A Comparison of COVID-19 and Influenza-Associated Myocarditis: A Nationwide Study in the United States.

We aimed to compare the characteristics and outcomes of adult patients hospitalized with myocarditis and either concomitant corona virus disease 2019 (COVID-19) or influenza, and elucidate clinical predictors associated with adverse outcomes in both groups. The study used the national inpatient sample (NIS) from 2019 to 2020 to identify 27,725 adult myocarditis hospitalizations, of which 5840 had concomitant COVID-19 and 1045 had concomitant influenza. After propensity score matching, the in-hospital mortality from myocarditis was significantly higher in COVID-19 compared to influenza. Patients with myocarditis and COVID-19 were more likely to have cardiovascular comorbidities and be older than those with influenza-associated myocarditis. Predictors of mortality were also different in both groups.