Myocardial Inflammation at FDG PET/MRI and Clinical Outcomes in Symptomatic and Asymptomatic Participants after COVID-19 Vaccination

PURPOSE: To evaluate potential cardiac sequelae of COVID-19 vaccination at 2-month follow-up and to relate cardiac symptoms to myocardial tissue changes at fluorodeoxyglucose (FDG) PET/MRI, blood biomarkers, health-related quality of life, and adverse outcomes. MATERIALS AND METHODS: In this prospective study (ClinicalTrials.gov identifier: NCT04967807), a convenience sample of individuals aged 17 years or older were enrolled after COVID-19 vaccination and were categorized as symptomatic myocarditis (new cardiac symptoms within 14 days of vaccination and met diagnostic criteria for acute myocarditis); symptomatic, no myocarditis (new cardiac symptoms but did not meet criteria for myocarditis); and asymptomatic (no new cardiac symptoms). Standardized evaluation was performed 2 months after vaccination, including cardiac fluorine 18–FDG PET/MRI, assessment of blood biomarkers, and health-related quality of life. Statistical analysis included Kruskal-Wallis and Fisher exact tests. RESULTS: Fifty-four participants were evaluated a median of 72 days (IQR, 42–91 days) after COVID-19 vaccination: 17 symptomatic with myocarditis (mean age, 36 years ± 15 [SD]; 13 men), 17 symptomatic without myocarditis (mean age, 42 years ± 12; seven men), and 20 asymptomatic (mean age, 45 years ± 14; nine men). No participants in the symptomatic without myocarditis or asymptomatic groups had focal FDG uptake, myocardial edema, or impaired ventricular function. Two participants with symptomatic myocarditis had focal FDG uptake, and three had high T2 mapping values on MR images. Health-related quality of life was lower in the symptomatic myocarditis group than in the asymptomatic group. There were no adverse cardiac events beyond myocarditis in any participant. CONCLUSION: At 2-month follow-up, FDG PET/MRI showed evidence of myocardial inflammation in two of 17 participants diagnosed with acute myocarditis early after COVID-19 vaccination, but not in symptomatic and asymptomatic participants without acute myocarditis. Keywords: Molecular Imaging, MR Imaging, Heart, Inflammation ClinicalTrials.gov identifier: NCT04967807 Supplemental material is available for this article. © RSNA, 2023