Cardiac MRI for COVID-19-Related Late Myocarditis: Functional Parameters and T1 and T2 Mapping

Background/Objectives: Myocarditis is a recognized complication of COVID-19 infection, with potential long-term cardiac sequelae. While acute cardiac involvement has been frequently reported, late-stage myocardial effects remain less well characterized. Cardiac magnetic resonance (CMR) imaging, particularly T1 and T2 mapping, offers non-invasive tissue characterization for myocardial inflammation and fibrosis. This study aimed to evaluate segmental myocardial tissue changes in patients with late-stage COVID-19-related myocarditis using CMR and compare findings with patients with non-COVID-19 myocarditis and healthy controls. Methods: This retrospective, single-center study included 25 patients with clinically suspected COVID-19 myocarditis who underwent CMR between 36 and 565 days post-infection. T1 and T2 mapping values and late gadolinium enhancement (LGE) patterns were assessed and compared with 14 non-COVID-19 myocarditis patients and 19 healthy controls. Subgroup analyses were performed according to vaccination status and left ventricular ejection fraction (LVEF). Results: Patients with reduced LVEF had significantly higher T1 and T2 values in several myocardial segments. Compared to controls, the COVID-19 myocarditis group showed significantly elevated T1 values in all segments except 2 and 3. No significant difference in T2 values was observed. LGE was present in 61% of COVID-19 myocarditis patients, predominantly with a subepicardial pattern. No significant differences were observed between vaccinated and unvaccinated patients. Conclusions: Late-stage COVID-19 myocarditis is associated with persistent segmental myocardial tissue abnormalities, particularly elevated T1 values and subepicardial LGE. Segmental CMR mapping may provide additional diagnostic value in identifying residual myocardial injury in patients with ongoing cardiac symptoms after COVID-19 infection.