Clinical characteristics, diagnosis and short-term outcomes of COVID-19-associated acute myocarditis in China.

AIMS Acute myocarditis (AM) has been recognized as a rare complication of coronavirus disease 2019 (COVID-19) infection. This study was conducted to present the clinical characteristics, disease courses and short-term prognoses of Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induced AM in China, which has been unavailable so far. METHODS AND RESULTS Data from 28 patients diagnosed with definite COVID-19-associated AM from 6 hospitals in China between 1 December 2022 and 30 June 2023 were collected and analysed. The diagnosis of AM was based on increased troponin level plus typical findings of AM on cardiac magnetic resonance (CMR) imaging and/or endomyocardial biopsy. Among 28 patients with definite COVID-19-related AM, median age was 37 years (Q1-Q3: 22-52) and 53.6% were men. Twenty-three patients occurred within 2 weeks of the onset of COVID-19 infection, 10 patients underwent endomyocardial biopsy and CMR was performed in all patients. Seven (25.0%) patients developed fulminant myocarditis that required inotropic agents or temporary mechanical circulatory support. Of the nine patients (32.1%) with left ventricular ejection fraction (LVEF) below 50% on admission, five had fully recovered LVEF and two demonstrated improvement but to levels below normal at discharge. The comparison of CMR parameters between the baseline and first follow-up showed that ECV was decreased at the first follow-up [28.95 (25.38, 32.55)% vs. 33.65 (31.58, 37.55)%, P = 0.028), while other CMR parameters had no significant changes. Eighteen patients (64.3%) were prescribed with corticosteroids, and seven patients (25.0%) underwent temporary mechanical circulatory support. Only two patients died during hospitalization. CONCLUSIONS The majority of COVID-19-associated AM occurred within 2 weeks of Omicron variant infection. Fulminant myocarditis complicated by hemodynamic instability requiring temporary mechanical circulatory support was not uncommon. However, short-term outcome was generally good and most AM patients fully recovered.