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

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 Multisystem Inflammatory Syndrome in Children patients. 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. A total of 263 CMRs from 255 Multisystem Inflammatory Syndrome in Children patients 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. In this largest published multiinstitutional longitudinal CMR evaluation of confirmed Multisystem Inflammatory Syndrome in Children patients, 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. URL: https://www.clinicaltrials.gov; Unique identifier: NCT05287412.