Figure legends:
Figure 1 shows 12 lead ECG lined up with intracardiac His electrogram (His-d represents the distal bipole and His-p represents the proximal bipole) traces
Figure 2 Explanation for Figure 1
Upper panel corresponds to the 12 lead ECG and intracardiac EGMs as in figure 1 (with annotated EGMs). It shows that the atrial and His potentials are occurring near simultaneously and hence could be isorhythmically dissociated or each His potential could be the result of the previous atrial potential. There is progressive HV prolongation and RR shortening followed by a block; Annotations H- His, A- atrium, V- ventricle. The origin of atrial depolarisation is depicted by the dotted lines
Lower panel shows ladder diagrams corresponding to the intracardiac EGMs depicts 4:3 infra-Hisian Wenckebach sequence and presumed isorhythmic dissociation of atrium and His signals.