INTRACORONARY IRRADIATION FOR THE PREVENTION OF RESTENOSIS

Restenosis after coronary angioplasty is a major limitation of an othe rwise highly effective and safe procedure for the treatment of atheros clerotic coronary artery disease. Although the advent of coronary sten ting has reduced restenosis rates for selected patients, an overall re stenosis rate of 20% to 25% remains. Despite numerous trials, no effec tive pharmacologic therapy has been found. Intracoronary irradiation i s a new technique proposed to prevent restenosis after angioplasty, In animal models of restenosis after balloon injury, there is marked red uction of neointimal proliferation when the injured vessel is irradiat ed, using a variety of radiation sources and delivery systems. Early h uman trials have underscored the importance of careful source calibrat ion and dosimetry. A small, randomized, double-blind, placebo-controll ed study of intracoronary irradiation to prevent recurrent restenosis recently reported striking reductions in angiographic restenosis as we ll as clinical event rates. A number of important issues remain unreso lved, such as defining which component of the arterial wall serves as the target tissue for radiation, the minimal effective dose, the maxim um tolerable dose, and user-friendly radiation delivery systems. Furth er studies are needed to define the safety, efficacy and the ultimate usefulness of intracoronary irradiation as an adjunct to current proce dures in interventional cardiology.