Diseases of the AortaDiseases of the Aorta

Seoul National University HospitalDepartment of Thoracic & Cardiovascular Surgery

Anatomy of Aorta Aortic root

aortic valve, sinus of Valsalva, coronary artery

Ascending aorta aortic root ~ innominate artery

Aortic arch proximal, distal

Descending thoracic aorta distal to LSCA ~ 12th ICS

Thoracoabdominal aorta descending thoracic aorta & abd

ominal aorta

Properties of Aorta & Major Conduit

1. Aorta

Compliant vessel (Windkessel function)

; transforms pulsatile hydraulic energy into a more steady flow by elastic distension & contraction

2. Synthetic conduit

Noncompliant

; must result in alteration of arterial hemodynamics & LV load (increased impedance & afterload)

Diseases of Thoracic Aorta

Aortic aneurysm

Aortic dissection

Obstructive disease of branches

of the thoracic aorta

Traumatic aortic rupture

Pathophysiology of Aortic AneurysmDefinition

localized or diffuse dilatation > 50% of normal diam. Most common aortic disease that require surgery

Etiology Atherosclerosis ( + underlying weakness) Chronic aortic dissection Annuloaortic ectasia (Marfan syndrome) Trauma Infection Associated with aortic valve disease

Histopathology of Ascending Aortic Aneurysm

1. Cystic medial necrosis by pooling of mucoid material

2. Elastin fragmentation by disruption of elastin lamellae

3. Fibrosis as an increase in collagen at the expense of smooth muscle cells

4. Medionecrosis as areas with apparent loss of nuclei

Pathophysiology of Ascending AA

Marfan syndrome Incidence

– 1 / 5,000 Annuloaortic ectasia is very common Associated defects

– Aortic regurgitation, mitral valve prolapse, dysrhythmia

– Tall stature, long limbs and digits, anterior chest deformity, joint laxity, vertebral column deformity

– High arched palate, lens disorder

Marfan’s Syndrome * Definition

1) A heritable disorder (AD) of connective tissue involving biochemical

abnormality of extracellular matrix by a mutation in fibrillin gene on chr

omosome 15 (Fibrillin-1, 350-KD glycoprotein : integral structural comp

onent of 10-nm noncollagenous microfibrils of extracellular matrix in

most tissue)

2) The absence of structural integrity of skeletal, ocular, & cardiova

scular system

3) Adult patients demonstrate abnormal elastic properties manifest

ed by decreased aortic distensibility & increased stiffness index

Marfan’s Syndrome

Clinical manifestations Cardiovascular Ocular Skeletal abnormality Cardiovascular manifestations Progress with time Mitral valve prolapse in 100% Aortic root dilatation in 80% Rarely atrial septal aneurysm

Manifestations of Marfan’s Syndrome

1. Patterns of aortic dilatation 1) 80% of the patients shows aortic dilation 2) more commonly generalized form than localized form 3) more commonly aortic regurgitation in generalized form

2. Natural prognosis 1) Life expectancy is significantly reduced (40~50) as a consequence of aortic dilatation & its complications (aortic dissection, fatal rupture, AR, heart failure)

Marfan’s Syndrome in Children 1. Diagnosis can be made at any age with marked variation in clinical expression. 2. Patients without family history (in one third of patients of all age) have more severe manifestation probably due to sporadic mutation. 3. Surgery should be carried out even in asymptomatic patients, once the diameter of the aortic root or ascending aorta reaches 5 to 6cm as in adults. 4. Mitral valve prolapse is as common as aortic root dilatation and progression can cause significant morbidity & mortality.

Patterns of Aortic Aneurysm

Locations of Aneurysm

Ascending aorta 45 %

Aortic arch 10 %

Descending thoracic aorta 35 %

Thoracoabdominal aorta 10 %

Natural History of AA Aortic aneurysm

Incidence – 5.9 new aneurysms / 100,000 person-years

Life time probability of rupture : 75~80% 5-yr untreated survival rate : 10~20% Median time to rupture : 2~3 yrs

Size Risk of rupture within 1yr < 5 cm 4 % 6 cm 43 % 8 cm 80 %

Clinical Presentation of AA Symptoms & signs

Asymptomatic Compressive symptoms

– recurrent laryngeal n. or vagus n. : hoarseness– tracheobronchial tree : dyspnea– pulmonary a. : fistula, bleeding pulmonary HT & edema– esophagus : dysphagia– stomach : sensation of satiety wt. loss

