The Relationship Between the Remnant Cholesterol Inflammation Index and Coronary Collateral Circulation in Patients with Chronic Total Occlusion

Background and Objectives: Although chronic total occlusion (CTO) often presents with varying degrees of coronary collateral circulation (CCC), the biological factors accompanying inadequate collateralization are not fully established. The Remnant Cholesterol Inflammation Index (RCII) is a composite metric integrating atherogenic lipid load and systemic inflammation. This study examined the association between RCII and CCC and the discriminative ability of RCII for identifying insufficient collateral networks in patients with CTO. Materials and Methods: This retrospective, single-center analysis evaluated 359 patients with at least one major epicardial CTO who underwent diagnostic coronary angiography between 15 January 2023 and 15 January 2026. Participants were stratified via the Rentrop scoring system into poor (grades 0–1; n = 168) and good (grades 2–3; n = 191) CCC cohorts. RCII was calculated as [remnant cholesterol (mg/dL) × high-sensitivity C-reactive protein (hs-CRP, mg/L)]/10, with remnant cholesterol derived as total cholesterol minus LDL-C and HDL-C. Univariable and multivariable logistic regression models, together with receiver operating characteristic (ROC) curve analysis, were used to assess the association of RCII with poor CCC and its discriminative ability. Results: Patients with poor CCC exhibited significantly higher RCII values compared with the good CCC cohort (19.7 ± 4.7 vs. 6.5 ± 2.4, p < 0.001). Following multivariable adjustment, higher RCII remained independently associated with poor collateralization (OR 1.120, 95% CI 1.052–1.199; p < 0.001), alongside right coronary artery (RCA) CTO and the systemic immune-inflammation index (SII). RCII showed discriminative ability for poor CCC (AUC 0.792, 95% CI 0.745–0.835; p < 0.001), which was greater than that of remnant cholesterol, hs-CRP, or SII considered separately. In this cohort, an RCII threshold above 12.3 identified poor CCC with 80% sensitivity and 71% specificity. Conclusions: In this retrospective cohort, higher RCII was independently associated with inadequate coronary collateralization in the setting of CTO. RCII may represent a candidate marker of the combined residual lipid and inflammatory burden; prospective studies and external validation, together with formal assessment of clinical utility, are required before any clinical application can be considered.