Cardiovascular Features of Multisystem Inflammatory Syndrome in Children and Kawasaki Disease

Multisystem Inflammatory Syndrome in Children (MIS-C) was a new condition with clinical features overlapping with Kawasaki disease (KD) observed during the COVID-19 pandemic. Differences emerged that supported distinguishing between the two conditions, including distinct cardiac presentations and sequelae. The study objective was to compare echocardiographic findings between MIS-C and KD utilizing prospectively collected longitudinal cohort data from a multicenter consortium and the Kawasaki Disease Research Center. Pre-COVID KD cases (2017–2019) and MIS-C cases (April 2020-March 2022) were analyzed for differences in coronary artery (CA) Z-score and left ventricular ejection fraction (EF) during admission and follow up. Relative risks (RRs) were calculated between disease category and cardiac presentation (diminished EF and aneurysm status). We analyzed 480 subjects (MIS-C n=262; KD n=218). KD subjects had a higher risk of CA aneurysm (RR= 1.86; 95% CI: 1.23, 2.79). Conversely, KD subjects had a lower risk of diminished EF (RR=0.09; 95% CI: 0.04, 0.18). Although most cardiovascular abnormalities resolved by follow-up, diminished EF persisted in 6 MIS-C patients (6%). None of the KD subjects had diminished EF at follow-up. CA Z-score ≥2.5 persisted in 3 MIS-C patients (10%) and 13 KD patients (25%). At follow-up, newly documented diminished EF was observed in 1 MIS-C subject, while a CA Z-score ≥2.5 was newly identified in 1 MIS-C subject and 2 KD subjects. MIS-C and KD demonstrate distinct cardiovascular phenotypes, with diminished EF more prominent in MIS-C and CA aneurysms more characteristic of KD. These findings support disease-specific approaches to cardiac monitoring and longitudinal follow-up.