Early assessment of cardiac synchrony in patients with atrioventricular block after simplified left bundle branch area pacing

To evaluate early cardiac electrical conduction and mechanical synchrony in patients with atrioventricular block (AVB) treated with simplified left bundle branch area pacing (LBBAP) via electrocardiogram (ECG) and echocardiogram, and to explore the disparities in cardiac synchrony between left bundle branch pacing (LBBP) and left ventricular septum pacing (LVSP). A retrospective analysis was performed on AVB patients undergoing permanent pacemaker implantation with successful LBBAP at TEDA International Cardiovascular Hospital (Nov 2022–Jun 2025). Ventricular lead implantation was guided by fluoroscopic “nine-zone method”. Baseline, intraoperative ventricular lead, 1-week postoperative ECG/echocardiography cardiac synchrony parameters, and 3-month follow-up data on complications and pacemaker programming were collected. Based on intraoperative parameters, patients with a right bundle branch block morphology in lead V1 during unipolar pacing and meeting at least one criterion were defined as the LBBP group: (1) selective left bundle branch block features(LBBB) ; (2) Stimulus to Left Ventricular Activation Time (stim-LVAT) ≤ 75 ms (non-LBBB) or ≤ 85 ms (LBBB); (3) V6-V1 R-wave peak interval difference > 44 ms. Cardiac synchrony was compared between LBBP and LVSP groups. A total of 51 patients were enrolled, with intraoperative ventricular lead parameters: threshold 0.72 ± 0.18 V, sensing 11.4 ± 4.2 mV, impedance 622.2 ± 97.8 Ω, and stim-LVAT 70.1 ± 11.0 ms. Per criteria, 30 patients (58.8%) met LBBP requirements. Postoperative QRS width was 118.8 ± 9.9 ms (LBBP) vs. 123.4 ± 10.2 ms (LVSP, P = 0.114). Echocardiographic synchrony assessments showed no significant between-group differences in the ratios of left ventricular filling time (LVFT) to the R-R interval of the electrocardiogram (LVFT/RR) (49.2 ± 0.7% vs. 46.7 ± 0.7%, P = 0.236),the interventricular mechanical delay time (IVMD) (11.2 ± 8.7 ms vs. 11.7 ± 8.7 ms, P = 0.847), or the peak strain dispersion indices (PSD) of each segment of the left ventricle (57.2 ± 22.7 ms vs. 56.0 ± 15.5 ms, P = 0.836). All patients completed 3-month follow-up, with pacing threshold unchanged from intraoperative levels (< 1.5 V) and no ventricular lead-related complications observed. In patients with normal cardiac function and AVB, there were no significant differences in early postoperative cardiac synchrony between the LVSP and LBBP groups.Therefore, LVSP may be considered as a potential alternative to LBBP or His pacing (HBP) in cases where the latter are not feasible.