Preexcitation Secondary to Fasciculoventricular Pathways in Children: A Report of Three Cases

INTRODUCTION: Fasciculoventricular connections are the rarest form of accessory pathways leading to preexcitation. Electrophysiologic characteristics of these pathways include ventricular preexcitation with normal PR and AH intervals and short HV intervals during sinus rhythm. In addition, atrial overdrive pacing prolongs the PR interval without affecting the HV interval or the degree of preexcitation. METHODS AND RESULTS: From March 1994 through February 1997, 3 of 59 pediatric patients referred for electrophysiologic study for preexcitation on surface ECGs were found to have fasciculoventricular pathways. Two patients had no inducible supraventricular tachycardia. One patient had successful ablation of both a left lateral pathway and a concealed anterolateral pathway that had facilitated antidromic and orthodromic supraventricular tachycardias, respectively. CONCLUSION: Children often manifest minimal preexcitation via accessory AV pathways due to rapid AV conduction and/or left lateral pathway location. Fasciculoventricular pathways may masquerade as Wolff-Parkinson-White syndrome. Separation of the two diagnoses depends on the demonstration of specific electrophysiologic criteria.