Body surface and intracardiac recordings in a patient with Wolff-Parkinson-White syndrome (type A) with complete infra-His bundle block.

Electrocardiograms, vectorcardiograms and His bundle electrograms were recorded in a patient with Wolff-Parkinson-White syndrome (type A) who developed complete infra-Hisian block and advanced A-V block in the Kent bundle. The atrial impulses reaching the ventricles exclusively through the Kent bundle produced QRS complexes and vector loops showing diffuse (leftward initial and rightward pre-terminal) delays and slurrings. These abnormalities were not due to Wolff-Parkinson-White type A coexisting with right bundle branch block, but reflected the activation sequence characteristic of arrival of excitation; spontaneous impulse formation; or electrical stimulation, at the postero-superior wall of the left ventricle. Intracardiac recordings were a complement to body surface recordings in the study of Wolff-Parkinson-White syndrome complicated by A-V conduction disturbances.