Acute aortic dissection and medial degeneration in patients with 'floppy' mitral valves.

Mitral regurgitation due to 'floppy' valves is frequently associated with areas of medical necrosis in the ascending aorta. Application of the aortic clamp to such an area during valve replacement may produce an intimal tear followed by acute dissection. This complication occurred in three patients and was treated successfully by repair of the tear in the two cases where the dissection was observed at the time of operation. Is is suggested that infrequent clamping of the aorta and careful control of the pefusion pressure may decrease the risk of intimal trauma and acute dissection.