Significant exercise limitations after recovery from MIS-C related myocarditis

Background Myocarditis is one of the presentations of multisystemic infammatory syndrome in children(MIS-C)following coronavirus disease 2019(COVID-19).Although the reported short-term prognosis is good,data regarding medium-term functional capacity and limitations are scarce.This study aimed to evaluate exercise capacity as well as possible cardiac and respiratory limitations in children recovered from MIS-C related myocarditis.Methods Fourteen patients who recovered from MIS-C related myocarditis underwent spirometry and cardiopulmonary exercise testing(CPET),and their results were compared with an age-,sex-,weight-and activity level-matched healthy control group(n=14).Results All participants completed the CPET with peak oxygen uptake(peak.V O2),and the results were within the normal range(MIS-C 89.3%±8.9%and Control 87.9%±13.7%predicted.V O2).Five post-MIS-C patients(35%)had exerciserelated cardio-respiratory abnormalities,including oxygen desaturation and oxygen-pulse fattening,compared to none in the control group.The MIS-C group also had lower peak exercise saturation(95.6±3.5 vs.97.6±1.1)and lower breathing reserve(17.4%±7.5%vs.27.4%±14.0%of MVV).Conclusions Patients who recovered from MIS-C related myocarditis may present exercise limitations.Functional assessment(e.g.,CPET)should be included in routine examinations before allowing a return to physical activity in post-MIS-C myocarditis.Larger,longer term studies assessing functional capacity and focusing on physiological mechanisms are needed.