Left bundle branch pacing vs left ventricular septal pacing in the same patients with heart failure and left bundle branch block

Left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP) are considered to be acceptable as left bundle branch area pacing (LBBAP) strategies. The differences in cardiac mechanical performance between LBBP and LVSP in the same patients with heart failure (HF) and left bundle branch block (LBBB) are yet to be determined. The purpose of this study was to compare mechanical function and resynchronization effect of LBBP and LVSP as CRTP modalities. Fourteen patients with reduced left ventricular ejection fraction (LVEF) and typical complete LBBB who received cardiac resynchronization therapy pacing (CRTP) implantation were enrolled. All patient implantation with two ventricular pacing leads, enabling both LBBP and LVSP. Acute cardiac function and resynchronization effect were assessed by echocardiography and electrocardiography to compare the differences in LBBB mode, LBBP mode, and LVSP mode within the same patients undergoing CRTP. Both pacing modes significantly reduced QRS duration (QRSd) and left ventricular activation time (LVAT) versus LBBB (all P<0.001), with LVSP yielding wider QRSd than LBBP (P<0.001). LBBP showed better performance in LV mechanical synchrony parameter (SDI) than LVSP, and both pacing modes were superior to that of LBBB condition (all P < 0.001). LVEF increased significantly with both pacing modes, with a greater increase observed in LBBP compared to LVSP. No significant differences in right ventricular function were observed among the three modes. In this pilot study of patients with HF and LBBB, both LBBP and LVSP significantly improved left ventricular hemodynamics and mechanical synchrony without compromising RV function. LBBP potentially has superior left ventricular hemodynamic effects to LVSP.