Serial Intravascular Ultrasound Assessment of the Efficacy of Intracoronary γ-Radiation Therapy for Preventing Recurrence in Very Long, Diffuse, In-Stent Restenosis Lesions

Background —The efficacy of coronary γ-irradiation in preventing recurrent in-stent restenosis (ISR) is well established. However, brachytherapy may be less effective in very long, diffuse ISR lesions.Methods and Results —We used serial intravascular ultrasound (IVUS) to study patients with long, diffuse ISR lesions (length, 36 to 80 mm) who were enrolled in (1) Long WRIST (Washington Radiation In-Stent Restenosis Trial), a double-blind, placebo-controlled trial of intracoronary γ-irradiation (15 Gy at 2 mm from the source) and (2) high-dose (HD) Long WRIST, a registry that used a dose prescription of 18 Gy at 2 mm from the source. IVUS was performed using automated pullback (0.5 mm/s). Stent, lumen, and intimal hyperplasia were measured at 2-mm intervals. Complete postintervention and follow-up IVUS imaging was available in 30 irradiated and 34 placebo patients from Long WRIST and in 25 patients from HD Long WRIST. Stent length was longer in HD Long WRIST than in placebo or treated patients in Long WRIST (P =0.0064 andP =0.0125, respectively). Otherwise, baseline measurements were similar. At follow-up, the minimum lumen area was largest in the HD Long WRIST patients (4.0±1.4 mm2 ); areas were 2.9±1.0 mm2 in irradiated patients in Long WRIST and 1.9±1.1 mm2 in placebo patients in Long WRIST (P <0.005 for all comparisons).Conclusions —Serial IVUS analysis shows that γ-irradiation reduces recurrent in-stent neointimal hyperplasia in long, diffuse ISR lesions; however, it is even more effective when given at a higher dose.