Background: While prognosis of acute myocarditis with uncomplicated presentation is perceived as benign, data on long-term outcomes is scarce. We evaluated rates of myocarditis-associated cardiovascular events after a first-time hospitalization with uncomplicated acute myocarditis in patients without known heart disease.
Methods: In this retrospective nationwide population-based cohort study from 2013 to 2020, hospitalized patients with uncomplicated acute myocarditis but without known heart disease were 1:1 propensity score-matched with surgical controls hospitalized for laparoscopic appendectomy. As assessed in time-to-event analyses, the primary outcome was a composite of rehospitalization for myocarditis, pericardial disease, heart failure and its complications, arrhythmias, implantation of cardiac devices, and heart transplant.
Results: After matching, we identified 1,439 patients with uncomplicated acute myocarditis (median age of 35 years, 74.0% male) and 1,439 surgical controls (median age of 36 years, 74.4% male). Over a median follow-up of 39 months, compared with surgical controls, the hazard ratio (HR) for the primary composite outcome was 42.3 (95% confidence interval [CI], 17.4 to 102.8), corresponding to an incidence rate (IR) of 43.7 vs. 0.9 per 1,000 patient-years (py) and an incidence rate difference (IRD) of 42.7 (95% CI, 36.7 to 48.8) per 1,000 py.
Conclusion: Patients hospitalized with uncomplicated acute myocarditis and no known prior heart disease were associated with substantial risk for cardiovascular events over a follow-up of up to 8 years. This calls for a more efficient therapeutic management of this population of patients.
Keywords: Acute myocarditis; Cardiovascular events; Follow-up; Nationwide; Outcomes.
© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.