The morphology of ascending aortic aneurysms.

To determine the frequency of morphologic abnormalities of the aorta, especially of the media, in patients with aneurysms of the ascending aorta, tissue specimens from surgically resected ascending aortic aneurysms of 339 patients were studied. Included were 232 men and 107 women; 53 (29 men, 23 women) had clinical signs of Marfan's disease. Features evaluated and graded included fragmentation of elastic fibers, cystic medial change, medial fibrosis, medial necrosis, atherosclerosis, periaortic fibrosis, and thickening of the vasa vasorum. Both elastic fragmentation and cystic medial change were present in a high percentage of patients. Cystic medial change was inversely correlated with increasing age of patients, especially in the group of patients without clinical evidence of Marfan's syndrome. Marked changes of these types in many younger patients without Marfan's syndrome could reflect a "tissue insufficiency" in early life that causes the aortic wall to weaken and dilate. Medial necrosis, fibrosis, and atherosclerosis were directly correlated with age. Hemodynamic events are considered to initiate injury and repair within the aortic wall. Dissection was more frequently seen with medial abnormalities than with atherosclerosis.