Short-term outcome of late gadolinium changes detected on cardiovascular magnetic resonance imaging following coronavirus disease 2019 Pfizer/BioNTech vaccine-related myocarditis in adolescents

Background Rare cases of cardiac inflammation following vaccination for severe acute respiratory coronavirus 2 (SARS-CoV-2) have been reported. Objective To study paediatric patients with clinical findings of acute inflammation post coronavirus disease 2019 (COVID-19) Pfizer/BioNTech vaccination using cardiovascular magnetic resonance imaging (MRI) in acute and subacute phases. Materials and methods We enrolled adolescents younger than 18 years who presented at one of two institutions between July 2021 and August 2022 with clinical and laboratory findings of acute myocarditis shortly following COVID-19 Pfizer/BioNTech vaccination. They all underwent cardiovascular MRI using the institutional myocarditis protocol. Results Five adolescents (four boys) underwent eight scans between 3 days and 109 days (mean 49 days) after the onset of symptoms following COVID-19 vaccination. Myocardial oedema appeared on short tau inversion recovery (STIR) T2-weighted images in three adolescents at presentation (3–12 days after symptom onset). In these children, the myocardial oedema/acute inflammation had resolved at follow-up cardiovascular MRI (53–68 days after first MRI). However, in all three adolescents, a persistent area of late gadolinium enhancement was evident at follow-up, suggesting post-myocarditic fibrosis. One adolescent scanned only once, 66 days after being symptomatic, had no acute inflammation but persistent fibrotic changes. This last adolescent, who underwent the first scan 109 days after symptom onset, had findings compatible with an episode of previous myocarditis, with mild ongoing regional myocardial oedema/inflammation. Conclusion This study on post-vaccine myocarditis demonstrates residual lesions with persistent areas of late gadolinium enhancement/myocardial fibrosis with ongoing myocardial oedema after resolution of the initial myocardial oedema a few weeks after Pfizer/BioNTech vaccination. There is an urgent need to recognise and fully investigate the outcome of post-vaccination myocarditis.