Acute Aortic Dissection

Abstract

Aortic dissection may be fatal without early diagnosis and appropriate medical, surgical, or endovascular treatment. The presenting symptoms and signs are so myriad and nonspecific that dissection may be overlooked initially in up to 40% of cases. In addition, the diagnosis is established only postmortem in a substantial number of cases.1 Few other conditions demand such prompt diagnosis and treatment, because the mortality rate of untreated dissection approaches 1%/h during the first 48 hours, 80% at 14 days, and 90% at three months.2 If unrecognized and untreated, fewer than 10% of patients with proximal aortic dissection survive a year. Most patients succumb within the first 3 months,3 usually of acute aortic insufficiency, major branch vessel occlusion, or rupture into the pericardium, mediastinum, or left hemithorax. In 20 years of follow-up of 527 patients with aortic dissection, nearly 30% of late deaths were due to ruptured aortic aneurysm.4 See page 1839 The most frequently used modalities to identify dissection and define the sites of origin and termination are computerized tomography (CT), transesophageal echocardiography (TEE), and magnetic resonance (MR) imaging. The primary diagnostic criterion for diagnosis of aortic dissection by CT is demonstration of two contrast-filled lumens separated by an intimal flap.5 The sensitivity of CT ranges from 93% to 100% and specificity from 87% to 100%.5,6 Inaccuracy may result from inadequate contrast opacification, nonvisualization of the intimal flap, artifacts extending across the aortic lumen that simulate an intimal flap, misinterpretation of adjacent vessels or prominent sinus of Valsalva as the flap, atelectasis, pleural thickening, or thrombosis of the false lumen. Multidetector-row CT scanners offer more rapid image acquisition, variable section thickness, 3-dimensional rendering, diminished helical artifacts, and smaller contrast requirements, overcoming many of the limitations discussed above.7 The sensitivity and specificity of MR imaging …