Case of the Month #30 Aortic Dissection
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).