Methylprednisolone-Induced Delayed and Sustained Bradycardia in Multisystem Inflammatory Syndrome in Children

Background: Therapeutic immunomodulation using pulse methylprednisolone is one of the cornerstones of management in multisystem inflammatory syndrome in children (MIS-C). This study examines whether bradycardia was possibly methylprednisolone-induced and if the risk and time taken to develop or recover from bradycardia depend on the dose or presence of shock. Methods: A longitudinal study of those with MIS-C who received methylprednisolone treatment was conducted. Baseline heart rate (HR) prior to starting treatment was documented, and heart rate was monitored every two hours by bedside cardiac monitors. Student's t-test was used to test the difference in means after log transformation if required. Kaplan-Meier curves were used to estimate the median time to onset and recovery of bradycardia, and Mood's two-sample test was used to test the difference in medians. Results: Out of 89 children with MIS-C included in the study, most (84.3%) developed bradycardia after methylprednisolone administration, with a significant drop in heart rate irrespective of age. The median time of onset was 31.0 (interquartile range (IQR): 10.0-80.0) hours after the administration of methylprednisolone, and recovery occurred 57.0 (IQR: 14.0-202.0) hours later. This was not significantly different by dose or by the presence of shock. Although the proportion of bradycardia were similar across groups, the heart rate was significantly lower at bradycardia for those on pulse dose and those with shock when compared to those on conventional dose and those who did not have shock, respectively. Conclusion: A high proportion of delayed and sustained bradycardia in children with MIS-C, irrespective of age, dose of methylprednisolone, or presence of shock, which is possibly induced by the steroid, was observed. The time to onset and the time to recovery were independent of the above factors. However, the heart rate at bradycardia varied significantly by dose and by the presence of shock.