Po-02-013 efficacy of left bundle branch pacing in patients with different left bundle branch block morphologies

Left bundle branch pacing (LBBP) is a novel technique to deliver cardiac resynchronization therapy (CRT) by correcting intrinsic LBBB to achieve electrical and mechanical resynchrony. Whether the efficacy of LBBP is different across different LBBB morphologies has not been reported. To explore the efficacy of LBBP in patients with different LBBB morphologies. Consecutive patients who received LBBP due to either heart failure (HF) with LBBB or atrioventricular block accompanied with a LBBB pattern escape rhythm were recruited. The changes of QRS duration (ΔQRSd) and left ventricular activation time (ΔLVAT) were compared before and after LBBP. Relationships of ΔQRSd and ΔLVAT with cardiac function in HF patients were also explored. HF patients were followed up for at least 6 months. Electrical resynchrony and cardiac function were compared based on 4 major LBBB morphological criteria. Comparison 1: LBBB meeting Strauss criteria vs not; Comparison 2: presence of q wave in lead I and aVL vs not; Comparison 3: presence of QS vs rS morphology of QRS in lead V1; and Comparison 4: presence of S wave in lead V6 vs not. A total of 82 patients were enrolled from January 2018 to August 2022. In Comparison 1, 59 patients had LBBB meeting Strauss criteria vs 23 not meeting criteria. Patients with LBBB meeting Strauss criteria had greater reduction in QRSd (56.95±24.10ms vs 36.83±32.16ms, P<0.05) and LVAT (56.47±14.90ms vs 41.52±17.13ms, P<0.001). Forty-two HF patients met the Strauss criteria had greater LVEF improvement (19.92±6.89% vs 12.41±13.10%, P<0.05) compared to those not meeting the criteria. Comparison 4 included 61 patients without S wave in lead V6 and these patients exhibited better electrical synchrony after LBBP (ΔQRSd: -55.18±24.79ms vs -40.05±33.67ms, P<0.05; ΔLVAT: -55.74±14.70ms vs -41.67±18.55ms, P<0.05) than patients with S wave in V6. Among them, 51 patients without S wave in V6 had HF and showed greater LVEF improvements than those with S wave in V6 (ΔLVEF: 18.65±10.13% vs 6.61±7.78%, P<0.05). Correlation analyses showed significant associations between both ΔQRSd (R=0.55, P <0.001) and ΔLVAT (R=0.39, P <0.01) with LVEF improvement. In multivariate analysis, ΔQRSd>53 ms is an independent predictor of cardiac super response (LVEF improvement>15%). LBBB pattern meeting the Strauss criteria and absence of S wave in lead V6 can predict better electrical resynchrony and LVEF improvement by LBBP.