Experimental Results with 90Yttrium Beta-Particle Emitting Radioactive Stents in a Porcine Model of Restenosis

Background: Radioactive stents have been proposed as a means to prevent restenosis. The ideal radioisotope to deliver endovascular irradiation via a radioactive stent is unknown. Objectives: To evaluate the dose response effects of “high” dose rate irradiation delivered by a high energy, short half-life, beta-particle emitting 90yttrium (90Y) radioactive stent on neointimal formation in a porcine coronary model of restenosis. Methods: Fifty-two 0–16.0 μCi 90y radioactive stents were implanted in the coronary arteries of 19 swine. Stents were oversized 10% to 20% greater than the baseline angiographic lumen diameter. After 28 days, quantitative histological analysis was completed to determine neointimal area and percent in-stent stenosis. Results: The mean vessel injury scores were similar for the control and each of the 90Y radioactive stent groups. Neointimal area correlated with vessel injury for the control (r =0.54, P < 0.0001) stents. The percent in-stent stenosis was similar for the nonradioactive control and the 0.25, 0.5, 1.0, 1.25, 2.0, 8.0, and 16.0 μCi 90Y radioactive stents. The neointimal area was greater for the 4.0 μCi (3.95 ± 1.16 mm2) and 8.0 μCi (3.55 ± 1.09 mm2) 90Y stents as compared with the nonradioactive control stents (2.40 ± 7.72 mm2, P ≤ 0.03). The increased neointimal area for the 4.0 μ90Y stents resulted in significantly greater percent in-stent stenosis (55 ± 12) versus control nonradioactive stents (36 ± 18, P < 0.05). Conclusions: A radioactive stent manufactured with the short half-life beta-particle emitting radioisotope 90Y, designed to deliver a higher dose rate at implant than a 32P radioactive stent, is ineffective in reducing neointimal formation in the porcine coronary model of restenosis. Further study is required to define effective cumulative dose and dose rate delivery for radioactive stents.