Serial Intravascular Ultrasound Analysis of the Impact of Lesion Length on the Efficacy of Intracoronary γ-Irradiation for Preventing Recurrent In-Stent Restenosis

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Abstract
Background —The relation between lesion length and effectiveness of brachytherapy is not well studied. Methods and Results —We compared serial (postintervention and follow-up) intravascular ultrasound findings in 66 patients with native coronary artery in-stent restenosis (ISR) who were treated with 192 Ir (15 Gy delivered 2 mm away from the radiation source). Patients were enrolled in the Washington Radiation for In-Stent Restenosis Trial (WRIST; ISR length, 10 to 47 mm; n=36) or Long WRIST (ISR length, 36 to 80 mm; n=30). External elastic membrane, stent, lumen, and intimal hyperplasia (IH; stent minus lumen) areas and source-to-target (intravascular ultrasound catheter to external elastic membrane) distances were measured. Postintervention stent areas were larger in WRIST and smaller in Long WRIST patients ( P P P =0.0006). Similarly, minimum lumen cross-sectional area significantly decreased in both WRIST and Long WRIST patients ( P P P =0.0567). The maximum source-to-target distance was longer in Long WRIST than in WRIST, and it correlated directly with ISR length ( r =0.547, P r =0.352, P =0.0038 and r =0.523, P r =0.378, P Conclusions —Brachytherapy may be less effective in longer ISR lesions because of the greater variability and longer source-to-target distances in diffuse ISR.