Serial duplex scans elucidate the evolving hemodynamics of distal arteriovenous fistulas.

Arteriovenous fistulas at the distal anastomosis have been suggested to improve the patency of prosthetic femorocrural bypasses. We have followed nine patient with bypasses to the crural vessels and distal arteriovenous fistulas using physical examination, pulse volume recordings, and segmental pressure indices. Duplex scans of the distal anastomosis were employed to determine the contribution of arterial and venous outflow to total graft flow. Early graft patency was achieved in all patients. One patient went on to amputation at one week postoperatively for progressive ischemia despite a patent graft. The other eight patients achieved successful revascularization. Healing of ulcers, relief of rest pain, the presence of palpable pulses, good pulse wave amplitude, and normal pressure indices are consistent findings as long as the bypass is patent. One patient died on the fourth postoperative day from a myocardial infarction. The remaining patients have been followed from one to 23 months with follow-up examination every three to four months. Sequential duplex scans show that flow continues into distal arteries while venous outflow diminishes. This corresponds to a reduction in the diameter of the outflow veins while the caliber of arterial runoff is maintained. Patency has been achieved up to 23 months with a mean of 12 months. Venous outflow occlusion precedes graft thrombosis by two to 15 months. Graft occlusion has uniformly necessitated amputation. It may be possible to improve long-term graft patency and limb salvage by surgical revision of the distal anastomosis to reestablish venous outflow.