Remnant cholesterol inflammation index predicts adverse outcomes in patients with acute myocardial infarction: a single-center retrospective study

Background Despite treatment, residual cardiovascular and cerebrovascular risk persists post-acute myocardial infarction (AMI). The Remnant Cholesterol Inflammation Index (RCII), combining residual cholesterol and hsCRP, reflects lipid and inflammatory burdens; however, its prognostic value in the acute phase remains unclear. This study evaluated RCII for predicting 30-day major adverse cardiovascular and cerebrovascular events (MACCE). Methods A single-centre, retrospective study enrolled 3,280 AMI patients. The primary endpoint was a composite of all-cause mortality, recurrent myocardial infarction and non-fatal stroke within 30 days. Covariates were selected via Boruta and LASSO algorithms. Restricted cubic spline (RCS) and segmented Cox regression analysed the dose-response relationship and threshold effects between lnRCII and outcomes. Subgroup and sensitivity analyses were performed. Results lnRCII showed a U-shaped association with 30-day MACCE risk (inflection point: 1.83). Compared to the middle quartile (Q2), patients in Q1, Q3, and Q4 had significantly higher risks (80%, 102%, and 109%, respectively). The association differed by hypertension status ( p for interaction = 0.039), with sensitivity analyses confirming robustness. Conclusion This study suggests that RCII may be an independent predictor of 30-day MACCE post-AMI, with both high and low levels correlating with increased risk. These findings should be interpreted as hypothesis-generating. RCII may serve as an integrated biomarker reflecting both lipid and inflammatory burdens for early risk stratification. Trial registration The study was approved by the Ethics Committee of the First Hospital of Hebei Medical University (approval no. Y277) and was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki. The need for informed consent was waived by the board.