Acute myocarditis (AM) is considered an uncommon cardiovascular consequence of COVID-19, while data beyond case reports is limited. Therefore, based on a retrospective cohort from 23 hospitals, researchers sought to present the prevalence, baseline features, in-hospital care, and outcomes for patients with COVID-19–associated AM. Between February 1, 2020, and April 30, 2021, 112 patients with probable AM from 56,963 hospitalized patients with COVID-19 were assessed. Inclusion criteria included hospitalization for COVID-19 and a diagnosis of AM based on endomyocardial biopsy or an elevated troponin level, as well as typical AM symptoms on cardiac magnetic resonance imaging. They identified 97 individuals with suspected AM, and 54 of them had definite/probable AM supported by endomyocardial biopsies in 17 (31.5%) or magnetic resonance imaging in 50 patients (92.6%). In addition, they looked at patient characteristics, therapies, and outcomes in COVID-19–associated AM.

AM prevalence among COVID-19 hospitalized patients was 2.4 per 1,000 hospitalizations when definite/probable AM was included and 4.1 per 1,000 when potential AM was considered. The median age of definite/probable cases was 38 years, 38.9% female. On admission, the most common symptoms were chest discomfort and dyspnea (55.5% and 53.7%, respectively). In the absence of COVID-19–associated pneumonia, 31 cases (57.4%) occurred. Twenty-one patients (38.9%) had a fulminant presentation requiring inotropic support or interim mechanical circulatory support. In-hospital death or temporary mechanical circulatory assistance occurred in 20.4% of cases. At 120 days, the estimated death was 6.6% in patients with concomitant pneumonia and 15.1% in patients without pneumonia (P=0.044). As measured by echocardiography, left ventricular ejection fraction increased from a median of 40% on admission to 55% at discharge (n=47; P<0.0001) in patients with and without pneumonia. Corticosteroids were regularly used (55.5%).

The incidence of AM is expected to be between 2.4 and 4.1 per 1,000 COVID-19 hospitalized patients. The majority of AM occurs without pneumonia and is frequently accompanied by hemodynamic instability. AM was an uncommon complication in COVID-19 patients, with outcomes varying depending on the occurrence of associated pneumonia.