Factors influencing the outcome of paramalleolar bypass grafts

Reported patency rates for paramalleolar bypass grafts have varied widely. To determine factors predictive of outcome, we reviewed our experience with 80 consecutive paramalleolar reconstructions in 68 patients performed between December 1986 and May 1995. All procedures were performed for critical limb ischemia defined as nonhealing ulcer or gangrene (n = 72, 90%) and rest pain (n = 8, 10%). Risk factors present were diabetes (n = 52, 65%), hypertension (n = 64, 80%), and history of smoking (n = 57, 71%). Of the 80 bypasses, in situ saphenous vein conduits were used in 39 (49%). In the remainder non-in situ grafts were used including reversed vein (n = 25, 31%), composite vein (n = 11, 14%), polytetrafluoroethylene (PTFE; n = 4, 5%), and composite PTFE/vein (n = 1, 1%). The recipient vessel was the dorsalis pedis artery in 26 procedures (33%), the posterior tibial artery in 32 (40%), the distal anterior tibial artery in 18 (22%), and tarsal or plantar vessels in four (5%). Primary and secondary patency rates were 52% and 68% at 36 months, respectively, by life-table analysis. The limb salvage rate was 86% and patient survival was 56% at 36 months. Secondary patency was significantly higher in diabetic patients than in their nondiabetic counterparts (86% vs. 50% at 36 months, p < 0.03). Similarly, patients undergoing in situ reconstructions had better secondary patency than patients with non-in situ conduits (86% vs. 51% at 36 months, p = 0.03). Diabetic patients tended to be younger (median age 69 years vs. 72 years) and had fewer prior reconstructions (7 [13%] vs. 13 [46%], p < 0.01). Diabetic patients received a higher proportion of in situ reconstructions (54% vs. 39%) but the difference did not achieve statistical significance (p = 0.09). We conclude that the long-term patency for paramalleolar bypass is acceptable but inferior to reported figures for more proximal reconstructions. The factors that most influence patency are the quality of the venous conduit and the presence of diabetes. The improved patency seen in diabetic patients is likely related to the fact that these patients require paramalleolar bypass at an earlier age, are less likely to have had previous reconstructions, and are therefore more likely to have a good quality venous conduit.