Myocardial Injury Pattern at MRI in COVID-19 Vaccine-Associated Myocarditis.

Abstract

BackgroundThere is limited data on the pattern and severity of myocardial injury in patients with COVID-19 vaccination associated myocarditis.PurposeTo describe myocardial injury following COVID-19 vaccination and to compare these findings to other causes of myocarditis.MethodsIn this retrospective cohort study, consecutive adult patients with myocarditis with at least one T1-based and at least one T2-based abnormality on cardiac MRI performed at a tertiary referral hospital between 2019-2021 were included. Patients were classified into one of three groups: myocarditis following COVID-19 vaccination, myocarditis following COVID-19 illness, and other myocarditis not associated COVID-19 vaccination or illness.ResultsOf the 92 included patients, 21 (22%) had myocarditis following COVID-19 vaccination (mean age 31 years ±14 [standard deviation]; 17 men; mRNA-1273 in 12 [57%] and BNT162b2 in 9 [43%]). Ten patients (11%) had myocarditis following COVID-19 illness (mean age 51 years ±14; 3 men), and 61 (66%) had other myocarditis (mean age 44 years ±18; 36 men). MRI findings in vaccine associated myocarditis included late gadolinium enhancement (LGE) in 17 (81%) and left ventricular dysfunction in 6 (29%). Compared with other causes of myocarditis, patients with vaccine associated myocarditis had higher left ventricular ejection fraction and less extensive LGE, even after controlling for age, sex, and duration between symptom onset and MRI. The most frequent location of LGE in all groups was subepicardial at the basal inferolateral wall, although septal involvement was less common in vaccine associated myocarditis. At short-term follow-up (median 22 [IQR 7-48] days), all patients with vaccine associated myocarditis were asymptomatic with no adverse events.ConclusionsCardiac MRI demonstrated a similar pattern of myocardial injury in vaccine associated myocarditis compared to other causes, although abnormalities were less severe, with less frequent septal involvement, and no adverse events over short-term follow-up.See also the editorial by Raman and Neubauer.