Nodoventricular accessory atrioventricular connection associated with dual atrioventricular pathways: a case report and review of the literature.

A case is presented of a patient free from tachyarrhythmias or prior evidence of pre-excitation syndrome, in whom electrophysiologic study revealed evidence of dual AV nodal pathways associated with a nodoventricular bypass tract. Programmed atrial extrastimuli testing revealed that conduction through the fast AV nodal pathway was associated with a normal HV interval and normal QRS morphology. Conduction through the slow AV nodal pathway was always associated with a short HV interval and ventricular pre-excitation. No tachyarrhythmias could be induced with atrial extrastimuli or rapid atrial pacing. Previously reported cases of this pre-excitation variant (all of whom were symptomatic from tachyarrhythmias) are reviewed and the features summarized. This pre-excitation syndrome can occur in individuals without clinical evidence of tachyarrhythmias or overt pre-excitation and as such may be more common than previously suspected.