The CTA for this gentleman has revealed a Stanford type B aortic dissection. How does the anatomy effect the pathophysiology and classification?
The aorta consists of three layers: tunica intima, media and adventitia. Aortic dissection involes tearing of the tunica intima allowing intramural bleeding into the tunica media, with resultant separation of the wall layers (1).
Organ damage occurs when the dissection occludes side branches of the aorta. This can either be due to static compression as a direct result of the dissection, or dynamic compression affecting branches on the opposite side to the dissection; in diastole the true aorta lumen collapses and the dissecion flap occludes the opposing side branch. Complications are therefore dependent on the location of the dissection (4).
There are two commonly used classfication systems based on anatomical origin (5). Stanford classification divides dissection into type A (dissection involving the ascending aorta) and type B (not involving the ascending aorta). DeBakey classification divides dissection into type I (ascending aorta, aortic arch and typically descending aorta), type II (only aortic arch) and type III (descending aorta).
