O0016: Cardiac Magnetic Resonance Follow-up of Patients Treated for Multisystem Inflammatory Syndrome in Children

Background: Multisystem Inflammatory Syndrome in Children (MIS-C) is a post-infectious hyperinflammatory response to SARS-CoV-2 infection that typically occurs several weeks after acute infection. It is characterized by fever, elevated inflammatory markers, and involvement of multiple organ systems. Cardiovascular involvement can include abnormal laboratory markers, ventricular dysfunction, coronary artery aneurysms (CAAs), and conduction system abnormalities. In severe cases patients can present in cardiogenic shock. While most patients appear to fully recover, long-term cardiovascular sequelae remain unknown. The purpose of this study was to assess the incidence of residual myocardial injury on cardiac magnetic resonance (CMR) imaging at midterm follow-up for MIS-C.

Methods: All patients who were seen for MIS-C follow-up were referred for CMR at approximately 6 months after initial admission if they could undergo imaging without sedation. Younger patients who required anesthesia (n=5) were referred for CMR if there was clinical indication, including history of decreased systolic function or complex/giant CAAs. MIS-C was diagnosed based on the Centers for Disease Control and Prevention criteria. Only patients who had positive SARS-CoV-2 PCR or serology were included. Myocardial health was assessed based on T1 and T2 mapping, ejection fraction (EF), extracellular volume (ECV), presence of late gadolinium enhancement (LGE), and presence of CAA.

Results: Thirty-eight patients underwent CMR at a median follow-up time of 6.8 months (IQR 5.6-8.4 months) and median age of 11.5 years (IQR 9.5-15.4 years). Twenty-six patients (68%) were male. Mean left ventricular EF was 62% (SD 6.8%); 1 patient had reduced LV EF of 43%. Mean native T1 mapping was 1044 ms (SD 34 ms); T1 was elevated in 4/36 patients (11%). Mean ECV was 27.8% (SD 3.2%); ECV was elevated in 11/35 patients (31%). Mean T2 was 49.4 ms (SD 4.5 ms); T2 was borderline elevated in 1/33 patients (3%). LGE was present in 3 patients (8%). CAAs were present in 3 patients (8%). Of the 15 patients with at least one abnormality identified on CMR, 8 required inotropes, 7 had elevated troponin, and 5 had decreased LVEF on echocardiogram during acute illness. Twenty-three percent of patients with no myocardial injury during acute illness had late CMR abnormalities.

Conclusion: In this mid-term follow-up study of patients with MIS-C cardiovascular pathology was present in 39% of CMR studies. Patients with and without clear evidence of myocardial injury during acute illness had abnormal findings on CMR. Elevated T1, ECV, and LGE can all be reflective of myocardial inflammation or development of fibrosis, and longer-term follow-up imaging is necessary to define the incidence and clinical implications of residual disease.