Long-Term Follow-Up of Cardiac MRI Findings in MIS-C

Source: Lang SM, Truong DT, Powell AJ, et al. CMR findings in the long-term outcomes after multisystem inflammatory syndrome in children (MUSIC) study. Circ Cardiovasc Imaging. 2025 Apr 4:e017420; doi: 10.1161/CIRCIMAGING.124.017420.Investigators from multiple institutions conducted a prospective observational study to evaluate cardiac outcomes in children with Multisystem Inflammatory Syndrome in Children (MIS-C). Study participants were patients ≤21 years old who were diagnosed with MIS-C at 1 of 32 centers in North America and had a cardiac MRI (CMR) performed. The diagnosis of MIS-C was based on the 2020 CDC definition. Although the decision to obtain a CMR and the timing of the study were left to the discretion of providers at each participating center, it was anticipated that most CMRs would be obtained 1–6 months after onset of illness in children with moderate or worse ventricular function dysfunction (left ventricular [LV] ejection fraction, <45%) on echocardiogram at presentation. The main study outcomes were ventricular dysfunction, myocarditis, and coronary artery dilation present on CMR. Standardized criteria were used for each of these outcomes. For the primary analyses, the results of the initial CMR, performed anytime between hospital admission and 1 year following onset of symptoms, were used. The rates of outcomes in patients with CMRs performed at specific time points also were calculated.A total of 255 children with MIS-C were included in the analyses. The mean age of study participants at the time of hospitalization was 11.4 ±4.4 years. The mean hospital length of stay was 8 ±7 days, and 81% of patients required ICU management. A total of 263 CMR were obtained on the 255 study children. Overall, 33.1% of CMR were performed 3 months after onset of symptoms and 45.2% approximately 6 months following symptom onset. At the time of the first CMR in patients, LV dysfunction was present in 17 (6.7%) children. The rate of LV dysfunction was 6.9% and 4.2%, respectively, in CMRs performed 3 and 6 months after MIS-C symptom onset. There were 9 (3.5%) patients who met criteria for myocarditis on their first CMR; in 15 children, the CMR findings were classified as indeterminate. Rates of myocarditis were 1.1% in CMRs performed 3 months following onset of MIS-C symptoms and 2.5% in CMRs performed 6 months after symptom onset. Coronary artery dilation could be evaluated in 174 children. Among these patients, 7.5% had coronary artery dilation visible on their first CMR. Among those with CMRs 3 and 6 months post symptom onset, coronary artery dilation was present in 6.6% and 9.3%, respectively.The authors conclude the prevalence of LV dysfunction and myocarditis in children following hospitalization for MIS-C was low.Dr Philip has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.MIS-C secondary to COVID-19 infection in previously healthy children can result in myocarditis (inflammation of the myocardium) as evidenced by troponin leak, left ventricular dysfunction on echocardiogram, and coronary artery dilation. (See AAP Grand Rounds. 2024;52[6]:70.)1 The gold standard test for myocardial characterization is CMR, which not only evaluates cardiac function but also residual fibrosis. This information can aid in the determination of the risks of sudden cardiac death and sports participation.2In the current multicenter study, a very small percentage of participants had LV dysfunction on their first CMR, possibly because it was done after the inflammation was resolved. Similarly, most participants had normal CMR myocardial findings at 3 and 6 months post hospital discharge. What is more reassuring is the fact that the patients who demonstrated CMR criteria for myocarditis and LV dysfunction during their hospitalization for MIS-C had resolution on follow up CMR. This suggests that while the highest diagnostic yield of CMR in suspected myocarditis is within the first 2 weeks of symptoms when the edema/inflammation is present to the degree that is detectable, the 3- and 6-month CMR may be more clinically valuable for risk stratification and sports participation. During the COVID-19 pandemic, the 'return to play' conundrum for the clinician and athlete was a significant consideration.3 The current data on 3-, 6- and 12-month CMR findings in this cohort provide guidance for follow-up protocols for the medical community, coaches, and athletes.4The unavoidable study limitation is that the diverse vendor CMR scanners may have variability in tissue characterization and mapping. These differences were potentially neutralized by their core-laboratory interpretation. Albeit not the primary outcome, another limitation inherent to CMR is the assessment of coronary arteries, which are better assessed by a CT angiogram. Additionally, not all participants had more than 1 CMR, which limited the assessment of the evolution of CMR findings with time.Cardiac function and myocardial inflammation as assessed by CMR resolves in the majority of the patients with MIS-C.Although routine COVID-19 vaccination of children and adolescents is not currently recommended, multiple studies have found that COVID-19 vaccination is effective at reducing the risk of MIS-C (as well as long COVID).5