Matching based on quantitative coronary angiography as a surrogate for randomized studies: Comparison between stent implantation and balloon angioplasty of native coronary artery lesions

Although intracoronary stenting has been advocated as an adjunct to balloon angioplasty to circumvent late restenosis, its effectiveness has not yet been verified. Therefore the aim of this study was to determine the differences in the immediate and long-term changes in stenosis geometry between Wallstent implantation and balloon angioplasty in native coronary artery lesions. To obtain two study populations with identical baseline stenosis characteristics, patients were matched for lesion site, vessel size, and minimal luminal diameter. Only patients undergoing elective and successful coronary intervention of a native coronary artery, in whom a control angiographic study had been performed, were included. A total of 186 patients (93 in each group) were selected. The coronary angiograms were analyzed with the computer-assisted cardiovascular angiographic analysis system. Matching was considered adequate, since there was an equal number of lesion sites in each study population and there were no differences in baseline reference diameter and minimal luminal diameter. Wallstent implantation resulted in a significantly greater increase in minimal luminal diameter (from 1.22 ± 0.34 mm to 2.49 ± 0.40 mm, p < 0.00001) compared with balloon angioplasty (from 1.21 ± 0.29 mm to 1.92 ± 0.35 mm, p < 0.00001). Despite a greater decrease in minimal luminal diameter after Wallstent implantation (0.48 ± 0.74 mm) than after balloon angioplasty (0.20 ± 0.46 mm), the minimal luminal diameter at follow-up was significantly greater after stent implantation (2.01 ± 0.75 mm vs 1.72 ± 0.54, p < 0.0001). It was concluded that Wallstent implantation results in a superior immediate and long-term increase in minimal luminal diameter compared with balloon angioplasty. The larger initial gain after stent implantation compensates for the late loss, and thus an improved initial result and not lessened neointimal hyperplasia is responsible for a reduced incidence of restenosis. Studies based on matching of angiographic variables are a surrogate for randomized studies, forecasting their results and offering insight into the effects of different interventional techniques. Moreover, these studies yield statistical information that may be helpful for the proper design of a randomized study (sample size, type II error).