Edge restenosis after implantation of high activity 32P radioactive β-emitting stents

Abstract

Background - A high restenosis rate has been reported at the edges ('edge restenosis') of 32P radioactive stents with an initial activity level of 3 to 12 μCi. This edge effect might be due to balloon injury and to a low dose of radiation at the stent margins. The aim of this study was to evaluate whether the implantation of 32P radioactive stents with a higher activity level (12 to 21 μCi) combined with a nonaggressive stent implantation strategy could solve the problem of edge restenosis. Methods and Results - We compared the results of lesions treated with single radioactive BX stents with an activity of 12 to 21 μCi (group 2, n=54 lesions) with the results of lesions treated by single radioactive BX stents with an initial activity level of 3 to 12 μCi (group 1, n=42 lesions). There were no procedural events. At the 6-month follow-up, no myocardial infarctions, deaths, or stent thromboses had occurred. Intrastent binary restenosis was 0% in group 1 versus 4% in group 2 (n=2, both at the ostium of the right coronary artery, P=NS). Intrastent neointimal hyperplasia was significantly lower in group 2 than in group 1. The intralesion (intrastent plus peri- stent) restenosis rate was 38% in group 1 versus 30% in group 2 (P=NS). Conclusions - Single 32P radioactive stents with an initial activity level of 12 to 21 μCi reduced intrastent neointimal hyperplasia compared with stents of 3 to 12 μCi, but they did not solve the problem of edge restenosis, even if a nonaggressive stent implantation strategy was used.