testToxicology screen Amphetamines, cocaine, meta-amphetamines, fenfluramine, and phenylpropanolamineLiver evaluation Abdominal ultrasonography

Liver function tests with γ-glutaryl transferaseHepatitis profile

BNP/ NT-proBNP Bone morphogenic protein/N-terminal probrain natriuretic protein at diagnosis and follow-upUric acid At diagnosis and follow-upLung evaluation Pulmonary function tests (to exclude obstructive / restrictive lung disease)

Ventilation-perfusion (V/Q) lung scintigraphyPulmonary wedge angiographyHigh-resolution computed tomography (to evaluate obstructive / restrictive lung disease)Pulse oximetry polysomnography (to evaluate hypoxia, diminished ventilator drive, sleep-related breathing disorders)Lung biopsy

Exercise tests 6-minute walk test / treadmill exercise testCardiopulmonary exercise testing


invasive evaluation by right heart catheterization.

To measure systolic right ventricular (RV) pressure from tricuspid regurgitation (TR) velocity. The peak systolic transtricuspid pressure gradient from the RV to the right atrium (RA) is represented by 4 × (peak TR velocity). Therefore, systolic RV pressure is estimated by adding RA pressure to the pressure gradient derived from TR velocity.

Echocardiography can identify potential causes for pulmonary hypertension such as left-heart or congenital hear disease. Left atrial enlargement suggests elevated left-sided filling pressures that may contribute to a pulmonary pressure increase. Two-dimensional echocardiography is helpful in visualizing intracardiac defects and identifying associated cardiac or valvular abnormalities. Color flow Doppler imaging usually can detect intracardiac shunting[33-36] although contrast echocardiography may be more suited to visualize right-to-left shunting in patients with a small atrial communication.[37] Transesophageal echocardiography may be warranted in older children for optimum anatomic definition and may be superior to the transthoracic approach for detecting atrial septal abnormalities.[36-41] Indeed, more complex heart defects such as Tetralogy of Fallot, transposition of the great arteries and atrioventricular canal defects are scheduled for surgical repair solely on the basis of echocardiographic evaluation.

Ultrasound color M-mode imaging during cardiac catheterization has been investigated in children with PAH and may provide an additional method to estimate the pulmonary vascular resistance, pulmonary vascular compliance, and right ventricular afterload from instantaneous measurements of pressure and flow.[33,34]

Specialized echocardiography such as intravascular ultrasound has been used in children to detect medial hypertrophy associated with PAH and provide an evaluation of the pulmonary vascular bed.[32] Potential clinical advantages of this technique include the capability of examining multiple pulmonary arteries by a less invasive means than lung biopsy, thereby assessing information on a larger proportion of the pulmonary vascular bed.

Right heart catheterization to confi rm PAH diagnosisRight heart catheterization is required to confirm the diagnosis of PAH, assess the severity of the hemodynamic impairment, and to target therapy. In this procedure, the pulmonary artery pressures and pulmonary wedge pressure are measured, shunt size and pulmonary blood flow are determined and pulmonary vascular resistance is calculated by dividing the pressure gradient across the lungs by the pulmonary blood flow. Blood flow can be measured by the thermodilution technique in patients without shunt[42] or by the Fick method with measured oxygen consumption. Because oxygen consumption may be difficult to measure in pediatric patients, especially in small, intubated children, it is often derived from predictive tables based on body weight or surface area,[43] although measurement is preferred. With currently available techniques, the risks of pediatric cardiac catheterization are relatively low.[44] Special precautions should be taken, though, with children who may have a more reactive pulmonary vascular bed than adults and may be prone to acute pulmonary hypertensive crises. Sedation may be necessary to minimize a child’s agitation. Care should be taken to avoid rebound effects of inhaled nitric oxide withdrawal acutely and

within the first 12 hours after the procedure.

If right heart catheterization confirms the presence of PAH requiring treatment, a vasodilator study should be performed during the catheterization to determine the acute pulmonary vasoreactivity to short-acting vasodilators (inhaled nitric oxide, intravenous adenosine, and intravenous epoprostenol) and identify patients who may be responders to calcium channel blockade. A significantly greater percentage of children with IPAH (40%) are acute responders compared to adults (20%) and the younger the child, the greater the likelihood of acute pulmonary vasodilation in response to vasoreactivity testing.[6,45] Using the new definition (drop of mean pulmonary arterial pressure > 10 mmHg from baseline to <40 mmHg in the presence of a normal cardiac output) of an acute response, this percentage may be lower as described recently in adults (8%). In patients with a congenital heart defect, the assessment of pulmonary vasoreactivity can discriminate between patients with fixed, irreversible pulmonary hypertension, in whom surgical repair is associated with significant morbidity and mortality, and patients with reversible pulmonary hypertension, who may benefit from corrective surgery.

The sudden development of pulmonary edema during acute vasodilator testing may be indicative of pulmonary veno-occlusive disease of pulmonary capillary hemangiomatosis. As epoprostenol may ease pulmonary edema in the presence of pulmonary veno-occlusive disease, this diagnosis should be excluded before trying epoprostenol treatment. Additional information provided by right heart catheterization includes quantification of intracardiac or extracardiac shunting and measures of pulmonary venous pressures. An elevated pulmonary capillary wedge pressure suggests the presence of left heart disease or pulmonary vein obstruction but pulmonary veno-occlusive disease may be present despite a normal pulmonary capillary wedge pressure.[46] Measurements of capillary wedge pressure at several sites may be necessary to reveal increased pressure in some vascular segments. Alternatively, right heart catheterization may reveal elevations in hepatic wedge pressure indicative of portal hypertension, a condition that can cause PAH.[47]

The severity of PH is classified as mild (PmAP from 25 to 40 mmHg), moderate (PmAP from 41 to 55 mmHg) or severe (PmAP > 55 mmHg).[48,49] Cases of PH secondary to heart disease or chronic lung disease are generally related to mild to moderate increases in pulmonary pressure. Patients with severe PH are generally suffering from PPH, connective tissue disease, or chronic thromboembolism.[13] Some patients with mild to moderate PH, secondary to chronic hypoxemia, pulmonary pathologies or collagen disorders, can be monitored serially with echocardiograms (every 3 to 6 months) and cardiac catheterization can be reserved for those cases that pass functional class III on the New York Heart Association (NYHA) scale.[13]

Serological testingSerological testing for evaluation of PAH includes routine biochemistry and hematology tests. Thyroid function should be checked as thyroid disease may be associated with PAH.[50] Certain conditions, such as chronic thromboembolic disease or autoimmune disease, are less common in pediatric patients than in adults[51,52] but warrant assessment nevertheless. Bone




morphogenic protein (BNP) / N-terminal probrain natriuretic protein (NT-proBNP) and uric acid level as it interferes with Nitric-Oxide Synthase and blocks production of NO in the lung vascular endothelial cells.[51-56]

Computerized tomographyIndicated for differential diagnosis of PH patients.[57]

Angiotomography (ventilation/perfusion or V/Q lung scan and Pulmonary angiography:):[13,58]

Only useful screening test for pulmonary thromboembolism in adults but not common in children.

Magnetic resonance imagingProvides information on the size and function of the RV, myocardial thickness, presence of chronic thromboembolism and pulmonary and cardiac pressures.

Lung biopsyis rarely necessary for the diagnosis of PAH.[59,60] Consequently, it may be used when the clinical diagnosis is unclear (e.g. suspicion of alveolar capillary dysplasia, active vasculitis, granulomatous pulmonary disease, pulmonary veno-occlusive disease, pulmonary capillary hemangiomatosis, interstitial lung disease, or bronchiolitis).

Children with chronic respiratory symptoms and diffuse infiltrates on the chest roentgenogram present a diagnostic challenge, and attention has been drawn to pulmonary vascular disorders being misdiagnosed as interstitial lung disease.[60]

Pulse oximetry should be used to evaluate hypoxia caused by airway obstruction or diminished ventilatory drive.

Polysomnography (overnight monitoring of sleep stages, respiratory effort, air flow, electrocardiogram, oxygen saturation, and body position and movement) should be considered to rule out underlying sleep-related breathing disorders such as obstructive sleep apnea (overlap syndrome) or obesity hypoventilation syndrome, which may have a contributory role to pulmonary hypertension.[61,62]

Exercise capacityThe most commonly used exercise tests for pulmonary hypertension are the 6-minute walk test (6MWT),[63-65] the treadmill exercise test, and cardiopulmonary exercise testing (CPET) with gas exchange measurements, However, exercise testing may not be reliable in children less than 8 years of age.

The 6MWT is currently the only exercise test approved by the FDA for the assessment of disease progression. It was found to be predictive of survival in adults with IPAH and correlates with functional class, cardiac output, total pulmonary resistance, and oxygen saturation parameters determined by CPET.[66] However, the 6MWT is not as reliable in young children.

Therapeutic options [Table 5]GeneralThe aim is to maintain sufficient pulmonary blood flow and avoid complications, until resolution of the raised PVR. The

aim is to improve alveolar oxygenation, minimize pulmonary vasoconstriction, and maintain systemic pressure and perfusion. Complications may result either from hypoxia or barotrauma. The degree of hypoxia depends upon the ratio of PVR to systemic resistance.[66-73]

Increased oxygen demand may aggravate PH and diastolic heart failure (DHF), therefore physical activities are restricted (risk of effort syncope).[48] Respiratory infections should be treated and prevented immunization for influenza (flu-vaccine), respiratory S+ syncytial virus (RSV vaccine) (Synagis or Plaivizumab) and pneumococcal vaccine (Prevenar).

AlkalosisReduces PVR, an approach using muscle relaxants, sedation, and aggressive hyperventilation to render the infant alkalotic has been used. Rapid ventilation rates with high peak pressures produce a higher minute volume with low arterial carbon dioxide, producing a respiratory alkalosis.

Digitalis and diureticsPatients with PH accompanied by signs of documented right ventricular failure and low pulmonary flow (DHF), with hepatic and systemic congestion, should obtain some benefit from reduced after load and a certain inotropic effect, but great care must be taken because of the risk of concomitant preload reduction, which would worsen cardiac output.[74]

Oxygen therapyOxygen therapy is recommended for patients with PH secondary to parenchymatous pulmonary disease.[74] Children who exhibit reduced oxygen saturation during the night (in the absence obstructive disease or apnea) may benefit from the administration of nocturnal oxygen. It is recommended for patients who will

Table 5: Suggested assessments and timing for the follow-up of patients with PAH

At baseline(before therapy)

Every 3-6 monthsa

3-4 months after

initiation or changes in therapy

Incase of clinical

worsening

Clinical assessmentWHO-FCECG6MWTb

Cardio-pulmonary exercise testingb

BNP/NT-proBNPEchocar-diographyRHC c d d

aIntervals should to be adjusted to individual patients needs. bUsually one of the two exercise tests is performed. cIs recommended. dShould be performed. BNP = Brain natriuretic peptide; ECG = Electrocardiogram; RHC = Right heart catheterization; 6MWT = 6-minute walking test; WHO-FC = WHO functional class.


travel by air or have symptomatic respiratory infections, because of the risk of triggering PH crises.[75] The objective is to maintain oxygen saturation above 90% (except in those patients who have cyanotic congenital heart disease).[48]

Inhaled nitric oxideThe use of NO for persistent PH in the neonate[75,76] and for the management of congenital heart disease (especially during the immediate postoperative period)[13] are well-established. Prophylactic use for patients with risk of PH during post-op for correction of congenital heart disease is controversial.

