ASSESSMENT OF OPERABILITY OF LEFT TO RIGHT SHUNTS

DR MAHENDRA

JIPMER,CARDIOLOGY

INTRODUCTION

• PAH associated with CHD remains a problem

Mainly in pts in whom the LR shunt wasn’t diagnosed until childhood or even adulthood

In patients who didn’t have access to cardiovascular care and surgical management as infants, particularly in developing countries

• The 2009 ESC/ERS/ISHLT guidelines on the management of PAH subdivided PAH-CHD into 4 clinical groups:

(1) Eisenmenger syndrome

(2) PAH associated with systemic-to-pulmonary shunts

(3) PAH with small defects

(4) PAH after surgical repairEur Heart J 2009

Congenital Heart Disease (L-R shunts) and Pulmonary Hypertension

Maurice Beghetti, and Nazzareno Gali, J. Am. Coll. Cardiol. 2009;53;733-740

• The response of the pulmonary vasculature to high pulmonary blood flow is however not uniform and does not occur in a predictable fashion

What determines the development of pulmonary vascular obstructive disease?

Anatomy of defect

Associated conditions

Time

Pre vs. post tricuspidSize

Associated lesions: pulmonary venous

hypertension

Lungs and airways obstructionAltitudeSyndromes: Tri-21

Unknown influences

Genetic???

*

Large Fossa ovalis ASD

SV ASD

Unrestrictive VSD or PDA

TruncusTGA VSD/PDA

100%Li

kelih

oo

d o

f o

per

abili

ty

Age

Infancy Early childhood

Adolescence Adulthood

Defect vs. PVOD Risk

• Pre-tricuspid shunts: gradual increase in Qp as RV accommodates and enlarges – ASD, PAPVC, TAPVC*

• Post tricuspid shunts: Direct transmission of pressure head: VSD (systolic), PDA, AP-Window (systolic and diastolic)

• Pulmonary venous hypertension, associated mitral stenosis, other forms of LV inflow obstruction:

– May introduce a substantial element of reversibility

– May protect pulmonary vasculature from the effects of increased pulmonary blood flow???

Hypoxia elevates pulmonary vascular resistance • Diseases of pulmonary parenchyma• Airways (upper and lower)• Hypoventilation• High altitude

Time• The likelihood of development of PVOD increases with

time• The rate of increase in PVR varies depending on a

number of influences

Risk of development of PVOD: Other (unknown) influences

Remarkable individual variability

• ASD with severe PAH in a child

• VSD with shunt reversal in an infant

• Operable AP window in a teenager

• Operable large VSD in an adult

Prediction for an individual patient is sometimes quite challenging

Deciding operability of L to R shunts

• Clinical evaluation

• Chest X-ray and ECG

• Measurement of oxygen saturation

• Echocardiography

• Resting and post exercise ABG (PO2)

• MRI

• Cardiac catheterization

What principles govern decision on operability?

• Post tricuspid shunts: Generally operable if there is evidence of a significant shunt in the basal state irrespective of PA pressure

• Pre-tricuspid shunts: Pulmonary hypertension (anything more than mild) warrants concern especially if basal shunt is not obvious

Deciding operability: Principles

• Age is an important variable and benefit of doubt must be given to younger patients.

– E.g. a 1 year old with VSD and severe PAH where basal shunt is not obvious

• Lung, airway and ventilation issues can elevate PVR and confound assessment

• Pulmonary venous hypertension can result in reversible elevations in PVR

CLINICAL ASSESSMENT

• Serial assessment by multiple experienced clinicians improves the reliability of clinical examination as a tool in determining operability

• The presence of ‘clinical cyanosis’ or saturations <90% is a strong predictor of inoperability whereas the clear detection of a MDM on serial assessment strongly favoursoperability.

