Resynchronization effects and clinical outcomes during left bundle branch area pacing with and without conduction system capture.

Background: Left bundle branch area pacing (LBBAP) includes left bundle branch pacing (LBBP) and left ventricular (LV) septal myocardial pacing (LVSP).

Hypothesis: The study aimed to assess resynchronization effects and clinical outcomes by LBBAP in heart failure (HF) patients with cardiac resynchronization therapy (CRT) indications.

Methods: LBBAP was successfully performed in 29 consecutive patients and further classified as the LBBP-group (N = 15) and LVSP-group (N = 14) based on the LBBP criteria and novel LV conduction time measurement (LV CT, between LBBAP site and LV pacing (LVP) site). AV-interval optimized LBBP or LVSP, or LVSP combined with LVP (LVSP-LVP) was applied. LV electrical and mechanical synchrony and clinical outcomes were assessed.

Results: All 15 patients in the LBBP-group received optimized LBBP while 14 patients in the LVSP-group received either optimized LVSP (5) or LVSP-LVP (9). The LV CT during LBBP was significantly faster than that during LVP (p < .001), while LV CT during LVSP were similar to LVP (p = .226). The stimulus to peak LV activation time (Stim-LVAT, 71.2 ± 8.3 ms) and LV mechanical synchrony (TSI-SD, 35.3 ± 9.5 ms) during LBBP were significantly shorter than those during LVSP (Stim-LVAT 89.1 ± 19.5 ms, TSI-SD 49.8 ± 14.4 ms, both p < .05). Following 17(IQR 8) months of follow-up, the improvement of LVEF (26.0%(IQR 16.0)) in the LBBP-group was significantly greater than that in the LVSP-group (6.0%(IQR 20.8), p = .001).

Conclusions: LV activation in LBBP propagated significantly faster than that of LVSP. LBBP generated superior electrical and mechanical resynchronization and better LVEF improvement over LVSP in HF patients with CRT indications.