Idiopathic premature ventricular contractions arising from the intraventricular septum adjacent to the his bundle.

A 57-year-old woman with idiopathic premature ventricular contractions (PVCs) exhibiting a left bundle branch block and left inferior axis QRS morphology underwent electrophysiological testing. Mapping revealed that the earliest ventricular activation times during the PVCs recorded on either side of the interventricular septum were the same and no excellent pace maps were reproduced at these sites. Successful radiofrequency catheter ablation was achieved in the right ventricular septum adjacent to the recording site of the His bundle electrogram. These findings suggested that the origin of this PVC was located in the intraventricular septum rather than the endocardial surface.