CMR Findings in the Long-Term Outcomes After Multisystem Inflammatory Syndrome in Children (MUSIC) Study

BACKGROUND: Multisystem Inflammatory Syndrome in Children is characterized by high rates of acute cardiovascular involvement with rapid recovery of organ dysfunction. However, information regarding long-term sequelae is lacking. We sought to characterize the systolic function and myocardial tissue properties using cardiac magnetic resonance (CMR) imaging in a multicenter observational cohort of patients with Multisystem Inflammatory Syndrome in Children. METHODS: In this observational cohort study, comprising 32 centers in North America, CMR studies were analyzed by a core laboratory to assess ventricular volumetric data, tissue characterization, and coronary involvement. RESULTS: A total of 263 CMRs from 255 patients with Multisystem Inflammatory Syndrome in Children were analyzed. The mean patient age was 11.4±4.4 years. Most studies were performed at 3 months (33%) or 6 months (45%) after hospitalization. Left ventricular dysfunction was present in 17 (6.7%) of the first CMRs and was never worse than mild. Dysfunction was observed in 4/7 (57%) patients at admission, 5/87 (6.9%) patients at 3 months, and 6/129 (4.6%) patients imaged either at 6 months or 1 year post-hospitalization. Late gadolinium enhancement was present in 2 (0.8%) patients, 1 at 3 months and another at 6 months following hospitalization. Coronary artery dilation was present in 13 of the 174 (7.5%) patients. Nine patients met the Lake Louise criteria for myocarditis (3.5%) at the time of CMR. CONCLUSIONS: In this largest published multiinstitutional longitudinal CMR evaluation of confirmed patients with Multisystem Inflammatory Syndrome in Children, the prevalence of ventricular dysfunction and myocardial tissue characterization abnormalities on medium-term follow-up was low. However, a small number of patients had mild residual abnormalities at 6 months and 1 year following hospitalization. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT05287412.