ABSTRACT
Objective: Multisystem inflammatory syndrome in children (MIS-C) may cause cardiovascular involvement and dysrhythmia. Although a variety of arrhythmias may be seen, sinus bradycardia was rarely reported. The aim of this study is to determine the frequency and clinical course of bradycardia in children with MIS-C. Material and Methods: Medical records of patients who were diag-nosed with MIS-C between August 2020 and March 2021 were retro-spectively evaluated. MIS-C diagnosis was made according to US Cen-ters for Disease Control and Prevention (CDC) criteria. All patients who had sinus bradycardia were included in the study. Results: Transient sinus bradycardia was observed in 7 of 40 (17.5%) patients (2 girls, 5 boys) with MIS-C. The median age was 10.8 years (range, 5.4-13.8 years). All patients were initially treated with intravenous immu-noglobulin (IVIG) and six out of the seven patients also received intravenous methylprednisolone (MPZ). Sinus bradycardia developed a median of four days (range, 2-6 days) after MIS-C diagnosis and continued for a median of four days (range, 2-6 days). In six of the seven patients, bra-dycardia was detected a median of 42 hours (range, 11-74 hours) after MPZ treatment and resolved a median of 36 hours (range, 20-50 hours) after tapering MPZ dosage. Electrocardiogram (ECG) of patients showed sinus bradycardia. All patients were asymptomatic and awake when bra-dycardia was observed. No patients had any underlying structural heart defect or electrolyte abnormalities. Bradycardia episodes resolved without any specific intervention. Conclusion: Sinus bradycardia may occur due to the cardiac involvement of MIS-C itself or as a possible side effect of MPZ therapy, which can resolve without any specific treatment.