Fig. 3.

High-resolution mapping of para-Hisian AP with (−) delta-wave in V1 A: High-resolution OWM during atrial pacing revealed the earliest activation septal to the RV summit directed towards the septum leading to a negative delta-wave in V1 (Video 2). The distal His (yellow tags) was located during narrow QRS complex paced beats and was also seen on the G spline micro-electrodes with close 2-mm spacing during paced pre-excitation (A-V-H sequence with identical stim-His interval) (Suppl Fig. 2). B: The second RF delivery (with sufficient CF) targeting the ventricular pathway insertion with a possible AP potential (H1-H2 bipole) led to instant loss of pre-excitation and bi-directional AP automaticity. Note one beat with retrograde VA conduction (asterisk) and absence of any atrial electrogram on the ablation catheter. C: Corresponding fluoroscopic images in RAO and LAO demonstrating sufficient stability (5 g mean CF) with the femoral approach.