Annulo-aortic ectasia. Light and electron microscopic changes in aortic media.

The aortic wall of the human ascending aorta from 44 patients operated on for annulo-aortic ectasia (AAE) was studied. Light microscopy revealed significantly greater cystic change, elastic fragmentation, fibrosis and disappearance of smooth muscle cells in aortic media in AAE than in control specimens taken at autopsy. Occasional aortae, however, were morphologically almost normal. Eight of the patients had Marfan's syndrome. No significant differences were observed between them and the other 36 patients, except for a tendency to have less pronounced fibrosis. There were 9 patients who, in addition to the changes mentioned, had advanced atherosclerosis, and their aortae showed more extensive fibrosis and medial necrosis. Pooling of proteoglycan matrix, degeneration of elastic lamellae, increased amount of collagen and necrosis of smooth muscle cells characterized the electron microscopic findings of 13 patients. The collagen fibers seemed to be of normal shape. In conclusion, changes in annulo-aortic ectasia are characterized by severe cystic medial necrosis. The changes are basically similar in Marfan and non-Marfan patients.