Intracoronary brachytherapy--clinical state and pathophysiological considerations

In-stent restenosis remains the limitation of coronary stent implantation despite numerous efforts of its prevention by catheter-based techniques or by drug therapy. Today, only intravascular irradiation has proven to effectively reduce neointima formation, restenosis rate and major adverse cardiovascular events by approximately 50%. Its efficiency is demonstrated for high-risk subsets like long lesions, lesions in saphenous venous bypass grafts or diabetic patients, indicating the extraordinary potential of vascular irradiation. Yet vascular irradiation has some limitations. Edge effect describes the phenomenon of excessive neointimal proliferation at the edges of an irradiated segment and is likely due to axial dose fall-off and/ or barotrauma by the angioplasty procedure. Geographic miss, the combination of dose fall-off and vessel injury may be deleterious, especially if a new stent is implanted. The use of appropriate radiation source lengths to avoid geographic miss substantially reduces the incidence of edge effect. Late thrombosis, occurring even years after irradiation, had significantly diminished the benefit of vascular irradiation in initial clinical trials, but extension of ntiplatelet therapy up to 12 months after irradiation has reduced its rates to placebo levels. Vascular brachytherapy is of considerable clinical benefit in the prevention of restenosis and the only proven option for the treatment of in-stent restenotic lesions. This review will focus on the mechanisms of action of vascular irradiation, on the pathophysiological reasons for its complications and therapeutic options. Both angiographic and clinical results of randomised and observational studies will be updated in detail.