The European consensus recommendation is to start at 20 ppm and observe the response for 10 min then sequentially increase to 40 ppm and observe the response over a short period of time, around 30 min (no more than 2 hours). The response criteria are a reduction in PAP and/or at least a 20% improvement in oxygenation saturation over baseline. Patients who do not respond to 40 ppm will probably not respond to 80 ppm either. As soon as a response is observed and the patient stabilized, it is recommended that NO be reduced to 10 to 5 ppm.[76]

Sildenafi l Is a selective type 5 phosphodiesterase inhibitor.[77] Its dosage in pediatrics should start at 0.1 mg/kg, with stepwise increases by 0.1 mg/kg) 1 up to 0.5 mg/kg every 6hrs. However, in patients with cardiac disease, initial dosage may be as high as 0.5 mg/g every 6hrs, with stepwise increases by 0.5 mg/kg up to 1.0–1.5 mg/kg. The IV dose has been started at 0.2 mg/kg/hr, although currently only available as part of clinical trials. As the effects of sildenafil are not selective to the pulmonary circulation, at higher concentrations, it may lead to a fall in systemic pressure. Furthermore, because of a longer half-life than NO, its effects are maintained for several hours.[1]

With relation to the pediatric population, there are only case reports that demonstrate possible clinical benefits from the use of sildenafil for PH.[78-88]

The largest patient sample used to assess the effects of sildenafil on pediatric patients was reported on by Schulze-Neick et al. The sample comprised 24 children with PH secondary to congenital heart disease. This study, controlled with inhaled NO, assessed 12 children by cardiac catheterization and 12 by hemodynamic monitoring during the immediate postoperative period. Intravenous sildenafil was more effective for reducing PVR than was NO.[85]

Oral sildenafil in infants with persistent pulmonary hypertension of the newborn was administered in a pilot, randomized, blinded study[87] in infants >35.5 weeks’ gestation and <3 days old with severe PPHN and oxygenation index (OI) >25 Intragastric sildenafil was administered easily and tolerated as well as placebo and improved OI in infants with severe PPHN, which suggests that oral sildenafil may be effective in the treatment of PPHN.

Endothelin antagonistsBosentanBosentan is an oral endothelin receptor antagonist, and has a discretely greater affinity for ET-A. It has been used successfully in children. Dosage is 1–2 mg/kg every 12 hrs, up to 2–4 mg/kg

every 12 hrs, (Actelion Pharmaceuticals, San Francisco, USA). AST enzymes should be monitored.[89-91]

Baseline and monthly liver function tests are required during the therapy. Patients with elevated liver enzyme levels should undergo biweekly assessment and the use of bosentan should be avoided in patients with moderate to severe hepatic insufficiency.

Evidence of usage in pediatric patients[90-99]

19 pediatric patients with pulmonary arterial hypertension were enrolled and stratified for body weight and epoprostenol use. Patients weighing between 10 and 20 kg, 20 and 40 kg or greater than 40 kg received a single dose of 31.25, 62.5 or 125 mg, respectively on day 1, and this was followed by 4 weeks of treatment with the initial dose. The dose was then up-titrated to the target dose (31.25, 62.5 or 125 mg twice daily). Bosentan produced hemodynamic improvement and was well tolerated. The mean change from baseline in mean pulmonary artery pressure was -8.0 mmHg (95% CI -12.2 to -3.7 mmHg) and that in pulmonary vascular resistance index was -300 dyne s cm-5 m2 (95% CI -576 to -24 dyne s cm-5 m2).

The recommended dose of Bosentan in the pediatric patient is 2mg/ Kg twice a day and the dose to be rounded to 16.5, 31.25, 62.5, and 125 mg.[92]

The summary of most studies in pediatrics have shown that: Bosentan treatment could be beneficial for patients with WHO FC II pulmonary arterial hypertension.[90-99]

Other selective ET-A inhibitors, such as sitaxsentan and ambrisentan, are under investigation for use in PH. These drugs’ action is based on a blockade of the vasoconstrictor effect of ET-A receptors, while maintaining vasodilation and clearance of ET-B receptors. The risk of hepatotoxicity is similar to that of Bosentan.[13]

Treatment should be stopped in patients who develop elevated transaminases (ALT or AST) in combination with symptoms of hepatic injury (unusual fatigue, jaundice, nausea, vomiting, abdominal pain, and/or fever) or elevated serum bilirubin ≥2 times upper limit of normal.[94]

ProstacyclinThe use of prostacyclins (epoprostenol) or prostacyclin analogues for PH treatment is based on an “imbalance” between thromboxane and prostacyclin metabolites.[48,75] Prostacyclins induce relaxation of the respiratory vascular musculature, stimulating production of cyclic adenosine monophosphate (AMP), and inhibit respiratory muscle cell growth and platelet aggregation.[48,75] It appears that the chronic benefits from their use are associated with an antiproliferative property. Used with patients with advanced disease (absence of pulmonary vascular reactivity) confirmed a “rescue” effect on the pulmonary vascular endothelium restoring normal function.[75]

EpoprostenolEpoprostenol is administered intravenously and appears to be effective with patients at functional classes II to IV, with a 6 minutes walking test ≤330 m.[13] It requires a “fully implantable” intravenous catheter for continuous infusion. Dosage is variable,



between 21±7 mg/kg/min during the first year and 32±10 mg/kg/min after 41 months.[48] Several adverse effects have been reported such as maxillary pain, headaches, diarrhea, nausea, leg pains, rubor and complications associated with the infusion system (risk of severe infections and sepsis: 0.1 to 0.6 case/patient/year).[48] It is not commonly used in pediatrics to due the difficulty to maintain central line for a long period of time.

IloprostIloprost is an inhaled prostacyclin analogue. Its particle size (0.5 to 3.0 µm) guarantees its pulmonary selectivity and improved tolerance.[18,75] However, its short half-life (45 minutes) demands frequent administrations (6 to 12 times per day).[18,75] Clinical experience with children is still extremely limited.[15] It is licensed for use in Europe and the USA. The dose varies depending upon the response of each patient. It is administered via a special nebulizer, and the maximum daily dose is 45 mcg. A small proportion of patients appear to respond in isolation.[100-102]

The combination of iloprost instilled endotracheally and inhaled was chosen as a last attempt at treatment in a critically ill patient who did not respond to advanced conventional treatments, including high frequency oscillation and inhalation of nitric oxide. The use of iloprost converted permanently the right-to-left shunting, leading to a substantial improvement in oxygenation.[103-106]

Most of the studies concluded that inhaled iloprost caused sustained functional improvement in some children with PAH, although inhaled iloprost occasionally induced bronchoconstriction. Most patients tolerated the transition from intravenous to inhaled prostanoid therapy.

PGI2 has been proposed as an alternative to iNO after the repair of CHD.[107] The nebulization of PGI2 or iloprost might have some advantages over the inhalation of NO, such as its lack of toxic reactions[108] (which require monitoring NO2 and methemoglobin formation during NO inhalation) and its easy administration by conventional nebulizers compared with the more complicated delivery systems required for NO. Furthermore, possibly life-threatening rebound phenomenon has been described with iNO[109,110] but not with aerosolized PGI2 or iloprost withdrawal.

The dose for pediatrics (<14 yo) is 2.5 mcg/kg nebulized for 10-20 minutes (dose used in case reports). The frequency is 6 to 9 times; dosing at intervals ≥2 hrs while awake via Inhalation (nebulization). Discontinue therapy If pulmonary edema occur, immediate discontinuation of therapy is warranted; could be a sign of pulmonary venous hypertension and the occurrence of exertional syncope may reflect a therapeutic gap or insufficient efficacy, and the need to adjust dose or change therapy should be considered.[104]

BeraprostIs an oral prostacyclin analogue which has around 50% of the effect of epoprostenol, with a longer half-life. Its hemodynamic effects over the long term (over 6 months) have not yet been fully confirmed.[111,112] This drug is not yet approved for pediatric use.

Combined treatment[83,88-114] The combined use of drugs which have different sites of action

appears to be promising for PH treatment. Adjuvant use of Bosentan and sildenafil with patients already on prostacyclin (oral, inhaled or intravenous) improved the variables under analysis.[113,114] A Long-term treatment with sildenafil and Bosentan improved both exercise capacity and functional class in patients with idiopathic pulmonary arterial hypertension and in those with hypertension due to congenital heart disease. The changes were more marked in patients with idiopathic pulmonary arterial hypertension.[83,88]

AdenosineIn a placebo-controlled trial, adenosine infused at (25–50 µg/kg/ min) improved oxygenation in infants with PPHN. No systemic hemodynamic consequences were seen. As adenosine is rapidly metabolized by the endothelium, its half-life is short.[115]

Atrial naturetic peptidePlasma atrial naturetic peptide (ANP) and brain naturetic peptide (BNP) reflect pressure and volume loads to the pulmonary artery and right ventricle and may help to identify children with ventricular septal defect complicated by PHT that demands early intervention.[116] BNP measurements may also be used to guide therapy, e.g. pulmonary vasorelaxants in PH as up regulation of the naturetic peptide pathway has been shown to reduce the cardiac hypertrophy and PAH. There may also be therapeutic potential via recombinant BNP or neutral end peptidase inhibitors in RV dysfunction and PAH.[116]

MagnesiumIs a powerful smooth muscle relaxant acting as a calcium antagonist. It is also an effective skeletal muscle relaxant, sedative, and controls dysrhythmias. Magnesium may also attenuate the effect of hypoxia on PVR. A magnesium infusion aiming for serum concentrations between 3 and 5.5 mmol/L has been effective in reducing hypoxia-induced PPHN. Improvements in oxygenation were seen contemporaneous with the increase in serum magnesium.[89]

High frequency oscillatory ventilationIn a randomized clinical trial of neonates with severe PPHN, high frequency oscillatory ventilation (HFOV) was as effective as inhaled NO. In the presence of severe lung disease, HFOV was more effective than inhaled NO. In the absence of parenchymal lung disease, inhaled NO was more effective than HFOV. Combining inhaled NO and HFOV was more successful than either alone.[117]

ECMOFor intractable potentially reversible PHT, which fails to respond to all the available therapeutic modalities, ECMO should be considered.[118] An oxygenation index (OI) of >40 should be a trigger for considering ECMO. However, in a unit with HFOV and iNO, a higher OI of 60–80 may be tolerated if ECMO is near or on site. With the addition of the vasodilators described, the need for ECMO is declining. The rate of increase in OI reflects the speed of deterioration and also indicates urgent consideration of ECMO.[118]

Surgical options (and transplantation)Children with frequent syncope and DHF have poor prognosis.



Effort-induced syncope occurs because of an inability to increase cardiac output to maintain cerebral blood flow. A patent foramen ovale is capable of increasing these patients’ survival. Systemic arterial oxygen saturation declines, but cardiac output and oxygen supply to tissues improve, through the shunt. Despite experience with more than 100 patients with atrial septostomies for PH, the procedure is still considered investigative.[119,120] Cardiopulmonary or just pulmonary (unilateral or bilateral) transplantation has been indicated for patients with PH since 1981. Currently, combined transplantation is only indicated in cases of anatomical cardiac defects, with no possibility of surgical correction, since morbidity and mortality are higher. Overall surgical mortality for lung transplantation is 16 to 29%. Pediatric data from the International Society for Heart and Lung Transplantation demonstrate 2-year survival of 65% and 5-year survival of 40%.[121,122]

Transplantation is not the perfect treatment for PH, being linked with greater post-transplantation morbidity and mortality than among those patients whose indication is a different disease. Currently, transplantation is recommended for a specific group of patients, who do not respond to vasodilatador therapy, or who exhibit clinical/hemodynamic deterioration during vasodilator therapy (isolated or combined drug use).[15,122,123]

Decrease fructose intake in the food There is ample evidence that increase in intake of High-Fructose-Corn-Syrup and Sugar that is added to almost all foods of Adults and Children including baby formulas will lead to increased production of large amounts of uric acid (secondary to metabolism of Fructose in the live ), which leads to first pass in the lungs. Uric acid interferes with Nitric-Oxide Synthase and


