[Experimental study on the dissecting aortic aneurysm].

Type I dissecting aortic aneurysm is not only the most common type of all but an extremely lethal event. It is important to create the experimental model of type I dissection for clarifying behavior of this disease and successful treatment. The purpose of this study is: (1) production of experimental model of type I aortic dissection; (2) examination of progression manner of dissection; (3) and investigation of influence of dissection upon aortic valve and coronary artery. The experimental model of type I aortic dissection was produced in adult mongrel dogs. Bilateral thoracotomy was made and intimal tear was created in the ascending aorta by modified Blanton's procedure. Hypertension and creation of large pocket of the aortic media were necessary to produce type I aortic dissection. Extension of dissection had a tendency toward the inner layer of the aortic wall at distal site. However, at proximal site the dissection progressed in the same layer of the aortic wall. In this series, retrograde extension of dissection remained blind above annulus of aortic valve, and no incidence of aortic regurgitation or coronary ischemia was occurred. But on histologic examination, degeneration of the aortic wall by the dissection was observed. Such weakness of aortic wall showed potentiality to developed into subsequent aortic regurgitation or coronary ischemia.