Myocarditis And COVID-19: An Analysis Of All Claims Administrative Data From Before And During The Pandemic

BACKGROUND: Myocarditis (MC) is an inflammatory condition of the myocardium often caused by a virus and can lead to hospitalization, heart failure, or death. Although rare, data suggest an increased incidence associated with the COVID-19 virus. However, the risk for COVID-19-induced MC remains poorly understood and debated. We sought to evaluate the prevalence of pandemic MC-related inpatient encounters during 2020 through a descriptive approach and compare it to the pre-pandemic era. Given that the first COVID-19 vaccine doses were administered on December 14, 2020, a significant increase in MC prevalence could be attributable to COVID-19 exposure. METHODS: Data were obtained from the PearlDiver database (PearlDiver Technologies, Fort Wayne, IN). The database provides all-payers administrative claims data on the patient level. Using ICD-10-CM codes, a cohort of patients who had their first inpatient encounter with MC was identified and divided into pre-pandemic (January- October 2019) and pandemic (January-October 2020) groups and classified by age, gender, and month of hospitalization. We described these patients' demographics, calculated the prevalence ratio (PR) and 95% CI of MC-related encounters during the pandemic, and compared it with the same period in the pre-pandemic period. A p-value <0.05 was deemed significant. RESULTS: The median age, length of stay in previous hospitalizations, mean gender and Elixhauser Comorbidity Index were similar between groups. The prevalence of MC was 22/100,000 cases in 2019 and 25/100,000 in 2020. The overall PR of hospitalization due to MC was 13% higher in 2020 than it was in 2019 (PR=1.13, p<0.0001), with a significantly higher risk in age groups 5-9 (PR=1.41 p=0.02), 60-64 (PR=1.24 p<0.0001), 65-69 (PR=1.14 p=0.01), 70-74 (PR=1.28 P<0.0001), and 80-85 (PR=1.36 p<0.0001). The risk was significantly higher in March (PR=1.27 p<0.0001), July (PR=1.41 p<0.0001, and September (PR=1.52 p<0.0001) in 2020. In 2020, the risk of MC in males with respect to females decreased by 3% compared to 2019. DISCUSSION: Our results suggest a temporal correlation between increased prevalence of inpatient encounters for MC since COVID-19′s inception. The risk was significantly higher in older adults and during months with a higher COVID-19 incidence. These findings do not demonstrate causation between the COVID-19 virus and MC and are limited by the typical biases associated with retrospective studies. CONCLUSIONS: Although MC is a less common hospitalization condition, our data supports a significantly increased prevalence of MC-related encounters during the initial year of the COVID-19 pandemic. We found risk variations according to age, gender, and month.