Should we be afraid of long-term cardiac consequences in children with multisystem inflammatory syndrome? Experience from subsequent waves of COVID-19.

The purpose of the study was to assess and compare short- and long-term cardiac complications of the multisystem inflammatory syndrome in children (MIS-C) by predominant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants throughout the pandemic. The analysis of prospectively collected data comparing cardiac complications of MIS-C during and after hospitalization across the original/alpha, delta, and omicron waves. Cardiac complications were defined as cardiac failure with systolic function impairment or hypotension or abnormalities in echocardiographic findings (decrease in LVEF, FS, valvular insufficiency, pericardial effusion, or coronary artery abnormalities). A total of 120 patients with MIS-C admitted to the Children's Hospital of Krakow between November 1, 2020, and May 5, 2023, were included in the study (74 during original/alpha dominance, 31 delta, and 15 omicron). Patients in the omicron group were found to be younger than those in the alpha and delta groups (37 vs. 75 vs. 80 months, p = 0.03). The frequency of cardiac failure with systolic function impairment or hypotension was diagnosed more frequently in the original/alpha and delta groups than in the omicron group (44.59% vs. 41.94% vs. 13.33%, p = 0.08) also echocardiographic abnormalities changed, with rates of 60.8%, 35.5%, and 13.3% (p < 0.001) accordingly. The multivariable regression revealed an older age (OR = 1.19, 95% CI = 1.07-1.33, p = 0.002) as the only independent factors of cardiac failure with systolic function impairment or hypotension. In all patients, signs of cardiac failure resolved during the hospitalization. Moreover, in 98.3% of patients, all echocardiagraphic abnormalities resolved completely during the observation period.    Conclusion: The cardiac complications of MIS-C appeared to advance less severely in younger children during the Omicron outbreak. In long-term observation, symptoms of cardiac failure resolve completely. Similarly, also echocardiographic abnormalities normalize in the vast majority of patients. What is Known: • Knowledge about the long-term cardiac complications of MIS-C is still evolving and uncertain. • The greatest concern of MIS-C is cardiac complications, including cardiac failure and coronary artery dilatation. What is New: • Long-term observations revealed complete resolution of cardiac complications in the vast majority of patients with MIS-C, irrespective of the dominant variant. • Cardiac complications of MIS-C were less common in younger children during subsequent pandemic waves in our patient population.

Comparison of the course of multisystem inflammatory syndrome in children during different pandemic waves.

The purpose of this study is to assess the rate, clinical picture, and management of multisystem inflammatory syndrome in children (MIS-C) during the different COVID-19 variants of concern (VOC) domination periods. This was a retrospective analysis of prospectively collected data. The incidence and clinical picture of MIS-C during the original/Alpha (group 1) and Delta/Omicron (Group 2) variant domination periods were compared. Among 108 eligible patients, 74 (68.5%) were hospitalized during the group 1 domination period, and 34 (31.5%) were hospitalized during the group 2 domination period. The median (Me) patient ages were 76 months (interquartile range [IQR] 35-130) and 73 months (IQR 45-118), and 61% and 65% of patients were male, respectively. There was no significant difference in the presence of positive SARS-CoV 2 antibody test results (IgM or IgG) between the groups (84 vs. 90%; p = 0.54).No differences between groups were observed in fever duration prior to admission (Me [IQR]: 5 days [3-6] vs. 5 days [4-6]; p = 0.26) or the presence of mucocutaneous (95 vs. 100%; p = 0.41), circulatory (70.3 vs. 61.8%; p = 0.86), neurological (6.8 vs. 2.9%; p = 0.662), or gastrointestinal symptoms (84 vs. 79%; p = 0.59). Respiratory symptoms were more common in group 2 (70 vs. 91%; p = 0.015). The need for intensive care unit admission was similar in both groups (16.2 vs. 17.6%, p = 1.0). No deaths occurred in the entire cohort. The studied children were characterized by high C-reactive protein and procalcitonin levels, concentrations of ferritin within normal limits, lymphopenia, moderate hypoalbuminemia, and high B-type natriuretic peptide/brain natriuretic peptide (NT-proBNP) concentrations; however, there were no differences between the groups. Intravenous immunoglobulins were administered as a first-line treatment for almost all patients. There was no significant difference in corticosteroid administration between the groups (87% vs. 74%; p = 0.11); however, the summary dose of methylprednisolone was higher in group 2 (Me [IQR]″ 12.6 mg/kg [10.5-17.8] vs. 16.4 mg/kg [13.3-19.5]; p = 0.03). The median length of stay was 11 days [IQR]: [9-14] and 10 days [8-12], respectively (p = 0.065). CONCLUSION: The clinical course of MIS-C is similar in subsequent pandemic waves; however, the incidence of MIS-C seems to be decreasing. WHAT IS KNOWN: • The clinical picture of COVID-19 is evolving. Multisystem inflammatory syndrome in children (MIS-C) is a relatively new serious disease connected with SARS-CoV-2 infection, and in subsequent waves of the pandemic, new cases of the disease have been recorded. WHAT IS NEW: • The clinical picture of MIS-C is not specific, but the course is still severe. • The incidence of MIS-C during the different pandemic waves is decreasing and the diagnosis in the period of lower prevalance is challenging.