Electrophysiologic properties of the atrioventricular node in pediatric patients.

OBJECTIVES: The purpose of this study was to characterize anterograde and retrograde properties of the atrioventricular (AV) node in children and to determine the presence of ventriculoatrial (VA) conduction and dual AV node pathways.

BACKGROUND: Although AV node reentry is common in adults, it accounts for 13% of pediatric supraventricular tachycardia (SVT). The age-related changes in the AV node with development are poorly understood. The incidence of dual AV node pathways and VA conduction in the pediatric population is unknown.

METHODS: Electrophysiologic studies were performed in 79 patients with normal hearts and no evidence of AV node arrhythmias. Patients were classified into two groups by age: group I = 49 patients (0.39 to 12.8 years old, mean [+/- SD] age 8.5 +/- 3.6); group II = 30 patients (13.4 to 20.0 years old, mean age 15.6 +/- 1.8).

RESULTS: There was a significant difference (p < 0.05) in the cycle length (CL) at which anterograde AV block occurred between group I (305 +/- 63 ms) and group II (350 +/- 91 ms). Sixty-one percent of children had VA conduction with no age-related differences. There was no significant difference in the mean CL of retrograde VA block (360 ms). The incidence of dual AV node pathways in group I was 15% and 44% in group II (p < 0.05).

CONCLUSIONS: These findings suggest that AV node electrophysiology undergoes maturational changes. The increase in AV node reentrant tachycardia in adults may relate to changes in the relative refractoriness and conduction of the AV node or to differences in autonomic input into the AV node that allow dual pathway physiology to progress to SVT.