Incidence of Myocarditis among Patients Recovered from COVID-19 Identified using Cardiac Magnetic Resonance: A 1-year Single-centre Retrospective Study

Background: COVID-19 continues to engender significant morbidity and mortality globally and is associated with cardiac injuries, such as myocarditis. This study reports the incidence of myocarditis identified using cardiac magnetic resonance (CMR) in patients recovered from COVID-19. Methods: This is a single-centre retrospective cohort study conducted among recovered COVID-19 patients who underwent CMR from 1 January 2020 to 31 December 2021. Results: Most patients with evidence of myocardial oedema on CMR had a mild-type infection (31 of 54 [57%]), with dyspnoea (15 [28%]) and palpitations (12 [22%]) being the most common symptoms. Twenty-nine of 54 (54%) patients had increased T2 signal indicative of myocarditis; eight (28%) of them had evidence of myocardial fibrosis on late gadolinium enhancement primarily located at the lateral walls with sub-epicardial and mid-wall involvement dispersed in the basal to apical segments. Myocardial oedema was noted in nine (31%) patients. Six (20%) of them had an impaired left ventricular ejection fraction of <50% and three patients (10%) had an impaired right ventricular ejection fraction of <50%. There was no significant difference in left ventricular (57% versus 61%; p=0.13) and right ventricular (57% versus 60%; p=0.51) systolic function between the two groups. Conclusion: Myocarditis after COVID-19 can be a lasting consequence, and CMR may serve as a sensitive imaging tool to investigate any suspected cardiac injury after treatment of the infection. The findings of the study may aid in determining the other possible long-term effects in patients who have recovered from COVID-19, particularly those who continue to experience symptoms.