Epidemiology of acute heart failure admissions in Iceland: phenotype distribution and prognostic implications

Abstract

Abstract Background/Introduction Contemporary data that describe underlying causes of acute heart failure (AHF) epidemiology in a nation-wide unselected real-life cohort is lacking. Advances in diagnostics, including imaging and genetics, have facilitated the identification of the underlying cause of heart failure (HF). This is the first Icelandic nation-wide study on HF epidemiology of patients hospitalised for AHF. Purpose Investigate the underlying causes of AHF in Iceland and the patients‘ prognosis according to phenotypes. Methods This study used data from the Icelandic Heart Failure Registry (IHFR) and included all hospital admissions for AHF at Landspitali University Hospital from January 2020 to June 2022 (n = 1723). Differences in survival between HF phenotypes were analysed using a multivariate log-rank test, both after diagnosis and after the first discharge. Results The study found that 39.8% of the cases had heart failure with reduced ejection fraction (HFrEF), 17.4% had HF with mildly reduced ejection fraction (HFmrEF), 40.3% had HF with preserved ejection fraction (HFpEF), 0.9% had HF with improved ejection fraction (HFimpEF), and 1.5% had unknown ejection fraction (EF). The average length of hospital admission varied by phenotype, ranging from 8.1 to 15.9 days. Women accounted for 41.15% of all admissions, with the most common phenotype amongst women being HFpEF (57.8%) and the least common being HFrEF (25.1%). The mean age at admission was 75.8 years. Roughly 79% of the whole cohort had NYHA class III-IV at admission; 33% of HFrEF, 13% of HFmrEF and 32% of HFpEF admissions. The most common underlying cause of AHF was coronary artery disease (CAD, 30.9%) followed by atrial fibrillation (15.0%), hypertension (9.8%), diastolic dysfunction (9.4%) and valvular heart disease (9.2%). Other more rare causes were dilated cardiomyopathy (4.4%), amyloidosis (3.2%), broken heart disease (1.5%), myocarditis (0.4%), postpartum cardiomyopathy (0.2%) and Fabry disease (0.1%). During the study period, 422 mortalities were recorded, with 106 in-hospital deaths. After excluding in-hospital mortalities, no significant difference in survival between phenotypes was observed after the first discharge. However, a significant difference in survival was observed with respect to the date of diagnosis (p = 0.0191). Conclusion This study provides new insights into the underlying causes of AHF and patients' prognosis according to phenotypes in Iceland. Our results demonstrate that the most common underlying cause of AHF was CAD, followed by atrial fibrillation and hypertension and that the cohort was highly symptomatic, with a large proportion of patients having NYHA class III-IV at admission. Our findings also highlight significant differences in the prevalence of HF phenotypes between genders, with women more commonly presenting with HFpEF and less commonly with HFrEF.