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Figure 2 Electrocardiogram and intracardiac electrograms during sinus rhythm, showing atrial, His, and ventricular electrograms from an octapolar catheter at the atrioventricular junction. Bipoles are labeled Intra-P (proximal, atrial), Intra-3 (atrioventricular junction), Intra-2 (His position), and Intra-D (distal, ventricular), respectively. Scale markings are in ms and intervals are marked. AH = atrial-to-His; HV = His-to-ventricular.