Cardiovascular magnetic resonance imaging and clinical follow-up in patients with clinically suspected myocarditis after COVID-19 vaccination.

Background: The purpose of this study was to evaluate cardiovascular magnetic resonance (CMR) findings and their relationship to longer-term clinical outcomes in patients with suspected myocarditis following coronavirus disease 2019 (COVID-19) vaccination.

Methods: Consecutive adult patients who underwent clinically indicated CMR for evaluation of suspected myocarditis following messenger ribonucleic acid (mRNA)-based COVID-19 vaccination at a single center between 2021 and 2022 were retrospectively evaluated. Patients were classified based on the revised Lake Louise criteria for T1-based abnormalities (late gadolinium enhancement [LGE] or high T1 values) and T2-based abnormalities (regional T2-hyperintensity or high T2 values).

Results: Eighty-nine patients were included (64% [57/89] male, mean age 34 ± 13 years, 38% [32/89] mRNA-1273, and 62% [52/89] BNT162b2). On baseline CMR, 42 (47%) had at least one abnormality; 25 (28%) met both T1- and T2-criteria; 17 (19%) met T1-criteria but not T2-criteria; and 47 (53%) did not meet either. The interval between vaccination and CMR was shorter in those who met T1- and T2-criteria (28 days, IQR 8-69) compared to those who met T1-criteria only (110 days, IQR 66-255, p < 0.001) and those who did not meet either (120 days, interquartile range (IQR) 80-252, p < 0.001). In the subset of 21 patients who met both T1- and T2-criteria at baseline and had follow-up CMR, myocardial edema had resolved and left ventricular ejection fraction had normalized in all at median imaging follow-up of 214 days (IQR 132-304). However, minimal LGE persisted in 10 (48%). At median clinical follow-up of 232 days (IQR 156-405, n = 60), there were no adverse cardiac events. However, mild cardiac symptoms persisted in 7 (12%).

Conclusion: In a cohort of patients who underwent clinically indicated CMR for suspected myocarditis following COVID-19 vaccination, 47% had at least one abnormality at baseline CMR. Detection of myocardial edema was associated with the timing of CMR after vaccination. There were no adverse cardiac events. However, minimal LGE persisted in 48% at follow-up.