Abnormal venous valves: a cause of early obstruction of saphenous vein bypass grafts.

Factors other than technical error and poor run-off may account for occlusion or obstruction of aortocoronary vein bypass grafts in the early postoperative period. Four cases are presented in which graft obstruction was caused by venous valves. Discussion of the etiology of this problem and recommendations for its prevention are included.