108 - CARDIAC MAGNETIC RESONANCE FOLLOW-UP OF PATIENTS TREATED FOR MULTISYSTEM INFLAMMATORY SYNDROME IN CHILDREN

Aim: To assess the prevalence of residual cardiovascular pathology by cardiac MRI (CMR) in patients 6-24 months after treatment for multisystem inflammatory syndrome in children (MIS-C).

Methods: Patients seen for MIS-C follow-up were referred for CMR approximately 6 months after illness if they were able to undergo CMR without sedation. Patients were referred for repeat CMR in one to two years if the initial study was abnormal. Data analysis was limited to summary statistics due to the number of patients with follow-up CMR.

Results: Fifty-eight of 153 patients (mean age 10.5 years) seen for MIS-C follow-up had CMR performed between October 2020 and December 2023 at a mean of 8 months after hospitalization. Twenty-seven patients (47%) had >1 abnormality, including elevated extracellular volume (ECV) in 17/55 (31%), elevated T1 in 10/55 (18%), late gadolinium enhancement in 5/55 (9%), and decreased left ventricular ejection fraction (LVEF) in 5/58 (7%).  Four of 27 patients (7%) with >1 abnormality on CMR reported cardiovascular symptoms at most recent cardiology follow-up. Seven of 31 patients (12%) with normal CMR reported symptoms. Of those with an initial abnormal CMR, twelve had repeat CMR at a mean of 19 months later. ECV was elevated in 11/12 patients (92%) on initial CMR and remained elevated in 4/11 (36%) on follow-up. ECV was not measurable on one follow-up study. T1 was elevated in 2/12 patients (17%) on initial CMR; T1 normalized in one and remained elevated in one on follow-up. LGE was present in 3/10 patients (30%) on the initial CMR and resolved in all three on follow-up. In one patient new LGE was demonstrated on follow-up CMR that was not present initially. One patient had reduced LVEF on initial CMR that normalized on follow-up. Of the five patients with >1 abnormality on follow-up CMR, one reported symptoms at most recent follow-up. One patient of 7 with a normal follow-up CMR reported symptoms.

Conclusion: Elevated ECV, elevated T1, and LGE can be markers of myocardial inflammation or fibrosis, and were present in 47% of patients who underwent CMR at a mean of 8 months after treatment for MIS-C. In a small sample of patients with repeat imaging, normalization of these findings appears heterogeneous. The high prevalence of abnormal findings on CMR after MIS-C suggests that all patients treated for MIS-C warrant cardiology follow-up. Additional studies and longer-term follow-up are needed to better understand the long-term cardiovascular outcomes of MIS-C.