[Communicating acute aortic dissection (pathogenetic study)].

Thirty-five dissecting aneurisms of the aorta (D.A.). have been microscopically and ultramicroscopically examined. These data have been compared to those obtained from personal experiences on human aorta aging, as well as from Beta Aminopropionitrile treated rats. The authors conceive D.A. as a non-obligatory complication of a precocious and intense medianecrosis of the aortic wall, particularly characterized by a mucous imbibition and a loss elastic laminae. This medianecrosis is identical in dysplasic D.A. (Martan's syndrome for example) and in acquired D.A. (rapid aging or arteriosclerosis). The simultaneous occurence of a medianecrosis and conditions triggering tunica intima rupture, with blood afflux in the necrotic zone are undoubtedly rare. This explains the small number of observed D.A. in comparison to the large number of aortas with accentuated medial lesions.