Cardiac MRI Helps Evaluate Myocarditis After COVID-19 Vaccination

A small case series found that all patients with myocarditis after COVID-19 mRNA vaccination were adolescent males and had a favorable initial clinical course. The research, which was recently published in the American Journal of Roentgenology, also found that all patients showed cardiac MRI findings typical of myocarditis of other causes.

“Radiologists should be aware of the possible association of COVID-19 mRNA vaccination and myocarditis, and recognize the role of cardiac MRI in assessment of suspected myocarditis after COVID-19 vaccination,” wrote Lydia Chelala, MD, assistant professor of radiology at the University of Chicago Medicine.

A possible association between COVID-19 mRNA vaccination and myocarditis in young individuals was first reported in Israel. While uncommon, occurrences of myopericarditis in adolescents and young adults after COVID-19 mRNA vaccination have since been reported in the US. In May, the US FDA expanded the emergency approval of the Pfizer mRNA vaccine to include adolescents aged 12 to 15 years.

In this retrospective study, researchers aimed to describe the cardiac MRI findings in five patients who underwent MRI from May 14 to June 14, 2021 for suspected myocarditis within two weeks of COVID-19 mRNA vaccination, without known prior COVID-19. 

All the patients were male, aged 16 to 19 years (mean age 17.2) and presented within four days of the second vaccine dose. They all had elevated troponin levels. Based on medical history, physical examination, myocarditis viral panel and toxicology screen, alternate possible causes of myocarditis were considered clinically unlikely. The cardiac MRI findings were consistent with myocarditis in all patients, with early gadolinium enhancement and late gadolinium enhancement (LGE). All patients were discharged from hospital in a stable condition with improved or resolved symptoms after 4.8 days on average. After discharge, three of the patients reported mild intermittent self-resolving chest pain. In two patients, persistent though decreased subepicardial LGE was found on repeat cardiac MRI.

The authors noted several limitations, including the retrospective design of the study, the descriptive nature of the findings and the small number of participants. 

“All patients underwent cardiac MRI due to clinical suspicion for myocarditis. Thus, the sample represents a high-risk group, which may have introduced a selection bias that contributed to the high frequency of abnormalities on cardiac MRI,” the authors wrote.

They suggested that additional research is warranted to establish causality. 

In an accompany editorial, Gloria Caredda, MD, of the department of radiology, Azienda Ospedaliero Universitaria, in Monserrato, Italy, suggested that the findings provide “additional insights into this emerging clinical condition, which might be misdiagnosed given its lack of clear symptoms.” She added, “When assessing patients with suspected myocarditis after COVID-19 mRNA vaccination, referring clinicians and radiologists should consider the specific imaging features described by this study.

“An additional helpful follow-up study would be to systematically evaluate patients for whom there was not a high suspicion for myocarditis, to reduce this study’s selection bias,” Dr. Caredda wrote.