Pain aneurysmal expansion Intestinal angina, renovascular HT associated atherosclerotic obstructive disease (5% in TAAA)

Physical finding - usually unremarkable Wide pulse pressure, diastolic murmur AR

Indications for Aortic Aneurysm

Aneurysm diameter 5cm Aneurysm with documented enlargementSymptomatic aneurysm

― chest pain or back pain indicating expansion― significant aortic regurgitation

Dissecting Aortic Aneurysm Catastrophic event Intimal tear False channel

in the outer half of the media

highly susceptible to rupture

Acute dissection < 2 wks from Sx onset

Chronic dissection > 2 wks from Sx onset

Pathophysiology of Aortic Dissection

Malperfusion Reentry

Predisposing Factors of DA

Hypertension Cystic medial necrosis Marfan syndrome AAE(annuloaortic ectasia) Bicuspid aortic valve Coarctation Pregnancy Chest trauma

Classification of Dissection

Standford Type A

Involvement of the a-Ao ( arch or d-Ao) regardless of site of primary intimal tear

Type BAll others without involvement of a-Ao

DeBakey I, II, IIIAccording to the location of intimal tear

Classification of Aortic Dissection

A B

II I III

Natural History of DA Annual incidence

5~10 / million Sex ratio

M:F = 2:1 ~ 5:1 Acute dissection

Median time to rupture : 3 days Mortality rate ; 50 % within 2 days 75 % within 2 wks

Chronic dissection Median time to rupture : 1~3 Yrs Follows patterns of non-dissecting aneurysm

Clinical Presentation of DA

Acute dissection Excruciating pain

– abrupt onset– sudden rise to peak – Chest pain

2/3 of a-Ao dissection– Back pain

dissection distal to aortic arch– Pain may migrate as the dissection moves distally.

Various extent of peripheral & central vessel occlusion– from progression of dissection through the false lumen

Failure of diagnosis : major problem

Clinical Presentation of DA

Type A Type B Frequency Pain anterior substernal posterior, midscapular,

abdominalSyncope +++ rareDyspnea + ―Blood pressure elevated 50%, low 20% elevated 80%Asymmetric pulses upper, lower extremity lower extremity 30-50%Diastolic murmur 50% 10%Pericardial effusion +++ rarePleural effusion ± +++Hemiparesis or plegia + ― 5-6%Paraparesis or plegia + + 2-6%Renal, intestinal infarction + + 3-5%Myocardial infarction + rare 10 %

Principle of Treatment in DA

Type A acute aortic dissection Emergent operation

Type B acute aortic dissection Medical Tx and observation unless life threateni

ng Surgical indication

– Persistent pain– Aneurysmal dilatation ( 5cm)– End organ (kidney, bowel) or limb ischemia– Evidence of retrograde dissection to the a-Ao

Medical Management of DA Initial management

Immediate ICU care BP control & Monitoring

– Central line, arterial line, urine output Imaging studies

– Daily Chest X-ray, weekly CT scan during hospitalization

Pharmacologic therapy Vasodilator : Sodium nitroprusside β-blocker : Esmolol (β-1 selective & short acting)

Diagnostic Studies for DA

CT & CT angiography Aneurysm size, location, extent, intimal tear site Other pathologies in the chest & abdomen Follow-up study : aneurysm growth Limitation

– unreliable detection of root enlargement Contraindication

– renal insufficiency, allergy to contrast agents

MRI Noninvasive study Do not require contrast medium Better than CT at detecting aortic root dila

tation Disadvantages

cost required time (esp, in acute dissection)

Contraindication pacemaker, claustrophobia

Diagnostic Studies for DA

Transesophageal Echocardiography (TEE) Accuracy in imaging intimal tear : 90% Assessment of cardiac structure & function Highly sensitive in aortic pathology diagnosis

– aortic valve disease, aortic dilatation, dissection, thrombi, atherosclerotic disease

Intraoperative monitoring– check cardiac function, aortic valve competency, atheroscl

erosis in the thoracic aorta Limitation

– requires a skilled cardiologist

Diagnostic Studies for DA

Diagnostic Studies for DA Aortography

Geography of the aorta & condition of smaller vessels Previous gold standard in dissection

– double lumen, tear site, extent Indication

– renovascular HT, intermittent claudication, atherosclerotic occlusive abdominal aorta, symptoms of carotid artery occlusion

Disadvantages– invasive procedure using radiopaque dyes

Cardiac cath & coronary angiography Evaluation of the concomitant coronary artery disease

