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Misra et al. Vessel Plus 2022;6:14 https://dx.doi.org/10.20517/2574-1209.2021.89 Page 3 of 11

[7]
Table 1 highlights some of the clinical features from our institution’s patient cohort .

Many patients with MIS-C have significant hypotension secondary to cardiogenic or vasodilatory shock,
[8,9]
requiring additional supportive measures in up to 77% of patients . In addition, cardiac dysfunction,
including a myocarditis-like picture, can be present in third or more cases, with other centers reporting
significantly higher prevalence [6,12,13] .

We have previously described our experience with 54 patients diagnosed with MIS-C, with a median age of
6.8 ± 4.4 years . Similar to other studies, cardiovascular involvement was prevalent in our cohort.
[7]
Significant hypotension due to depressed left ventricular (LV) systolic function, persistent tachycardia, and
signs of low cardiac output were present on admission or developed early during the admission in 52% of
patients in our cohort. Moreover, fulminant heart failure developed in four patients, requiring veno-arterial
[7]
extracorporeal membrane oxygenation (ECMO) support .
Compared to COVID-19 infection, MIS-C tends to lead to more significant acute hemodynamic
manifestations. A recent report from Feldstein et al. reviewed 1314 hospitalized children and adolescents
[12]
younger than 21 years of age with COVID-19-related illness from 66 hospitals in 31 states and compared
clinical presenting characteristics of patients with MIS-C to those with acute COVID-19 infection. In their
cohort, patients with MIS-C were more likely to have cardiorespiratory involvement (56.0% vs. 8.8%; 95%CI:
42.4%-52.0%), cardiovascular without respiratory involvement (10.6% vs. 2.9%; 95%CI: 4.7%-10.6%), and
[12]
mucocutaneous symptoms without cardiorespiratory involvement (7.1% vs. 2.3%; 95%CI: 2.3%-7.3%) .

In summary, the acute clinical presentation is variable with overlapping signs and symptoms.
Unfortunately, many patients present with significant hemodynamic instability requiring critical care at
presentation or short after initial admission.

Myocardial dysfunction
LV dysfunction, with a left ventricular ejection fraction (LVEF) less than 55%, is relatively common among
[13]
patients presenting with MIS-C, with the majority of patients having some degree of cardiac dysfunction .
In New York City, Kaushik et al. reported 33 patients with MIS-C and noted that greater than 50%
[14]
developed LVEF less than 50% in their cohort. The degree of myocardial involvement can be quite
significant, requiring significant inotropic and circulatory support. Our center saw at least 2 cases of
myocardial stunning, with both patients requiring ECMO support [Supplementary Video 1].
[15]
Belhadjer et al. reviewed 35 patients presenting with acute cardiogenic shock secondary to MIS-C; they
reported that 28% of their patients had significantly reduced LVEF < 30%, with another 28% requiring
ECMO support due to poor clinical condition. Their study focused on only patients with LV systolic
dysfunction, so their reported percentage of patients with severely reduced LV function is higher than other
studies.

Recent studies have looked at sensitive markers of LV dysfunction, and particularly global left ventricular
longitudinal strain in relation to patients with MIS-C. For example, in a study of 28 patients with MIS-C,
compared to patients with Kawasaki disease and those with structurally normal hearts, patients with MIS-C
[16]
had reduced global left ventricular longitudinal strain and left atrial strain ; another study of 25 patients
through Boston Children’s Hospital found similar results .
[17]

Interestingly, while they noted that 80% of patients with initially decreased LVEF normalized prior to
discharge, 36% of the patients continued to have abnormal strain at 8 days post discharge .
[17]