Non-Invasive Conference: Aortic Dissection Ali R. Rahimi, MD MPH September 24, 2008

Anatomy Tunica intima, media and adventitia

Aortic Dissection “a splitting of the layers of the aortic wall (within the media), permitting longitudinal propagation of a blood-filled space within the aortic wall” Most common cause of death related to the human aorta Incidence  2.6 to 3.5 per 100,000 person-years 65% men with mean age of 63 years

Pathophysiology Degeneration of aortic media, or cystic medial necrosis, is prerequisite for nontraumatic dissection Primary rupture of intima with secondary dissection of the media vs. hemorrhage within the media and subsequent rupture of overlying intima Propagation can occur both distal and proximal

Risk Factors Systemic hypertension (72%) Atherosclerosis (31%) Pre-existing aortic aneurysm (13% known) more common < 40 yo (19%) Vasculitis (giant cell arteritis, Takayasu arteritis, rheumatoid arthritis, syphilitic aortitis)

Risk Factors Disorders of collagen (eg, *Marfan syndrome, Ehlers-Danlos syndrome, annuloaortic ectasia) *Present in 50% of those < 40 yo vs. 2% of older patients Bicuspid aortic valve Present in 9% < 40 yo vs. 1% over age 40 Enlargement of aortic root and/or ascending aorta Aortic coarctation, Turner Syndrome, CABG (0.04%), Prior AVR, Cardiac Cath (2%), Trauma (deceleration injury), Weight lifting, Crack cocaine

Ascending aortic dissections ~ 2x as common It classifies dissections that involve the ascending aorta as type A, regardless of the site of the primary intimal tear, and all other dissections as type B. In comparison, the DeBakey system is based upon the site of origin with type 1 originating in the ascending aorta and propagating to at least the aortic arch, type 2 originating in and confined to the ascending aorta, and type 3 originating in the descending aorta and extending distally or proximally Ascending aortic dissections ~ 2x as common Right lateral wall of ascending aorta most common site Aortic arch involvement ~ 30%

Variants Class I - classic separation of intima/media and dual lumens; flap between true and false aneurysm and clot in false lumen; Class II - intramural hematoma with separation of intima/media but no tear or flap; Class III - limited intimal tear without hematoma and eccentric bulge at tear site; Class IV - atherosclerotic ulcer penetrating to adventitia with surrounding hematoma; Class V- iatrogenic or traumatic dissection

Clinical Presentation Severe, sharp or "tearing" posterior chest or back pain (distal to L subclavian) or anterior CP (ascending dissection) Isolation or with syncope, CVA, MI, CHF, … HTN more common in type B dissection (70% vs. 36%) Pulse deficit in 19-30% with an acute type A dissection vs. 9-21% with a type B dissection

Clinical Finding Artery or Structure Aortic insufficiency or CHF Aortic valve AMI Coronary artery (right) Tamponade Pericardium Hemothorax Thorax CVA or Syncope Brachiocephalic, CC, Left subclavian UE pulselesness, low BP, pain Subclavian Paraplegia Intercostal LE pain, pulselessness, weakness Common iliac Abdominal pain, mesenteric ischemia Celiac or mesenteric Back or flank pain; ARF Renal artery Horner syndrome Superior cervical sympathetic ganglion

Differential Diagnosis Acute Coronary Syndrome Pericarditis Pulmonary embolus Aortic regurgitation without dissection Aortic aneurysm without dissection Musculoskeletal pain Mediastinal tumors Pleuritis Cholecystitis Atherosclerotic or cholesterol embolism Peptic ulcer disease or perforating ulcer Acute pancreatitis

Diagnosis Clinical Prediction of Aortic Dissection Study of 250 pts with acute chest and/or back pain (128 with AD) found 96% with acute AD identified using 3 clinical features: Abrupt onset of thoracic or abdominal pain with a sharp, tearing and/or ripping character Mediastinal and/or aortic widening on chest radiograph Variation in pulse (absence of a proximal extremity or carotid pulse) and/or blood pressure (>20 mmHg difference in the right and left arm) Any 2 out of 3 variables (77% of dissections): ≥83% Additional imaging studies obtained in 98% of pts due to limited sensitivity of CXR, especially in type B dissections

