Outcomes of viral myocarditis in patients with and without COVID-19: a nationwide analysis from the United States

Background: Cardiovascular complications contribute to 40% of coronavirus disease 2019 (COVID-19) related deaths. The viral myocarditis associated with COVID-19 accounts for significant morbidity and mortality. How COVID-19 myocarditis compares to other viral myocardites is unknown. Methods: The authors conducted a retrospective cohort study using the National Inpatient Sample database to identify adult patients hospitalized for viral myocarditis in 2020 and to compare outcomes between those with and without COVID-19. The primary study outcome was in-hospital mortality. Secondary outcomes included in-hospital complications, length of stay, and total costs. Results: The study population included 15 390 patients with viral myocarditis, of whom 5540 (36%) had COVID-19. After adjustment for baseline characteristics, patients with COVID-19 had higher odds of in-hospital mortality [adjusted odds ratio (aOR) 3.46, 95% CI 2.57–4.67], cardiovascular complications (aOR 1.46, 95% CI 1.14–1.87) including cardiac arrest (aOR 2.07, 95% CI 1.36–3.14), myocardial infarction (aOR 2.97, 95% CI 2.10–4.20), venous thromboembolism (aOR 2.01, 95% CI 1.25–3.22), neurologic complications (aOR 1.82, 95% CI 1.10–2.84), renal complications (aOR 1.72, 95% CI 1.38–2.13), and hematologic complications (aOR 1.32, 95% CI 1.10–1.74), but lower odds of acute heart failure (aOR 0.60, 95% CI 0.44–0.80). The odds of pericarditis, pericardial effusion/tamponade, cardiogenic shock, and the need for vasopressors or mechanical circulatory support were similar. Patients with COVID-19 had longer length of stay (7 days vs. 4 days, P<0.01) and higher total costs ($21,308 vs. $14,089, P<0.01). Conclusions: Among patients with viral myocarditis, COVID-19 is associated with higher in-hospital mortality and cardiovascular, neurologic, renal, and hematologic complications compared to non-COVID-19 viruses.