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Saphenous vein is the primary conduit used for lower limb arterial bypass grafting because of both demonstrated and thoretic advantages that have resulted in excellent short- and long-term patency rates and resultant limb salvage. The cause of failure of lower extremity autogenous vein bypass grafts falls into two categories. The first occurs in the perioperative period and is related to the technical aspects of the procedure, the availability and quality of the saphenous vein, proper selection of patients with sufficient outflow arterial bed to sustain a bypass graft, and miscellaneous causes such as cardiac and coagulation abnormalities that can cause failure of the bypass graft. The second group consists of those factors that occur in the follow-up period after the first 30 days. These factors are a result of dynamic changes that occur in the arterial bed and venous conduit. Understanding the biologic characteristics of these changes will allow detection of lesions before the development of graft thrombosis to allow remedial secondary procedures, which will prolong graft survival. To improve long-term patency, we instituted a rigorous postoperative surveillance program to identify potential graft problems before they result in graft thrombosis so that secondary procedures can correct the defect and prolong graft survival. Since 1981 we have exclusively used the in situ saphenous vein technique. The surveillance program begins intraoperatively with the measurement of graft flow velocities and examination of the grafts for evidence of arteriovenous (AV) fistulas and the completeness of valve incision. The patients then have graft flow velocities and ankle/brachial pressure measurements performed before discharge from the hospital, at 6 weeks, and then every 3 months. Indications for repeat angiography include a drop of the ankle/brachial index of 0.15 or greater, a decrease in the graft flow velocity to less than 40 cm/sec or a drop of greater than 20 cm/sec or both on subsequent evaluations. Because of this postoperative surveillance protocol, we have been able to identify the failing graft and determine the cause of the failing graft. Graft failures occurring within the first 30 days are primarily related to technical problems with the procedure. These include technical errors in construction of the anastomosis, injury to the saphenous vein during valve ablation, and inadequate saphenous vein because of small size or previous phlebitic processes. In a series of 192 consecutive in situ bypass graftings to the popliteal (64) and tibial vessels (128), graft failure occurred within 30 days of operation in six patients (3.1%). All early failures occurred in patients with severe ischemia, involved grafts to tibial arteries, and occurred despite attempts at revision within 3 days of the original operation. In two patients early failure was related to trauma of valve incision in veins of 2.5 mm diameter or less. Because of the small caliber of these veins, the valvulotome scored the intima of the vein providing a site for aggregation of platelets and subsequent formation of thrombus. The cause of early graft failure in one patient was the development of heparin-induced platelet aggregation, which was not promptly detected. The three remaining graft failures occurred in patients with low peak systolic flow velocity of less than 40 cm/sec. Fifteen of the grafts (8%) were successfully revised within the first 30 days. The graft lesion responsible for revision within the first 30 days included retained valve in five patients, AV
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