Evaluating aortic dissection: when is coronary angiography indicated?

Transoesophageal echocardiography (TOE), rapid sequence spiral computed tomography with intravenous contrast (CT), and magnetic resonance angiography (MRA) have become increasingly useful in the evaluation and diagnosis of acute dissection of the ascending aorta. These diagnostic modalities are fast, safe, non-invasive, and highly accurate, with sensitivity and specificity approaching 100%. 1 And although most surgeons agree that aortography is no longer necessary before surgical intervention for acute aortic dissection, the role of coronary angiography remains controversial. Clinical presentation Acute dissection of the ascending aorta is a highly lethal event. Without surgical intervention, 50% of these patients die within the first 24 hours, 75% die within two weeks, and 90% die within one month. 2 Most patients with acute aortic dissection present with sudden onset of severe chest pain that may migrate to the neck or back. Occlusion of aortic branch vessels may cause stroke, abdominal pain, or limb ischaemia. A history of hypertension, known thoracic aortic aneurysm, or characteristics of Marfan's syndrome should alert the physician to the possibility of aortic dissection. On arrival to the emergency room, these patients may appear pale, cool, or clammy, and hyper-tension is typically present. Hypotension or profound shock usually indicates a catastrophic complication, including pericardial tamponade, aortic rupture, coronary artery obstruction, or severe aortic regurgitation. Diagnostic modalities Echocardiography should be used as the initial diagnostic procedure in patients with suspected aortic dissection. Initially , a transthoracic echocardiogram (TTE) is performed. With this examination, the dissection can be identified and the tear site in the aorta may be located. Left ventricular function, aortic and mitral valve function, regional wall motion, and coronary artery involvement are also assessed. In addition, complications of dissection can be demonstrated , including aortic regurgitation, pericardial eVusion, and cardiac tamponade. While TTE provides limited views of the aortic arch and descending aorta, TOE provides excellent images of these structures. Spiral CT with intravenous contrast allows for identification and evaluation of the aortic dissection and demonstrates any involvement of aortic branch vessels. In addition, a CT scan may identify pericardial fluid, thrombosis of the false lumen, periaortic haematoma or aortic rupture. Magnetic resonance angiography produces images of the aorta in multiple planes and provides information on flow properties within the aorta. Current MRA technology can distinguish blood from thrombus, diVerentiate between the true and false lumen, determine location and extent of dis-section, and define origins of aortic branch vessels. MRA may also …