Cardiac Manifestations and Persistent Myocardial Dysfunction in Multisystem Inflammatory Syndrome in Children: Insights from Conventional and Strain Echocardiography

Background: Multisystem inflammatory syndrome in children (MIS-C) is a severe post-infectious complication of SARS-CoV-2, often with cardiac involvement. Myocardial strain imaging may detect dysfunction missed by conventional echocardiography. The objectives of this study are to characterize cardiac manifestations of MIS-C and assess the value of strain imaging in children with preserved and reduced left ventricular ejection fraction (LV-EF). Methods: We retrospectively analyzed 22 MIS-C patients admitted between September 2020 and January 2024, all with cardiac involvement. Clinical, laboratory, and echocardiographic data—including 2D and speckle-tracking strain—were collected at the day of worst dysfunction (DWD) and discharge (DD) and compared with 22 matched controls. Results: Median age was 4.65 years; 59% male; 45% overweight/obese. LV systolic dysfunction (LV-EF < 50%) occurred in 54.5%, coronary abnormalities in 36.4%, and pericardial effusion in 95.5%. LV global longitudinal strain (LVGLS) was significantly lower than controls at the DWD (−15.45 ± 4.76%, p < 0.0001) and DD (−20.63 ± 4.66%, p = 0.014). Strain abnormalities persisted despite LV-EF recovery, and even patients with preserved LV-EF showed significant segmental strain reduction. LVGLS and apical infero-septal strain were strongest predictors of reduced LV-EF. Conclusions: MIS-C often causes systolic dysfunction and coronary changes, but strain imaging reveals persistent subclinical myocardial injury. Long-term cardiac monitoring is warranted.