Edge Restenosis After Implantation of High Activity 32 P Radioactive β-Emitting Stents

Background —A high restenosis rate has been reported at the edges (“edge restenosis”) of 32 P 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 32 P 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 32 P 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.