Sample size: Power calculations were performed by the statistician (Jill Barker, Ph.D.) on the basis of our preliminary data from the outcome of thrombosed grafts at UAB. The estimated sample of 130 patients, evenly divided between the two groups, was sufficient to detect a tripling in median graft survival from 1 month on the control arm to 3 months on the stent arm, assuming an exponential distribution, 3 years of accrual, 1 year of followup, two-sided significance level of 0.05, and power of 0.80.