Case report: mRNA COVID-19 vaccine-related acute pericarditis with evolution to myopericarditis.

Background: Both acute pericarditis and myocarditis have been reported as rare complications following vaccination with the Pfizer-Biotech and Moderna mRNA COVID-19 vaccines.

Case Summary: An 18-year-old man presented with clinical and electrocardiographic changes of acute pericarditis 2 days after receiving the second dose of the BNT162b2 (Pfizer-BioNTech) vaccine. His electrocardiogram also showed an incomplete right bundle branch block. Troponin T on presentation was normal (reference <14 ng/L) but subsequently increased to a peak 1080 ng/L by day 4 post vaccination. Evolving electrocardiographic changes and cardiac MRI findings were consistent with acute myopericarditis.

Discussion: This patient's clinical course was uncomplicated, which is consistent with studies indicating that post-COVID vaccine myocarditis usually has a mild course with a low chance of arrhythmia or heart failure. Troponin elevation is a part of the diagnostic criteria for myocarditis. This case is consistent with another report demonstrating that troponin levels can be within the normal range early in the clinical course of post-COVID vaccine myopericarditis. The incomplete right bundle branch block resolved by day 4 post-vaccination and thus may have represented early myocardial involvement at presentation. Further testing and monitoring should be considered in patients who present soon after COVID-19 mRNA vaccination with pericarditis features or minor conduction delays, in order to rule out progression to myopericarditis. Identifying myocardial involvement is clinically relevant as it indicates a risk of developing arrhythmia or heart failure, as well as having implications for physical activity advice and future booster vaccination.