Prognostic value of twelve systemic inflammatory indices for composite cardiovascular events in chronic coronary syndrome patients with or without diabetes undergoing PCI

Background Inflammation is widely recognized as a central contributor to the pathogenesis and prognosis of repeat revascularization (RR) and in-stent restenosis (ISR) following percutaneous coronary intervention (PCI). Diabetes mellitus (DM) not only markedly increases the risk of coronary artery disease (CAD) but also accelerates atherosclerosis progression by exacerbating insulin resistance, promoting chronic low-grade inflammation, and impairing endothelial function. Recent evidence indicates that elevated inflammatory indices independently predict adverse cardiovascular outcomes, particularly in patients with DM. This study aimed to evaluate the prognostic value of twelve inflammatory indices for predicting RR and ISR in diabetic patients with chronic coronary syndrome (CCS) undergoing PCI. Methods A total of 2,079 patients were enrolled, including 867 with diabetes mellitus (DM). Patients were categorized into tertiles based on each inflammatory index. The primary endpoint was a composite of PCI-related complications, including repeat revascularization (RR) and in-stent restenosis (ISR). Associations between the twelve inflammatory indices and outcomes were evaluated using multivariable Cox proportional hazards models and restricted cubic spline (RCS) analyses. Results During a median follow-up of 60 months, 961 patients (46.2%) experienced at least one composite endpoint. In the overall population, LnSII remained an independent predictor of the composite endpoint after adjustment (HR 1.13, 95% CI 1.01–1.28, P=0.037), while other inflammatory indices showed no significant association. Among non-diabetic patients, none of the indices were predictive. In diabetic patients, SII, NLR, and PAR remained significant independent predictors after adjustment (SII: HR 1.25, 95% CI 1.06–1.47, P=0.009; NLR: HR 1.22, 95% CI 1.01–1.47, P=0.040; PAR: HR 1.38, 95% CI 1.04–1.84, P=0.028). Compared with the lowest tertile (T1), patients in the highest tertile (T3) had a 37%, 33%, and 38% higher risk, respectively. Restricted cubic spline analysis revealed a nonlinear association between SII and the composite endpoint in diabetic patients, while NLR and PAR showed linear associations. Kaplan–Meier analysis further confirmed significantly higher event rates in the T3 groups of SII and NLR among diabetic patients (SII P=0.026; NLR P=0.037), with no significant differences observed in the overall population. Conclusions In diabetic patients with CCS, inflammatory indices such as SII, NLR, and PAR are strong predictors of PCI-related complications, including RR and ISR, and may serve as practical tools for risk stratification.