Cardiac MRI six months after the onset of multisystem inflammatory syndrome in children and adolescents temporally related to COVID-19: A retrospective follow-up study

Background: In 2020, reports revealed cases called multisystem inflammatory syndrome in children and adolescents temporally related to COVID-19 or multisystem inflammatory syndrome in children. A small proportion of patients suffer from persistent left ventricular dysfunction at discharge. The primary aim was to investigate if myocardial impairment persists during follow-up in these patients. Methods: Children fulfilling the criteria for multisystem inflammatory syndrome in children with cardiac involvement hospitalized between December 2020 and February 2022 were included in this retrospective single centre study. Cardiac MRI was performed six months after the onset of symptoms to evaluate possible persistent myocardial damage. Results: Fifteen patients (80% male) with a median age of 8 years (interquartile range 4.5 - 13.5 years) were included. Upon admission, eight patients (53%) presented with reduced left ventricular function, with a median left ventricular ejection fraction of 54% (interquartile range 49.5%-61.5%) on transthoracic echocardiography. Elevated levels of cardiac-specific markers were found in 14 patients (93%). Cardiac MRI was performed in 12 patients at a median of 190.5 days after the onset of symptoms. Nine patients (75%) had normal left ventricular function, with a median left ventricular ejection fraction of 59.45%, while the remaining patients showed mildly to moderately reduced values. None of the patients showed signs of late gadolinium enhancement, indicating the absence of persistent myocardial scarring. Conclusion: During a follow-up of 6.2 months, mild to moderate cardiac impairment was revealed in 25% of patients evaluated by cardiac MRI. Although a majority of patients do not show signs of cardiac impairment, close follow-ups should be performed in a proportion of patients.