Principles of Surgical Tx in Acute Dissection Resection of aortic segment containing intimal tear Obliteration of false lumen in both end of remained aorta Graft replacement of resected aortic segment

Techniques Median sternotomy Femoral-femoral bypass Trendelenburg position Circulatory arrest with deep hypothermia Retrograde cerebral perfusion Reinforcement of the intima & adventitia together

(sandwich technique)

Surgery of Type A Dissection

Operation of Type A Dissection

Type A Dissection

Techniques Similar to the techniques for aneurysm Rechanneling blood into the true lumen Ligation of all intercostal arteries in acute dissection

Surgical indications Persistent pain Aneurysmal dilatation ( 5cm) End organ(kidney, bowel) or limb ischemia Evidence of retrograde dissection to the a-Ao

Surgery of Acute Type B Dissection

Acute Type A Dissection Early mortality : 20~30 % Main cause of death underlying end-organ injury Major complications stroke (9%) Major risk factors for postop. stroke

– pump time, episode of severe hypotension

Acute Type B Dissection Early mortality : 25~50 % (cf. medical treatment : 7~32 %) Major complications : ischemic spinal cord injury

Surgical Results of DA

Surgical Treatment of AA Aneurysm : Aortic Root, a-Ao, Aortic Arch

Historical evolution 1950s : Cardiopulmonary Bypass (Gibbon)

1955 : 1st successful a-Ao repair (Cooley & DeBakey)

1964 : 1st successful replacement of entire a-Ao (Wheat)– CPB, coronary perfusion, myocardial cooling, cold cardiac arrest

1968 : Composite valve graft (Bentall & de Bono)

1975 : Replacement of entire aortic arch (Griepp)– profound hypothermia & circulatory arrest

Aortic Root, Ascending Aorta, Aortic Arch

Limitation of profound hypothermia< 30 min : safe duration > 45 min : increased incidence of stroke> 65 min : increased incidence of death

Calculated safe duration of hypothermic circulatory arrest Temperature Cerebral Metabolic Rate Safe Duration of HCA

(C) (% of baseline) (min)

37 100 5

30 56 ( 52 ~ 60 ) 9 ( 8 ~ 10 )

25 37 ( 33 ~ 42 ) 14 ( 12 ~ 15 )

20 24 ( 21 ~ 29 ) 21 ( 17 ~ 24 )

15 16 ( 13 ~ 20 ) 31 ( 25 ~ 38 )

10 11 ( 8 ~ 14 ) 45 ( 36 ~ 62 )

Aortic Root, Ascending Aorta, Aortic Arch

Adjuncts for brain protection Reintroduction of antegrade cere

bral perfusion (Frist, 1987)

Retrograde cerebral perfusion (Ueda, 1989)

Aortic Root - Techniques Median sternotomy Antegrade and/or retrograde cardioplegic perfusion Techniques for aortic root

– Wheat – Composite graft (esp, for Marfan)

Bentall Cabrol modified Cabrol button

– Homograft– Valve sparing procedure Choice of tube graft ; diameter of 10%

smaller than the length of the free

margin of the aortic leaflet

Valve-sparing Operation

Resorting aortic root dimensions in an aortic valve-sparing operation when aortic annulus is normal and sinotubular junctio

n is enlarged

Valve-sparing Operation

Resorting aortic root dimensions when aortic annulus & sinotubular junction are normal, as in aortic dissection

Valve-sparing Operation

Resorting aortic root dimensions when aortic annulus and sinotubular junction are enla

rged, as in anuloaortic ectasia with Marfan syndrome

Valve-sparing Operation

Reconstructing aortic root using a graft with the aortic valve placed within it

Separate valve/graft replacement For older patients with mild to moderate sinus

dilatation

Aortic Root – Wheat Technique

Bentall technique Coronary artery reattachment

side-to-side anastomosis Disadvantage

bleeding d/t anastomosis tension → pseudoaneurysm (7~25%)

Aortic Root – Composite Valve Graft

Cabrol technique Coronary artery reattachment

– a small graft to the both coronary arteries

– side-to-side anastomosis of the small graft & composite graft

Advantage– ↓anastomosis tension

Disadvantage– kinking at the anastomosis sites

Aortic Root – Composite Valve Graft

Modified Cabrol technique Coronary artery reattachment

– a small graft to the LCA– end-to-side anastomosis of the small graft

& composite graft– button attachment of the RCA

Advantage– ↓kinking

Aortic Root – Composite Valve Graft

Button technique Coronary artery reattachment Carrel patch for both coronary a.

