On CT angiography, which finding differentiates a Type A (DeBakey I/II) from a Type B (DeBakey III) aortic dissection?

• A Involvement of the abdominal aorta
• B Extension into the iliac vessels
• C Presence of an intimal flap in the ascending aorta ✓
• D Involvement of renal arteries

Explanation

The Stanford classification divides aortic dissection into Type A (involving the ascending aorta, regardless of origin or extent) and Type B (not involving the ascending aorta, origin distal to the left subclavian artery). The key CTA finding that defines Type A is an intimal flap visible within the ascending aorta. Type A requires urgent surgical management due to risk of aortic rupture, pericardial tamponade, coronary involvement, and acute aortic regurgitation. Type B is typically managed medically unless complicated (malperfusion, rupture).

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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