Fig. 1.

Point-by-point mapping of para-Hisian AP with (−) delta-wave in V1. A: Point-by-point mapping with the ablation catheter revealed a broad activation within the first 5 msec directed towards the septum leading to a negative delta-wave in V1. The AP potential (blue tag) is fused with the atrial and ventricular EGMs and a concealed His EGM cannot be ruled out. Note perpendicular catheter orientation with the femoral approach which led to persistent AP bumping during ablation catheter mapping when the patient took a deep breath. Catheter ablation at the bumping site was ultimately successful confirmed by absence of AP recovery with 24 mg Adenosine and no recurrence during follow-up. B: Distal His bundle localization (yellow tag) at the AP potential site (blue tag) during orthodromic reciprocating tachycardia. C: Concealed His EGM on quadripolar catheter due to fused atrial and ventricular EGMs during pre-excitation.