Late intravascular ultrasound findings of patients treated with brachytherapy for diffuse in-stent restenosis

This study aimed at evaluating long-term (24-month) effects of β-irradiation (¹⁸⁸Re-MAG₃-filled balloon) using intravascular ultrasound (IVUS) in patients with in-stent restenosis (ISR). Long-term effects of β-irradiation on intimal hyperplasia (IH) within the stented segment and vessel and lumen dimensions of nonstented adjacent segments in patients with ISR have not been sufficiently evaluated. Two-year follow-up IVUS was performed in 30 patients with patent ISR segments at 6-month follow-up angiography. Serial IVUS images were acquired at five equidistant intrastent sites and at three different reference segment sites. IH burden (%) was defined as 100 × (IH/stent area). Mean intrastent IH area and IH burden significantly increased between 6 and 24 months, from 2.1 ± 1.1 to 2.6 ±v 1.4 mm² (P < 0.001) and from 26% ± 10% to 33% ± 14% (P < 0.001), respectively. There was a significant decrease of mean external elastic membrane (from 10.1 ± 3.9 to 9.7 ± 3.9 mm²; P = 0.015) and lumen area (from 5.6 ± 2.3 to 5.1 ± 2.3 mm²; P = 0.021) within distal reference segments between 6 and 24 months. Target lesion revascularization (TLR) was performed in six patients (20%) between 6 and 24 months after β-irradiation therapy. There were no significant differences between TLR and non-TLR groups except for a smaller minimum lumen area at 24 months in the TLR group. Because of a small amount of late loss between 6 and 24 months, most irradiated ISR vessel segments remained stable for up to 2 years. However, quantitative evidence of late catch-up was evident in most patients and was significantly associated with 24-month TLR in some patients.