Comparison of Multisystem Inflammatory Syndrome in Children–Related Myocarditis, Classic Viral Myocarditis, and COVID‐19 Vaccine‐Related Myocarditis in Children

Abstract

Background Although rare, classic viral myocarditis in the pediatric population is a disease that carries significant morbidity and mortality. Since 2020, myocarditis has been a common component of multisystem inflammatory syndrome in children (MIS‐C) following SARS‐CoV‐2 infection. In 2021, myocarditis related to mRNA COVID‐19 vaccines was recognized as a rare adverse event. This study aims to compare classic, MIS‐C, and COVID‐19 vaccine‐related myocarditis with regard to clinical presentation, course, and outcomes. Methods and Results In this retrospective cohort study, we compared patients aged <21 years hospitalized at our institution with classic viral myocarditis from 2015 to 2019, MIS‐C myocarditis from March 2020 to February 2021, and vaccine‐related myocarditis from May 2021 to June 2021. Of 201 total participants, 43 patients had classic myocarditis, 149 had MIS‐C myocarditis, and 9 had vaccine‐related myocarditis. At presentation, ejection fraction was lowest for those with classic myocarditis, with ejection fraction <55% present in 58% of patients. Nearly all patients with MIS‐C myocarditis (n=139, 93%) and all patients with vaccine‐related myocarditis (n=9, 100%) had normal left ventricular ejection fraction at the time of discharge compared with 70% (n=30) of the classic myocarditis group ( P <0.001). At 3 months after discharge, of the 21 children discharged with depressed ejection fraction, none of the 10 children with MIS‐C myocarditis had residual dysfunction compared with 3 of the 11 (27%) patients in the classic myocarditis group. Conclusions Compared with classic myocarditis, those with MIS‐C myocarditis had better clinical outcomes, including rapid recovery of cardiac function. Patients with vaccine‐related myocarditis had prompt resolution of symptoms and improvement of cardiac function.

Cardiac Magnetic Resonance Findings of COVID-19 Vaccine Associated Myocarditis at Intermediate Follow Up: a Comparison to Classic Myocarditis and MIS-C Related Myocarditis

“…In our comparison, the classic myocarditis group had a higher burden of LGE than the C-VAM group at intermediate term follow-up. These findings suggest the possibility of a more favorable prognosis in children with C-VAM as opposed to classic myocarditis and extend earlier findings from our group comparing early clinical outcomes among patients with C-VAM, classic myocarditis, and MIS-C(12). The pattern of LGE at intermediate CMR was exclusively subepicardial in our group, compared to the classic myocarditis group, which showed a wider variety in patterns of enhancement.…”

“…Many children with classic myocarditis have ventricular systolic dysfunction and myocardial fibrosis that persist beyond the acute phase (7)(8)(9) whereas these findings largely resolve in children with MIS-C (10,11). While the short-term outcomes of COVID-19 vaccine associated myocarditis (C-VAM) have been shown to be less severe than those with classic viral myocarditis or MIS-C (12), the intermediate-term effects are unknown. We aimed 1) to describe the CMR findings of COVID-19 vaccine associated myocarditis patients at intermediate follow up and 2) to compare these findings to those of children with classic myocarditis and MIS-C.…”

Outcomes at least 90 days since onset of myocarditis after mRNA COVID-19 vaccination in adolescents and young adults in the USA: a follow-up surveillance study

“…Consistent with our findings, a recent report comparing classic myocarditis to COVID-19 vaccine-related myocarditis in individuals aged younger than 21 years observed similar clinical presentations and found COVID-19 vaccine-related myocarditis had better outcomes and a more rapid cardiac recovery. 28 …”

Myocarditis Following COVID-19 Vaccine Use: Can It Play a Role for Conditioning Immunization Schedules?

“…Use of non-steroidal anti-inflammatory drugs, immune globulin (IVIG), and steroids is not common ( 48 ) and remains controversial ( 49 ). A pediatric study comparing drug use in patients with viral MYO, MIS-C MYO and vaccine-related MYO has shown that intravenous immunoglobulin (IVIG) and steroids were frequently used in patients with classic MYO and MIS-C MYO but in only one and in none of the 9 patients with previous COVID-19 immunization ( 50 ). Vasopressors were most often used in patients with traditional viral MYO (42%) or MIS‐C MYO (52%) and rarely used in vaccine‐related MYO (22%), although this difference was not statistically significant.…”