Outcomes of intravascular brachytherapy for in-stent restenosis in small versus large coronary vessels

Background: In-stent restenosis (ISR) remains a significant challenge in coronary intervention. Vessel size is recognized as an important predictor of outcomes following percutaneous coronary interventions, with smaller vessels traditionally associated with higher rates of restenosis. This study evaluates the clinical outcomes of vascular brachytherapy for ISR stratified by vessel size. Methods: We conducted a retrospective analysis of 224 patients who underwent vascular brachytherapy for coronary ISR between June 2016 and January 2024 at the Houston Methodist Hospital. Patients were stratified based on vessel size: small vessel (≤3 mm, n = 70) or large vessel (>3 mm, n = 154). The primary endpoint was major adverse cardiovascular events (MACE) at one year. Secondary endpoints included target lesion revascularization (TLR), stent thrombosis, bleeding complications, and mortality. Results: Patients with small vessel disease were younger (62.8 ± 10.2 vs. 66.6 ± 10.7 years, p = 0.01). Procedural characteristics revealed similar fluoroscopy radiation doses (DAP), although a trend toward lower radiation dose area products in the small vessel group was observed (18,836 ± 17,655 vs. 24,908 ± 24,811 mGy/cm², p = 0.07). Small vessels were more frequently prepared with semi-compliant balloons (17.1 % vs. 3.2 %, p = 0.0009), while cutting balloons were more commonly used in large vessels (22.9 % vs. 35.1 %, p = 0.04). At one-year follow-up, MACE rates for patients with small vessels were 27.1 % vs. 32.5 %, (p = 0.44); Similarly, TLR rates were 18.6 % vs. 23.4 % (p = 0.49). Notably, a small number of thromboses and bleeding complications were observed exclusively in the large vessel group. Conclusions: Despite traditional concerns regarding higher restenosis rates in small vessels, our analysis demonstrates comparable outcomes following vascular brachytherapy for in-stent restenosis regardless of vessel size. These findings suggest that vascular brachytherapy may help mitigate the historically poor outcomes associated with small vessel interventions, potentially by effectively suppressing neointimal hyperplasia across different vessel diameters with our precise and effective radiation dosing protocol.