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fistula in four, graft torsion in two, anastomotic stenosis in two, and unexplained thrombosis in six. Eleven of the 19 (58%) early graft revisions corrected problems in the in situ vein graft, such as retained valves, residual AV fistula, or graft torsion. All bypass graftings revised for problems with the in situ vein remained patent for more than 90 days. Patency was successfully restored in seven of 11 (64%) occluded grafts that underwent thrombectomy and revision. Occasionally valves may be missed during the operative procedure because they are in an open position adjacent to the lumen of the graft at operation and perioperative period and float down to a closed position at some later time in the postoperative period. The persistence of AV fistulas is likewise related to the operative procedure. Vein side branches usually are missed, but more commonly vein branches are not visualized because of initially competent valves at their origins from the saphenous vein. In the period after the procedure, arterial pressure can cause dilation of the vein side branch, which results in valve incompetence and a subsequent AV fistula. Graft torsion is also more common with the in situ grafting because of the very short segment of the vein that is free. Twisting short segments of vein grafts less than 3 mm in diameter is easier than twisting a total excised reversed saphenous vein. The second category of early graft failure is caused by technical problems and the construction of the anastomosis. Many authors reporting femoral distal bypass techniques have documented these problems. The third category includes problems related to miscellaneous causes, for example, coagulopathy, such as heparin-induced platelet aggregation, antithrombin insufficiency, and occasionally abnormalities in the fibrinolytic system. Occlusion in the first 30 days postoperatively occurs in patients with poor runoff whose occlusive disease is too advanced to prevent successful arterial reconstruction or in whom the saphenous vein is not usable as a conduit, because of its extremely small size or areas of stenosis or scarring as a result of previous phlebitic processes. Problems beyond 30 days after surgery can be separated into two time periods based on cause of problem. Those occurring less than 2 years after surgery are generally associated with the in situ graft, including scarring at the valve incision sites, fibrointimal hyperplasia at the distal anastomosis, and persistence or development of AV fistula. Problems occurring after 2 years are generally related to the progression of the atherosclerotic occlusive disease in the arterial bed both proximal and distal to the conduit. In our series 29 grafts were revised more than 1 month after operation because of sudden occlusion or to correct hemodynamic abnormalities in the patent graft found on noninvasive testing or angiography. Graft revisions were performed on an average of 337 days after operation and ranged from 45 to 1087 days. Morphologic characteristics included, anastomotic stricture (10), stenosis of vein graft at valve site (eight), graft entrapment (three), pseudoaneurysm repair (two), iliac artery stenosis (one), AV fistula (two), and aneurysm (one). Vein graft angioplasty or jump grafting with stenosis involving an anastomotic or valve incision were the most common secondary operations performed. All grafts were patent for more than 90 days after revision. Four grafts required multiple revisions because of recurrent anastomotic stenosis or jump graft occlusion. In an attempt to ascertain the role of fibrointimal hyperplasia as a cause of failure of autogenous saphenous vein grafts, we have limited our examinations to those grafts requiring revision after the first 30 days. This study is somewhat complicated by the fact that it is sometimes difficult to entirely separate factors such as
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