Direct anastomosis to the composite graft

Aortic Root – Composite valve graft

Composite Valve Graft

A; aortic valve is excised B; composite prosthetic valve conduit is

attached to annulus of aortic valve

Results Early mortality : 2~15% Early complications : thromboembolism, bleeding Late complications : endocarditis, thromboembolism pseudoaneurysmTechnique Major Complications 30-Day Survival (%) 5-Yr Survival (%)

Wheat Endocarditis (5%) 85 70

Bentall Thromboembolism (5~10%), endocarditis (5%)

85~90 70~85

Cabrol 90 75 Button Thromboembolism (2~10%),

endocarditis (5%) 85~95 70~85

Surgery of Aortic Root

Surgery of Aortic Root Results

Closed technique Limited to a-Ao Aorta cross clamp

Ascending Aorta & Arch

Open techniqueArch involvementDeep hypothermia & circulatory arrest

–EEG monitoring–Retrograde cerebral perfusion

Elephant Trunk Technique (by Borst, 1988) for extensive aortic aneurysm

(“mega-aorta”)

Elephant Trunk Technique (Staged op.)

Results

Major complications – stroke, encephalopathy

Major risk factors – circulatory arrest time, transverse arch involvement

Technique Major Complications 30-Day Survival (30%)

Normothermia Not reported 25

+ Antegrade cerebral perfusion Not reported 75

TCA with profound hypothermia Stroke (2~10%) 85~90

+ Antegrade cerebral perfusion Stroke (5~6%) 80~100

+ Retrograde cerebral perfusion Stroke (3%) 95

Surgery of Ascending Aorta & Arch

Spinal protection Arterial radicularis magna (Adamkiewicz a.) Technique

– Shunt– Hypothermic circulatory arrest– Spinal cord cooling – Pharmacologic agent – Sequential aortic clamp– Distal aortic perfusion– CSF drainage– Intercostal artery reattachment (T9~12)

Descending Thoracic & Thoracoabdominal Aorta

Indications – Poor surgical candidates for t

horacic aneurysm – Expected survival time < 5 yrs

Problem – Endoleaks (→ graft migration)– Exclusion of intercostal arteries– Lack of long-term data

Results– Early mortality : 9%– Complications

stroke (7%) paraplegia (3%) early endoleak (24%) reintervention (5%)

Endovascular Stent Graft

Modified Crawford’s classification for TAAA

Thoracoabdominal Aorta

–Technique Thoracoabdominal incision Descending thoracic aorta involvement

Distal aortic perfusionCSF drainageIntercostal artery reattachment

(T9~12) Celiac axis, SMA, IMA, renal arteries

Visceral perfusionCarrel patch or bypass graft

Thoracoabdominal Aorta

Thoracoabdominal Aorta

Descending Thoracic & Thoracoabdominal Aorta Results

Risk Factors for poor outcome– aneurysm extent (type II)– preop. renal dysfunction– aortic cross clamp time

Technique Major Complications 30-Day Survival 5-Yr SurvivalDescendingthoracic

Neurologic deficit (2~15%),renal failure (14%) 50~80%

TAAA type I, II& IV

Neurologic deficit (0~15%),renal failure (5~25%) 90~95 % 60~75%

TAAA type II,no adjuncts

Neurologic deficit (30~40%),renal failure (17%) 78% 35%

TAAA type II,with adjuncts

Neurologic deficit (12%), renalfailure (7%) 90% 60~70%

Abdominal Aortic Aneurysm1. Type Fusiform : most Sacciform Dissecting : rare False

2. Etiology Atherosclerosis : 90%

Traumatic Syphilitic Congenital Infected Pregnancy related

Anastomotic

Pathophysiology of Abdominal Aorta

Nature of the aortic wall 1) Contain more elastin, deposition of

cholesterol and calcium

2) Stress factor and turbulent flow due to

origin of major branches

3) Stability of proximal abdominal aorta and

presence of large bifurcation

Hemodynamic factor

Physical factor

Procedures for Abdominal AA

1 Heparin 1mg/kg IV2 Mannitol 0.5g/kg in suprarenal clamp3 Inferior mesenteric artery occlusion4 Lumbar arteries oversewn5 Proximal and distal anastomosis6 Reimplantation of inferior mesenteric artery

Operative Complications

1 Division of parasympathetic and sympathetic nerves crossing the proximal common iliac arteries 2 Peripheral embolism3 Paralytic ileus4 Aortoenteric fistula