Post Covid MIS-C Myocarditis Medium Term Exercise Limitations

PURPOSE: Myocarditis is one of the presentations of multisystemic inflammatory syndrome in children (MIS-C) following Coronavirus disease 2019 (COVID 19). Good short term prognosis is reported, however, data regarding long term functional capacity are scarce. our purpose was to evaluate exercise capacity and possible limitations in children post myocarditis caused by MIS-C following COVID 19. METHODS: Children with MIS-C myocarditis underwent spirometry and cardiopulmonary exercise testing (CPET) and compared with age, sex, weight and activity level matched control group. RESULTS: Twenty-eight children (14 with MIS-C) completed CPET. No significant differences were noticed between the groups. Pulmonary function tests were similar between the groups (MIS-C FEV1=92±9.4%pred, Control FEV1=95±10%pred) with three patients with abnormal values in the MIS-C group and one in the control group. Peak oxygen uptake (peak VO2) were within the normal range in both groups (MIS-C 89 ±8.9%pred of predicted VO2; Control 87 ±13.7%pred) . However, in the MIS-C group five patients (35%) presented abnormal responses to exercise, necessitating further follow up before returning back to routine activity compared to no patient in the control group. Two patients had flattening of the oxygen pulse curve suggesting possible stroke volume limitation and three patients showed oxygen desaturation (88-92%) at peak effort. CONCLUSIONS: Post MIS-C pediatric patients may present with exercise limitations. Functional assessment (e.g. CPET) should be considered as part of the routine examination before returning to normal active routine in children post MIS-C myocarditis. Larger prospective long-term studies assessing functional capacity and focusing on physiological and molecular mechanisms are needed.