Abstract
Myocarditis is common in Multisystem Inflammatory Syndrome in Children (MIS-C), and the mechanism may differ from idiopathic/viral myocarditis as MIS-C involves a hyper-inflammatory state weeks after COVID-19. We sought to evaluate exercise stress testing (EST) in these patients as EST may help guide return-to-play recommendations. Retrospective cohort study evaluating ESTs (standard Bruce treadmill protocol) from MIS-C patients from 2020 to 2022, compared to myocarditis patients and age, sex, and weight matched controls from 2005 to 2019. ESTs included 22 MIS-C patients (mean age 11.9 years) with 14 cardiopulmonary and 8 cardiovascular tests, 33 myocarditis (15.5 years), and 44 controls (12.0 years). Percent-predicted peak VO2 was abnormal (< 80% predicted in 11 14 79 mis-c patients 13 33 39 myocarditis and 17 44 39 controls p=" 0.04)." exercise duration was shorter in mis-c than myocarditis or control cohorts p=" 0.01)." isolated atrial or ventricular ectopy was seen in 8 22 36 mis-c 9 33 27 myocarditis and 5 44 11 controls p=" 0.049)." no arrhythmias complex ectopy or evidence of ischemia were noted though non-specific st t wave abnormalities occurred in 4 22 18 mis-c 5 33 15 myocarditis and 3 44 7 controls. exercise duration and percent-predicted peak vo2 were significantly reduced in mis-c at mean 6-month follow-up compared to pre-covid era idiopathic viral myocarditis and control cohorts. this may be secondary to deconditioning during the pandemic and or chronic cardiopulmonary or autonomic effects of covid mis-c. although there were no exercise-induced arrhythmias in our mis-c patients larger cohort studies are warranted. est in mis-c follow-up may help evaluate safety and timing of return to play and potentially mitigate further deconditioning.>