Pulmonary Arterial Hypertension

Evaluation of pulmonary vasoreactivity– acute vasodilator testing

• Inhaled nitric oxide

• Intravenous epoprostenol

• Intreavenous adenosine

• Inhaled Iloprost

Responder Non-responder

Acute calcium channel

blockade testing

Responder Non-responder

Anticoagulation

Chronic oral CCB

? ERA

? PGI2 analogue

Functional class I or II

Anticoagulation

ERA

PGI2 analogue

Right heart

failure

Anticoagulation

ERA

PGI2 analogue

IV epoprostenol

? PDE 5

inhibitor

Lung or

Heart-lung

transplantation

Functional

Class III or IV

Functional

Class I or II

Anticoagulation

ERA

PGI2 analogue

?PDE 5 inhibitor

Anticoagulation

ERA

PGI2 analogue

? PDE 5

inhibitor

Lung or

Heart-Lung

transplantation

Functional class III

Treatment

failure

Treatment

failure

Figure 1a: CCB = Calcium channel blockade; ERA = Endothelin receptor antagonist; PGI2 = Prostacyclin; iNO = Inhaled nitric oxide; PDE 5 = Phosphodiesterase type 5.Treatment guidelines for paediatric pulmonary arterial hypertension (PAH). Treatment strategies for children with idiopathic PAH. Reproduced from reference.[123] Acute responders identifi ed by ≥ 20% decrease in mean pulmonary arterial pressure (mPAP) without alterations in cardiac index and no change in the ratio between pulmonary vascular resistance and systemic vascular resistance in response to vasodilator testing. CCB = Calcium channel-blocker; FC = Functional class; IV = Intravenous; RHF = Right heart failure; †Bosentan became available. Reproduced from reference.[91]


blocks production of NO in the lung vascular endothelial cells ; The high uric acid can also be a late stage of non-alcoholic Fatty liver secondary to chronic High fructose intake. This might not be an acute problem, for diseased states will exacerbate pulmonary hypertension. Some Scientific articles suggest adding Allopurinol for patients with pulmonary hypertension and elevated Uric acid to their medications.[124,125]

PrognosisAlthough much fewer data on the natural history of PAH are available for children than for adults, prospective and retrospective data have indicated that the prognosis of children with IPAH may be even more detrimental than that in adults.[126,127] While the estimated median survival is 2-8 years for all patients, it was reported to be approximately 10 months for children.[128] However, similarly to adults, there is substantial variability in the course of disease progression, with some patients showing deterioration within weeks and others remaining stable for decades.

CONCLUSION

In children with suspected PAH, a methodical evaluation using various diagnostic techniques is necessary to confirm PAH, elucidate its etiology, and determine vasoreactivity. Unlike many pediatric disorders, PAH in children may have a multifocal etiology. The noninvasive diagnosis (clinical examination, electrocardiography, chest radiography and transthoracic echocardiography) is important to detect PAH but lacks sufficient sensitivity to ascertain a diagnosis. Right heart catheterization is required to confirm the presence of PAH and to assess the severity of the hemodynamic impairment. Additional liver, blood, and

lung evaluations may be necessary to determine the clinical class of pulmonary hypertension according to the revised diagnostic classification. Evaluating disease severity from right ventricular function, functional limitation and blood markers of survival and response to therapy will subsequently allow deciding on the most appropriate treatment. Future developments may include additional progress in noninvasive diagnostic studies, especially imaging techniques, and the identification of biomarkers that are specific for the presence, severity and clinical course of PAH [Figure 1a and b].

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Pulmonary Arterial Hypertension

Acute responder Non-responder

CCB IV epoprostenol

Add bosentan ↑

Add IV

epoprostenol

Functional class (FC) I in the presence of moderate-severe

PAH

FC II FC III FC IV

Bosentan ↑

Bosentan↑ IV

epoprostenol

Add

Bosentan ↑

Bosentan ↑ and/or

IV epoprostenol/

prostacyclin

analog

Persistent symptoms

Persistent symptoms

Persistent symptoms

RHF

Figure 1b: Treatment guidelines for paediatric pulmonary arterial hypertension (PAH). Paediatric PAH treatment guidelines for patients with, or without, concomitant intravenous epoprostenol or subcutaneous treprostinil treatment. Acute responders identifi ed by ≥20% decrease in mean pulmonary arterial pressure (mPAP) without alterations in cardiac index and no change in the ratio between pulmonary vascular resistance and systemic vascular resistance in response to vasodilator testing. CCB = Calcium channel-blocker; FC = Functional class; IV = Intravenous; RHF = Right heart failure; †Bosentan became available. Reproduced from reference.[91]


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Pulmonary Arterial Hypertension Associated with HIV Infection – Transcription of the WebinarSonia C. FloresPulmonary Division, University of Colorado Denver, 12700 E. 19th Ave., Aurora, CO 80045W

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Address for correspondence: Prof. Sonia C. Flores, University of Colorado Denver Pulmonary Division, 12700 E. 19th Ave., Aurora, CO 80045, E-mail: sonia.fl [email protected]

DOI: 10.4103/0974-6013.73630

Figure 1: In the PAH Forum webinar on 06/07/10, Professor Sonia Flores discussed the role that HIV Nef may play in the lesions in HIV-associated pulmonary hypertension. She attempted to shed a little light on the basic science and mechanisms which may account for the vascular remodeling that we see in the lungs of these patients

Figure 2: The incidence of pulmonary arterial hypertension (PAH) is much higher in HIV infected individuals than in the general population. However, in some collaborative studies that we are doing with UCSF, a slightly higher prevalence is found than what is reported elsewhere

Figure 3: Lung vascular lesions in HIV related pulmonary hypertension are very similar to those found in iPAH

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Figure 5: Unfortunately, when we fi rst started doing these studies, an appropriate animal model was not available, so we moved onto non-human primate models. We asked several questions

Figure 4: What is the connection between HIV and pulmonary hypertension. Not all patients with HIV get PAH. So, what is the link? There must be something about the virus itself or perhaps some environmental or genetic factor that contributes to this disease

Figure 6: SIV is the monkey counterpart for HIV. The monkeys infected with SIV get a disease very similar to human AIDS. We turned to these infected monkeys in the hope of understanding the natural history for HIV associated pulmonary hypertension

Figure 7: We obtained lungs from several non human primate centers. We acquired archived lungs from California National Primate Centre at UC Davis and the New England Primate Research Centre at Harvard. We also obtained lungs from the John Hopkins Non Human Primate Centre. We looked at SIV infected lungs to try and fi nd lesions, and lo and behold we only found the lesions in the monkeys’ lungs infected with a chimeric virus called SHIV-nef. We did NOT fi nd lesions in any of the monkeys infected only with SIV. We were very surprised because similar fi ndings were also observed in monkeys from two different primate centers. We also tried to fi nd out whether Nef was present in these lesions

Flores: HIV Nef


Figure 9: The picture on the right shows the anatomy of HIV. It contains the usual structural genes but it also contains some accessory proteins like Tat, Nef and VPR. These do not have any enzymatic activity and they do not play a role in structural function, but they are important to the pathogenesis of HIV

Figure 11: Nef is highly immunogenic and essential for pathogenesis of AIDS.So, what do we know about HIV Nef in primates? Macaques infected with SIV in which Nef had been deleted did not progress to primate (simian) AIDS

Figure 8: You would not see human Nef in a macaque infected with SIV (top row). The second row shows that Nef is detected in SHIV-nef infected lungs, which is surprising since the lung vascular cells lack the appropriate HIV receptors. One of the characteristics of Nef is that it can be secreted by infected cells and taken up by uninfected cells. So, we have to see what is Nef. What are the biological effects of the Nef protein, both in infected cells and in innocent bystander cells ?

Figure 10: So to look at little more closely at what Nef does, we focused on its biology

Flores: HIV Nef


Figure 13: Then, there will be transcription and translation of the viral gene Nef

Figure 14: Nef will be myristoylated. When it is myristoylated it associates with cellular membranes

Figure 12: In this picture of a cell infected with HIV, the HIV virus has been integrated into the infected cell

Flores: HIV Nef


Figure 15: As it associates with cellular membranes, it also recruits a variety of cellular proteins, and induces the downregulation of both CD4 (which is then sent to the endocytotic pathway for degradation) and MHC-1

Figure 17: We infected a new cohort of monkeys although we already had some evidence from monkeys previously infected (Marecki et al. 2006). The monkey designations are shown here (Mmu #), and the numbers which you see below them represent the time (in weeks, W) post-infection. What we wanted to do is to follow the natural history by looking at the histology as well as echocardiographic evidence of right heart changes. We have here H and E stained lungs from all the monkeys enrolled in these studies. At 12 weeks post-infection, we see a lot of infl ammation but the pulmonary arteries are still intact. By 13 weeks post-infection, we see a little bit of remodeling

Figure 16: So, it is not a direct effect of Nef downregulating these cellular proteins; it actually affects where they go in the intracellular traffi cking pathways, which is a very interesting characteristic of Nef and something which our collaborator Dr. Pravin Sehgal is investigating in New York. We tried to study the monkey model of SHIV-Nef; the picture on the Figure shows the map for SIVmac 239. This is the SIVmac backbone and the HIV Nef is substituted for the SIV Nef, generating a chimeric virus called SHIV Nef

Figure 18: We quantifi ed immunofl uorescence signals from several markers. The Y-axis is the fl uorescence signal's intensity and the X-axis is weeks post-infection. We have excluded from the analysis a monkey whose genetic background was not identical to that of the previous monkeys. We also excluded a monkey which had severe proteinosis which made it almost impossible to conclude anything because of the antibodies we were using

Flores: HIV Nef


Figure 19: What we see here in the Figure is that there is a linear relationship in terms of CD34 staining, smooth muscle actin as well as Nef staining, and it is directly co-related to the time post-infection. Indeed, as the disease progresses, we see not only increased Nef but also increased CD34 and smooth muscle actin

Figure 21: We did fi nd Nef in two lungs from HIV infected patients with pulmonary hypertension, and you can see that as noted by the arrows in this fi gure. In one case, we can see a pulmonary artery that is still patent but we see Nef staining in both endothelial cells as well surrounding infl ammatory cells, and in the right panel we have a lesion showing Nef positivity

Figure 20: We went back and started asking why Nef induces this remodeling. We found several mutations which were consistently found in monkeys which had been infected with SHIV Nef after passage in vivo, and these mutations are actually denoted by arrows. In the SHIV Nef infected macaques, a histidine to a tyrosine mutation and alanine to either an aspartic acid or a proline mutation were found in Dr. Paul Luciw's lab. We found exactly the same mutations in our cohort of monkeys when we infected them, again suggesting that these mutations may have provided a selective advantage for these virions. Then, we moved to HIV infected patients with pulmonary hypertension. We asked, do we fi nd Nef in these lungs as well?

Figure 22: We did the co-localization. As you can see in the Figure at the top, we have a normal control; in the middle we have an idiopathic pulmonary hypertension patient with a very severe lesion. You can see that there is absolutely no Nef staining. At the bottom, we have an HIV infected patient with pulmonary hypertension and again we can see the color for Factor 8 and Nef, both in the intimal region and in what appear to be parenchymal cells

Flores: HIV Nef


Figure 23: We then hypothesized that changes in the amino acid sequence of Nef in patients with pulmonary hypertension would change vascular endothelial and smooth muscle cell physiology. We postulated that these sequence motifs would be more prevalent in alleles from HIV infected patients with pulmonary hypertension. Our hypothesis includes the structure of Nef or what has been deduced from the structure of Nef, and as you can see, Nef contains several domains capable of interaction with cellular proteins. Nef is a pleiotropic adapter protein that interacts with different cellular proteins. We looked at patients with and without pulmonary hypertension from three different cohorts: the French cohort, kindly provided by Drs. Marc Humbert and Cecile Goujard, one patient from Dr. Nicola Petrosillo and from Dr. Priscilla Hsue from UCSF. And here the demographic characteristics of these patients and the number of patients are shown: Ten from France, six from California and one from Dr. Petrosillo. We also included normotensive controls, both from France as well as from California. We obtained PBMC DNA, plasma and lung tissue, and again the majority had been diagnosed by the Standard Diagnostic Algorithm

Figure 24: The demographics were not remarkable except that HIV patients with pulmonary hypertension were more likely to be on antiretroviral therapy. In terms of CD4 T cell counts and the duration of HIV infection, they were very similar. We catalogued the mutations which were mentioned before in each and every one of the clones we obtained from the patients, and we found not only the same mutations that we had found in the monkeys but also mutations in functional domains. What we found were the mean pulmonary arterial pressures and the hemodynamic characteristics. The French HRPAH and the UCSF HRPAH were higher than the UCSF normotensive. These were statistically different from each other. As we are currently trying to publish our results, I could not include a slide. However, the results can be seen at www.pahforum.com at the 53:15 minute mark. We did the following• DNA sequencing and analysis methods• DNA, plasma or archived lungs shipped to UCD• PCR analyses• Cloning• Sequencing (5–20 clones per patient, n=26)• Phylogenetic analyses Our summary of the sequence results was as follows• A total of 440 HIV-1 Nef clone sequences generated from 27 patients (5–20

clone sequences per patient).• Exclusion of defective proviruses (myristylation, premature stop codons).• Analyses of the entire coding region (about 600 bp) only of subtype B.

