Clinical characteristics and prognosis in patients with acute myocarditis or unexplained acute chest pain: a nationwide longitudinal cohort study

Abstract Background Acute myocarditis is a disease with variable prognosis, ranging from complete recovery to end-stage heart failure (HF) and death. The aim of this study was to examine the risk of mortality and HF in patients with suspected acute myocarditis (AM) in comparison to patients hospitalized for unexplained acute chest pain (ACP). Methods We used the SWEDEHEART-registry to identify patients >16 years admitted to hospital between 1 January 1998 and 31 December 2018 with either AM or ACP. Risks of all-cause mortality and development of HF were calculated and compared by use of adjusted Cox regression analyses. Results A total of 3,792 patients with AM and 109,934 patients with ACP were included. Median follow-up time was 7.8 years (Q1, Q3; 3.4, 12.3). AM patients were younger compared to ACP patients, median age 37 years (Q1, Q3; 26, 52) vs 59 years (Q1, Q3; 49, 69), and more likely to be men (79.9% vs 51.4%, p <0.001). Comorbidity burden was lower within the AM cohort. Chest pain was the most common presenting symptom in both groups. Mortality rate at 30 days (OR 3.75, 95% CI 1.9-7.3, p<0,001) as well as long term (OR 2.0, 95% CI 1.69-2.39, p <0.001) were significantly higher among AM patients and AM patients were more likely to develop HF during follow-up (OR 2.3, 95% CI 1.81-2.93, p<0,001). Conclusions AM patients had a worse short -and long-term outcome compared with ACP. The risk for development of HF was higher for AM patients even after the first year.