Factors affecting the patency of infrainguinal bypass.

Two hundred forty-nine well-characterized difficult distal bypasses, entered into a multicenter dextran 40 trial, were reevaluated after 3 years. Seventy in situ (IS) vein grafts, 49 reversed saphenous (RS) vein grafts, 60 polytetrafluoroethylene (PTFE) grafts, and 70 umbilical vein (UV) grafts were used. Primary and secondary patency rates at 3 years were, respectively, 84% and 90% for IS, 66% and 73% for RS, 35% and 48% for PTFE, and 24% and 32% for UV. Subgroup analysis according to the site of distal anastomosis showed no significant differences in primary patency among these grafts at the above-knee level but significant differences between both vein grafts (IS and RV) and the others (PTFE and UV) below the knee (78% vs 31%, respectively). This difference increased at the tibial level (78% vs 10%) but there was also a significant difference between IS grafts (88%) and RS grafts (63%) at this level. Hazard functional analysis showed all grafts except IS grafts begin to fail at an increasing rate again by 24 months. Although overall results appeared to favor PTFE over UV, 62% of PTFE vs 16% of UV terminated at the above-knee level and the patency results of these two grafts were not significantly different at any level. The only other factor than graft type and distal anastomotic site that consistently correlated with late patency was tobacco use. Diabetic patients actually fared significantly better than nondiabetic patients, presumably because of the higher use of IS grafts and lower use of tobacco. The choice of graft overshadows all other factors affecting patency and its influence is magnified with more distal terminal anastomosis.