Clinical and cardiac magnetic resonance profile of patients with COVID-19 vaccine-related myocarditis compared with other acute myocarditis

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Spanish Cardiology Society, Cardiac Imaging Association. Grant for short extern fellowship in national centers. Background Reports have suggested an association between the development of myocarditis and mRNA vaccines against COVID-19 coronavirus disease. Cardiac magnetic resonance (CMR) findings in this setting have not been widely explored. Purpose The present study explores the clinical profile and CMR imaging findings in patients with a diagnosis of myocarditis during the period of 1 month after COVID-19 vaccination compared to non-related myocarditis during the same period. Methods All patients who underwent a CMR for suspected myocardial infarction with non-obstructive coronary arteries (MINOCA) during a period of 1 year from June 2021 to June 2022 were retrospectively evaluated. Myocarditis was defined by modified Lake Louise criteria (mLLC) and vaccine-related myocarditis was defined as a myocarditis episode in the period of 1 month after vaccination. Electronic medical records were analyzed to collect data on baseline clinical variables, CMR features and clinical events. Results A total of 118 consecutive patients undergoing a CMR for suspected MINOCA were included in the study of whom 48 (40,7%) fulfilled mLLC for myocarditis, of those, 15 cases (31,25%) were vaccine-related myocarditis. Both related and non-vaccine related myocarditis were more frequent among men and there were no differences in cardiovascular risk factors or baseline comorbidities between groups. CMR findings showed that vaccine-related myocarditis had similar LVEF and RVEF compared to other myocarditis and there were no differences in native T1, native T2 or extracellular volume (ECV). (Table 1). Edema in non-vaccine related myocarditis was more frequently observed in inferolateral mid and basal segments (segment 11) whilst in vaccine-related myocarditis edema was more frequently observed in inferoseptal mid segment (segment 9). There were no differences in the localization of the late gadolinium enhancement (LGE). (Table 2.) CMR follow-up was performed in 30 patients between 6 to 8 months after admission, showing LGE persistence without edema in 70% of non-vaccine related patients and 77,8% of vaccine-related patients. There were only 2 myocarditis recurrences. During the clinical follow up there were no deaths or ventricular arrhythmias, there were 3 hos