Clinical, SMuRF-related, and angiographic characteristics associated with long-term all-cause mortality in patients aged ≤ 40 years with acute coronary syndrome: a retrospective cohort study

Background Acute coronary syndrome (ACS) in adults aged ≤40 years is uncommon, and evidence on long-term mortality predictors in this age group remains limited. We evaluated clinical, angiographic, and standard modifiable cardiovascular risk factor (SMuRF)-related predictors of all-cause mortality in a large cohort of very young patients with ACS. Methods This retrospective cohort study included 903 consecutive patients aged ≤40 years who were treated for ACS at a tertiary center between January 2011 and June 2024. ACS presentation, cardiovascular risk factors, SMuRF status, coronary angiographic findings, and mortality were assessed. SMuRFs were defined as hypertension, diabetes mellitus, hyperlipidemia, and current smoking, while obesity was analyzed separately. Survival was evaluated using Kaplan–Meier analysis and Cox proportional hazards regression. Sensitivity analyses included administrative censoring at 10 years and a parsimonious Cox model. Results The cohort included 528 patients with ST-segment elevation myocardial infarction, 293 with non-ST-segment elevation myocardial infarction, and 82 with unstable angina. During a median follow-up of 4.93 years [95% confidence interval (CI) 4.69–5.18], 51 deaths occurred. Obesity was present in 180 patients (19.9%), left anterior descending artery (LAD) involvement in 436 (48.3%), and multivessel disease in 190 (21.0%). In the multivariable Cox model, obesity [adjusted hazard ratio (HR) 2.677, 95% CI 1.430–5.010; p = 0.002] and LAD involvement [adjusted HR 3.586, 95% CI 1.849–6.956; p < 0.001] were independently associated with mortality. SMuRF-less patients comprised 10.6% of the cohort and had higher proportions of female sex, obesity, LAD involvement, and multivessel disease than SMuRF-positive patients, although mortality did not differ significantly between the groups. Kaplan–Meier analysis showed lower survival among patients with obesity and among those with LAD involvement. Mortality occurred in 6.3% of SMuRF-less and 5.6% of SMuRF-positive patients. The 10-year sensitivity analysis supported the main findings. Conclusions In patients aged ≤40 years with ACS, obesity and LAD involvement were independently associated with long-term all-cause mortality, whereas SMuRF status was not. These findings support risk assessment that considers cardiometabolic burden and coronary anatomy alongside conventional risk-factor status in very young patients with ACS.