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 childre n and to determine the presence of ventriculoatrial (VA) conduction an d dual AV node pathways.Background. Although AV node reentry is common in adults, it accounts for 13% of pediatric supraventricular tachycar dia (SVT), The age-related changes in the AV node with development are poorly understood, The incidence of dual AV node pathways and VA cond uction in the pediatric population is unknown. Methods. Electrophysiol ogic studies were performed in 79 patients with normal hearts and no e vidence of AV node arrhythmias. Patients were classified into two grou ps by age: group I = 49 patients (0.39 to 12.8 gears 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 betw een group I (305+/-63 ms) and group II (350+/-91 ms), Sixty one percen t 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 t he relative refractoriness and conduction of the AV node or to differe nces in autonomic input into the AV node that allow dual pathway physi ology to progress to SVT. (C) 1997 by the American College of Cardiolo gy.