Procedural Success and Long‐Term Outcomes of Percutaneous Coronary Intervention for Chronic Total Occlusion in Small Versus Large Vessels

Background Chronic total occlusion (CTO) percutaneous coronary intervention in small vessels (<3.0 mm) poses distinct technical challenges that may affect procedural success and long‐term outcomes. Methods We analyzed 507 consecutive CTO percutaneous coronary intervention procedures in 456 patients (January 2018–December 2023), categorized as small vessel (n=178, 35.1%) or large vessel (n=329, 64.9%) by reference vessel diameter. The primary end point was a composite of target lesion revascularization, heart failure hospitalization, myocardial infarction, and stroke at median 704‐day follow‐up. Results Small vessel CTOs were more frequent in women (27.5% versus 17.3%, P =0.007) and associated with higher rates of diabetes (57.9% versus 45.3%, P =0.007) and chronic kidney disease (42.7% versus 31.0%, P =0.008). Technical success (66.3% versus 88.5%, P <0.001) and procedural success (65.7% versus 88.2%, P <0.001) were lower in small vessels. Composite end point rates were similar at follow‐up (19.1% versus 12.4%, P =0.058); large vessel size was not independently protective (hazard ratio, 0.60 [95% CI, 0.34–1.07]). Small vessel size strongly predicted guidewire crossing failure (odds ratio, 0.31 [95% CI, 0.18–0.55], P <0.001). Adding vessel size to Japan CTO score improved discrimination (area under the curve, 0.66 versus 0.60) but yielded unfavorable reclassification. Conclusions CTO percutaneous coronary intervention in small vessels is associated with significantly lower procedural success but comparable long‐term outcomes. Vessel size is a strong determinant of procedural difficulty; routine incorporation into complexity scoring requires multicenter validation. Current scoring systems may underestimate the complexity of small vessel CTOs, underscoring the need for refined techniques and careful patient selection.