Background: Cardiac involvement can lead to significant morbidity in children with acute COVID-19 or Multisystem Inflammatory Syndrome in Children (MIS-C). However, the presentation and outcomes of cardiac involvement may differ among these two conditions. We aimed to compare the frequency and extent of cardiac involvement among children admitted with acute COVID-19 vs those with MIS-C.

Methods: We conducted a cross sectional study of patients admitted to our hospital from March 2020 to August 2021 with symptomatic acute COVID-19 or MIS-C. Cardiac involvement was defined by presence of one or more of the following: elevated troponin, elevated brain natriuretic peptide, reduced left ventricular ejection fraction on echocardiogram, coronary dilation on echocardiogram, or abnormal electrocardiogram reading.

Results: Among 346 acute COVID-19 patients with median age of 8.9 years and 304 MIS-C patients with median age of 9.1 years, cardiac involvement was present in 33 acute COVID-19 patients (9.5%) and 253 MIS-C patients (83.2%). The most common cardiac abnormality was abnormal electrocardiogram in acute COVID-19 patients (7.5%) and elevated troponin in MIS-C patients (67.8%). Among acute COVID-19 patients, obesity was significantly associated with cardiac involvement. Among MIS-C patients, non-Hispanic Black race/ethnicity was significantly associated with cardiac involvement.

Conclusions: Cardiac involvement is much more common in children with MIS-C than in those with acute COVID-19. These results reinforce our standardized practice of performing full cardiac evaluations and follow-up in all patients with MIS-C but only in acute COVID-19 patients with signs or symptoms of cardiac involvement.