Chest X-Ray Type A Type B 63% with mediastinal widening, 11% with no abnormality Type B 56% with mediastinal widening, 16% with no abnormality

Electrocardiogram 31% normal 42% non-specific ST and T wave changes 15% ischemic changes 5% changes c/w AMI

Advanced Imaging Modalities Aortic Dissection Involvement of the ascending aorta The extent of dissection and the sites of entry and reentry Thrombus in the false lumen Branch vessel or coronary artery involvement Aortic insufficiency Pericardial effusion

Advanced Imaging Modalities Based on year 2000 IRAD: mean 1.83 studies per patient 61% CT 33% Echocardiography 4% Aortography 2% MRI

ESC Guidelines for Diagnostic Imaging of Acute Aortic Dissection Class I - TTE followed by TEE Class II – CT, CTA to define anatomy Class IIa – CTA in stable pts, MRI in stable pts, Intravascular US Class IIb - CT if detection of tears is crucial, CTA in unstable pts, intravascular US to guide intervention Class III – MRI in hemodynamically unstable patients, routine pre-op CTA

ESC Guidelines for Diagnostic Imaging of Chronic Aortic Dissection Class I – MRI Class IIa – TTE, TEE, CTA

CT Scan

CT Scan

CT Scan

CT Scan Sensitivity 83-98% Specificity 87-100% Advantages: availability at most hospitals ID of intraluminal thrombus and pericardial effusion Disadvantages: Intimal flap seen < 75% of cases and site of entry is rarely identified Potentially nephrotoxic iodinated contrast Unable to assess for aortic insufficiency Accuracy of CT is improved with spiral CT and electron beam or multidetector CT Spiral CT may be more accurate than MRI or TEE in the detection of aortic arch vessel involvement Limitation: Without ECG gating  simulate artifact ~ aortic dissection

TTE

TTE

TTE

TTE

TTE

TTE

TTE Limited utility for evaluation of the thoracic aorta for dissection unable to adequately visualize distal ascending, transverse, and descending aorta in a substantial majority of patients Intimal flap in the proximal aorta may be seen, though the sensitivity and specificity of TTE are inferior compared to CT, MRI, and TEE Most useful for assessment of cardiac complications of dissection, including AI, pericardial effusion/tamponade, and regional LV dysfunction

TEE

TEE

TEE

TEE

TEE

TEE

TEE

TEE Advantages sensitivity 97 – 99% close proximity of esophagus to thoracic aorta and absence of an intervening lung or chest wall portable procedure diagnosis within minutes useful in patients too unstable for CT or MRI intimal dissection flaps can be identified with high spatial resolution true and false lumens can be identified thrombosis in the false lumen, pericardial effusion, aortic regurgitation, and the proximal coronary arteries can be visualized 135º long axis view can define severity and mechanism of aortic regurgitation that complicates acute type A dissections

TEE Disadvantages Specificity as low as 77-85% false-positive findings in the ascending aorta artifacts can be detected by addition of M-mode imaging, increasing specificity to almost 100% Requires sedation and esophageal intubation TEE requires availability of experienced operators (both physicians and technicians) to assure accurate results

30 Day Mortality Rates for Acute Aortic Dissection Data from the international registry of acute aortic dissection – published in JAMA in 2000 Acute Type A dissection treated medically - 20% mortality rate at 24 hours 30% at 48 hours 40% at one week 50% by one month Hagan, Etc, JAMA 2000 283:897

Mechanical Composite Root Repair with and w/o Hemiarch Repair

Homograft Repair

Porcine BioRoot Replacement

Valve Sparing Replacement

Aortic Dissection Repair: Teflon Felt as Neomedia

Endovascular Aortic Stent Grafts

Endovascular Aortic Stents

References Hurst the Heart, 11th Edition Manning, W. UpToDate Online 16.2. Clinical manifestations and diagnosis of aortic dissection.