Abstract Background and purpose: Acute coronary syndrome (ACS) includes ST elevation myocardial infarction (STEMI), non–ST-segment elevation myocardial infarction (NSTEMI), and unstable angina. This study was conducted to determine the characteristics of patients with ACS and determinants of their mortality in Iran. Materials and methods: This study was a hospital-based prospective cohort study in which we used the data of 20,750 patients registered in National Registry of myocardial infarction in hospitals with cardiology ward in 31 provinces in Iran. To determine the factors associated with patients’ mortality, Cox regression (relative hazards model) was used. Results: Mortality rate in followed up patients with STEMI and NSTEMI was 3698.4 and 4573.3 per 1000 person-year, respectively. The mean age of patients with STEMI was 60.5± 13.1 years and in those with NSTEMI was 62.9± 13.4 years. The prevalence of STEMI and NSTEMI was 75.8% and 24.2%, respectively. The most important determinants of mortality in patients were age over 84 years of old, female sex, illiteracy, lack of receiving thrombolytic therapy, right bundle branch block, STEMI, heart failure, and receiving angioplasty. Conclusion: The characteristics of patients with ACS, could help the health system personnel in strategy adoption and decision making as well as assessment, monitoring, and treatment of patients. Training people to refer early for emergency care in case of manifesting ACS symptoms, and providing them with treatment at golden time could be of great benefit in reducing the rate of mortality
