Cardiac Magnetic Resonance Findings of COVID-19 Vaccine-Associated Myopericarditis at Intermediate Follow Up: A Comparison with Classic Myocarditis

OBJECTIVE: To report intermediate cardiac magnetic resonance (CMR) findings of COVID-19 vaccine associated myopericarditis (C-VAM) and compare with classic myocarditis. STUDY DESIGN: Retrospective cohort study including children diagnosed with C-VAM from 5/2021 through 12/2021 with early and intermediate CMR. Patients with classic myocarditis from 1/2015 through 12/2021 and intermediate CMR were included for comparison. RESULTS: There were 8 patients with C-VAM and 20 with classic myocarditis. Among those with C-VAM, CMR performed at median 3 days (IQR 3, 7) revealed 2/8 patients with left ventricular ejection fraction (LVEF)<55%, 7/7 patients receiving contrast with late gadolinium enhancement (LGE), and 5/8 patients with elevated native T1 values. Borderline T2 values suggestive of myocardial edema were present in 6/8. Follow-up CMRs performed at median 107 days (IQR 97, 177) showed normal ventricular systolic function, T1, and T2 values; 3/7 patients had LGE. At intermediate follow-up, C-VAM patients had fewer myocardial segments with LGE than classic myocarditis patients (4/119 vs 42/340, p=0.004). C-VAM patients also had a lower frequency of LGE (42.9 vs 75.0%) and lower percentage of LVEF<55% compared with classic myocarditis (0.0 vs 30.0%), although these differences were not statistically significant. Five classic myocarditis patients did not receive an early CMR, leading to some selection bias in study design. CONCLUSION: Patients with C-VAM had no evidence of active inflammation or ventricular dysfunction on intermediate CMR, although a minority had persistent LGE. Intermediate findings in C-VAM revealed less LGE burden compared with classic myocarditis.