Factors contributing to success and failure of femorotibial bypass grafts

Abstract

Femorodistal bypass grafting is an important technique in the armamentarium of vascular surgeons, and it has been found that the cost of such procedures justifies their performance in patients who have sustained critical ischemia. Graft material remains the most important factor in causation of graft failure, with all prosthetics having disadvantages when compared to the saphenous vein. In attempts to use biological materials, both bovine heterografts and human umbilical vein grafts have been seen to form aneurysms and undergo thrombosis. Meanwhile, many variations on the theme of prosthetic grafts have been tried and found wanting when used as bypasses from the femoral artery to the distal circulation. Among configurations tried have been polytetrafluoroethylene with and without external support; Dacron® in woven and knitted format, with or without internal and external velour; and combinations of these. As patency rates of these reconstructions have proven inferior to others using the saphenous vein, attempts have been made to extend the use of autogenous biologic material. Such attempts have included cephalic vein bypass grafts, short vein bypass grafts originating distal to the femoral artery, deep veins used as grafts, and the in situ bypass. Lately, it has been recognized that the in situ bypass, when compared to concurrent controls, shows no significant advantage to the popliteal level but is the technique of choice when distal anastomoses are at or distal to the midcalf. Compositesequential bypasses represent another technique developed to utilize the autogenous vein as a distal segment. While this has increased the rate of patency of distal bypass grafting, other aids to patency such as use of anticoagulants, antiplatelet agents, and adjunctive arteriovenous fistula have not. Dynamics of the coagulation system show an intrinsic change in patient status toward coagulation in the postoperative period, and although this factor is of some significance in causing early graft thrombosis, technical defects do not seem to play an important part. This review details some of these important causes of graft failure and places them in proper perspective.