Diseases of the Aorta Seoul National University Hospital
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Seoul National University Hospital Department of Thoracic & Cardiovascular Surgery Anatomy of Aorta Aortic root aortic valve, sinus of Valsalva, coronary artery Ascending aorta aortic root ~ innominate artery Aortic arch Descending thoracic aorta distal to LSCA ~ 12th ICS Thoracoabdominal aorta descending thoracic aorta & abdominal 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 Aneurysm Definition 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 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 A heritable disorder (AD) of connective tissue involving biochemical abnormality of extracellular matrix by a mutation in fibrillin gene on chromosome 15 (Fibrillin-1, 350-KD glycoprotein : integral structural component of 10-nm noncollagenous microfibrils of extracellular matrix in most tissue) The absence of structural integrity of skeletal, ocular, & cardiovascular system Adult patients demonstrate abnormal elastic properties manifested 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. 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 enlargement Symptomatic 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 Chronic dissection Pathophysiology of Aortic Dissection Predisposing Factors of DA Hypertension Cystic medial necrosis Marfan syndrome AAE(annuloaortic ectasia) Bicuspid aortic valve 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 B All others without involvement of a-Ao DeBakey I, II, III According to the location of intimal tear Natural History of DA Annual incidence Sex ratio 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 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 Pain anterior substernal posterior, midscapular, abdominal Syncope +++ rare Dyspnea + ― Blood pressure elevated 50%, low 20% elevated 80% Asymmetric pulses upper, lower extremity lower extremity 30-50% Diastolic murmur 50% 10% Pericardial effusion +++ rare Pleural 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 Type B acute aortic dissection Medical Tx and observation unless life threatening 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 Diagnostic Studies for DA MRI Noninvasive study Do not require contrast medium Better than CT at detecting aortic root dilatation 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, atherosclerosis in the thoracic aorta Limitation 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 Surgery of Type A Dissection 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) Operation of Type A Dissection Type A Dissection Surgery of Acute Type B 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 Surgical Results of DA 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 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 cerebral 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 Valve-sparing Operation Valve-sparing Operation Valve-sparing Operation Aortic Root – Wheat Technique Separate valve/graft replacement For older patients with mild to moderate sinus dilatation Aortic Root – Composite Valve Graft Coronary artery reattachment 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 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 Aortic Root – Composite valve graft Button technique Coronary artery reattachment Carrel patch for both coronary a. Direct anastomosis to the composite graft Composite Valve Graft Surgery of Aortic Root Results Early mortality : 2~15% Early complications : thromboembolism, bleeding Late complications : endocarditis, thromboembolism pseudoaneurysm Surgery of Aortic Root Ascending Aorta & Arch Closed technique Limited to a-Ao Aorta cross clamp Elephant Trunk Technique (by Borst, 1988) Elephant Trunk Technique (by Borst, 1988) for extensive aortic aneurysm (“mega-aorta”) Elephant Trunk Technique (Staged op.) Elephant Trunk Technique (Staged op.) Surgery of Ascending Aorta & Arch Results Major complications Major risk factors circulatory arrest time, transverse arch involvement Descending Thoracic & Thoracoabdominal Aorta 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) Endovascular Stent Graft Indications Poor surgical candidates for thoracic 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%) Thoracoabdominal Aorta Modified Crawford’s classification for TAAA Thoracoabdominal Aorta Technique Thoracoabdominal incision Descending thoracic aorta involvement Distal aortic perfusion CSF drainage Intercostal artery reattachment (T9~12) Celiac axis, SMA, IMA, renal arteries Visceral perfusion Carrel patch or bypass graft Thoracoabdominal Aorta Descending Thoracic & Thoracoabdominal Aorta Results Risk Factors for poor outcome aneurysm extent (type II) preop. renal dysfunction aortic cross clamp time Abdominal Aortic Aneurysm 1. Type Fusiform : most Sacciform Dissecting : rare False 2. Etiology Atherosclerosis : 90% Traumatic Syphilitic Congenital Infected 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 Heparin 1mg/kg IV Mannitol 0.5g/kg in suprarenal clamp Inferior mesenteric artery occlusion Lumbar arteries oversewn Proximal and distal anastomosis Reimplantation of inferior mesenteric artery Operative Complications Division of parasympathetic and sympathetic nerves crossing the proximal common iliac arteries Peripheral embolism Paralytic ileus Aortoenteric fistula Dostları ilə paylaş:
