Figure 3
At times (Figure 3A), when the Hisian automaticity usurped the sinus rate, the atrium was captured retrogradely as can be inferred by the inverted P waves in inferior leads. Thus, there was intermittently, a H-A association with regular HA intervals (Figure 3B).
Panel A shows 12 lead ECG, intracardiac EGMs and corresponding ladder diagrams, which depicts atrioventricular dissociation with the Junctional/ Hisian escape rate exceeding the sinus rate leading to 1:1 retrograde conduction and activation of the atrium (note the transition in P wave morphology in the fourth beat- fusion in the atrium between sinus and His discharge depicted in the ladder diagram attached)
Panel B corresponds to 12 lead ECG, the intracardiac EGMs and corresponding ladder diagrams, which depicts atrioventricular dissociation with the Hisian escape rhythm conducting antegradely with 3:2 infra-Hisian Wenckebach sequence (note the progressive HV prolongation and then drop) and conducing retrogradely with a 1:1 HA (HA interval constant) association. The retrograde activation of atrium is also evident from the surface P wave morphology (onset marked by dotted lines); Annotations H- His, A- atrium, V- ventricle. Ladder diagrams {interatrial intervals (763 ms), inter-Hisian intervals (763 ms) and V-V intervals (763ms) are depicted in milliseconds}; corresponds to the intracardiac EGMs in panel A. HV progressively prolongs followed by the block to the ventricle