Descriptive data are given as means ± SD, or, for non-normal distributions or censored data sets, as medians with interquartile ranges (range from the 25th to the 75th percentile), and were analyzed by Mann Whitney U tests. Proportions were compared by Chi square statistics with Yates’ correction or exact tests, as appropriate. Kappa statistics with 95% confidence intervals were used to assess agreement between angiography and duplex ultrasound. Multivariable logistic regression analysis was applied to assess the association between treatment and restenosis and to adjust for potentially confounding factors. We converted the odds ratios derived from the multivariate model to risk ratios (RR) with 95% confidence intervals (CI). Multiplicative interaction terms and log likelihood ratio tests were used to test for interactions. Calculations were performed using Stata release 8.0 (Stata Inc. College Station, TX, U.S.).