Predictive Value of the Systemic Immune-Inflammation Index for Cardiovascular Events in Patients With Chronic Total Coronary Occlusion

Background: This large-scale cohort study aimed to evaluate the prognostic role of the systemic immune-inflammation index (SII) in patients with chronic total occlusion (CTO) undergoing percutaneous coronary intervention (PCI). Methods: A total of 3107 patients with CTO lesions who underwent PCI were enrolled in this study. Clinical characteristics were collected, and post-discharge major adverse cardiovascular events (MACEs) were recorded during follow-up, including all-cause mortality, non-fatal myocardial infarction, unplanned revascularization, and heart failure-related readmission. Patients were stratified into three groups according to SII tertiles: the low SII group (SII ≤447.66, n = 1036), the intermediate SII group (447.66 < SII < 679.89, n = 1039), and the high SII group (SII ≥679.89, n = 1032). Results: Over a median follow-up of 2.58 (2.33–2.92) years, 356 (11.5%) MACEs occurred, including 49 (1.6%) all-cause deaths, 105 (3.4%) non-fatal myocardial infarctions, 164 (5.3%) revascularizations, and 38 (1.2%) heart failure rehospitalizations. Multivariable Cox regression analyses demonstrated that elevated SII was independently linked to higher risks of MACEs (hazard ratio [HR] = 1.51, 95% confidence interval [CI]: 1.20–1.90; p = 0.001), all-cause death (HR = 2.06, 95% CI: 1.11–3.84; p = 0.022), non-fatal myocardial infarction (HR = 1.76, 95% CI: 1.15–2.69; p = 0.009), and repeat revascularization (HR = 1.32, 95% CI: 1.01–1.76; p = 0.046) after full adjustment. Kaplan–Meier survival curves showed significantly higher rates of adverse events in patients with elevated SII. Adding SII to traditional risk models improved predictive performance, as reflected by increases in the concordance index (C-index), net reclassification improvement (NRI), and integrated discrimination improvement (IDI). Conclusions: Baseline SII is a reliable and independent predictor of MACEs in patients with CTO after PCI, with superior predictive performance compared with conventional inflammatory markers.