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.