Leg Bypass Best With Ideal Greater Saphenous Veins

BY MITCHEL L. ZOLER

BALTIMORE -- A wide, short, single-segment, greater saphenous vein is the ideal conduit for lower extremity bypass, based on an analysis of data collected from more than 1,400 patients.

When suboptimal veins are used for bypassing infrainguinal arteries, patients may benefit if more aggressive surveillance is used during follow-up to quickly identify cases of lost patency, Dr. Andres Schanzer said at the Vascular Annual Meeting.

Patients who undergo leg bypass with an inferior conduit have about a 20% reduced primary patency and primary assisted patency after 1 year, compared with those revascularized with an ideal conduit, said Dr. Schanzer, a vascular surgeon at Brigham and Women's Hospital in Boston.

He and his associates made these findings by a post hoc analysis of patients who had been enrolled in a failed drug trial from November 2001 to October 2003 at 83 North American hospitals. Although the results were negative for the study's primary end point, the trial was the "best accumulated cohort to date of patients with critical limb ischemia who underwent infrainguinal bypass," he said.

The Project of Ex-Vivo Vein Graft Engineering via Transfection (PREVENT)-III trial was designed to test whether ex-vivo treatment of vein grafts with the drug edifoligide was successful at blocking smooth muscle growth and reducing the rate of vein graft failure following infrainguinal bypass.

The study was sponsored by Corgentech Inc. and Bristol-Myers Squibb; results for the primary end point were published last year (J. Vasc. Surg. 2006;43: 742-51). Data collected on the 1,404 patients in the study were analyzed to identify technical factors of vein grafting that were linked with the best 1-year outcomes.

The analysis looked at four parameters of the vein grafts used in the study. The grafts were sorted by diameter into three groups: less than 3 mm, 3.0-3.49 mm, and 3.5 mm or larger. They were sorted by length in four groups: less than 40 cm, 40-50 cm, 51-60 cm, and more than 60 cm. They were sorted by vessel type: single-segment greater saphenous vein, lesser saphenous vein or arm vein, or composite vein graft. And they were sorted by proximal and distal anastomosis site, but this category showed no bearing on outcome.

In a multivariate analysis that adjusted for variations in all four graft parameters as well as age, gender, race, tobacco use, diabetes, dialysis, prior limb bypass, and study drug used, the researchers found that graft diameter, length, and type all had a significant impact on primary patency, primary assisted patency, and secondary patency measured 1 year after surgery.

Grafts that were less than 3 mm in diameter were about 2.5-fold more likely to fail for all three patency measures, compared with grafts that were more than 3.5 mm in diameter. Grafts that were more than 60 cm long were about 30%-50% more likely to fail, compared with those that were less than 40 cm long. And grafts that were composite vessels of either lesser saphenous veins or arm veins were about 50%-80% more likely to fail, compared with single-segment, greater saphenous vein grafts.

Slightly less than half of the patients in the study received completely optimal conduits: single-segment, greater saphenous vein grafts that were more than 3.5-mm wide and less than 40-cm long. The 1-year patency rates for these grafts, as well as the rates of limb salvage and survival, were "excellent," said Dr. Schanzer.

When asked to comment on this article, Dr. Frank Pomposelli, Chief of Vascular and Endo Vascular Surgery, Harvard University, stated: "This study is yet another excellent analysis of the PREVENT II cohort. It re-emphasizes a point that should be well known to all vascular surgeons--that the quality of the vein conduit is the most important determinant in the outcome of lower extremity arterial reconstructions. It should be no surprise that short length high quality saphenous vein that is 3 or more mm in diameter performs the best.

"What is important to realize is that while such an optimal conduit was only available in slightly less than half of the procedures, that patency and limb salvage rates were much higher, suggesting that even small alternative conduits or composites perform reasonably well and are superior to prosthetic grafts especially when crossing the knee joint.

"While good quality saphenous vein is indisputably the gold standard, careful, life-long postoperative follow-up is critical to maintain patency since we must deal with less than ideal conduits frequently." Dr. Pomposelli is an associate medical editor for VASCULAR SPECIALIST