Imaging description

Aortic dissection results from a tear in the aortic intima. Blood flow through the intimal defect results in a true and a false aortic lumen separated by an intimomedial flap. While there is considerable variability, the true lumen is generally smaller than the false lumen and opacifies more quickly following contrast administration (Figure 45.1). With current CT technology, continuity can usually be demonstrated between the true lumen and an unaffected segment of the aorta. The most widely used classification system is the Stanford classification: Stanford A dissection involves the ascending aorta (Figure 45.2) while Stanford B involves only the descending aorta (Figure 45.3). “Acute aortic syndrome” is a term encompassing several related aortic diseases: aortic dissection, intramural hematoma, and penetrating atheromatous ulcer, which have similar clinical features [1–3].

Importance

Stanford A dissection may result in pericardial tamponade or occlusion of coronary, carotid, or vertebral arteries and is usually treated surgically. Type B dissections are generally treated medically, unless there are signs of significant end-organ compromise, such as acute renal failure or bowel ischemia. Either type of dissection may progress to pseudoaneurysm formation or aortic rupture.