Adults who have contracted SARS-CoV-2 may experience fulminant myocarditis as part of the multisystem inflammatory syndrome (MIS-A). However, a number of patients do not fulfill the MIS-A criteria, indicating that there are many phenotypes of fulminant myocarditis caused by COVID-19. For a study, researchers compared whether patients with fulminant COVID-19-related myocarditis met the MIS-A criteria (MIS-A+) or not (MIS-A-) in terms of patient features and clinical outcome.

A 26-bed intensive care unit’s (ICU) consecutive fulminant COVID-19-related myocarditis cases were retrospectively examined in a single location.

For suspected fulminant COVID-19-related myocarditis, 38 patients (males 66%; mean age 32±15 years) needed ICU hospitalization between March 2020 and June 2021. Dobutamine 79%, norepinephrine 60%, mechanical ventilation 50%, venoarterial extracorporeal membrane oxygenation  42%, and renal replacement therapy 29% made up the majority of in-ICU treatments for organ failure. There was a 13% in-hospital death rate. About 25 patients (or 66%) satisfied the MIS-A requirements. A shorter time interval between the onset of COVID-19 symptoms and myocarditis, a lower left ventricular ejection fraction, a higher rate of in-ICU organ failure, and a higher likelihood of mechanical circulatory support with venoarterial extracorporeal membrane oxygenation were all characteristics of MIS-A- patients compared to MIS-A+ patients (92% vs 16%; P<0.0001). Patients with MIS-A- had a greater rate of in-hospital death (31% vs 4%). Interleukin (IL)-22, IL-17, and tumor necrosis factor-α (TNF-α) levels were greater in MIS-A+ than MIS-A-, although interferon-α2 (IFN-α2) and IL-8 levels were higher in MIS-A-. About 7 of the 13 MIS-A- patients (or 54%) had RNA polymerase III autoantibodies, whereas none of the MIS-A+ patients did.

In MIS-A- fulminant and MIS-A+, there are 2 separate phenotypes of COVID-19-related myocarditis patients, each with a unique clinical presentation, prognosis, and immunological profile. It was important to distinguish between these 2 phenotypes in order to manage patients and learn more about their biology.