Prevalence and clinical outcomes of myocarditis and pericarditis in 718,365 COVID‐19 patients

Background COVID‐19 has a wide spectrum of cardiovascular sequelae including myocarditis and pericarditis; however, the prevalence and clinical impact are unclear. We investigated the prevalence of new‐onset myocarditis/pericarditis and associated adverse cardiovascular events in patients with COVID‐19. Methods and results A retrospective cohort study was conducted using electronic medical records from a global federated health research network. Patients were included based on a diagnosis of COVID‐19 and new‐onset myocarditis or pericarditis. Patients with COVID‐19 and myocarditis/pericarditis were 1:1 propensity score matched for age, sex, race and comorbidities to patients with COVID‐19 but without myocarditis/pericarditis. The outcomes of interest were 6‐month all‐cause mortality, hospitalisation, cardiac arrest, incident heart failure, incident atrial fibrillation and acute myocardial infarction, comparing patients with and without myocarditis/pericarditis. Of 718,365 patients with COVID‐19, 35,820 (5.0%) developed new‐onset myocarditis and 10,706 (1.5%) developed new‐onset pericarditis. Six‐month all‐cause mortality was 3.9% (n = 702) in patients with myocarditis and 2.9% (n = 523) in matched controls (p