The effect of adjunctive arteriovenous fistula on prosthetic graft patency: a controlled study in a canine model. Bilateral 6 mm PTFE grafts were placed from the external iliac artery to the femoral artery with ligation of the intervening segment of the iliofemoral artery in 14 dogs. An arteriovenous fistula was constructed at the distal anastomosis on one randomly selected side in each animal while the contralateral graft served as a control. Graft follow-up ranged between 8 and 12 months in all animals. Serial arteriography was performed to confirm graft and fistula patency and demonstrated persistence of antegrade flow into the arterial tree distal to all patent bypasses. Femoral intraarterial pressures distal to patent grafts were identical on both sides in each animal throughout the study. Cumulative life-table patency rates showed higher patency for the arteriovenous fistula bypasses than the control grafts at all time intervals: 71% vs. 57% at 3 months, 48% vs. 25% at 6 months, and 40% vs. 22% at 12 months, respectively. This is the first controlled study that provides experimental evidence suggesting that these bypasses may produce increased patency of prosthetic arterial grafts and lends support to their use in a clinical, prospective, randomized study. 