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Cardiovascular Magnetic Resonance in Myocarditis Related to Multisystem Inflammatory Syndrome

Updated: May 7

in Children Associated with COVID-19

Supriya Jain, MD, FACC, FAAP; Sheila M. Nolan, MD, MSCE; Rachel Biller, MD, FAAP; Alan Pinto, MD; Anthon R. Fuisz, MD; Michael H. Gewitz, MD, FAHA, FACC, FAAP

Cardiac involvement, including myocarditis, has been reported in patients with Multisystem Inflammatory Syndrome in Children (MIS-C) temporally associated with the Coronavirus Disease 2019 (COVID-19).[1] The pathophysiology of myocarditis in these children remains unclear. Cardiovascular magnetic resonance (CMR) has the unique potential to evaluate tissue changes in these patients, but scheduling a CMR examination in the acute phase of the illness with the risk of unnecessary exposure to others is often challenging. CMR data on these children is, hence, limited so far.[2] We performed CMR examinations in children with MIS-C associated with COVID-19 by following a specific protocol that enabled us to obtain important CMR findings.

Between April 20th and June 20th, 2020, 32 children were diagnosed with MIS-C at Maria Fareri Children’s Hospital at Westchester Medical Center, a Level 1 Trauma and Tertiary Care Center, in Westchester County, New York. Nine children and adolescents were identified to have clinically suspected myocarditis based on their clinical presentation, abnormal cardiac enzymes and evidence of ventricular dysfunction on echocardiogram. Five of these patients, who were older and were assessed to not require sedation, had CMR examination to confirm the diagnosis. Following the infection control guidelines of our hospital, we developed a specific protocol, which involved performing CMR examinations on these patients as the last case of the day, typically at night, with only the pediatric CMR physician and the technologist being present for the study. Studies were performed using a 1.5T CMR system (Philips Achieva). The CMR protocol included: balanced steady-state free precession (SSFP) cine imaging, T2 –weighted short tau inversion recovery (T2-STIR), native T1 mapping, T2 mapping, First-pass perfusion imaging (FPP), T1-weighted imaging precontrast and postcontrast for early gadolinium enhancement (EGE) and late gadolinium enhancement (LGE) imaging 10 minutes after gadolinium administration. Two experienced CMR physicians reviewed the CMR findings on the five patients independently. This report was granted an exemption status by the Institutional Independent Review Board (IRB).

FIGURE 1   CMR images in five children with clinical diagnosis of myocarditis associated with Multisystem Inflammatory Syndrome in Children (MIS-C) related to COVID-19. The top panel shows T2- weighted images (T2 STIR) which demonstrate areas of high signal intensity (arrows) with average ratios of myocardium over skeletal muscle > 2 denoting myocardial edema in patients 1, 2, 3 and 5. The second and third panel shows T1-weighted images before and shortly after gadolinium administration, respectively. In patients 1, 2 and 4, there is evidence of early gadolinium enhancement (arrows) with calculated myocardial early gadolinium enhancement ratio between myocardium and skeletal muscle >4 in patients 1, 2 and absolute myocardial enhancement >45% in patient 4. The bottom panel demonstrates late gadolinium enhancement in patients 2 and 4 as a small focal lesion in the inferolateral segment of the sub-epicardial region of the left ventricle (arrows).

On echocardiogram at presentation, the patients had severe-mild left ventricular dysfunction (EF: 25%-50%). They all had evidence of current/recent Severe Acute Respiratory Syndrome coronavirus 2 (SARS-COV-2) infection/exposure (three patients were both nasopharyngeal SARS-COV-2 RT PCR + and serum IgG +, while two were serum IgG +). They had elevated acute inflammatory markers including C-reactive protein, erythrocyte sedimentation rate (ESR), ferritin, procalcitonin, interleukin-6 and D-dimer. Troponin and B-type natriuretic peptide were elevated in all. They required inotropic support in the Intensive Critical Care Unit, including one child requiring extracorporeal membrane oxygenation. With immunomodulatory treatment and heart failure management, the ventricular dysfunction resolved in all children prior to discharge. CMR was performed on four children during the initial hospitalization and after discharge on one. Using the recommended Lake Louise diagnostic CMR imaging criteria for patients with suspected myocarditis,[3] tissue-based CMR markers consisting of T2-weighted ratio, EGE and LGE were evaluated to assess for myocardial edema, hyperemia/capillary leak and fibrosis/necrosis, respectively (Figure 1). Based on the myocardial signal intensity increase in T2-weighted images (T2 STIR), myocardial edema was diagnosed in four patients. Three patients had evidence of early gadolinium enhancement and in two patients, a small focal area of late gadolinium enhancement was noted in the inferolateral segment of the subepicardial region of the left ventricle (Figure 1). Newer parametric imaging techniques such as native T1 and T2 mapping done in a few patients were supportive of myocardial inflammation.[4,5] FPP imaging was normal in all.

To read the full article, please go to the August 2020 Issue of CCT.