CMR Myocardial Changes in MIS-C: Admission Clinical Features and Longitudinal Findings

Multisystem inflammatory syndrome in children (MIS-C) is a sequela of SARS-CoV-2 infection; however, longitudinal cardiac outcomes are unclear. Herein, we test the association between MIS-C biomarkers, inpatient echocardiographic features, and outcomes of interest: presence of myocarditis and myocardial delayed enhancement (MDE) on cardiac magnetic resonance (CMR). Furthermore, we describe the evolution of CMR features in MIS-C.

Patients diagnosed with MIS-C from 2020-2021 with CMR were included. Admission and serial biomarkers and echocardiographic features were collected. Primary outcomes measured were diagnosis of myocarditis (using modified Lake Louise criteria) and myocardial delayed enhancement (quantified by full width at half maximum method) on CMR. Secondary outcomes included abnormal LVEF on admission echocardiogram and changes in parametric mapping with serial CMR.

A total of 66 patients were included (median age 9.7 IQR [7.2-14.7] years). Admission BNP (P=0.016), CRP (P=0.027), and ESR (P=0.002) associated with LV dysfunction on inpatient echocardiogram. CMR1 was obtained a median of 38 [26-61] days after hospital presentation. Myocarditis was present in 44% and MDE in 52% on CMR1, with median MDE burden of 10.8 [8.5-16.8]% in those affected. Inpatient echocardiographic features were not associated with presence of myocarditis or MDE. Admission ESR (P=0.031) associated with MDE. Admission platelets associated with myocarditis (P=0.040) and MDE (P=0.004). CMR2 (n=19), occurring a median of 11 [7-14] months after baseline CMR, demonstrated lower global T2 z-scores (P=0.035) without significant change in global T1 z-scores or ECV. Myocarditis (16% [3/19]) and MDE (28% [5/18]) were less frequent on CMR2.

For MIS-C patients, initial echocardiographic indices do not associate with myocarditis or MDE by CMR one month later; admission ESR and platelet levels may portend myocarditis or MDE on initial CMR. Reduced T2 z-score over serial CMR suggests resolving edema.