Evidence for a unidirectional retrograde communication between distal His bundle and atria.

Intracardiac electrogram recordings are presented suggesting the existence in one patient with recurrent supraventricular tachycardia of a functionally unidirectional retrograde connection between the distal His bundle and the low right atrium. Recordings obtained during junctional rhythm showed a short ventriculoatrial conduction time which did not lengthen during rapid or premature ventricular pacing. During an episode of supraventricular tachycardia induced by a single atrial premature stimulus, an infra-His Wenckebach period occurred during which retrograde ventriculoatrial conduction remained constant until ventricular capture was blocked, but atrial activation persisted with the same retrograde atrial activation sequence seen in the previous beats of supraventricular tachycardia. The findings appear to document participation in supraventricular tachycardia of a type of atrio-His fibre originally described by Brechenmacher.