COVID-19 MRNA vaccine associated myocarditis - 1 year follow-up from a tertiary children's hospital in Australia.

Abstract

Background: Myocarditis in adolescents and young adults is a recognized rare complication after COVID-19 vaccination. We describe cardiac sequelae at 1 year follow-up for vaccine-associated myocarditis (VAM) from a tertiary Children's Hospital in Australia. Case Description: Methods: Prospective surveillance of VAM cases between January 2022 and May 2023. Myocarditis was defined by standard criteria. Clinical findings, ECG, echocardiogram and Cardiac MRI (CMR) findings were evaluated. Result(s): 33 cases were included (median age at presentation 14.6 years (IQR 13- 16.4), 82% male). 29 out of 33 (87.9%) had complete follow up including repeat CMR after 1 year (median 420 days, IQR 407-439 days). There were no deaths. There were no patients with symptoms at follow up. ECG changes typical of pericarditis (8/33) had resolved early in the course of the illness, with no arrhythmias recorded. Echocardiography showed normal left ventricular systolic function at presentation in 29 patients and mildly impaired LVF in 4, all of which resolved within 2 days and remained normal at follow up. CMR was performed early (median 2 days; IQR 1- 2.5 days) with abnormal findings in 27 of 33 patients (81%). Repeat CMR after 1 year showed that 21 out 29 (72.4%) had late Gadolinium enhancement (LGE). There was no evidence of oedema. A decrease in LGE intensity or distribution was noted in 17/21 (81%). 24 patients with CMR abnormalities on their acute scans have had repeat CMR after 1 year; complete resolution of LGE was noted in only 4 patients (16.7%). Conclusion(s): None of the patients had persistent clinical or echocardiographic abnormalities after acute VAM. Majority of the patients had fibrosis on CMR after 1 year follow up with a decrease in LGE intensity or distribution compared to their acute CMR studies. While it is heartening to note that all patients have remained well, the potential long-term consequences of fibrosis are unknown and warrant further surveillance.