Bradiarrhythmia is an alteration of heart rhythm, either regular or irregular, in which heart rate is below what would be normal for the child’s age. They are generally related to another underlying disease or appear following a surgical intervention in the heart. They can occasionally be present since birth, being complete congenital heart block the most frequent. They are generally diagnosed with an electrocardiogram and require treatment when they cause symptoms such as dizziness or sudden loss of consciousness (syncope), or when they affect the child’s hemodynamic status. In these cases, pacemaker implantation is usually necessary.