Figure 25: We analyzed the entire coding region. In the Y-axis, we have the sum of the Nef mutations and in the X-axis we have the comparison between the French normotensives and the French HRPAH and the San Francisco normotensives and the French HRPAH. These were statistically signifi cantly different from each other.

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Figure 29: Here what we can see is that our CD4 positive Hela cells, which have been transfected with either GFP alone or Nef fused to GFP, have 70% CD4 expression with the GFP alone and only 28% when fused with the Nef. This provides us with a molecular tool which allows us to ask the question whether specifi c Nef alleles cause apoptosis

Figure 28: There have been several in vitro studies of HIV pathogenesis, but I want to call your attention to the one which has shown Nef apoptotic activity on human brain endothelial cells. We wanted to measure this but Nef has no enzymatic activity, so how does one measure this? It may be context- or location-dependent and might differ from cell to cell. We are developing molecular tools, and one of those tools uses a Nef that is fused to a green fl uorescent protein

Figure 26 and 27: These mutations might be used as an early screening tool for those patients likely to develop pulmonary hypertension. We think that Nef, either directly or indirectly, can be taken up by uninfected cells. These cells can then undergo apoptosis and release growth factors, and these growth factors can affect adjacent cells in a paracrine fashion. Or it can be a direct effect whereby HIV infected cells produce growth factors which in turn induce the proliferation of both vascular and smooth muscle endothelial cells

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ACKNOWLEDGMENT

I wanted to conclude here and thank everyone, especially Dr. Sharilyn Almodovar, as she has done most of these studies.

Figure 30: These results suggest that different Nef alleles have a differential effect on CD4 downregulation

Flores: HIV Nef

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Address for correspondence: Ms. Swapna Menon, School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Mehrauli Road, New Delhi 110067, India E-mail: [email protected]

DOI: 10.4103/0974-6013.73631

Disease Genes and Pathways Exploration: A Listing of Basic Bioinformatics Resources

Swapna MenonSchool of Computational and Integrative Sciences, Jawaharlal Nehru University, New Mehrauli Road, New Delhi 110067, India

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Over the past few decades a lot of molecular and genomic data, in general and in the context of various diseases, has accumulated. Public domain data has been databased and curated and is freely available. Multiple databases provide novel views of the underlying genetic, genomic, proteomic or literature data. This in turn facilitates knowledge discovery and disease research. The current article provides an overview of bioinformatics tools and databases to support and enhance research on disease mechanism.

Key words: Bioinformatics, disease genes, literature, transcriptomics, genomics, proteomics, signalling, pathways, mouse, rat

INTRODUCTION

Progress in technology and various branches of life sciences and medical, pharmaceutical, and pharmacological sciences has contributed to greater appreciation of human disease processes. On one hand, high throughput molecular data like genomic sequence, gene expression, and proteomics has accumulated while on the other, bioinformatic databasing, data mining, and knowledge discovery methods are under constant development, so as to convert this data deluge into useful information.

The tracing of transmission routes and epidemiological studies of viruses in recent times exemplify the power and contributions of bioinformatics to real-life situations. There are many examples of the utility of bioinformatics in the study of epidemiology, molecular typing of pathogens, as well as design of vaccines and drugs for infectious diseases. The interfacing of bioinformatics with clinical practice, research, and public health has fostered the development of the field of translational bioinformatics. Among the complex, non-infectious diseases, cancer research and diagnostics has converged well with bioinformatics. For example, biomarkers that distinguish between subtypes of particular carcinomas have been derived from microarray studies. In fact, cancer bioinformatics has grown into a field of its own.[1]

The histopathology, genetics, and molecular biology of pulmonary hypertension have been widely studied using human tissue samples and fluids, and animal models. A bioinformatic perspective in the context of gene sequences, epigenetics, polymorphisms, regulatory regions, post-transcriptional mechanisms, protein sequence, post-translational modifications, protein structure, gene expression analyses, pathway modeling, systems biology,

etc. would yield an enhanced, integrative understanding.

This review briefly lists some of the databases and tools that can be used to explore disease-related genes. Primary bioinformatic databases store the raw molecular data generated from various studies. Secondary or derived databases organize, annotate and/or curate the data from primary databases, such that useful information may be mined. The sources listed here are basic starting points for bioinformatics-led research and knowledge discovery within any disease domain. More comprehensive, specialized lists and/or descriptions are available elsewhere.[2-4]

CURATED AND ANNOTATED RESOURCES AS STARTING POINTS FOR GENE/DISEASE INFORMATION

GeneCards is a consolidated database of all predicted and known human genes including genetic, genomic, transcriptomic, proteomic, function and disease-related information with links to primary and curated databases. Hosted by the Weissman Institute of Science, it is free for academic nonprofit users and requires licensing from corporate users.

UniProt (http://www.uniprot.org/) is the central resource for protein sequence data that includes the well-curated SwissProt database with information on protein function, localization, and disease association.

OMIM (ht tp: / /www.ncbi.nlm.nih.gov/omim) is a comprehensive, curated source of information on human diseases with genetic associations and human genes linked to diseases. Each article is researched and written with pertinent literature references provided for disease gene discovery, genetic association studies, clinical correlations, gene and protein functional studies related to basis of disease, etc. PharmaGKB (http://www.pharmgkb.org/) is a database classified by disease, genes, and drug molecules.

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LITERATURE DATABASES AND TEXT MINING

Peer-reviewed literature is the primary basis of in silico research on disease. Search engines for literature include PubMed (http://www.ncbi.nlm.nih.gov/pubmed/) for links to articles indexed in Medline database and Google scholar (http://scholar.google.com/). PubMed Central (http://www.pubmedcentral.nih.gov/), HighWire Press (http://highwire.stanford.edu/), and E-Biosci (http://www.e-biosci.org/) are databases of freely accessible, full text articles. These databases are searchable by keyword. Other curated databases with search engines for extracting information from literature include: EBIMed (http://www.ebi.ac.uk/Rebholz-srv/ebimed/index.jsp)InfoPubMed (http://www-tsujii.is.s.u-tokyo.ac.jp/info-pubmed/)GoPubMed (http://www.gopubmed.org/)Textpresso (http://www.textpresso.org/)SciMiner (http://jdrf.neurology.med.umich.edu/SciMiner/)Chilibot (http://www.chilibot.net/)BioRAT (http://bioinf.cs.ucl.ac.uk/biorat/)ABNER (http://pages.cs.wisc.edu/~bsettles/abner/)iHOP (http://www.ihop-net.org/UniPub/iHOP/)GeneWays (http://geneways.genomcenter.columbia.edu/)Facta (http://text0.mib.man.ac.uk/software/facta/main.html).

Different databases offer different views of related literature. Thus, patterns and associations that are not evident in keyword-based search and time-consuming manual perusal of hits from primary literature databases may be discovered and appreciated.

GENOMICS

Three of the main sources for genomic maps and data include the NCBI Map Viewer (http://www.ncbi.nlm.nih.gov/mapview), the UCSC genome browser (http://genome.ucsc.edu/cgi-bin/hgGateway), and www.ensembl.org. A number of other resources are hosted by various centers involved in genome sequencing efforts. These databases are annotated with relevant information about genes and markers. Databases devoted to information on polymorphic markers like SNPs include dbSNP (http://www.ncbi.nlm.nih.gov/SNP), HapMap (http://www.hapmap.org), HGVBase (http://www.hgvbaseg2p.org/), JSNP (http://snp.ims.u-tokyo.ac.jp), the SNP consortium (http://snp.cshl.org), and others.

TRANSCRIPTOMICS

The largest public source for raw microarray data is Gene Expression Omnibus (http://www.ncbi.nlm.nih.gov/geo/), hosted at NCBI. Much of the GEO data is mirrored at ArrayExpress hosted by EBI. Gene Expression Atlas (http://www.ebi.ac.uk/gxa/) is a curated subset of ArrayExpress data, searchable by organism and experimental condition. The Stanford microarray database or SMD (http://genome-www5.stanford.edu/) has raw microarray data generated at Stanford University, free for Stanford users and charged for non-Stanford users. However, it hosts a number of microarray analysis tools that are freely available to the public. Users can upload their own data and analyze these online. Standalone versions of tools are also available for local download and use.

The Broad Institute hosts tools for gene expression analysis (http://www.broadinstitute.org/scie nce/software) including GenePattern, Gene Set Enrichment Analysis, GeneCruiser, and

Connectivity Map. Free, open-source tools for microarray analyis include R/Bioconductor, SAM, and TM4.

PROTEIN STRUCTURE AND PROTEOMICS

Databases rich in information on protein families, domains, motifs, and functional sites include InterPro that compiles information from four individually accessible sites, viz., PROSITE, Pfam, PRINTS, and ProDom.

Homology modeling for protein sequences of unknown tertiary structure can be performed using various proprietary tools. One of the best free tools for homology modeling is Modeller from the Sali lab (http://www.salilab.org/modeller/). Various tools are available for visualization of structures like DeepView (http://us.expasy.org/spdbv) and VMD (http://www.ks.uiuc.edu/Research/vmd/). These need to be downloaded locally and provide powerful graphics and manipulations of protein structure and modeling. Publication quality images of these structures can be made using POVray software (http://www.povray.org). Quality check of structures can be performed using PROCHECK (http://www.ebi.ac.uk/thornton-srv/software/PROCHECK/) and VADAR (http://redpoll.pharmacy.ualberta.ca/vadar/).

High throughput proteomics data are available at ExPASy (http://www.expasy.org) and other sites that also provide various tools for in silico protein structure and function analysis.

PATHWAYS

KEGG (http://www.genome.jp/kegg/) is a comprehensive database of interrelated pathways, genomes, and chemicals. KEGG BRITE (http://www.genome.jp/kegg/brite.html) provides functional hierarchies and ontologies. Reactome (http://www.reactome.org/), BioCyc (http://biocyc.org/), and Biocarta (http://www.biocarta.com/) are other comprehensive resources for pathway information on various genomes/organisms. INOH (http://www.inoh.org/) and LINNEA pathways (http://www.invitrogen.com/site/us/en/home/LINNEA-Online-Guides/LINNEA-Pathways.html) are also curated pathway databases.

Databases with different views of pathways, genes, and signaling networks include tools to map microarray expression data onto pathways• PathwayExplorer (http://pathwayexplorer.genome.tugraz.

at/) linked to pathway databases in KEGG, BioCarta, and GenMapp

• GenMAPP (http://www.genmapp.org/)• Molecular Interaction Map (http://discover.nci.nih.gov/mim/

index.jsp)• Pathguide(http://www.pathguide.org/) - a warehouse of

information on genetic interaction networks , transcription factors/gene regulatory networks, metabolic and signaling pathways, protein sequences, protein-protein interactions, and protein-compound interactions.

