Association Between the Intermountain Risk Score and Angiographic Coronary Collateral Development in Patients With Chronic Total Occlusion

Objective: To evaluate the association between the Intermountain Risk Score (IMRS) and coronary collateral development and assess its performance in predicting poor collateralization in patients with coronary chronic total occlusion (CTO).
Method: We retrospectively analyzed 342 patients with angiographically documented CTO. Collateral status was dichotomized as poor (Rentrop grades 0–1) or good (Rentrop grades 2–3). Associations with collateralization were examined using logistic regression, while receiver operating characteristic (ROC) analysis was used to assess the ability of the IMRS to identify poor collateral development.
Results: Poor collateral development was present in 157 patients (45.9%). The mean IMRS was higher in the poor collateral group than in the good collateral group (12.53±2.88 vs 11.02±2.54; P < 0.001). Rates of poor collateral development increased across the low-, intermediate-, and high-risk categories (27.0%, 52.1%, and 65.5%, respectively; p for trend<0.001). After multivariable adjustment, a higher IMRS was independently associated with lower odds of good collateral development (odds ratio [OR], 0.83; 95% confidence interval [CI], 0.76–0.90; P < 0.001). The IMRS showed modest discrimination for poor collateral development (area under the curve [AUC], 0.650; 95% CI, 0.592–0.709). A cutoff of ≥12.5 provided 48.4% sensitivity and 74.1% specificity.
Conclusion: A higher IMRS was independently associated with poor coronary collateral development in patients with CTO. Its modest discriminatory ability limits its standalone use, but it may serve as a complementary marker of systemic risk burden.

Keywords: Chronic total occlusion, coronary collateral circulation, Intermountain Risk Score, Rentrop classification, risk assessment.