Cardiovascular Involvement of Multisystem Inflammatory Syndrome in Children: A Multicentric Observational Study on Mid- and Long-term Follow-up with Cardiovascular Imaging

Background: Multisystem inflammatory syndrome in children (MIS-C) is a relatively rare complication of COVID-19, with frequent cardiovascular involvement, in terms of pericarditis, valvulitis, coronary aneurysms, and myocardial dysfunction/cardiogenic shock. Prognosis appears to be benign, but data about long-term follow-up are limited. Aims and Objectives: We aimed at describing acute cardiovascular complications and evaluating residual abnormalities in the mid-term (1-6 months) and long-term (>7 months) follow-up in children with MIS-C and cardiovascular involvement. Materials and Methods: We retrospectively reviewed data of all patients aged <16 years with MIS-C and cardiovascular involvement (2021-2023). Evaluation at admission included electrocardiogram (ECG), echocardiography, cardiac magnetic resonance (CMR), TroponinT, N-terminal prohormone of brain natriuretic peptide (NT-proBNP), and signs of macrophage activation syndrome (MAS). Follow-up was based on ECG, echocardiography and, when appropriate, CMR. Results: Twenty-nine consecutive patients (20 males, mean age 7.16 +/- 5.12 years) with MIS-C showed cardiovascular involvement. Pericarditis was the most frequent feature (72. 4%), followed by valvulitis (51.7%), myocardial dysfunction (34.5%), and coronary artery dilatation (10.3%). Receiver operating characteristic curves identified TroponinT >105.05 and NT-proBNP >5817.5 as potential predictors of myocardial dysfunction. MAS was associated to 12-fold higher risk of myocardial dysfunction (P = 0.036). In the long-term, mild abnormalities were still documented in up to 10.3% of cases. Conclusions: MIS-C with cardiovascular involvement has a substantial incidence of acute myocardial dysfunction, particularly in patients with higher levels of TroponinT and BNP and in those who developed MAS. Cardiovascular abnormalities are usually transient. However, in 10% of cases, mild abnormalities are still detected by cardiovascular imaging in the long-term, without any correlation with the severity of the acute phase.