ACUTE AORTIC SYNDROMES

ACUTE AORTIC SYNDROMESRAJESH K FAcute aortic syndromes consist of 3 interrelated conditions with similar clinical characteristicsAortic dissectionIntramural hematomaPenetrating aortic ulcer

Erbel R, Alfonso F, Boileau C, Dirsch O, Eber B, Haverich A, et al. Diagnosis and management of aortic dissection. Eur Heart J 2001;22:1642-81.

AORTIC DISSECTION Most common aortic catastropheIncidence - 5 to 30 per 1 million people/yearPrimary tear in aortic intima with bleed into diseased mediaRupture of vasa vasorum - Hemorrhage in aortic wall with subsequent intimal disruption

Most ascending aortic dissections begin within a few centimeters of aortic valveMost descending aortic dissections have their origin just distal to left subclavian artery

DeBakey classification

I: Ascending aorta -> arch +/- descending aorta II: Ascending aorta only III:Descending aortaIIIa: Limited to descending thoracic aortaIIIb: Extending below diaphragmStanford classificationType AAffect ascending aorta, regardless of site of originType BDo not affect ascending aorta

ClassificationBased on time of onset of initial symptoms to time of presentationAcute dissection < 2 weeksSubacute- between 2 and 6 weeksChronic > 6 weeks Behave like aneurysm Rupture is the risk Malperfusion is rareRISK FACTORSHypertension (75%)Genetically triggered Marfan syndrome Bicuspid aortic valve (5 to 10 times risk) Loeys-Dietz syndrome Hereditary thoracic AA or dissection Vascular Ehlers-Danlos syndrome Congenital diseases or syndromes Coarctation of the aorta Turner syndrome(dissection at small aortic dimensions) Tetralogy of Fallot Atherosclerosis Penetrating atherosclerotic ulcer

Trauma, blunt or iatrogenic Catheter or stent Intra-aortic balloon pump Aortic or vascular surgery Motor vehicle accident CABG or AVR Cocaine use Inflammatory or infectious disease Giant cell arteritis Takayasu arteritis Behcet disease Aortitis Syphilis Pregnancy (typically in third trimester)

Patients 20 or spondylolisthesisReduced extension at elbows (5 mm) -calcium sign 20%Displacement of trachea to rightDistortion of left main-stem bronchusPleural effusion (more common left sided)CardiomegalyNormal in 12% to 15% of cases

D-dimer levels Rise in acute aortic dissection as in pulmonary embolismLevel >1,600 ng/mL within first 6 hours - positive likelihood ratio of 12.8 for dissectionIn first 24 hours after symptom onset - D-dimer level < 500 ng/Ml has negative predictive value of 95%IMAGING 1 Establish presence of AD or variant (IMH,PAU) 2 Location of the dissection (Type A, Type B) 3 Anatomical features a Extent of dissection b Sites of entry and reentry c False lumen patency, partial thrombosis, thrombosis 4 Complications of dissection a Type A i Aortic regurgitation ii Coronary artery involvement iii Pericardial effusion/hemopericardium b Aortic rupture or leaking c Branch vessel involvement d Malperfusion

Contrast-enhanced CT Most commonly usedSensitivity and specificity of 95% to 98% ECG gating or multi detector scanning eliminate pulsation artifactsIntravenous contrast is necessary to visualize true and false channelsVisualize hemopericardium, aortic rupture, and branch vessel involvement

MRISensitivity of 98% and specificity of 98% with diagnostic odds ratio of 6.8 Capable of multiplanar imaging with 3D reconstruction Cine MRI visualize blood flow, differentiating slow flow and clot and ARMRA -detect and quantify AR & branch vessel morphology

TTE78.3% sensitivity and 83.0% specificity for diagnosing proximal dissection2 lumens separated by flap

TEEAccurately visualise entire thoracic aorta (sensitivity 98.0%, specificity 95.0%, diagnostic odds ratio 6.1)2 lumens separated by flap Visualize coronary ostiaARPericardial effusionLV & RV functionMay not adequately visualize distal ascending aorta and aortic arch

Aortography

Identify intimal flap, true and false lumen Thickened wall (thrombosed false lumen) AR, branch vessel involvementDiagnostic accuracy 90-95%5-10% false negative rate thrombosed false lumen simultaneous opacification of both lumens misses IMHRisks of procedure

Comparative study with nonhelical CT, 0.5 Tesla MR and TEE showed 100% sensitivity for all modalities,Better specificity of CT (100%) than for TEE and MRFalse-negative studies can and do occur

Shiga T, Wajima Z, Apfel CC, Inoue T, Ohe Y. Diagnostic accuracy of transesohageal echocardiography, helical computed tomography,and magnetic resonance imaging for suspected thoracic aortic dissection. Arch Intern Med. 2006;166:1350-6.INITIAL MANAGEMENT IV beta blockade -Target HR of 60 /min or less(LOE : C) Esmolol -Initial bolus of 500microg/kg and continuous infusion of 50 to 200 microg/kg/minLabetolol-Initial dose of 20 mg IV over 2 minutes and 40 to 80 mg IV every 15 minutes (max 300 mg), continuous infusion 2 to 8 mg/minPropranolol and metoprolol IV or oralBBs blockers- compensatory tachycardia in acute AR

BB Action

CIs to BB-Nondihydropyridine CCB(LOE : C)IV diltiazem 0.25 mg/kg over 2 minutes > infusion 5 to 15 mg/hrSBP > 120 mm Hg after adequate HR control- ACEI and/or other vasodilators IV (LOE : C)Should not be initiated prior to rate control - reflex tachycardia increase aortic wall stress (LOE : C)

IV sodium nitroprusside - most established agent, rapidly titratable , 20 microg/min, with titration to 0.5 to 5 microg/kg/min Renal insufficiency or prolonged use-cyanide toxicityIV enalaprilat,nitroglycerin,nicardipine,nitroglycerin, fenoldopam Refractory hypertension - consider renal artery hypertension due to dissection causing renal malperfusionAppropriate analgesia opiate Surgical Therapy Acute type A aortic dissection Retrograde dissection into ascending aorta Surgical Therapy and/or Endovascular Therapy Acute type B aortic dissection complicated by Visceral ischemia Limb ischemia Rupture or impending rupture Aneurysmal dilation Refractory pain Medical Therapy Uncomplicated type B aortic dissection Uncomplicated isolated arch dissection

GOALS OF SURGERYExcise intimal tearObliterate false channel by oversewing aortic edges Reconstitute aorta,usually by placing a dacron interposition graft

Type A aortic dissection

Replace affected ascending aorta with or without aortic arch with prosthetic graftIn-hospital mortality 15-35%Proximal extension of dissection to aortic valve or ostia of coronary arteries may require replacement or resuspension of aortic valve (24% )or coronary artery bypass (15% )Valve sparing -David or Yacoub Procedures

43 AVR required if annular supports of leaflets damaged (composite graft or homograft) AVR required if aortic root >5 cm

Modified Bentalls operationPreoperative Prediction Model of Surgical Mortality Risk

VARIABLEOVERALL TYPE A (%)AMONG SURVIVORS (%)AMONG DEATH (%)COEFFICIENTSCORE ASSIGNEDP VALUEODDS RATIO, DEATH (95% CI)Age 70yr27.324.137.40.680.7