Flow disturbance due to venous valves: a cause of graft failure.

Late (greater than 1 year) postoperative angiographic studies in five patients revealed evidence of flow disturbance at the distal valve, when two valves were present in the body of a saphenous vein graft (SVG). This was associated with delayed clearance of radiopaque dye due to reduced velocity of flow. On follow-up, occlusion, thrombus formation, or development of atherosclerosis seemed to have occurred in anatomic relation to these valves. All five patients had one additional graft in a good state of preservation; three internal mammary artery (IMA) grafts, and 2 SVGs. The latter had only one venous valve, and the velocity of flow was good. It appears that good velocity of flow is essential to the integrity of coronary bypass grafts. The presence of more than one venous valve in a graft appears to cause flow disturbance and sluggish velocity, factors adversely affecting their integrity.