Diverse QRS morphology reflecting variations in lead placement for left bundle branch area pacing.

Aims: Left bundle branch area pacing (LBBAP) is a potential alternative to His bundle pacing. This study aimed to investigate the impact of different septal locations of pacing leads on the diversity of QRS morphology during non-selective LBBAP.

Methods And Results: Non-selective LBBAP and left ventricular septal pacing (LVSP) were achieved in 50 and 21 patients with atrioventricular block, respectively. The electrophysiological properties of LBBAP and their relationship with the lead location were investigated. QRS morphology and axis showed broad variations during LBBAP. Echocardiography demonstrated a widespread distribution of LBBAP leads in the septum. During non-selective LBBAP, the qR-wave in lead V1 indicated that the primary location for pacing lead was the inferior septum (93%). The non-selective LBBAP lead was deployed deeper than the LVSP lead in the inferior septum. The Qr-wave in lead V1 with the inferior axis in aVF suggested pacing lead placement in the anterior septum. The penetration depth of the non-selective LBBAP lead in the anterior septum was significantly shallower than that in the inferior septum (72 ± 11 and 87 ± 8%, respectively). In lead V6, the deep S-wave indicated the time lag between the R-wave peak and the latest ventricular activation in the coronary sinus trunk, with pacemaker leads deployed closer to the left ventricular apex.

Conclusion: Different QRS morphologies and axes were linked to the location of the non-selective LBBAP lead in the septum. Various lead deployments are feasible for LBBAP, allowing diversity in the conduction system capture in patients with atrioventricular block.