The bypass versus angioplasty in severe ischemia of the leg (BASIL) trial is the only large, prospective, randomized trial published to date to compare surgical bypass and endovascular therapy as treatments for patients with severe limb ischemia.1 It indicated that autog-enous vein is superior to prosthetic conduits for patients undergoing bypass in this setting. Multiple studies have confirmed the overall superiority of vein conduits for leg bypass.2,3
When autogenous vein is truly lacking, there is gen-eral consensus that a short graft above the knee joint is the most favorable location for use of a prosthetic conduit. Below the knee, many of the published studies are confounded by the use of patches and cuffs; different surgeons employ a variety of distal anastomotic adjuncts. The challenge therefore lies in determining whether improved clinical outcomes are the result of the conduit or a result of the adjunct. Taylor vein patches likely improve prosthetic bypass outcomes below the knee.4 Dr. Neville’s distal vein patch is another important prosthetic bypass adjunctive technique.5 Dr. Neville has published research suggesting that even at 1 year, a separation in outcomes between patients who receive heparin-bonded expanded polytetrafluoroethylene and patients who receive saphenous vein may begin to appear.6
The spectrum of peripheral artery disease (PAD) is broad, and therefore surgical outcomes will be markedly different depending upon which patient is selected for which intervention. Critical limb ischemia was defined in 1982 in a one-page consensus document7 written by vascular surgeons. There are major problems with this definition, in particular its lack of applicability to patients with diabetes. The Society for Vascular Surgery (SVS) Wound, Ischemia, and foot Infection (Wlfl) limb classification system may be a useful tool for controlling study outcomes and determining which therapeutic option is best for a particular patient. The classification is based on three major factors that influence amputation risk and clinical management.8 When the WIfI scores are combined, patients can be classified into four clinical stages of disease. Two recent studies have already validated the concept of the SVS WIfI classification and confirm its utility in predicting amputation risk.9,10
A uniform classification system is required in order to accurately assess outcomes and relative efficacy of interven-tions intended to prevent limb amputation in patients with PAD and diabetes. The WIfI index includes critical factors that must be considered and graded for patient evaluation. In many ways, the WIfI index is similar to the TNM (tumor, nodes, metastasis) classification of malignant tumors because it is intended to allow assessment, compari-son, and improvement of outcomes. It is acknowledged that therapies will change over time, so therefore WIfI is not intended to dictate therapy. The WIfI index would also benefit from an updated practical arterial anatomic classification system.
Joseph L. Mills, Sr, MD, is from the Division of Vascular Surgery and Endovascular Therapy, Michael E. DeBakey Department of Surgery, Baylor College of Medicine in Houston, Texas. He has disclosed that he has received compensation from Gore for participating in the Summit and has received honoraria from Gore for writing this article. Dr. Mills may be reached at [email protected]
- Adam DJ, Beard JD, Cleveland T, et al. Bypass versus angioplasty in severe ischaemia of the leg (BASIL): multicentre, randomised controlled trial. Lancet. 2005;366:1925-1934.
- Mills JL. Infrainguinal bypass. In: Cronenwett JC, Johnston W, editors. Rutherford’s Textbook of Vascular Surgery. 8th edition. Philadelphia: Elsevier Saunders; 2014:1758-1781.
- Mills JL. Open bypass and endoluminal therapy: complementary techniques for revascularization in diabetic patients with critical limb ischemia. Diabetes Metab Res Rev. 2008;24(Suppl 1):S34-39.
- Yeung KK, Mills JL, Hughes JD, et al. Improved patency of infrainguinal PTFE bypass with distal Taylor vein patch. Am J Surg. 2001;182:578-83.
- Neville RF, Tempesta B, Sidway AN. Tibial bypass for limb salvage using polytetrafluoroethylene and a distal vein patch. J Vasc Surg. 2001;33:266-271; discussion 271-262.
- Neville RF, Capone A, Amdur R, et al. A comparison of tibial artery bypass performed with heparin-bonded expanded polytetrafluoroethylene and great saphenous vein to treat critical limb ischemia. J Vasc Surg. 2012;56:1008-1014.
- Bell PRF, Charlesworth D, DePalma RG, et al. The definition of critical ischemia of a limb. Working Party of the International Vascular Symposium. Br J Surg. 1982;69(Suppl):S2.
- Mills JL Sr, Conte MS, Armstrong DG, et al. The Society for Vascular Surgery Lower Extremity Threatened Limb Classification System: risk stratification based on wound, ischemia, and foot infection (WIfI). J Vasc Surg. 2014;59:220-234, e221-222.
- Cull DL, Manos G, Hartley M, et al. Prospective analysis of wound characteristics and degree of ischemia on time to wound healing and limb salvage: an early validation of the Society for Vascular Surgery Lower Extremity Threatened Limb Classifica-tion System. J Vasc Surg. 2014;59:28s.
- Zhan LX, Branco BC, Armstrong DG, Mills JL. The Society for Vascular Surgery (SVS) lower extremity threatened limb classification system based on Wound, Ischemia, and foot Infection (WIfI) correlates with risk of major amputation and time to wound healing. J Vasc Surg. 2015;61:939-944.