EVOLUTION OF THE WOLFF-PARKINSON-WHITE SY NDROME IN CHILDHOOD - TRANSESOPHAGEAL RECORDINGS OF ANTEROGRADE-CONDUCTION OF THE ACCESSORY PATHWAY AND OF ATRIAL VULNERABILITY

Twenty-nine children with the Wolff-Parkinson-White syndrome (WPW) wer e evaluated by transoesophageal electrophysiological studies to determ ine the quality of anterograde conduction in the accessory pathway and the atrial vulnerability. The study group included 15 neonates, 1 to 30 days old, and 14 children from 5 to 15 years of age; Anterograde co nduction through the bundle of Kent was tested by incremental transoes ophageal atrial pacing and by the determination of the shortest conduc ted cycle with preexcited RR waves: bursts of atrial pacing were then used to try to trigger an atrial arrhythmia. In the group of the 15 ne onates, 11 had accessory pathways capable of conduction to the ventric ules at frequencies > 300/min (stimulation cycle less-than-or-equal-to 2,00 ms) but no atrial arrhythmias could be induced. The older childr en had slower conduction in the accessory pathways with the shortest c onducted cycle lenght > 200 ms in 11/14 cases; on the other hand, atri al fibrillation was easily induced in 4 children, all over 12 years of age. The risk of syncope by rapid conduction of an atrial arrhythmia through the accessory pathway is negligeable in young children, includ ing those on digoxin. This study suggests that this low risk is explai ned more by the absence of atrial vulnerability than by the electrophy siological properties of the accessory pathways.