Differentiating left bundle branch pacing and left ventricular septal pacing: An algorithm based on intracardiac electrophysiology.

Background: Left bundle branch pacing (LBBP) is a new near-physiological pacing modality. Distinguishing left ventricular septal only pacing (LVSP) from nonselective LBBP still needs clarification. This prospective study sought to establish a differentiation algorithm to confirm LBBP.

Methods And Results: LBBP was attempted in consecutive patients. If direct LBB capture (LBBP) could not be confirmed, LVSP was considered to have been achieved. Intracardiac left ventricular (LV) activation sequence and activation time were analyzed using coronary sinus (CS) electrogram mapping. Electrophysiological parameters including S-CSmax, S-CSmin, LV lateral wall activation time, ΔLV, and LBB potential were compared between LBBP and LVSP. Stimulated LV activation time (S-LVAT) and stimulated QRS duration (S-QRSd) were also compared between the two groups. Multivariate logistic regression analysis was used to develop a prediction algorithm for LBBP. Of the 43 prospectively enrolled patients, 27 underwent LBBP and 16 underwent LVSP. All LBBP patients showed identical LV activation sequences to their intrinsic rhythm while no LVSP patients maintained their intrinsic sequence. S-CSmax, ΔLV, LV lateral wall activation time, and S-LVAT during LBBP were significantly shorter than those during LVSP. Combining LBB potential with S-LVAT had the largest area under the curve (AUC) of 0.985 for confirming LBBP with a sensitivity of 95.2% and a specificity of 93.7%.

Conclusions: Compared with LVSP, LBBP preserves a normal LV activation sequence and better electrical synchrony. A combination of LBB potential with S-LVAT can be an effective and practical model to distinguish LBBP from LVSP during implantation in patients with normal LBB activation.