Invited commentary

Abstract

Bosiers et al herein report the first clinical series of infrainguinal bypass with a new, heparin-bonded, expanded polytetrafluoroethylene (ePTFE) prosthesis. This option has now been added to the smorgasbord of options from which vascular surgeons may choose when performing infrainguinal bypass. The menu includes reversed, nonreversed, and in situ great and short saphenous vein; alternate (arm) vein; Dacron; heparin-bonded Dacron; human umbilical vein (HUV); Distaflo (Bard Peripheral Vascular, Inc, Tempe, Ariz) ePTFE; and standard ePTFE, to which one may add adjuncts such as a Miller cuff, St. Mary’s collar, Taylor patch, or distal arteriovenous fistula. Although this report is interesting and provocative, it represents at most a tantalizing tidbit on the smorgasbord of vascular grafts rather than a substantial main course. The study was conducted in a relatively low-risk group of patients and was limited by small sample size, short follow-up, and lack of a control group. Fifty-five of the 99 procedures were above-knee (AK) femoropopliteal (FP) bypasses, and 58 of the procedures were performed for claudication (Rutherford grade I, category 3); only 16 procedures were performed in patients with rest pain (grade II, category 4), and 26 bypasses were performed in individuals with minor tissue loss (category 5). Among 45 infrageniculate bypasses, the insertion site was the below-knee (BK) popliteal artery in 24 patients and a crural vessel in 21. Ten of 86 patients died during the first follow-up year, and 15 of 99 implanted grafts occluded during the first year after surgery, leaving small numbers of patients and grafts available for even short, 1-year follow-up. Reported, 1-year life-table primary patency rates were 84% for AK FP bypasses and 81% for BK FP grafts. The numbers were so small for the crural subgroup that the standard of error was >10% at both 6 and 12 months, making the Kaplan-Meier curve unreliable. Skeptics will note that almost any material performs well for the first 1 to 3 years in claudicants with an AK popliteal insertion site. At least three prospective, randomized trials have demonstrated equivalence between ePTFE and Dacron for AK FP bypass. Although a single study of 209 patients reported early improvement in FP graft patency for heparin-bonded Dacron compared with standard ePTFE at 3 years, by 5 years, results were equivalent. Randomized prospective trials have demonstrated that vein outperforms all prosthetic conduits for all infrainguinal insertion sites; while the demonstration of vein superiority in the AK position requires 3 to 5 years of follow-up, the superiority of vein over prosthetic has been readily demonstrated for BK FP and femorocrural bypasses with only 1 to 2 years of follow-up. A single study of PTFE with a Miller cuff for BK popliteal bypass reported dramatically improved 2-year patency (52% vs 29%) associated with the addition of a distal cuff. If the vascular surgeon of 2005 were to approach the infrainguinal graft smorgasbord and find that vein is unavailable, what conduit should he select? The present study will not help him reach a decision. Available in vitro animal studies suggest that heparin is detectable for up to 4 weeks on polyester Dacron grafts. Heparin activity has been reported to be measurable for up to 12 weeks on heparin-bonded ePTFE grafts. Whether this possibly longer duration of heparin activity confers increased thromboresistance as well as a patency advantage for heparin-bonded ePTFE grafts is uncertain. The clinical utility of this potentially promising off-the-shelf prosthesis will require prospective, randomized trials. Suitable control groups would include standard ePTFE, PTFE with a distal venous adjunct (cuff, collar, or patch), and perhaps ePTFE with a modified distal cuff such as Distaflo. Given the apparent aversion of vascular surgeons to prospective, randomized trials of infrainguinal bypass grafts, we may have to wait for quite a while before we know. Until then, the conduit choice in the absence of suitable vein remains a highly subjective matter of taste.