One-to-two atrioventricular conduction in Wolff-Parkinson-White syndrome: a mechanism of initiating supraventricular tachycardia.

A patient with Wolff-Parkinson-White syndrome and recurrent supraventricular tachycardia manifested the unusual finding of two ventricular responses to a single atrial depolarization. The second response occurred due to delay in the His-Purkinje system (H-V prolongation). This phenomenon was a mechanism of initiation of supraventricular tachycardia, not previously described to our knowledge.