Safety of intracoronary γ-radiation on uninjured reference segments during the first 6 months after treatment of in-stent restenosis -: A serial intravascular ultrasound study

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 gamma-irradiation (Ir-192) 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 Ir-192 and placebo patients. However, in the Ir-192 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 gamma-irradiation on angiographically normal uninjured reference segments in the first 6 months after the treatment of in-stent restenosis.