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

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 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; n536) or Long WRIST (ISR length, 36 to 80 mm; n530). 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,0.0001). At follow-up, maximum IH area significantly increased in both WRIST and Long WRIST patients (P,0.0001 for both), but this increase was greater in Long WRIST patients (P50.0006). Similarly, minimum lumen cross-sectional area significantly decreased in both WRIST and Long WRIST patients (P,0.05 and P,0.0001, respectively), but this decrease was more pronounced in Long WRIST patients (P50.0567). The maximum source-to-target distance was longer in Long WRIST than in WRIST, and it correlated directly with ISR length (r50.547, P,0.0001). Overall, the change in minimum lumen area and the change in maximum IH area correlated with the maximum source-to-target distance (r50.352, P50.0038 and r50.523, P,0.0001 for WRIST and Long WRIST, respectively). The variability (maximum/minimum) in IH area at follow-up also correlated with the maximum source-to-target distance (r50.378, P,0.0001). Conclusions—Brachytherapy may be less effective in longer ISR lesions because of the greater variability and longer source-to-target distances in diffuse ISR. (Circulation. 2001;103:188-191.)