Fig. 2

Morphology of intrinsic intracardiac EGM of the LBB lead tip during the LBBP procedure and comparison with the morphology before screwing in. A Morphology of intrinsic intracardiac EGM when the LBB lead tip was located at different sites in the interventricular septum. B Taking the mapping recorded at 210 s as an example to demonstrate the method of overlapping and comparing the morphologies of two different sites. The intrinsic QRS complexes on surface ECG recorded at 210 s and 1 s (before screwing into the interventricular septum) were matched, such that the morphologies of intracardiac EGMs at 210 s and 1 s were overlapped and compared to avoid time errors. C Comparison of the morphology of the intrinsic intracardiac EGM at different sites in the interventricular septum and before screwing (1 s) (marked as 2.0, which means the amplitude was halved). EGM, electrogram; LBB, left bundle branch; LBBP, left bundle branch pacing; ECG, electrocardiogram