Comparison of cardiac function between left bundle branch pacing and right ventricular outflow tract septal pacing in the short-term: A registered controlled clinical trial

Abstract

Background: The novel method of left bundle branch pacing (LBBP) has been reported to produce a narrower QRS duration and lower pacing threshold than right ventricular outflow tract septal pacing (RVOP). However, whether LBBP is superior to traditional RVOP in improving cardiac function still lacks sufficient evidence.

Objective: The purpose of this study was to compare the changes in cardiac function (especially in brain natriuretic peptide (BNP)levels, left atrial function, and left ventricular diastolic function) within 7 days between LBBP and RVOP.

Methods and results: A single-centre prospective controlled registered clinical study was conducted with 84 patients with bradycardia indications. Forty-two patients underwent RVOP, and 42 patients underwent LBBP. The pacemaker parameters were adjusted so that the ventricular ratio was over 90% and rate was 60-70 bpm. The changes in BNP levels and echocardiogram and speckle-tracking echocardiagraphy findings were compared between the two groups before and within 7 days after implantation: (1) BNP: there was no significant difference in BNP level between the two groups before and 1 day after implantation, while the LBBP group had significantly lower levels than the RVOP group on day 7 [(65.15 ± 56.96)pg/ml vs.(129.82 ± 101.92)pg/ml, P < 0.001]. (2) Cardiac echocardiography: the e' value of the LBBP group was higher than that of the RVOP group 7 days after implantation[(6.39 ± 2.65) cm/s vs. (5.45 ± 1.35)cm/s, P = 0.049]. The E/e' and peak E-wave velocity in the LBBP group decreased significantly after 7 days [16.57 ± 6.55 vs. 12.75 ± 5.16 P = 0.043, (88.6 ± 24.37)cm/s vs. (75.68 ± 28.10)cm/s P = 0.030]; in contrast, there were no significant changes in the RVOP group [14.13 ± 3.85 vs.14.10 ± 4.85 P = 0.50, (77.33 ± 21.14)cm/s vs. (74.45 ± 23.03)cm/s P = 0.56). (3)Speckle-tracking echocardiagraphy: there was no significant difference in left atrial strain or the strain rate between the LBBP and RVOP groups，but the absolute values of left atrial strain and strain rate in the LBBP group increased, while those in the RVOP group decreased.

Conclusion: This study demonstrates that compared to RVOP, LBBP can increase left ventricular early diastolic function, improve BNP levels, and has a tendency to increase left atrial myocardial elasticity and left atrial strain capacity in the short term in pacemaker-dependent patients.

Keywords: Cardiac function; Left bundle branch pacing; Permanent pacemaker; Physiological pacing; Right ventricular outflow tract pacing.