• UCSD-Nature Signaling Gateway Molecule Pages (http://www.signaling-gateway.org/molecule)

• Pathway Interaction Database (http://pid.nci.nih.gov/)• Database of Cell Signaling (http://stke.sciencemag.org/cm/)• Database of Quantitative Cellular Signaling (http://doqcs.

ncbs.res.in/)

Menon: Listing of bioinformatics resources


Proprietary databases and tools for pathway analysis include:• http://www.ingenuity.com/- Ingenuity Pathways Knowledge

Base created by Ingenuity Systems, Inc.• http://www.biobase-international.com/- TRANSPATH created

by BIOBASE, which contains information about transcription factors and downstream targets.

• http://www.ariadnegenomics.com/- ResNet created by Ariadne Genomics

ANIMAL MODELS

Sequence level data from different organisms and phylogenetic information can be found at CORG (http://corg.molgen.mpg.de), EGO (http://compbio.dfci.harvard.edu/tgi/ego/), HomoloGene (http://www.ncbi.nlm.nih.gov/sites/entrez?db=homologene), OrthoDB (http://cegg.unige.ch/orthodb), Phylome (http://phylomedb.org/), PhyloPat (http://www.cmbi.ru.nl/cdd/phylopat/52/), RatMap (http://ratmap.org/), and TreeFam (http://www.treefam.org/).

BodyMap (http://bodymap.ims.u-tokyo.ac.jp/) is an expression database for mouse and human genes.

Other expression data organized by tissue and developmental stages are available at GXD - Mouse Gene Expression Database (http://www.informatics.jax.org/mgihome/GXD/) and MUGEN Mouse Database (http://bioit.fleming.gr/mugen/). Edinburgh Mouse (EMAP) Atlas (http://genex.hgu.mrc.ac.uk/intro.html) consists of a gallery of 3D models of various developmental stages of the mouse and a connected, text searchable gene expression database, EMAGE. SAGE data from mouse cell lines and tissues have been archived from GEO, as well as individual laboratories

and are available at http://mouse.img.cas.cz/sage/. Mouse phenotype data are available at EuroPhenome (http://www.europhenome.org/about.html), Mouse Phenome Database (http://phenome.jax.org/), and OMIA (Online Mendelian Inheritance in Animals). Histopathological images of mutant and genetically modified mice is available at PathBase (http://www.pathbase.net/). MGD or Mouse Genome Database (http://www.informatics.jax.org/) is a comprehensive resource for genes, phenotypes, pathways, orthology, expression, and strains. The equivalent comprehensive resource for another valuable rodent model is the Rat Genome Database (http://rgd.mcw.edu/).

In conclusion, a number of valuable resources are available for streamlining and supporting the research and discovery process in any disease domain. Complementing various search strategies, bioinformatics techniques, and databases leads to a holistic view of disease at the cellular, molecular and pathway level.

REFERENCES

1. Nagl S. Cancer Bioinformatics: From Therapy Design to Treatment, ISBN: 978-0-470-86304-6. 2006.

2. Cochrane GR, Galperin MY. The 2010 Nucleic Acids Research Database Issue and online Database Collection: a community of data resources. Nucleic Acids Res 2010;38:D1-4.

3. Yang Y, Adelstein SJ, Kassis AI. Target discovery from data mining approaches. Drug Discov Today 2009;14:147-54.

4. Baxevanis AD , Ouellett e BFF. Bioinformatics: A Practical Guide to the Analysis of Genes and Proteins. 3rd ed. ISBN: 978-0-471-47878-2, 2004.

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Author Help: Reference checking facility

The manuscript system (www.journalonweb.com) allows the authors to check and verify the accuracy and style of references. The tool checks the references with PubMed as per a predefined style. Authors are encouraged to use this facility, before submitting articles to the journal.

• The style as well as bibliographic elements should be 100% accurate, to help get the references verified from the system. Even a single spelling error or addition of issue number/month of publication will lead to an error when verifying the reference.

• Example of a correct style Sheahan P, O’leary G, Lee G, Fitzgibbon J. Cystic cervical metastases: Incidence and diagnosis using fine needle aspiration biopsy.

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Address for correspondence: Dr. Bhupesh Kumar, Department of Anaesthesia and Intensive Care, Post Graduate Institute of Medical Education and Research, Chandigarh, India. E-mail: [email protected]

DOI: 10.4103/0974-6013.73632

Persistent Pulmonary Artery Hypertension Following Supracardiac Total Anomalous Pulmonary Venous Connection Repair

Kumar B., Mutu R., Puri G. D., Singh Anju1, Rana S. S.2

Department of Anaesthesia & Intensive Care, 1Obstretics & Gynaecology and 2Cardiac Surgery, Post Graduate Institute of Medical Education and Research, Chandigarh, IndiaC

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We report a case of supracardiac total anomalous pulmonary venous connection (TAPVC) with persistent post operative pulmonary hypertension unresponsive to sildenafi l. Only after ligation of vertical vein, echocardiography could detect a perimembranous ventricular septal defect (VSD). Following VSD closure, pulmonary artery pressure declined and patient improved.

Key words: pulmonary hypertension, Sildenafi l, total anomalous pulmonary venous connection, vertican vein

INTRODUCTION

Pulmonary hypertension persists with ill-defined frequency in few patients(0-18%), after successful repair of total anomalous pulmonary venous connection (TAPVC).[1,2] We describe a case of persistent pulmonary hypertension following TAPVC repair, that subsided following ligation of vertical vein and closure of a residual ventricular septal defect (VSD).

CASE REPORT

A 2½-year-old female, weight 8 kg, with history of repeated episodes of pneumonia and intermittent episodes of cyanotic spells since 3 months of age, presented to the pediatric cardiology outpatient department of our institution. On admission the child was lethargic and tachypnoeic (RR 48/min) with central cyanosis. Her heart rate was 128/min. Clinically the patient had features of severe pulmonary hypertension and congestive heart failure. Chest X-ray showed typical snowman appearance [Figure 1]. Echocardiogram revealed obstructed supracardiac TAPVC with enlarged right atrium, right ventricle and dilated main pulmonary artery. All four pulmonary veins formed a common chamber that drained into the innominate vein through a vertical vein. There was severe tricuspid regurgitation with right ventricular systolic pressure (RSVP) of 90 mmHg.

The patient underwent intracardiac repair under cardiopulmonary bypass (CPB). The common chamber was anastomosed to left atrial posterior wall and vertical vein was left open. The postoperative echocardiogram

revealed adequate flow at anastomotic site, flow in vertical vein, but the pulmonary pressure remained systemic. (RVSP= 100 mmHg + Right Atrial pressure). The patient was started on sildenafil 0.5 mg/kg 8th hourly besides continuation of ionotropes. There was no hemodynamic improvement till 4th postoperative day and the repeat echocardiogram revealed torrential flow across vertical vein. The patient was taken up for re-surgery and the vertical vein was snared. Postoperatively there was no hemodynamic improvement and the echocardiogram revealed persistent high PA pressures. A trial of weaning failed. Repeat echocardiogram done on day 8 revealed 8 mm residual perimembranous VSD. Re-surgery was performed on day 9 and the VSD was closed. Postoperatively the patient improved and PA pressure decreased to two-thirds of the systemic pressure. The echocardiogram done on day 11 revealed significant decrease in the pulmonary pressure (RVSP= 25 mmHg+ RAP) and no residual VSD. The patient was weaned off from the mechanical ventilator on 14th day and discharged from intensive care unit on day 16.

Figure 1: Preoperative chest X-ray. Showing typical snow man appearance along with bilateral infi ltrates

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DISCUSSION

Persistent pulmonary hypertension has a major impact on the outcome following correction of TAPVC. It may occur as a consequence of residual obstruction of the pulmonary venous system or, due to the other contributing factors like increased neonatal pulmonary vasoreactivity, endothelial injury induced by CPB and intrauterine anatomic changes in the pulmonary vascular bed due to the disease itself.[3,4]

In the present case, the postoperative echocardiogram revealed adequate flow at left atrial–common chamber anastomosis and in the vertical vein, ruling out obstruction of the pulmonary venous drainage. In addition, pulmonary hypertension persisted even after the addition of oral sildenafil, decreasing the possibility of the above mentioned contributory factors as the cause of pulmonary hypertension.[5] So initially it was felt that the torrential flow across the vertical vein must be producing enough left to right shunt to contribute to the persistence of pulmonary hypertension.

The vert ical vein is usually l igated during TAPVC correction.[6] Elective non-ligation is not favored as spontaneous closure does not happen all the time and hence cannot be taken for granted.[7] Some surgeons are in favor of elective non-ligation of the vertical vein as it minimizes the extent of surgical resection and reduces the duration of CPB. It is also postulated that the left atrium lacks its normal compliance and reservoir function during early infancy. In such a situation – the unligated vertical vein acts as a shunt providing early hemodynamic stability and survival.[8] In the present case the vertical vein was initially left unligated because of the obstructed nature of TAPVC and poor preoperative general condition of the child.

Subsequently, after ligation of the vertical vein the repeat postoperative echo showed another left-to-right shunt in form of VSD. Initial postoperative echo could not recognize VSD, possibly because of the systemic RV pressures; in addition the persistence of the vertical vein must have interfered with the echocardiographic recognition of the increased flow across the septum and the pulmonary valve. After the second surgery and ligation of the vertical vein, the absence of any other reason for the increase in pulmonary arterial flow made the recognition of VSD possible. The patient improved drastically after VSD closure and the PA pressure came down.

In cases where the pulmonary artery pressure fails to come down following surgery of TAPVC, residual shunts like the non-ligated vertical vein or VSD may be the culprits. So any anatomical defects causing a residual shunts should be excluded. In addition, intraoperative transesophageal echocardiography after

sternotomy, intraoperative pressure measurements and oximetry would have been valuable in this case.[9]

CONCLUSION

Elective nonligation of vertical vein is not favored during TAPVC correction, as spontaneous closure does not always happen. The vertical vein is left open if there is increased left atrial pressure or left ventricular dysfunction. However, a non-ligated vertical vein may the reason for a residual shunt and persisting PH. Also this case highlights the importance of excluding shunts at different anatomical levels which may be missed, in the presence of severe PH.

REFERENCES

1. Ricci M, Elliot M, Cohen GA, Catalan G, Stark J, De Leval MR, et al. Management of pulmonary venous obstruction aft er correction of TAPVC: Risk factors for adverse outcome. Eur. J. Cardiothoracic Surg 2003; 24:28-36.

2. Lincoln CR, Rigby ML, Mercanti C, Al-Fagih M, Joseph MC, Miller GA, et al. Surgical risk factors in total anomalous pulmonary venous connection. Am J Cardiol 1988;61:608-11.

3. Wessel DL, Adatia I, Giglia TM, Thompson JE, Kulik TJ. Use of inhaled nitric oxide and acetylcholine in the evaluation of pulmonary hypertension and endothelial function after cardiopulmonary bypass. Circulation 1993;88:2128-38.

4. Haworth SG. Total anomalous pulmonary venous return: Prenatal damage to pulmonary vascular bed and extrapulmonary veins. Br Heart J 1982;48:513-24.

5. Raja SG, MacArthur KJ, Pollock JC. Is sildenafi l eff ective for treating pulmonary hypertension aft er pediatric heart surgery. Interact CardioVasc Thorac Surg 2006;5:52-4.

6. Kirklin JW, Barratt -Boyes BG. Total anomalous pulmonary venous connection. In: Kirklin JW, Barratt -Boyes BG, editors. Cardiac Surgery. 2nd ed. New York: Churchill Livingstone; 1993. p. 645-73.

7. Kumar RN, Dharmapuram AK, Rao IM, Gopalakrishnan VC, Pillai VR, Nazer YA, et al. The fate of the unligated vertical vein after surgical correction of total anomalous pulmonary venous connection in early infancy. J Thorac Cardiovasc Surg 2001;122:615-7.

