Long-term prognosis following hospitalization for acute myocarditis – a matched nationwide cohort study

The aim of this study was to examine the long-term risk of heart failure (HF) and all-cause mortality, in patients discharged alive following hospitalization for myocarditis. Background. Prognosis in patients with apparently uncomplicated myocarditis is in general perceived as good, but data on long-term outcomes are sparse. Methods. From nationwide Danish registries we included patients without prior cardiac disease, discharged alive with a first-time diagnosis of myocarditis 1996-2016. Patients were matched 1:10 by age- and sex, with controls from the general population. Risk of HF hospitalization and death in cases and controls was compared by use of adjusted Cox regression analyses. Results. We identified 1557 patients with a first-time diagnosis of myocarditis, 72% men, median age 39 years. Patients with myocarditis had more hypertension, diabetes, and cancer, and received more pharmacotherapy prior to hospitalization compared to matched controls. During a mean follow-up of 8.5 years, the event rate of HF hospitalization was 8.7 vs. 2.2 per 1000 patient-years (py) in cases and controls; HR 4.59 (95% CI; 3.58-5.88) and for all-cause mortality, event rate 21.9 vs 11.2 per 1000 py; HR 2.10 (95% CI; 1.82-2.43). Among 784 patients with no events or HF medication one year after diagnosis, risk of HF hospitalization (HR 2.15; 95% CI; 1.18-3.92), and all-cause mortality (HR 1.62; 95% CI; 1.21-2.16) remained elevated compared to matched controls. Conclusion. Myocarditis in younger patients without prior cardiac disease was associated with a long-term excess risk of HF hospitalization, and death, even in patients free of events and HF medication 1 year after discharge.HighlightsMyocarditis ranges from chest discomfort to severe heart failure.In most patients, left ventricular ejection fraction recovers but the long-term adverse cardiac risk is unknown.Patients with myocarditis and no prior cardiac disease were at higher risk of death and heart failureRoutine follow-up may be warranted following an episode of acute myocarditis.