Vein graft injury during in-situ femorodistal bypass procedures.

Autologous saphenous vein remains the conduit of choice for femorodistal bypass grafts to the below knee popliteal artery, tibioperoneal trunk and single calf vessels. The vein is used non-reversed (in-situ) and a valvulotome is passed along the vein to render the valves incompetent. During the first post-operative year 20-30% of these grafts develop intrinsic lesions which may lead to graft failure. These lesions may be isolated graft stenoses or longer diffuse areas of intimal hyperplasia. The aetiology of these intrinsic graft lesions remains unknown. However it has been that the key pathophysiological process in intimal hyperplasia is the migration of smooth muscle cells from the media of the vein into the intima where they proliferate and cause thickening. Recently it has been suggested that intrinsic graft lesions in reversed vein grafts used for coronary artery bypass surgery may be due to injury to the vein during preparation for bypass grafting. However the preparation of in-situ femorodistal vein grafts differs from that of reversed grafts. Therefore a study has been performed to investigate whether damage to the vein occurs during preparation for in-situ femorodistal bypass grafting and to identify specific factors that may lead to injury. An organ chamber system was designed to allow endothelial and smooth muscle cell injury to be studied in saphenous vein segments obtained from patients undergoing bypass surgery. Smooth muscle cell function was assessed by the contractile response of the vein to noradrenaline and endothelial function was assessed by the release of endothelium-derived relaxing factor (EDRF). The results show that significant endothelial and smooth muscle cell injury occurs with the in-situ technique of vein grafting when compared to controls (p 0.05). This injury occurs during surgical preparation of the vein for use as an in-situ conduit. However, the use of x-ray contrast medium for intra-operative arteriography does not cause additional endothelial or smooth muscle cell injury. Intra-operative vasodilators such as papaverine and iloprost do not damage the endothelium or smooth muscle cells although papaverine does have a prolonged effect on smooth muscle cell function.