Age-Dependent Inflammatory, Lipid, and Echocardiographic Phenotypes in Acute Myocardial Infarction: Associations with In-Hospital Adverse Clinical Events

Background: Acute myocardial infarction (AMI) in younger adults represents a distinct clinical entity with biological features that may differ from those observed in later-onset disease. We aimed to characterize age-dependent clinical, inflammatory, lipid, and echocardiographic phenotypes and to explore their association with in-hospital adverse clinical events. Methods: In this prospective, single-center, age-stratified observational study conducted between 20 January 2024 and 20 January 2025, 90 patients with AMI undergoing successful percutaneous coronary intervention (PCI) were selected from 1051 AMI admissions: 30 aged 25–44 years and 60 aged ≥45 years. Admission biomarkers (including C-reactive protein, leukocyte-derived indices, and lipid parameters) and echocardiographic variables (left ventricular ejection fraction and global longitudinal strain) were assessed, and exploratory receiver operating characteristic analyses were performed for in-hospital adverse clinical events. Results: Younger patients demonstrated a predominantly atherogenic profile, with higher smoking prevalence (63.3% vs. 13.3%; p < 0.001) and markedly higher lipoprotein(a) concentrations (76.18 ± 10.10 vs. 17.61 ± 11.42 mg/dL; p < 0.001). Older patients exhibited higher inflammatory indices (NLR and SII), higher hs-cTnI and NT-proBNP concentrations, and worse ventricular function. STEMI predominated in both age groups (83.3% in each), and infarct localization did not differ significantly between younger and older patients. The rate of in-hospital adverse clinical events was numerically higher in older patients (18.3% vs. 10.0%), but this difference was not statistically significant. In exploratory ROC analyses, CRP (AUC = 0.874) and LVEF (AUC = 0.868) showed the highest discriminatory performance. Conclusions: AMI appears to manifest through age-related baseline phenotypes: a more atherogenic/thrombotic profile in younger patients and a more inflammatory/ventricular dysfunction profile in older patients. CRP and LVEF emerged as the strongest exploratory discriminators of in-hospital adverse clinical events, but these findings require validation in larger cohorts.