Cardiac Function Normalizes by 3 Months in MIS-C in Study

Most children with multisystem inflammatory syndrome related to COVID-19 infection show recovery of cardiac function by 3 months, but longer term follow-up is still needed, suggests a new retrospective longitudinal cohort study.

While 80%-85% of children with multisystem inflammatory syndrome have cardiovascular involvement, “lack of knowledge about the short-term consequences of MIS-C has led to uncertainty among physicians in making recommendations about follow-up,” Daisuke Matsubara, MD, PhD, and colleagues wrote in their paper, which was published in the Journal of the American Heart Association.

Matsubara, of the department of pediatrics at the Children’s Hospital of Philadelphia, and colleagues examined cardiac outcomes among 60 patients aged 18 years or under admitted to two Philadelphia hospitals with MIS-C between April 2020 and January 2021. They compared those with outcomes in 60 age-matched healthy children who had undergone echocardiography for a range of non–COVID-related conditions such as chest pain or syncope.

The study used echocardiography, MRI, biochemistry, and functional and clinical parameters to assess the degree of change and damage to the heart at 3 months after admission.

When the patients first presented to a hospital, 42 had biochemical signs of myocardial injury, such as elevated brain-type natriuretic peptide and troponin levels. However, most patients’ symptoms were no longer present by the time they were discharged from hospital.

The researchers found that 81% of patients who presented with myocardial injury had lost the left atrial contraction phase. This dropped to 51% during the subacute phase, then 30% at 1 month. By 3-4 months, all patients achieved normal left atrial contraction phase.

At 1 month after admission, all MIS-C patients had significant signs of cardiac strain, compared with controls, including changes to global longitudinal strain, global circumferential strain, circumferential early diastolic strain rate, and right ventricular free wall longitudinal strain.

Parameters of Strain Normalized by 3 Months

All parameters of strain had normalized, compared with controls, by 3 months. In the case of global longitudinal strain and left atrial strain, the median time to normalization was 6 days. For left ventricular ejection fraction the median time to normalization was 8 days and for right ventricular free wall longitudinal strain it was 9 days.

A small difference persisted with global longitudinal strain, but the authors said the difference was within the range of normal published values and not clinically relevant. The dysfunction appeared to be spread evenly across the heart rather than varying between segments, they noted.

“Deformation analysis could detect subtle myocardial changes; therefore, our study suggests the absence of persistent subclinical myocardial dysfunction after 3-4 months,” Matsubara said in an interview.

Four patients experienced small coronary aneurysms during the acute phase of MIS-C, but all had resolved within 2 months and none experienced any further lesions.

Among the 14 patients who underwent cardiac MRI at presentation, 2 had evidence of myocardial edema and fibrosis during the subacute phase of illness, despite having normal left ventricular systolic function and conventional echocardiography.

At follow-up, only one patient had residual edema; this individual had no evidence of fibrosis and had normal systolic function.

Study Provides Reassurance, but Longer Follow-Up Needed

Commenting on the study, pediatric cardiologist Devyani Chowdhury, MD, director of Cardiology Care for Children in Lancaster, Pa., said that overall it provided reassurance that most children do recover from MIS-C — and fits with her own clinical experience of the condition — but cautioned that longer-term follow-up was still needed.

“Three months is really not long term for a child,” Chowdhury said in an interview. “I’ve had a couple of patients whose MRIs have not normalized even after 1 year.”

Chowdhury also noted that it was a relatively small sample size, and it was also not yet possible to work out what host factors might play a role in increasing the risk of longer-term effects of MIS-C.

“I think it is a disease in evolution and we have to give it time, but in the very short term at least these kids are not dying, they are recovering, going home, and returning to activity and the heart is getting better,” she said.

The study authors suggested their findings could provide an evidence base for recommendations on when children with MIS-C can return to sports and physical activity, given that current consensus statements on the issue treat MIS-C as being equivalent to myocarditis in adults.

Matsubara noted that the cardiac outcomes of MIS-C were very different from those in COVID-19–affected adults, where echocardiography and MRI show longer-term evidence of myocardial impairments.

“This finding is also different from that of adult COVID-19, where the high troponin is reported to be the prognostic factor,” he said, suggesting this could explain different mechanisms of myocardial injury between MIS-C and COVID-19 myocarditis.

One author was supported by the National Institutes of Health. No conflicts of interest were declared.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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