Abstract: Background：There is a lack of report in China regarding sinus bradycardia (SB) caused by the use of methylprednisolone pulse therapy for the treatment of pediatric renal and rheumatic disease. There is no consensus on whether to stop pulse therapy after SB occurs. Objective：To summarize the clinical characteristics of SB during methylprednisolone pulse therapy in children with renal and rheumatic disease. Design:Case series report. Methods:Patients who were hospitalized in the Department of Nephrology and Immunology at Children's Hospital of Soochow University from January 1, 2018 to April 1, 2024 and received methylprednisolone pulse therapy were reviewed. During the treatment period, patient with any measurement of heart rate < 60 beats · min-1 and confirmed as SB by electrocardiogram were included in this study. The intercepted information included clinical manifestations, examinations, and prognosis. Main outcome measures：Characteristics of SB occuring after methylprednisolone pulse therapy. Results：There were a total of 11 children, including 7 females and 4 males, with an average age of (11.3 ± 2.5) years.There were 3 cases of systemic lupus erythematosus with macrophage activation syndrome (MAS), 2 cases of IgA vasculitis associated nephritis, 2 cases of juvenile idiopathic arthritis with MAS, and 2 case of dermatomyositis with MAS. There was also 1 case of ANCA-associated vasculitis and 1 case of C3 glomerulonephritis. The basal heart rate of the patients was （88±4）beats/min. The average dose of methylprednisolone pulse therapy was （10.7±3.0） mg·kg-1·d-1. The duration of pulse therapy was 3-5（4.3±0.9）d. The time from the start of the first dose of methylprednisolone pulse therapy to the occurrence of SB was 1-3（1.8±0.8）d. The minimum heart rate after pulse therapy was 48-58（53±4） beats/min. The decrease in heart rate was 32.6%-44.6%（40.0%±3.7%）. Blood gas analysis, electrolyte test, cardiac ultrasound, and thyroid function were all normal when SB occurred. No antiarrhythmic treatment was given. The time from the last dose of methylprednisolone pulse therapy to recovery to baseline heart rate was 4-8(6.1±1.1) d. All patients did not experience cardiovascular symptoms such as dizziness, chest tightness, or palpitations during the treatment period. During a follow-up period of (2.4±2.1) years, no cardiovascular abnormalities were found. Conclusion：The children have no discomfort symptoms when SB occurs after methylprednisolone pulse therapy and therefore the SB is easily overlooked. They generally don't require special treatment and can continue to complete the pulse therapy under close monitoring Their heart rate usually return to normal in a week after the cessation of the pulse therapy.

Key words: Methylprednisolone, Pulse therapy, Sinus bradycardia