Epidemiological pattern of myocardial infarction and modelling risk factors relevant to in-hospital mortality: the first results from the Iranian Myocardial Infarction Registry

Background: Myocardial infarction (MI) care and treatment contribute greatly to the patients' fatality and mortality. Assessing and monitoring mortalities and the effective factors are necessary in MI care and treatment programs. No comprehensive and population-based study has yet been conducted in Iran to determine the epidemiological pattern of MI, and particularly in-hospital mortality rate and the effective factors. Aim: To determine the epidemiological pattern of MI based on person-, time-, place-, and mortality-associated risk factors. Methods: This was a prospective, population-based cohort study, which analysed the data of 20,750 MI patients in Iran in 2012. MI was diagnosed based on ICD-10: codes I21 and I22. The cohort of the patients was defined in terms of the date at diagnosis, hospitalisation, and the date at discharge (recovery or death due to MI). The in-hospital mortality rate was calculated by Cox regression. Univariate analysis and multiple logistic regression were used to determine the effective factors on the patients' mortality. The odds ratio (95% confidence interval [CI]) was reported using Stata software. Results: The relative frequency of in-hospital mortality was 12.1%. The in-hospital mortality rate was higher in women than in men, and 6.74 (95% CI 6.4-7.0) per 100 person-years were at risk of death. The highest relative mortality (13.2%) was obtained in January (11 Dey to 11 Bahman in the Persian calendar) and the lowest (5.9%) in May (11 Ordibehest to 10 Khordad in the Persian calendar). Age of over 84 years, female gender, educational level, smoking, lack of thrombolytic therapy, type 2 diabetes, chest pain prior to arriving in hospital, right bundle branch block, ventricular tachycardia, percutaneous coronary intervention, lateral MIs, and ST segment elevation myocardial infarction (STEMI) were determinants of in-hospital mortality in the patients. The relative frequency of mortality was higher from STEMI (83.7% of deaths in registry) vs. non-STEMI (16.3% of deaths in registry). Conclusions: STEMI, lack of thrombolytic therapy, age of over 84 years, and ventricular tachycardia have the greatest effect on in-hospital mortality in MI patients. The results of this study are helpful in planning for monitoring and promotion of healthcare of the patients.