Prognostic Value of the Cumulative Inflammatory Index (IIC) in Patients with Non-ST-Segment Elevation Myocardial Infarction

Background/Objectives: Inflammation plays a central role in the pathophysiology and prognosis of non-ST-segment elevation myocardial infarction (NSTEMI). This study aimed to investigate the clinical and prognostic significance of the Cumulative Inflammatory Index (IIC) in patients with NSTEMI. Methods: This single-center, retrospective study included 2274 individuals, comprising 1172 patients with NSTEMI and 1102 angiographic controls without acute coronary syndrome or obstructive coronary artery disease. IIC was calculated using mean corpuscular volume, red cell distribution width, neutrophil count, and lymphocyte count. The primary outcome was 360-day all-cause mortality in the NSTEMI cohort. Logistic regression, receiver operating characteristic curve analysis, and DeLong testing were performed. Results: Patients with NSTEMI had significantly higher IIC values than controls [9.08 (4.05–15.03) vs. 1.90 (1.45–2.89), p < 0.001]. Among NSTEMI patients, non-survivors had significantly higher IIC levels than survivors [14.25 (8.56–26.59) vs. 8.57 (3.73–14.06), p < 0.001]. In multivariable logistic regression analysis, IIC remained independently associated with 360-day all-cause mortality after adjustment for age, diabetes mellitus, estimated glomerular filtration rate, hemoglobin, albumin, and C-reactive protein (OR: 1.045, 95% CI: 1.029–1.060; p < 0.001). IIC showed a modestly higher area under the curve among the evaluated indices (AUC: 0.704). Conclusions: IIC was significantly elevated in patients with NSTEMI and was independently associated with 360-day all-cause mortality. IIC may serve as a simple adjunctive marker for risk stratification in patients with NSTEMI.