Fig. 2.

High-resolution mapping of para-Hisian AP with (+) delta-wave in V1. A: High-resolution OWM revealed the earliest activation with distinct AP potential lateral to the RV summit with an oblique course towards the free wall leading to a positive delta-wave in V1 (Video 1). Despite a distance of less than 5 mm between the distal His and the distal AP potential, antegrade His bundle activation (yellow tags) was clearly visible during pre-excitation along the adjacent Octaray micro-electrodes with close 2-mm spacing (Suppl Fig. 1). B: The first RF delivery targeting the proximal AP potential (red tag) led to instant loss of pre-excitation along with bi-directional AP automaticity. Note two beats with retrograde VA conduction (asterisks) and absence of any atrial electrogram on the ablation catheter. C: Corresponding fluoroscopic images in RAO and LAO demonstrating a stable catheter position (33 g mean CF) with the femoral approach.