8. Cope JT, Banks D, McDaniel NC, Shockey KS, Nolan SP, Kron IL. Is vertical vein ligation necessary in repair of total anomalous pulmonary venous connection? Ann Thorac Surg 1997;64:23-9.

9. Chang YY, Chang CI, Wang MJ, Lin SM, Chen YS, Tsai SK, et al. The safe use of intraoperative transesophageal echocardiography in the management of total anomalous pulmonary venous connection in newborns and infants: A case series. Paediatr Anaesth 2005;15:939-43.

Kumar, et al.: Pulmonary hypertension following total anomalous pulmonary venous connection repair



Autophagy in Pulmonary Arterial Hypertension: CommentarySwapna MenonSchool of Computational and Integrative Sciences, Jawaharlal Nehru University, New Mehrauli Road, New Delhi - 110 067, India

Lee SJ, Smith A, Guo L, Alastalo TP, Li M, Sawada H, et al. Autophagic Protein LC3B Confers Resistance Against Hypoxia-Induced Pulmonary Hypertension. Am J Respir Crit Care Med 2010 [In Press].

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Address for correspondence: Dr. Swapna Menon, School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Mehrauli Road, New Delhi - 110 067, India. E-mail: [email protected]

DOI: 10.4103/0974-6013.73633

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BACKGROUND

Autophagy or digestion of self begins with a membrane that surrounds cellular organelles, like mitochondria and endoplasmic reticulum, and formation of the autophagic vacuole or autophagosome. Mammalian autophagy proceeds with a few maturation steps, including the fusion of this vacuole with endosomal vesicles and multivesicular bodies. The matured autophagosomes, finally, fuse with lysosomes leading to digestion of the engulfed organelles. Thus, for autophagy to occur, a healthy endomembrane system and lysosomes are required. Conversely, autophagy is required for turnover of these organelles, when they are old or damaged. Autophagy also has an important role in tissue differentiation and development, during normal health. Decreased autophagy is associated with organismal aging. The autophagy-related genes (ATGs) were discovered in the 1990s; each of these has a distinct role in this evolutionarily conserved pathway.[1] In the context of disease, autophagy is involved in adaptive and innate immunity, as well as, in pathological response of affected tissue. It is known to have a role in cancer, neurodegenerative disease, heart disease etc.

Pulmonary vasoconstriction and cellular proliferation, leading to muscularized arteries and plexiform lesions, are known to be the physiological and histological hallmarks of PAH. The role of autophagy in pulmonary arterial hypertension pathology has never been reported, prior to the publication by Lee et al.

SUMMARY

Microtubule-associated protein-1 light chain 3B (LC3B) is one of the key players of autophagic response. Conversion of LC3BI to the active form, LC3BII, is an important step for autophagy to proceed. This paper reports autophagy in lung samples from PAH patients and mouse models of hypoxia by immunohistochemical staining, as well as, protein and mRNA expression of LC3B. In primary cultures of human PAECs and PASMCs, exposed to hypoxia, the

authors demonstrated a time-dependent increase in protein levels of LC3B and its activated form, LC3BII, as well as, autophagosome formation.

C3B knockout mice, exposed to hypoxia, were evaluated for pulmonary hypertensive responsiveness. The normoxic measures for RVSP, RV hypertrophy and pulmonary vascular histology were comparable for both mutant and wild type mice. Hypoxia induced significantly greater responses in each of the three measures in the C3B knockouts, compared to wild type. Further, inhibiting LC3B expression by siRNA knockdown of PAECs and PASMCs, exposed to hypoxia and mitogens, increased cellular proliferation, while overexpressing LC3B decreased proliferation in these cells. The hyperproliferation appeared to be triggered through the ROS-HIF-1α, as indicated by increased levels of both effectors in LC3B knockdown PAECs.

Egr-1 regulation of LC3B in hypoxia was demonstrated by CHIP assays of Egr-1 binding to LC3B promoter, increased expression of Egr-1 and inhibition of LC3B expression, upon Egr-1 knockdown. Egr-1 knockout mice showed significantly increased RVSP, RV hypertrophy and pulmonary vascular remodeling, as well as, LC3B expression as compared to wild type mice.

Caveolae are membrane microdomains important for localization of effectors and signal transduction. The authors examined the localization of LC3B and Egr-1 in the caveolae in both PAECs and PASMCs. Under normoxia, these molecules were localized to the caveolae. Under hypoxic conditions, these molecules, as well as, caveolin-1 were shown to localize to the cytoplasm.

COMMENTARY

The valuable contribution of this work is the observation of autophagy in pulmonary vascular tissue from PAH patients. The studies were conducted on lung tissue from five IPAH and six APAH patients with different etiologies and on the hypoxic mouse model. The authors also have unpublished data on two other mouse models demonstrating increased LC3B expression. Further, according to the knockout and knockdown studies conducted, autophagy appears to be an adaptive and protective mechanism, acting through the hypoxic pathway and affected by caveolar trafficking.


Oxygen sensing, organellar dysfunction, membrane traffi cking to cellular proliferation, apoptosis, autophagy in pulmonary arterial hypertensionBy identifying autophagy in PAH, this paper has laid the ground for further dissection of organellar pathways that influence autophagy. These are briefly discussed below.

Mitochondrial dysfunctionMitochondrial maintenance and turnover is essential for cellular homeostasis and survival. Mitophagy is a specialized form of autophagy specifically targeted toward mitochondria. Mitochondrial dysfunction and abnormal morphology, ROS generation and oxidative stress as well as autophagic dysregulation are implicated in aging, neurodegenerative disease, diabetes etc.

In PAH: Mitochondrial dysfunction mediated through K+ channels and reactive oxygen species are implicated in hypoxic vasoconstriction,[2] as well as, cellular proliferation in pulmonary hypertension. In addition, the metabolic shift from oxidative to glycolytic pathway (Warburg effect) is implicated in increased proliferation, characteristic of pulmonary vascular remodeling.[3]

Lysosomal pathwayLysosomal membrane permeability (LMP)[4] is one of the early events leading to apoptosis. LMP leads to autophagy, which in turn, may lead to either caspase-independent apoptotic cell death or to cell repair. Lysosomes also act in concert with mitochondria in oxidative stress responses. Lysosomal disorders lead to altered calcium homeostasis, oxidative stress, inflammation, altered lipid trafficking, autophagy, endoplasmic reticulum stress, and autoimmune responses.[5]

In PAH: The role of lysosomes in BMPRII function/trafficking or in PAH, in general, has not been explored, previously. A recent publication, for the first time, identifies a lysosomal pathway involved in constitutive degradation of cell surface BMPRII in HeLa cells infected with KSHV.[6]

Golgi dysfunctionPerturbation of endoplasmic reticulum (ER) or Golgi morphology or trafficking/secretory function, for example, via blocks in NSF/SNARE and sec proteins can inhibit autophagy.[7]

In PAH: Ultrastructural studies on PAECs, human lung tissue and tissue from monocrotaline rat models and SHIV-nef infected macaques[8] have identified abnormal Golgi morphology, blocked trafficking and megalocytosis of PAECs.[9]

Membrane traffi ckingThe eukaryotic cell has a number of membrane trafficking or endocytic routes for fluid and particulate uptake. Endocytosis includes clathrin-mediated, caveolar and clathrin- and caveolin-independent pathways regulated by Cdc42, Arf6 or RhoA. Endocytic pathways result in plasma membrane remodeling, lipid homeostasis and signal transduction.

In PAH: The role of caveolin-1 association/inhibition and caveolar trafficking in PAH is well appreciated and has been

briefly discussed, in the context of eNOS regulation in a previous issue.[10] RhoA/MAP kinase pathways are also known to be perturbed in PAH.

To summarize, the broad questions regarding the mechanism of PAH are the following: What is the natural history or progression from hypoxic insult to autophagy, apoptosis versus hyperproliferation? Further, is hypoxic insult the necessary and sufficient trigger required to set the autophagic process in motion? Do the reported golgi and mitochondrial dysfunction and trafficking defects impair autophagic response in PAH or, conversely, are these markers of autophagy? What are the lysosomal pathways that aid or inhibit autophagy in PAH?

There is a complex relationship between redox signaling and autophagy in ventricular remodeling.[11] Development of cancer involves a tangled interplay between hypoxia, autophagy, apoptosis and hyperproliferation leading to angiogenesis versus necrosis.[12] While defective organelles impair autophagy, autophagy also leads to appearance of dysmorphic organelles. Thus, the cause, effect and mechanism question is understandably complex, especially with regard to PAH, where one is dealing with tissues that represent severe, late stages of human disease. Understanding cellular homeostatic balance and contributions of organelles and trafficking to autophagy, apoptosis and cellular proliferation in the development of other diseases like cancer has been and will be useful.

REFERENCES

1. Boulais J, Trost M, Landry CR, Dieckmann R, Levy ED, Soldati T, et al. Molecular characterization of the evolution of phagosomes. Mol Syst Biol 2010;6:423.

2. Michelakis ED, Thébaud B, Weir EK, Archer SL. Hypoxic pulmonary vasoconstriction: Redox regulation of O2-sensitive K+ channels by a mitochondrial O2-sensor in resistance artery smooth muscle cells. J Mol Cell Cardiol 2004;37:1119-36.

3. Archer SL, Gomberg-Maitland M, Maitland ML, Rich S, Garcia JG, Weir EK. Mitochondrial metabolism, redox signaling, and fusion: A mitochondria-ROS-HIF-1alpha-Kv1.5 O2-sensing pathway at the intersection of pulmonary hypertension and cancer. Am J Physiol Heart Circ Physiol 2008;294:H570-8.

4. Vitner EB, Platt FM, Futerman AH. Common and uncommon pathogenic cascades in lysosomal storage diseases. J Biol Chem 2010;285:20423-7.

5. Kurz T, Terman A, Gustafsson B, Brunk UT. Lysosomes and oxidative stress in aging and apoptosis. Biochim Biophys Acta 2008;1780:1291-303.

6. Durrington HJ, Upton PD, Hoer S, Boname J, Dunmore BJ, Yang J, et al. Identifi cation of a lysosomal pathway regulating degradation of the bone morphogenetic protein receptor type II. J Biol Chem 2010 [In Press].

7. Mĳ aljica D, Prescott M, Devenish RJ. Endoplasmic reticulum and golgi complex: Contributions to, and turnover by, autophagy. Traffi c 2006;7:1590-5.

8. Sehgal PB, Mukhopadhyay S, Patel K, Xu F, Almodóvar S, Tuder RM, et al. Golgi dysfunction is a common feature in idiopathic human pulmonary hypertension and vascular lesions in SHIV-nef-infected macaques. Am J Physiol Lung Cell Mol Physiol 2009;297:L729-37.

9. Sehgal PB, Mukhopadhyay S. Pulmonary arterial hypertension: A disease of tethers, SNAREs and SNAPs? Am J Physiol Heart

Menon: Autophagy in pulmonary arterial hypertension


Menon: Autophagy in pulmonary arterial hypertension

Circ Physiol 2007;293:H77-85.10. Zhao YY, Zhao YD, Mirza MK, Huang JH, Potula HH, Vogel

SM, et al. Persistent eNOS activation secondary to caveolin-1 defi ciency induces pulmonary hypertension in mice and humans through PKG nitration. J Clin Invest 2009;119:2009-18.

11. Gurusamy N, Das DK. Autophagy, redox signaling, and ventricular remodeling. Antioxid Redox Signal 2009;11:1975-88.

12. Eisenberg-Lerner A, Bialik S, Simon HU, Kimchi A. Life and death partners: Apoptosis, autophagy and the cross-talk between them. Cell Death Diff er 2009;16:966-75. Source of Support: Nil, Confl ict of Interest: None declared.

