Determinants and clinical outcomes of premature acute coronary syndrome

Background Acute coronary syndrome (ACS) in young adults represents a distinct clinical entity with unique risk profiles and outcomes. Identifying determinants of early-age ACS is essential to guide preventive strategies and reduce lifetime cardiovascular burden. Purpose To evaluate determinants of early-age ACS by comparing cardiovascular risk factors, clinical presentation, and in-hospital outcomes with older patients. Methods Single-centre study of 1455 patients admitted with ACS between October 2010 and June 2025, included in a voluntary, prospective registry. Patients with prior ACS were excluded. Participants were stratified into two age groups: <50 years and ≥50 years. Baseline characteristics, ACS type, presentation, and in-hospital complications were analysed. Results A total of 1260 patients were included (mean age of 66.6 ± 12.9 years; 28.8% were female). Male sex was predominated in the younger group (<50 years) compared to older patients (87.9% vs. 69.1%, p<0.001). Early-age ACS patients had higher rates of active smoking (64.3% vs. 20.6%, p<0.001), family history of coronary artery disease (20.7% vs. 3.3% p<0.001), and higher body mass index (27.7vs. 26.7 kg/m2, p=0.002). Conversely, they had lower prevalence of previous hypertension (21.6% vs. 66.3%, p<0.001), diabetes (8.8% vs. 31.2%, p<0.001), and dyslipidaemia (47.5% Vs. 59.4%, p=0.007). LDL cholesterol on admission was higher in younger patients (129 vs. 113 mg/dL, p=0.002). Multivariable analysis identified active smoking (OR 7.19), family history (OR 7.11), and higher BMI (OR 1.10 per unit) as independent predictors of early-age ACS (all p<0.001). Regarding ACS characteristics, ST-elevation myocardial infarction (STEMI) was more frequent in younger patients (62.1% vs. 49.1%, p=0.011), who also presented lower Killip class (Killip I: 97.9% vs. 85.5%, p<0.001). Younger patients experienced fewer in-hospital complications, including new-onset heart failure (5.0% vs. 20.2%, p<0.001), atrial fibrillation/flutter (0.7% vs. 8.2%, p=0.001), atrioventricular block (0.0% vs. 4.5%, p=0.011), and cardiogenic shock (0.7% vs. 4.7%, p=0.027). Left ventricle ejection fraction at discharge was similar between groups (p=0.191). In-hospital mortality was lower among early-age ACS patients, though not statistically significant (0.0% vs. 2.0%, p=0.161), while 1-year mortality was significantly lower in this group (0.0% vs. 3.1%, p=0.034). Conclusions Early-age ACS is strongly linked to modifiable risk factors—especially smoking, obesity, and dyslipidaemia—as well as family history of premature coronary disease. Despite fewer comorbidities, younger patients more often present with STEMI but experience more favourable in-hospital outcomes. These results emphasise the importance of targeted primary prevention in young high-risk individuals, especially smokers and those with familial predisposition.