Safety and efficacy of manual stepping and overlapping of β-emitter for diffuse in-stent restenosis lesions

Abstract Background: The effects of overlapping β-emitter sources on the treatment of in-stent restenosis (ISR) lesions as a result of manual stepping are unknown. Methods and results: In the BETA WRIST (Beta Washington Radiation for In-stent Restenosis Trial), 17 out of the 50 patients who received radiation treatment had diffuse ISR in native coronaries that required manual stepping of the β-emitter ( 90 Y) source in order to cover the lesion and the edges. Fourteen of those patients received radiation with an overlap of up to 3 mm in the middle of the stented segment. The prescribed dose was 20.6 Gy to a distance of 1.0 mm from the surface of the inflated balloon, and the calculated dose to the vessel wall at the overlapped area did not exceed 75 Gy. There was no difference in late total occlusion (7.1% vs. 9.0%, P =NS) and target lesion revascularization (28.5% vs. 27.2%, P =NS) between patients with stepping and those without stepping. At 6 months, there was no evidence of perforation or aneurysm at the overlapped segments. Quantitative coronary angiographic (QCA) analysis revealed significantly reduced late loss in the overlapped segment compared to the adjacent segment ( P =.04). Serial (postradiation vs. follow-up) IVUS measurement showed larger mean lumen cross-sectional area (CSA) ( P =.0035) and smaller mean intimal hyperplasia (IH) CSA ( P =.0010) in the overlapped segment compared to the adjacent segment. Conclusion: Manual stepping of β-emitter source with a short overlapped segment is safe for diffuse ISR. Further increase in lumen dimension and reduction in IH formation are observed at the overlapped segment.