Figure 3: Complete Conduction Block with Recruitment of Latent Purkinje Potentials During His Bundle Pacing with QRS Correction.

Complete conduction block at the level of the left-sided His without any left bundle recordings suggestive of block proximal to the left bundle. The PP are retrograde and passive after ventricular activation. With His bundle stimulation, QRS narrowing from 180 to 121 ms is observed. Non-selective His bundle capture is demonstrated by presystolic recruitment of the latent PP immediately after the pacing impulse. Normal physiological activation of the local ventricular electrograms is restored from apical to basal. NS = non-selective; PP = Purkinje potentials.