Effects of β – -Emitting 188 Re Balloon in Stented Porcine Coronary Arteries

Abstract

Background —Restenosis within stents may be prevented by ionizing radiation from an intravascular source. Methods and Results —A liquid β − radiation ( 188 Re) balloon was evaluated in a randomized and blinded porcine coronary model of stent restenosis. Group A pigs (n=17) received 0,16, 22, or 29 Gy at 0.5-mm depth, followed by stenting. Restenosis was quantified by angiography, ultrasound, and histomorphometry at 30 days. Group B (n=7) was stented first and then treated with 0 or 29 Gy with follow-up at 60 days. There was a measurable effect at 16 Gy, which improved with increasing doses. At 29 Gy, the histological stenotic area was reduced by 67% (22% versus 66% in controls, P <0.001). Radiation after stenting was equally effective; the stenotic area was reduced (21% versus 65%, P <0.001). At 16 Gy, the vessel just distal to the stent was significantly smaller than control vessels because of intimal thickening ( P =0.003). Radiated vessels had distinctive histology consisting of neointimal fibrin and reduced smooth muscle cells and matrix ( P <0.0001). Conclusions — 188 Re balloon brachytherapy in porcine coronary arteries results in dose-dependent and injury-independent inhibition of stent restenosis for up to 60 days. Restenosis at the borders of the irradiated zone is a potential limitation and may be related to underdosing. Brachytherapy with the 188 Re balloon appears to be safe and feasible for clinical studies.