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.