Radioactive stents delay but do not prevent in-stent neointimal hyperplasia

Abstract

Background - Restenosis after conventional stenting is almost exclusively caused by neointimal hyperplasia. β-Particle-emitting radioactive stents decrease in-stent neointimal hyperplasia at 6-month follow-up. The purpose of this study was to evaluate the 1-year outcome of 32P radioactive stents with an initial activity of 6 to 12 μCi using serial quantitative coronary angiography and volumetric ECG-gated 3D intravascular ultrasound (IVUS). Methods and Results - Of 40 patients undergoing initial stent implantation, 26 were event-free after the 6-month follow-up period and 22 underwent repeat catheterization and IVUS at 1 year; they comprised half of the study population. Significant luminal deterioration was observed within the stents between 6 months and 1 year, as evidenced by a decrease in the angiographic minimum lumen diameter (-0.43±0.56 mm; P=0.028) and in the mean lumen diameter in the stent (-0.55±0.63 mm; P=0.001); a significant increase in in-stent neointimal hyperplasia by IVUS (18.16±12.59 mm3 at 6 months to 27.75±11.99 mm3 at 1 year; P=0.001) was also observed. Target vessel revascularization was performed in 5 patients (23%). No patient experienced late occlusion, myocardial infarction, or death. By 1 year, 21 of the initial 40 patients (65%) remained event-free. Conclusions - Neointimal proliferation is delayed rather than prevented by radioactive stent implantation. Clinical outcome 1 year after the implantation of stents with an initial activity of 6 to 12 μCi is not favorable when compared with conventional stenting.