Cardiac MRI for four children with clinical diagnosis of acute myocarditis in the setting of COVID-19–related Kawasaki-like symptoms of MIS-C. The top panel demonstrates minimal pericardial effusion on cine images. The second panel demonstrates increased T2-STIR signal intensity with average ratios between myocardium and muscle > 2 in patient 2 (12-year-old male), patient 3 (11-year-old female) and patient 4 (6-year-old female). The third panel demonstrates abnormal native-T1 mapping, which was > 1,100 ms in patients 2, 3 and 4 and normal in patient 1 (8-year-old female). The bottom panel demonstrates absence of late gadolinium enhancement (LGE) in patients 2 and 3. Myocardial null times were recognized as too short in patient 4 but could not be repeated due to lack of further patient cooperation; however review of Look Locker images and additional sequences revealed no LGE. Image courtesy of RSNA.
July 8, 2020 — Cardiac magnetic resonance imaging (MRI) has been shown to be helpful in evaluating multisystem inflammatory syndrome in children (MIS-C), which presents with Kawasaki disease-like features related to the child's exposure to COVID-19 (SARS-CoV-2). A case series recently published in Radiology examines cardiac MRI findings in four children and adolescents admitted to the intensive care unit at Hôpital Trousseau - Assistance Publique-Hôpitaux Parisiens (AP-HP), Sorbonne Université, Paris, France in April 2020.[1]
This case series examines cardiac MRI findings in four children and adolescents admitted to intensive care in April 2020 for multisystem inflammatory syndrome and Kawasaki disease-like features related to COVID-19. Acute myocarditis occurred less than one week after onset of fever and gastrointestinal symptoms. Physical examination showed rash and cheilitis/conjunctivitis. All patients recovered after intravenous immunoglobulin therapy.
The children had prolonged fever and cheilitis, cervical lymphadenopathy, rash, pericarditis, myocarditis, elevated C-reactive protein level or mitral regurgitation suggestive of Kawasaki disease, the researchers said.
SARS-CoV-2 RT-PCR was negative on nasopharyngeal, stool and respiratory samples and was positive on serology. Cardiac MRI showed diffuse myocardial edema on T2-STIR sequences and native-T1 mapping, with no evidence of late gadolinium enhancement suggestive of replacement fibrosis or focal necrosis. These findings favor post-infectious myocarditis in children and adolescents with COVID-19.
"We found MRI signs of diffuse myocardial edema and hyperemia without evidence of focal myocardial necrosis/fibrosis, contrary to recent published data[11,12] for adults with myocarditis related to COVID-19," researchers said. "Our findings are consistent with histopathological analysis of hearts with Kawasaki disease, which demonstrated little evidence of myocardial cell degeneration or necrosis but mainly cell infiltration of macrophages and neutrophils in myocardial interstitium.[13] Our findings might be explained by the difference between viral myocarditis and post-infectious myocarditis related to MIS-C in COVID-19. Viral myocarditis results from injury by virus infiltration and immune response to this injury. As in Kawasaki disease, the MIS-C myocarditis corresponds to an inflammatory infiltration of the interstitial myocardium."
The myocarditis in all the patients resolved rapidly and confirmed in normal echocardiographic follow-up and cardiac MRI exams. They did not find complications such as circulatory failure in the acute phase, development of artery aneurysm as often found in Kawasaki disease or resistance to intravenous immunoglobulin.[16]
All the patients had elevated SARS-CoV-2 antibody levels (IgG without IgM except in patient 4 who had elevated IgG and IgM levels). They also had signs of cardiac involvement without coronary artery abnormalities. Longitudinal findings of transthoracic echocardiography showed transient systolic dysfunction that lasted for 48 hours to 5 days. Cardiac MRI findings revealed elevated T1 mapping values and T2-STIR ratio suggesting myocardial hyperemia and edema without evidence of fibrosis replacement at LGE at the acute disease phase. At admission to our ICU, patients 1, 3 and 4 had signs of cardiovascular collapse or hypotension but responded well to volume expanders and vasoactive agents. None had signs of intravenous immunoglobulin resistance or prolonged myocardial dysfunction.
Current evidence suggests COVID-19 infection in children and adolescents is associated with toxic shock syndrome and Kawasaki disease-like symptoms together with cardiac inflammation (4, 8). This new entity, called MIS-C for multisystem inflammatory syndrome in children, shares similarities with Kawasaki disease with different clinical signs and outcome. Kawasaki disease is an autoimmune systemic disease characterized by systemic inflammation in all medium-sized arteries during the acute febrile phase (9) that affects predominantly children < 5 years of age. In our series, patients were older, from 8 to 12 years old (9). In Kawasaki disease, a prominent feature is the appearance of coronary artery dilatation or aneurysm(9), which was not evidenced in our series.
Echocardiography Results in Multisystem Inflammatory Syndrome in Children (MIS-C)
ECG revealed ST-segment depression in patient 2 and decreased T-wave amplitude in inferior leads in patient 3. Initial transthoracic echocardiography showed severely decreased LV ejection fraction (LVEF) in one patient (LVEF < 30%) and low-normal LVEF in three patients (LVEF > 50%), although the four patients had transient systolic dysfunction (Table E1 Supplemental data). The initial LVEF was low-normal in patients 2, 3 and 4 due to marked vasoplegia with decreased afterload.
The myocardium appeared echogenic on 2-D echocardiography in patient 2 and normal in the other patients. Three patients showed global or septal hypokinesia. Patients 1 and 3 showed functional mitral regurgitation related to LV dilatation. LV diastolic function was not impaired. Three patients had moderate pericarditis. Coronary artery diameters were normal, without coronary artery dilatation or aneurysm at initial and follow-up echocardiography.
Related Content on MIS-C:
Kawasaki-like Inflammatory Disease Affects Children With COVID-19
New Study Looks at Post-COVID-19 Emerging Disease in Children
The Cardiovascular Impact of COVID-19
Reference:
November 13, 2024 
