Left bundle branch area pacing improving the left atrial outcomes in pace-dependent patients compared with right ventricular outflow tract septal pacing

Background Recent studies suggested that the left bundle branch area pacing (LBBAP) has a better efficacy to reduce QRS duration and produce a lower pacing threshold than the conventional right ventricular outflow tract septal pacing (RVOP), which resulted in a better cardiac function and ventricular synchronization. However, whether the LBBAP has a better efficacy in improving left atrial structure, function in pace-dependent patients compared with RVOP has not been well studied.Objective The purpose of this study was to compare the atrial outcomes of pace-dependent patients who received LBBAP or RVOP procedures.Methods and Results A total of 72 patients (including II degrees AVB, high AVB, and III degrees AVB, excluding atrial fibrillation patients with atrioventricular block) consecutively enrolled in this single-center prospective clinical study and randomly assigned to the RVOP group and the LBBP group with 36 patients. All patients were pace-dependent. The changes in echocardiogram, speckle-tracking echocardiography, brain natriuretic peptide (BNP), and 6-min walking distance were documented and compared between two groups at baseline, 7 days, 1, 3, and 6 months after the implantation. There were no significant differences in baseline characteristics between the two groups. The results of the study were as following: (1) left atrial structure index: Our study indicated that there are no significant differences in left atrial anteroposterior dimension (LAAPD), left atrial superoinferior dimension, and left atrial mediolateral dimension between two groups. While the LAAPD in the LBBAP group was significantly reduced at 6 months after implantation ([38.22 +/- 2.17] mm vs. [34.13 +/- 1.59] mm, p < .05). (2) Left atrial strain index: We observed that the S% was significantly improved in both groups at 3 and 6 months after implantation but more prominent in the LBBAP group at 6 months (36.94 +/- 11.67 vs. 25.87 +/- 8.93, p = .01). SRs, SRe were improved in the RVOP group at 6 months after implantation but was further significantly increased in the LBBAP group. Similarly, the SRa in the LBBAP group was significantly better than the RVOP group after 6 months (-2.11 +/- 0.75 vs. -2.51 +/- 0.70, p = .04). (3) Left atrial ejection index: LAEF% in the LBBAP group was significantly improved compared with the RVOP group (60.02 +/- 1.88 vs. 53.65 +/- 2.45, p = .047) and baseline (60.02 +/- 1.88 vs. 49.68 +/- 2.75, p < .05) at 6 months after the surgery. (4) Left ventricular ejection index: The LVEF% in the LBBAP group was significantly increased than the RVOP group after 6 months (69.14 +/- 4.99 vs. 64.60 +/- 4.84, p = .01) and the BNP level was significantly lower in the LBBAP group compared with the RVOP group at 7 days, 1, 3, and 6 months after implantation (p < .05). (5) 6-min walking distance: the 6-min walking distance was significantly increased at 3 and 6 months after implantation compared with that before (p < .05) in both groups, but was more prominent in LBBAP groups ([483.03 +/- 11.02] m vs. [431.09 +/- 10.69] m,p < .05).Conclusion Compared with the traditional RVOP, the LBBAP procedure increased left atrial myocardial stress as well as left atrial ejection in pace-dependent patients at follow-up to 6 months.