The Development of Permanent Unidirectional Anterograde Block in the Accessory Pathway of a Patient with Wolff-Parkinson-White Syndrome and Observations on the Mechanism of the Ensuing Incessant Circus Tachycardia

Abstract

A case is reported, the sixth in the literature, in which permanent anterograde block occurred in the accessory pathway of a patient with Wolff-Parkinson-White syndrome, so that pre-excitation no longer occurred. Retrograde conduction remained intact and the patient developed incessant tachycardia with ventriculo-atrial conduction occurring over the accessory pathway.

Retrogradely conducting pathways are a common cause of supraventricular tachycardia and this case raises the possibility that many of them may previously have had overt pre-excitation.