β-Particle–Emitting Radioactive Stent Implantation

Background —This study represents the Heart Center Rotterdam’s contribution to the Isostents for Restenosis Intervention Study, a nonrandomized multicenter trial evaluating the safety and feasibility of the radioactive Isostent in patients with single coronary artery disease. Restenosis after stent implantation is primarily caused by neointimal hyperplasia. In animal studies, β-particle–emitting radioactive stents decrease neointimal hyperplasia by inhibiting smooth muscle cell proliferation. Methods and Results —The radioisotope 32 P, a β-particle emitter with a half-life of 14.3 days, was directly embedded into the Isostent. The calculated range of radioactivity was 0.75 to 1.5 μCi. Quantitative coronary angiography measurements were performed before and after the procedure and at 6-month follow-up. A total of 31 radioactive stents were used in 26 patients; 30 (97%) were successfully implanted, and 1 was embolized. Treated lesions were in the left anterior descending coronary artery (n=12), the right coronary artery (n=8), or the left circumflex coronary artery (n=6). Five patients received additional, nonradioactive stents. Treated lesion lengths were 13±4 mm, with a reference diameter of 2.93±0.47 mm. Minimum lumen diameter increased from 0.87±0.28 mm preprocedure to 2.84±0.35 mm postprocedure. No in-hospital adverse cardiac events occurred. All patients received aspirin indefinitely and ticlopidine for 4 weeks. Twenty-three patients (88%) returned for 6-month angiographic follow-up; 17% of them had in-stent restenosis, and 13% had repeat revascularization. No restenosis was observed at the stent edges. Minimum lumen diameter at follow-up averaged 1.85±0.69 mm, which resulted in a late loss of 0.99±0.59 mm and a late loss index of 0.53±0.35. No other major cardiac events occurred during the 6-month follow-up. Conclusions —The use of radioactive stents with an activity of 0.75 to 1.5 μCi is safe and feasible.