Safety of Intracoronary γ-Radiation on Uninjured Reference Segments During the First 6 Months After Treatment of In-Stent Restenosis

Abstract

Background —The effects of endovascular irradiation on uninjured reference segments during the treatment of in-stent restenosis are unknown. Methods and Results —In the Washington Radiation for In-Stent restenosis Trial (WRIST), patients with in-stent restenosis were first treated with conventional catheter-based techniques and then randomized (blinded) to receive either γ-irradiation ( 192 Ir) or a placebo (dummy seeds). We identified all patients in whom the active (n=19) or dummy seeds (n=19) extended >10 mm proximal and distal to the in-stent restenosis lesion. Serial (postirradiation and follow-up) external elastic membrane (EEM), lumen, and plaque and media (EEM−lumen) areas were measured (using intravascular ultrasound) every 1 mm over 5-mm-long reference segments that were 6 to 10 mm proximal and distal to the in-stent restenosis lesion. During follow-up, a similar small increase occurred in the plaque and media area in the proximal and distal reference segments in both 192 Ir and placebo patients. However, in the 192 Ir patients, an increase in both proximal and distal EEM area occurred; as a result, no change in lumen area occurred. Conversely, in the placebo patients, the proximal reference EEM area decreased, and no change occurred in the distal reference EEM area; this contributed to a decrease in lumen area. Conclusions —There was no evidence of a deleterious effect of γ-irradiation on angiographically normal uninjured reference segments in the first 6 months after the treatment of in-stent restenosis.