Aortic dissection Ascending aortic dissection Type A aortic dissection UMLS:C1836653 According to the Stanford classification, type A aortic dissection affects the ascending aorta and arch. HP:0004933 A separation of the layers within the wall of the ascending aorta. Tears in the intimal layer result in the propagation of dissection (proximally or distally) secondary to blood entering the intima-media space. Abnormal ascending aorta morphology