LV

RVLA

LV

RA

RV

Clearly Operable: Cath not required

26 year old

Blue

Single loud

S2

Clearly Inoperable: Cath not required

RV

LV

RALA

ABG

• The role of ABG measurement has not been adequately investigated

• A decline in arterial PO2 after exercise may suggest fixed PVR as the fall in SVR during exercise is not balanced by a corresponding fall in PVR

• Also allows assessment of respiratory function• The presence of ‘hypercarbia’ should alert the

clinician to look for restrictive or obstructive pulmonary disease as a contributory factor to the PHT

Interventricular and Transductal velocity by Doppler

• Clear understanding of the hemodynamics

• Comprehensive clinical assessment

• Influenced by the pulmonary artery and aortic pressures at the time of examination

• Proper alignment is essential

• Left parasternal view or high parasternal view for ductus; no ‘best’ view for VSD

• Record peak systolic and end diastolic gradients in PDA

CORRELATION BETWEEN PREOPERATIVE HEMODYNAMICS AND CLINICAL OUTCOMES

• The degree of individual variability makes it difficult to apply a single cut-off to determine operability

Lopes AA, O’Leary PW. Cardiol Young 2009

PVR Estimation by Cardiac Catheterization

Pulmonary artery mean

pressurePulmonary venous

mean pressure

Trans-pulmonary gradientPVR =

Pulmonary blood flow

Oxygen consumption

PVO2 content PA O2 Content

• Operability is defined on the basis of the likelihood of a favorable vs an unfavorable outcome.

• All the operability thresholds are defined to predict short-term success, which is immediate post-operative survival

• Although these are the best current proposals on assessing operability in CHD and PAH, there is no consensus as to whether vasoreactivity testing is accurate enough to discriminate between patients who will or will not have a good long term outcome

• Precise values of hemodynamic measures cannot be derived as individual patient factors such as cardiac lesion type and genetic predisposition may alter the hemodynamic testing or have an impact on outcome after surgical repair

• Hemodynamic assessment also aids in appropriate device selection

• The fenestrated ASD device can be considered in selected pts

• ASD or VSD device for patients with PDA and pulmonary hypertension instead of AmplatzerPDO

HOW USEFUL IS IT TO STUDY THE EFFECTS OF TEMPORARY SHUNT OCCLUSION?

• ‘‘Responders’’ - 25% fall in PA pressures on balloon occlusion or a 50% fall in the ratio between pulmonary and aortic diastolic pressures

• Pts with a high baseline PVR and low Qp/Qs ratio still may respond favorably to balloon occlusion and tolerate duct occlusion with normalization of PA pressures

• Immediate fall in pulmonary pressures may not translate into long term benefits

• The data available remains inconclusive and further clarification by studies with larger numbers is warranted.

LUNG BIOPSY

• Used to be routinely done• Now less frequently done in clinical practice• The results aren’t sufficiently reliable and not

without risk• Younger patients (<2 years of age) are often

operable in spite of seemingly advanced changes on lung biopsy

• Provides only one randomly selected area of the lung and does not represent a comprehensive evaluation of the nature and extent of lesions throughout the lungs

NOVEL MARKERS OF ASSESSING OPERABILITY

BIOMARKERS :

• ANP,BNP,Nt-pro-BNP,cardiac troponin T,uricacid,urinary prostaglandin metabolites,eNOSand dimethylarginines,ET-1 and ET-1:ET3 ratio,circulating VWF , cytokines (IL-1a, -2, -4, -6, -8, -10 and 12p70, TNF-b, MCP-1 and osteopontin),CRP,pim-1 & HbA1c

• Circulating endothelial cells and micro-RNAs

CONCLUSION

• Determining operability is important in patients with left to right shunts who present late

• A number of unresolved issues exist with currently available methods

• A comprehensive assessment that incorporates clinical evaluation, noninvasive investigations and in selected cases, cardiac catheterization is needed

• When in doubt, do not send patient for surgery • Efforts to evolve clear guidelines through careful

prospective studies need to be undertaken