Details of the citation listThe list of citations related to pulmonary circulation is available at http://pvri.info/pulmonary-hypertensionThis section “Pulmonary Hypertension” is placed in E-books under Discussions tab. The list was obtained using the following search strategy in PubMed: Keywords: “pulmonary hypertension” OR “pulmonary arterial hypertension”

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Address for correspondence: Dr. Med Alexandra Heath, Pediatric Cardiologist and Interventionist, Head of the Pediatric Cardiology Unit, Kardiozentrum, Obrajes, Calle 14 No. 669, La Paz – Bolivia. E-mail: [email protected]

DOI: 10.4103/0974-6013.73634

Does High Altitude Protect Against Irreversible Pulmonary Hypertension?

Alexandra Heath, Stewart K.1, Mendes J., Ramirez M., Freudenthal F.Kardiozentrum, Obrajes, Calle 14 No. 669, La Paz – Bolivia and 1São Paulo’s Heart Institute (InCor), Brazil

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Aim: To present observations regarding the pulmonary pressure characteristics of children and young adults with congenital heart defects who were born and living in high altitude, before and after correction of the defect.Materials and Methods: We analyzed 2 groups of patients. Group 1: 21 patients were diagnosed with clinically signifi cant ventricle septum defects (VSD), measuring an average of 17 mm in its larger diameter (7–35 mm), aged 6.2 years on average (range: 1–23 years), with preoperative New York Heart Association (NYHA) class being an average of 2.1. Their arterial oxygen saturation was 92% on average (82%–99%) and systolic pulmonary pressure (SPP) was 64 mmHg, (range: 22–94 mmHg). Group 2: 60 patients were diagnosed with hemodynamically signifi cant patent ductus arteriosus (PDA), 4.85 mm in its minimum diameter (range: 1.8–13 mm), aged 9.2 years on average (range: 9 months–30 years), in whom the SPP measured preoperatively reached 50.6 mmHg (range: 21–94 mmHg). The intervention involved VSD surgical repair or interventional closure of the PDA. Results: Postinterventional results: Group 1 improved its NYHA functional class to an average of 1.2; the mean oxygen saturation rose to 93% (88%–96%) and the SPP dropped to 36 mmHg (range: 20–61 mmHg). In Group 2, the SPP dropped to an average of 39.8 mmHg (range: 16–79 mmHg). The preoperative SPP to systolic aortic pressure ratio was on average 53.15% (range: 22.58%–96.84%); postoperative, the ratio dropped to 38.39% (16.7%–82%). Conclusions: After intervention, the average SPP invariably dropped in both the groups, although its levels could not be considered normal in all the patients. In addition, the intervention led to clinical improvement. High altitude seems to give this group of patients a protection against irreversible changes in the pulmonary circulation. More prospective, controlled studies and a longer follow-up are needed to confi rm this observation.

Key words: Congenital heart disease, high altitude, PDA, pulmonary hypertension, VSD

INTRODUCTION

There are around 140 million people worldwide who live in cities located higher than 2500m above sea level.[1]

This includes almost 5 million Bolivians. The relationship between barometric pressure (BP) and high altitude (HA) is not linear and does not follow the standard atmosphere model. Instead, pressures are higher at certain altitude as the relationship between BP and altitude is latitude-dependent. The Bolivian highlands, as well as most high mountains of the world, are relatively near the equater [Figure 1]. In La Paz, the average bp is 560mmHg, the arterial oxygen saturation varies from 85% to 90% and the partial pressure of oxygen (PaO2) is about 60 mmHg.[2] Not only does bp vary with altitude, but there are marked variations according to the month of the year, the lowest point being reached during the winter. Other factors which must be considered at a HA are the temperature, which falls with increasing altitude at the rate of about 1°C for every 150m, and the very low absolute humidity, which frequently causes dehydration. It appears that people living at a very HA are in a state of chronic

volume depletion. Also of interest is that there is a marked increase in the intensity of solar radiation at HA, leading to an extreme variation in daily temperature. Thus the main environmental stresses of living in mountain regions are the low temperature and the hypoxia due to HA.

People have been living in the Bolivian highlands for approximately 600 generations; the earliest archeological evidence of human occupation dates back at least 12,000 years.[3] Living at sea level and suddenly arriving in the highlands is a challenge to our normal physiology: there are changes in the hypoxic ventilator response (HVR) and in the hypercapnic ventilator responses (HCVR). These changes in the chemical control of breathing causes the well-known increase in ventilation and result in a lower partial pressure of carbon dioxide and higher PaO2, which are characteristic of acclimatization. Most HA visitors are able to undergo normal daily activities after 2–3 days of adaptation time and to carry out exercises after 4 weeks, which is corroborated by the study of Lundby et al., 2004.[4]

Healthy HA residents have a lower ventilation at rest and exercise and blunted HVR. Despite these facts, their Oxygen saturation and PaO2 are normal. They have a higher lung diffusing capacity than lowlanders which is an important advantage at altitude where work rate is limited by diffusion. Their total lung capacity is about 500mL greater than at

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sea level, most of the increase being due to increased residual volume.[5] The lungs of long-term residents at HA show marked changes related to pulmonary hypertension (PH). Bands of smooth muscle develop in the pulmonary arterioles. These small vessels develop a media of circularly oriented smooth muscle bonded by internal and external elastic laminae. Occlusive intimal fibrosis apparently does not occur. These structural changes are consistent with the fact that the pulmonary arterial pressure falls only around 20% when oxygen is breathed.[1] It may be noted that Aymaras, unlike Tibetans, do not appear to have an increased expired nitric oxide as an adaptive advantage for life in the highlands.[6] Also of importance is the increase in the red cell number, and the hemoglobin concentration which increases the oxygen-carrying capacity. There is a combined influence of age and HA on the mean pulmonary artery pressure, and the degree of HA ancestry is another very important factor. Further exploring HA physiology is beyond the scope of this report. Some reports have shown that congenital heart disease (CHD) is more frequent with a different distribution of its incidence in HA populations. Patent ductus arteriosus (PDA) is almost 10 times more frequent in the HA population.[7,8] In addition, isolated elevated systolic pulmonary pressure (SPP) is more frequent, and its performance in the natural history of posttricuspid shunts has special characteristics.

The economic and geographic situation of Bolivia with people living in isolated areas without access to health providers, combined with the problems with the medical system, leads to a very late diagnosis and sometimes forbids any treatment. Another big problem is that neither the state nor the few health insurance companies pay for heart surgeries. As a result, we often see young adults (ie. Older children) who were not previously diagnosed and/or treated. We want to present our observations regarding the pulmonary pressure characteristics of children and young adults with congenital heart defects who were born and living in HA, before and after correction of the defect.

MATERIALS AND METHODS

We conducted a retrospective analysis of the health records of two patient groups living between 3600m and 5000m. All of them were diagnosed to have post-tricuspid shunts which have been correctd by surgical patch closure in cases of VSD and by interventional techniques in cases of PDA.

We included 21 subjects in Group 1, who were diagnosed to have hemodynamically relevant VSD with a size of, on average, 17mm in its larger dimension (range: 7–35mm). The mean age of the patients were 6.2 yrs(1-23 yrs). The mean preoperative New York Heart Association (NYHA) class was 2.1. Their oxygen saturation was 92% (range: 82%–99%). As previously stated, the financial recourses were limited, so it was not possible to perform a cardiac catheterization with the measurement of Qp/Qs and resistance of all the patients. All the patients underwent surgical repair using the standard technique and stayed in hospital for an average of 10 days.

We included 60 patients in Group 2, who were diagnosed with hemodynamically relevant PDA with an average diameter of 4.85mm (range: 1.74–13mm). The patients were on average aged 9.2 years (range: 9 months–30 years) and weighed 27.5

kg (range: 5.25–60 kg). There were 39 females and 21 males, who were candidates for percutaneous interventional closure. We used a PDA-R ductal occluder [Figure 2] made from nitinol wire with polyester membranes and a Nit-Occlud Coil, both from pfm (Nitocclud Coil® from pfm Medical, Cologne, Germany and PDA-R Ductal Occluder® from pfm srl, La Paz, Bolivia). All the patients were hospitalized for 1 day and received sildenafil 1 mg/kg/dose Q8 for at least 30 days after the procedure. There was no rebound in the pulmonary pressure during 6 months of follow-up. There were no early or late deaths. Only 1 patient of this series moved to a lower altitude, where he now lives with his family.

RESULTS

In Group 1, all the children had a good surgical outcome. The mean pulmonary artery pressure dropped from 64mmHg (range: 22–94 mmHg) to 36 mmHg (20–61 mmHg) after occlusion/repair of the defect [Figure 3]. In Group 2, the mean pulmonary arterial pressure was 39.8mmHg (range: 16–79 mmHg) and it dropped to 24 mmHg (range: 5–58 mmHg) immediately after the intervention. The pre-intervention ratio between systolic pulmonary and aortic pressures dropped from 53.15% to 38.39% after intervention (SPP divided by the systolic systemic pressure). In cases where the mean pulmonary artery pressure exceeded 25mmHg, a hyperoxia test was performed to ensure pulmonary bed reactivity, and we also waited 20mins before delivering the PDA occlusion device to ensure that PH was reversible.

DISCUSSION

The adaptation to HA follows a process of natural selection through millennia and countless generations of life. The findings suggest that the Tibetan natives would have reached optimal genotypic adaptation, whereas Andean natives are still undergoing the process, having reached phenotypic adaptation.[1] In La Paz, we have observed some differences in the distribution of CHDs: the incidence of PDA is 4 times the reported incidence in the general population; these PDAs are also wider and larger than in other published studies; there are 3 times more atrial septal defects; and also 10 times more PH cases in the absence of CHD. Not only is the distribution of CHD different, but the natural history of PH in posttricuspidal left-to-right shunting is too. These observations could be the result of the hypobaric hypoxic environment which they are subjected to. Moreover, we also speculate that there is a higher pressure set point, especially in the adapted HA dweller to establish the actual diagnosis of PH as a disease. We also wonder as to what extent PH in the HA inhabitant is physiologic and protective. Other authors have written about the protection factors for the HA inhabitants. Intermittent hypoxia has a protecting influence on the myocardium.[9] The presence of a thicker muscular layer in the pulmonary arterioles leads us to think that this feature can be responsible for the better outcomes of our patients. This is because the pulmonary artery does not undergo irreversible changes, and so it prevents necrosis of the intima or development of pulmonary artery aneurysms. These children develop early PH close to systemic levels, which might function as a natural band protecting their lungs. Clinically, these children usually develop milder forms of heart failure and can survive throughout infancy and childhood. The NYHA functional class in these patients improved after corrective surgery or intervention.

Heath: High altitude and protection against pulmonary hypertension


As the pulmonary vessels are protected from deforming, and the left-to-right shunting is repaired, the pulmonary pressure drops. We have not found cases of typical Eisenmenger syndrome in our patient group of people younger than 25 years.

LIMITATIONS OF THIS STUDY

Studies including larger number of patients and a longer period of follow-up are needed in conjunction with anatomopathologic studies, to support our hypothesis. Also, it is important to develop guidelines regarding when and how to intervene in CHD and/or PH in HA. Unfortunately, since we do not have a reliable database on mortality, it is possible that there are more children having a worse outcome than the ones we studied in our series. Source of Support: Nil, Confl ict of Interest: None declared.

Heath: High altitude and protection against pulmonary hypertension

Figure 2: PDA-R Ductal Occluder® from pfm srl, La Paz, Bolivia, lateral view

Figure 3: Systolic Pulmonary Presure (SPP) before and after the ductus closure

Figure 1: Illimani, the second highest peak in Bolivia in the Andes. The word Illimani means Golden Eagle. It is 6438 meters high

REFERENCES

1. Penaloza D, Arias-Stella C. The heart and pulmonary circulation at high altitudes-healthy highlanders and chronic mountain sickness. Circulation 2007;115:1132-46.

2. West J, Schoene R, Milledge J. Geography and human response to altitude. In: West J, editor. High altitude medicine and physiology. 4th ed. London: Hodder Arnold; 2007. p. 27-37.

3. Rupert J, Hochachka P. Genetic approaches to understanding the human adaptation to high altitude in the Andes. J Exp Biol 2001;204:3151-60.

