Bradycardia is defined as a heart rate below the lowest normal values set for age. The heart rate is set by the cardiac electric conduction system that also synchronizes the timing of atrial and ventricular contractions. The conduction system includes the sinus node, atrioventricular node (AV), and the His-Purkinje system (His bundle). Bradycardia is caused by intrinsic dysfunction or injury to the heart's conduction system or by extrinsic factors acting on a normal heart and its conduction system.
Although bradycardia is less common in children than adults, it can infrequently cause significant morbidity and rarely sudden cardiac death. In particular, the risk of death in untreated children with complete block of the AV node is 5 to 8 percent . With the advent of pediatric cardiac pacing, these deaths could be prevented. Hence, it is important for the clinician to identify those children with bradycardia who are at risk for morbidity and death and who might benefit from therapeutic intervention.
The diagnosis, evaluation, and treatment of bradycardia in children and adolescents will be discussed here.
The normal value for average heart rates varies with age. Younger patients have higher heart rates that decrease to adult values by the late teenage years. Bradycardia can be established by either using 12-lead electrocardiogram (ECG) or by 24-hour ambulatory monitoring.
Guidelines for bradycardia based on 12-lead ECG are as follows :