COVID-19 appears to have driven a sharp rise in myocarditis cases during the pandemic, and rates have remained elevated ever since, according to a study published this week in Catheterization & Cardiovascular Interventions. Myocarditis is inflammation of the heart muscle that often occurs after a viral infection.
For the retrospective cohort study, a research team at MedStar Washington Hospital Center in Washington, DC, analyzed electronic health record data from 778 patients with myocarditis across 10 hospitals from 2017 through 2024.
Cases rose 80% above baseline during COVID
Before the pandemic, myocarditis hospitalizations were relatively stable, with annual case counts ranging from 67 to 71 between 2017 and 2019. During the pandemic, hospitalizations climbed sharply, reaching 103 cases in 2020, 128 in 2021, and 139 in 2022, for an increase of roughly 80% above baseline. Population-level analyses have shown that COVID infection was tied to a roughly 16-fold increased risk of myocarditis, note the authors.
Myocarditis hospitalizations did not return to baseline after the pandemic began to wane. Researchers recorded 96 myocarditis admissions in 2023 and 105 in 2024, about 46% higher than prepandemic levels.
There are several plausible explanations for elevated myocarditis rates in the post-pandemic period, note the researchers, including persistent cardiac inflammation following a COVID infection, lingering immune system dysregulation, and ongoing circulation of COVID.
Those hospitalized during and after the pandemic peak were older…and more likely to have cardiometabolic conditions.
The study also pointed to a shift in the demographic characteristics of patients hospitalized with myocarditis. Compared with prepandemic patients, those hospitalized during and after the pandemic peak were older. The mean age increased from 46 years prepandemic to roughly 51 years during the pandemic.
Patients hospitalized for myocarditis during and after the pandemic peak were also more likely to have cardiometabolic conditions such as diabetes, hypertension, and hyperlipidemia. “This clinical profile mirrors the well‐described predilection of COVID‐19 to cause more severe disease in older patients with greater comorbidity burden,” write the researchers.
Disproportionate effects on Black patients
The study also found racial disparities. The proportion of Black patients hospitalized with myocarditis increased during and after the pandemic peak, rising from about 46% before the pandemic to approximately 58% during the pandemic and 53% after the peak, while the proportion of White patients decreased from 44% prepandemic to 30% during the pandemic and roughly 29% thereafter.
“This trend may reflect the disproportionate effects that COVID‐19 had on minority populations,” write the researchers. “During the pandemic, African American populations experienced higher rates of COVID‐19 exposure and lower vaccination uptake.
“In addition, due to longstanding barriers to healthcare access, African Americans carry a higher burden of cardiometabolic comorbidities, including hypertension [high blood pressure], diabetes, obesity, and chronic kidney disease, which may increase susceptibility to myocardial injury.”
Vaccine-related myocarditis ‘unlikely contributor’ to hospital cases
While myocarditis associated with mRNA vaccination has been documented, cases are rare, the authors note, and most occurred among young males. Post-pandemic myocarditis patients identified in this study were generally older and had multiple chronic conditions.
“Furthermore, observational studies have demonstrated vaccination to be associated with reduced COVID‐19 disease severity, mortality, and length of hospital stay, making vaccine-associated myocarditis an unlikely contributor to myocarditis-related hospital admissions.”
The study had several limitations, including diagnosis based on clinician assessment instead of magnetic resonance imaging (MRI) or biopsy and changes in healthcare-seeking behavior over the course of the pandemic. Nevertheless, they write, their findings underscore the need for ongoing surveillance and further study to better understand who is most at risk for myocarditis in the post-pandemic period.