4. Lundby C, Calber J, Van Hall G, Saltin B, Sander M. Pulmonary gas Exchange at maximal exercise in Danish lowlanders during 8 weeks of acclimatization to 4,100 m and in high altitude Aymara natives. Am J Physiol Reg Integr Comp Physiol 2004;287:R1202-8.

5. Greksa L. Growth and development of high altitude residents. High Alt Med Biol 2006;7:116-24.

6. Stuber T, Sartori C, Salmón C, Hutt er D, Thalmann S, Turini P, et al. Respiratory nitric oxide and pulmonary artery pressure in children of Aymara and European ancestry at high altitude. Chest 2008;134:996-1000.

7. Penaloza D, Sime F, Ruiz L. Pulmonary hemodynamics in children living at high altitudes. High Alt Med Biol 2008;9:199-207.

8. Miao CY, Zuberbuhler JS, Zuberbuhler JR. Prevalence of congenital cardiac anomalies at high altitude. J Am Coll Cardiol 1988;12:224-8.

9. Kolar F, Neckar J, Borchert G, Stakheev D, Ostadal B. On the Eff ects of Chronic Hypoxia on Diseases at High Altitude. In: Second Symposia on chronic hypoxia Aug 2th- 9th, 2008 – La Paz, Bolivia.


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Adnot S, Chaouat A. Pulmonary hypertension with chronic obstructive pulmonary disease 75Almodovar S see Petrosillo N et al.Archer SL see Yuan JX et al.Banjar HH. Review of management guidelines of pulmonary arterial hypertension in the pediatric population 100Barst RJ. Como O Epoprostenol Vem Mudando O Desfecho Dos Pacientes Com Hipertensão Arterial Pulmonar? S24Burton R. HIV-associated pulmonary hypertension: A South African perspective 97Butrous G, Morrell N. PVD in schistosomiasis task force 44Casserly B, Klinger JR. The clinical utility of brain natriuretic peptide in pulmonary arterial hypertension 85Chabot F see Chaouat A et al.Champion HC see Zeineh NS et al.Chaouat A see Adnot S et al.Chaouat A, Gomez E, Chabot F. Pulmonary hypertension in chronic obstructive pulmonary disease: Three case reports 80Chong CC. Ambrisentana: Um Novo Antagonista, Não Sulfonamídico, Seletivo Do Receptor Da Endotelina No Tratamento Da Hipertensão Arterial Pulmonar S51Dalmaschio AC see Lopes AA et al.Dalmaschio AC, Lopes AA. Hipertensão Arterial Pulmonar em Adultos com Cardiopatia Congênita. A Síndrome de Eisenmenger S31Dweik RA see Heresi GA et al.Flores SC see Petrosillo N et al.Flores SC. Pulmonary arterial hypertension associated with HIV infection - Transcription of the webinar 114Freudenthal F see Heath A et al.Gassmann M see Pasha Q et al.Gomez E see Chaouat A et al.Graham BB see Tuder RM et al.Harikrishnan S. From the Editor's Desk 1, 99Harikrishnan S. The new face of PVRI review 61Harikrishnan S. The Story of the Journal of PVRI Review 51Hassoun PM. Papel Da Infl amação Na Hipertensão Arterial Pulmonar S16Hassoun PM. Role of infl ammation in pulmonary arterial hypertension 2Haworth SG see Kumar RK et al.Heath A, Stewart K, Mendes J, Ramirez M, Freudenthal F. Does High Altitude Protect Against Irreversible Pulmonary Hypertension? 131Heresi GA, Dweik RA. Biomarcadores Em Hipertensão Pulmonar S10Heresi GA, Dweik RA. Biomarkers in pulmonary hypertension 12Idrees M. 2009 Annual report of the PVRI Eastern Mediterranean Region 25Klinger JR see Casserly B et al.Kumar B, Mutu R, Puri GD, Singh A, Rana SS. Persistent pulmonary artery hypertension following supracardiac total anomalous pulmonary venous connection repair 126Kumar RK, Haworth SG. Annual report of PVRI South East Asia 32Lopes AA see Dalmaschio AC et al.Lopes AA, Dalmaschio AC. Pulmonary arterial hypertension in adults with congenital heart disease: The Eisenmenger

syndrome 69Lopes AA, Rabinovitch M. Pulmonary hypertension associated with congenital heart disease task force (PAH-CHD) 47Lopes AA. PVRI Open Webcasts (PVRI Webinars)http://www.pahforum.com (2008-2009) 53Mendes J see Heath A et al.Menon S. Autophagy in pulmonary arterial hypertension: Commentary 128Menon S. Commentary - Distinct patterns of circulating endothelial cells in pulmonary hypertension 91Menon S. Commentary- Wnt signaling regulates smooth muscle precursor development in the mouse lung via a Tenascin C/PDGFR pathway 22Menon S. Disease genes and pathways exploration: A listing of basic bioinformatics resources 123Minai OA. Hipertensão Pulmonar Na DPOC : Revisão Da Literatura S44Mocumbi AH, Sliwa-Hahnle K. PVRI sub-saharan Africa region taskforce 29Mocumbi AO. Pulmonary hypertension in the young African 96Morrell N see Butrous G et al.Mutu R see Kumar B et al.Ogah OS. Pulmonary hypertension in Nigeria 95Pasha Q, Gassmann M. Taskforce: Pulmonary hypertension associated with high altitude and hypoxia - annual report 2009 36Petrosillo N, Flores SC, Almodovar S, Voelkel N. Pulmonary hypertension associated with HIV-taskforce 42Petrosillo N, Stefania C. A Hipertensão Arterial Pulmonar Nos Pacientes Infectados Pelo HIV S37Puri GD see Kumar B et al.Rabinovitch M see Lopes AA et al.Ramirez M see Heath A et al.Rana SS see Kumar B et al.Singh A see Kumar B et al.Sliwa K. Inaugural meeting of the PVRI Sub-Saharan African Task Force - Report 93Sliwa-Hahnle K see Mocumbi AH et al.Stefania C see Petrosillo N et al.Stewart K see Heath A et al.Tavares Santana MV. Carta do Editor S1Thébaud B. Angiogenesis in lung development, injury, and repair 62Tuder RM, Graham BB. O Endotélio Doente: Seria Esta A Explicação De Tudo? S2Tuder RM, Graham BB. The diseased endothelium: Would it explain it all? 5Voelkel N see Petrosillo N et al.Wang C, Wilkins M. PVRI western pacifi c region (China center) 30Wilkins M see Wang C et al.Yuan JX, Archer SL. Progress report on the Textbook of Pulmonary Vascular Disease 50Zeineh NS, Champion HC. Utilidade da Excursão Sistólica do Plano do Anel da Valva Tricúspide na Quantifi cação da Função Ventricular Direita S19Zeineh NS, Champion HC. Utility of tricuspid annular plane systolic excursion in the assessment of right ventricular function 17


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Author Institution Mapping (AIM)

Please note that not all the institutions may get mapped due to non-availability of the requisite information in the Google Map. For AIM of other issues, please check the Archives/Back Issues page on the journal’s website.

2009 Annual report of the PVRI Eastern Mediterranean Region 25A Hipertensão Arterial Pulmonar Nos Pacientes Infectados Pelo HIV S37Ambrisentana: Um Novo Antagonista, Não Sulfonamídico, Seletivo Do Receptor Da Endotelina No Tratamento Da Hipertensão Arterial Pulmonar S51Angiogenesis in lung development, injury, and repair 62Annual report of PVRI South East Asia 32Autophagy in pulmonary arterial hypertension: Commentary 128Biomarcadores Em Hipertensão Pulmonar S10Biomarkers in pulmonary hypertension 12Carta do Editor S1Commentary - Distinct patterns of circulating endothelial cells in pulmonary hypertension 91Commentary- Wnt signaling regulates smooth muscle precursor development in the mouse lung via a Tenascin C/PDGFR pathway 22Como O Epoprostenol Vem Mudando O Desfecho Dos Pacientes Com Hipertensão Arterial Pulmonar? S24Disease genes and pathways exploration: A listing of basic bioinformatics resources 123Does High Altitude Protect Against Irreversible Pulmonary Hypertension? 131From the Editor's desk 99From the Editor's Desk 1Hipertensão Arterial Pulmonar em Adultos com Cardiopatia Congênita. A Síndrome de Eisenmenger S31Hipertensão Pulmonar Na DPOC : Revisão Da Literatura S44HIV-associated pulmonary hypertension: A South African perspective 97Images from the 3rd PVRI Annual General Meeting in Mexico City, 25-28 January 2009 24Inaugural meeting of the PVRI Sub-Saharan African Task Force - Report 93O Endotélio Doente: Seria Esta A Explicação De Tudo? S2Papel Da Infl amação Na Hipertensão Arterial Pulmonar S16Persistent pulmonary artery hypertension following supracardiac total anomalous pulmonary venous connection repair 126

Progress report on the Textbook of Pulmonary Vascular Disease 50Pulmonary arterial hypertension associated with HIVinfection - Transcription of the webinar 114Pulmonary arterial hypertension in adults with congenital heart disease: The Eisenmenger syndrome 69Pulmonary hypertension associated with congenital heart disease task force (PAH-CHD) 47Pulmonary hypertension associated with HIV-taskforce 42Pulmonary hypertension in chronic obstructive pulmonary disease: Three case reports 80Pulmonary hypertension in Nigeria 95Pulmonary hypertension in the young African 96Pulmonary hypertension with chronic obstructive pulmonary disease 75PVD in schistosomiasis task force 44PVRI Brazil chapter 21PVRI get together in SAN DIEGO USA during ATS 2009 meeting 35PVRI activities 4PVRI International advisory board and board of directors extraordinary meeting 23PVRI Open Webcasts (PVRI Webinars) http://www.pahforum.com (2008-2009) 53PVRI sub-saharan Africa region taskforce 29PVRI western pacifi c region (China center) 30Review of management guidelines of pulmonary arterial hypertension in the pediatric population 100Role of infl ammation in pulmonary arterial hypertension 2Taskforce: Pulmonary hypertension associated with high altitude and hypoxia - annual report 2009 36The clinical utility of brain natriuretic peptide in pulmonary arterial hypertension 85The diseased endothelium: Would it explain it all? 5The new face of PVRI review 61The Story of the Journal of PVRI Review 51Utilidade da Excursão Sistólica do Plano do Anel da Valva Tricúspide na Quantifi cação da Função Ventricular Direita S19Utility of tricuspid annular plane systolic excursion in the assessment of right ventricular function 17

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Pulmonary VascularResearch Institute

The Pulmonary Vascular Research Institute (PVRI)

Pulmonary hypertension is

250,000 patientsthan

20 million affected patients

PVRI's organization of experts

research, education andclinical care countries with healthcare disparities

PVRI Membership?

is anindependent medical research organization comprised of leadingexperts, devoted to increasing the awareness and knowledge ofpulmonary vascular diseases, and to facilitating advances in thetreatment of affected people worldwide.

a fatal cause of heart failure that affectspeople of all ages, races, and socioeconomic groups.

Sadly, while there are more than with pulmonaryhypertension being treated in the Western world, there are more

in underprivileged countries with little orno therapy available.

allows basic and translationalclinical research to be conducted at a high level.

PVRI activities are focused on providingto in order to

best serve the academic community and pulmonary vascular diseasepatients.

Interested inPlease apply at www.pvri.info

Research

Clinical Care Education &KnowledgeExchange

Edited by Dr. S. Harikrishnan. Printed and published by Medknow Publications and Media Pvt. Ltd., on behalf of Pulmonary Vascular Research Institute, Trivandrum and Printed at Dhote Offset Technokraft Pvt. Ltd., Satyam Ind. Estate, Jogeshwari, Mumbai and published at Medknow Publications & Media Pvt. Ltd. from B5-12, Kanara Business Centre, Ghatkopar, Mumbai, India.

pvri review 2:2&3 2010

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