Baseline characteristics, treatment and mortality among acute myocardial infarction patients with varying left ventricular ejection fractions according to the Estonian Myocardial Infarction Registry

Background Studies describing the distribution of acute myocardial infarction (AMI) patients based on left ventricular ejection fraction (LVEF), along with associated baseline characteristics, in-hospital medication use and prognosis remain scarce. Purpose To describe the baseline characteristics, treatment as well as in-hospital and 1-year mortality of AMI patients divided in different LVEF groups. Methods The anonymised data of AMI patients used in the study was obtained from the Estonian Myocardial Infarction Registry (EMIR), which is a national registry collecting data on all hospitalised AMI cases (International Classification of Diseases 10th version, codes I12–I22). Submitting data online via a specific form is mandatory and the annual case-coverage is over 95%. Patients were divided into the groups based on their LVEF measured by echocardiography during their index episode at the hospital. For statistical analysis significance level of p<0.05 was chosen for evaluating the differences in the obtained results. The analysis was conducted using the statistical software "R" (version 3.6.0+). Results A total of 5231 AMI patient records from 2021-2022 were analysed. The distribution of subjects into different LVEF groups and their baseline characteristics are presented in Table 1. Echocardiography was performed in 86% of the patients. Approximately 44% of the sample consisted of patients with LVEF ≥50%. The smallest group included patients with unknown LVEF (14%). The unknown LVEF group exhibited a higher proportion of females (52%) and a higher mean age of 79 years. The prevalence of arterial hypertension was similar across all groups (81%). The highest rates of dyslipidemia and smoking (73% and 31%, respectively) were observed in the LVEF 41–49% group. Patients in the LVEF ≤40% and unknown LVEF groups had a higher prevalence of type 2 diabetes, previous stroke, peripheral artery disease, chronic heart failure, and previous myocardial infarction. Type 1 AMI was most common among patients with LVEF ≤40% and LVEF 41-49% (89%). The prevalence of type 2 AMI was highest in the unknown LVEF group. The in-hospital mortality was highest in the unknown LVEF group. The one-year mortality rate was the lowest in LVEF ≥50% patients. The use of medications in the hospital was similar across all groups, except for the unknown LVEF group, where all medications (except MRAs) were used less often (Figure 1). Conclusions Based on nationwide registry with a high case-coverage we found differences in baseline characteristics, treatment and mortality in AMI patients with varying LVEF. Further studies are needed to clarify the characteristics of the unknown LVEF group and to determine the factors contributing to their high-risk status.Table 1.Characteristics and mortality Figure 1.