Comparative Associations of Inflammation and Nutrition-Based Indices with No-Reflow and Mortality After Primary PCI for ST-Elevation Myocardial Infarction

Background/Objectives: Acute myocardial infarction is accompanied by thromboinflammation, immune-cell redistribution and changes in nutritional reserve. We compared six routinely calculable indices under a common modelling strategy in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). Methods: This retrospective cohort included 2613 patients. The primary endpoint was long-term all-cause mortality, analysed with Cox regression; angiographic no-reflow, in-hospital mortality and 30-day mortality were analysed with logistic regression. The global immune-nutrition-inflammation index (GINI), prognostic nutritional index (PNI), controlling nutritional status (CONUT) score, systemic immune-inflammation index (SII), neutrophil-to-lymphocyte ratio (NLR) and Naples prognostic score (NAPLES) were evaluated in separate models. Continuous indices were modelled flexibly, and every effect estimate compared the 75th with the 25th percentile. Results: No-reflow occurred in 353 patients (13.5%), in-hospital death in 102 (3.9%), 30-day death in 157 (6.0%) and long-term death in 466 (17.8%). Median recorded follow-up was 34 [14–46] months. After clinical adjustment, the Q3-versus-Q1 hazard ratios for long-term mortality were 1.17 (95% CI 1.00–1.36) for GINI, 0.79 (0.68–0.91) for PNI, 1.19 (1.01–1.40) for CONUT, 1.20 (1.04–1.39) for SII, 1.24 (1.07–1.44) for NLR and 1.13 (0.98–1.31) for NAPLES. After Holm correction across the six primary tests, PNI, SII and NLR retained evidence of association. In angiographically expanded no-reflow models, GINI and NLR retained Q3-versus-Q1 associations. Conclusions: Admission inflammatory and immune-nutrition indices showed outcome-specific prognostic associations. PNI, SII and NLR had the most consistent multiplicity-sensitive long-term associations, whereas GINI and NLR retained associations with no-reflow after angiographic adjustment. These findings do not establish causal effects, predictive superiority or readiness for clinical decision-making.