We describe a cohort of children referred with multisystem inflammatory syndrome in children associated with severe acute respiratory syndrome coronavirus 2 and compare this cohort with a 2019 cohort of children with Kawasaki disease.

We conducted a retrospective cohort study of 2019 and 2020 referrals to the inflammatory cardiology service at Great Ormond Street Hospital for Children. We compared cardiac and inflammatory parameters of a sub-section of the 2020 cohort who presented with reduced left ventricular ejection fraction with the remainder of the cohort.

Referrals significantly increased between February and June 2020 compared to 2019 (19.8/30 days versus 3.9/30 days). Frequency of coronary artery aneurysms (11/79 (13.9%) versus 7/47 (14.9%)) or severe coronary artery aneurysms (6/79 (7.6%) versus 3/47 (6.4%)) was similar between 2020 and 2019, respectively. The 2020 cohort was older (median age 9.07 years versus 2.38 years), more likely to be of Black, Asian, or other minority ethnic group (60/76 (78.9%) versus 25/42 (59.5%)), and more likely to require inotropic support (22 (27.5%) versus 0 (0%)). Even children with significantly reduced left ventricular ejection fraction demonstrated complete recovery of cardiac function within 10 days (mean 5.25 days ± 2.7).

We observed complete recovery of myocardial dysfunction and an overall low rate of permanent coronary sequelae, indicating that the majority of children with multisystem inflammatory syndrome in children are unlikely to encounter long-term cardiac morbidity. Although the frequency of myocardial dysfunction and inotropic support requirement is not consistent with a diagnosis of Kawasaki disease, the frequency of coronary artery abnormalities and severe coronary artery abnormalities suggests a degree of phenotypic overlap.