By IDSE News Staff

Heart function recovery returned within three months in children who developed COVID-19–related multisystem inflammatory syndrome (MIS-C), a new illness identified during the pandemic that affects children four to six weeks after exposure to SARS-CoV-2 (J Am Heart Assoc 2022 Jan 19).

Although the condition has some of the same symptoms as Kawasaki disease, MIS-C is associated with more profound inflammation that can affect the heart, lungs, kidneys and gastrointestinal organs. About 80% to 85% of MIS-C cases across the United States and Europe have involved the heart’s left ventricle.

The researchers retroactively reviewed data on 60 children with MIS-C who were treated at two Philadelphia hospitals between April 2020 and January 2021. None of the children were initially diagnosed with COVID-19 before the onset of MIS-C symptoms. Most of the children (60%) were boys, with an average age of 10 years. About 48% were Black, 27% white, 15% Hispanic, 4% Asian, and the race/ethnicity of 23% of the children was unknown. The participants were treated with IV immune globulin and/or systemic steroids. Researchers reviewed echocardiographic and clinical data from medical records, including demographic factors, testing, treatment and hospital outcomes.

Data on another 60 children who had structurally normal hearts and did not have MIS-C or COVID-19 exposure served as the control group. Their average age was 11.5 years, and 55% were boys; 62% were white, 27% Black, 7% Hispanic, 3% Asian, and the race/ethnicity of the remaining 8% was unknown. The control participants were divided into two groups: 60% had echocardiograms on file that were done prior to the pandemic, and 40% had echocardiograms under rigid COVID-19 protocols after October 2020.

For the children with MIS-C, researchers analyzed images of the heart taken during the acute phase when they were initially hospitalized and examined additional imaging for a portion of the children who also had scans up to three additional times: one week after the first scan (subacute phase); at the one-month follow-up; and at a three- or four-month follow-up. The children were screened using conventional echocardiography, speckle-tracking echocardiography—an imaging technique that analyzes the motion of the heart tissue—and cardiac MRI of the heart.

The study found the following:

• Based on echocardiogram imaging, systolic and diastolic function in the left ventricle and systolic function in the right ventricle improved quickly within the first week, followed by continued improvement and complete normalization by three months.
• 81% of patients lost some contractile function in the left ventricle during the acute phase of illness, but, by months 3 and 4, contraction function had returned to normal.
• MIS-C did not cause lasting coronary artery abnormalities. During the initial hospitalization, 7% of patients had evidence of some heart malfunction; however, all scans were normal by the three-month follow-up.
• Using strain parameters to measure cardiac function, the results reveal that there is no subclinical cardiac dysfunction after three months. (Strain testing is a more sensitive tool that can detect whether an area of the heart is deformed, or whether there are any subtle changes in heart function during cardiac contraction and relaxation.)
  

“Recovery among these children was excellent,” said the study’s senior author, Anirban Banerjee, MD, a professor of clinical pediatrics in the Perelman School of Medicine at the University of Pennsylvania and an attending cardiologist with the Cardiac Center at the Children’s Hospital of Philadelphia, both in Philadelphia.

“These results have important implications for our healthcare teams managing care for children with MIS-C. Our findings may also provide guidance for a gradual return to playing sports after cardiac clearance three to four months later. Tests needed for clearance include electrocardiogram and echocardiogram. We also recommend cardiac MRI for children who have highly abnormal baseline cardiac MRI during the acute stage or show evidence of continued severe left ventricle dysfunction.”

Because MIS-C is a newly identified disease, there are limited data about how often and how long heart function should be monitored. Treatment protocols are also not standardized, he said, and follow-up care varies greatly. 

The study had important limitations, the researchers said. The study was retrospective for clinical purposes and was not standardized for research. In addition, follow-up data were missing for some patients who dropped out of the study during the follow-up stages. Dr. Banerjee explained that because both COVID-19 and MIS-C were newly discovered diseases, the timing of follow-up echocardiograms was somewhat arbitrary and driven by preference of different clinicians, rather than standard research protocol.

“The strength of the study is that researchers performed a detailed, serial assessment of cardiac function over the initial three to four months of illness,” according to American Heart Association (AHA) volunteer expert Kevin G. Friedman, MD, a member of the AHA Young Hearts Council and the AHA Young Hearts Rheumatic Fever, Endocarditis and Kawasaki Disease Committee; an attending physician in pediatric cardiology at Boston Children’s Hospital; and an associate professor of pediatrics at Harvard Medical School, in Boston.

“This study provides additional evidence that myocardial involvement is transient and may not lead to long-term abnormalities in left ventricular diastolic or systolic function,” Dr. Friedman said.

“Although cardiac involvement in the acute stage of illness is common, it is reassuring that all patients recovered normal cardiac function within about one week. This data tells us that, fortunately, lasting heart injury is very uncommon in MIS-C. Even in those patients with significant cardiac abnormalities in the acute phase of illness, these changes resolved by three to four months.”

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