Impact on right ventricular performance in patients undergoing permanent pacemaker implantation: Left bundle branch pacing versus right ventricular septum pacing

Abstract

Background: The novel method of left bundle branch pacing (LBBP) has been reported to achieve better electrical and mechanical synchrony in the left ventricle than conventional right ventricular pacing (RVP). However, its effects on right ventricle (RV) performance are still unknown.

Methods: Consecutive patients undergoing dual-chamber pacemaker (PM) implantation for sick sinus syndrome (SSS) with normal cardiac function and a narrow QRS complex were recruited for the study. The pacing characteristics and echocardiogram parameters were measured to evaluate RV function, interventricular and RV synchrony, and were compared between ventricular pacing-on and native-conduction modes.

Results: A total of 84 patients diagnosed with SSS and an indication for pacing therapy were enrolled. Forty-two patients (50%; mean age 65.50 ± 9.30 years; 35% male) underwent successful LBBP and 42 patients (50%; mean age 69.26 ± 10.08 years; 33% male) RVSP, respectively. Baseline characteristics were similar between the two groups. We found no significant differences in RV function [RV-FAC (Fractional Area Change)%, 47.13 ± 5.69 versus 48.60 ± 5.83, p = .069; Endo-GLS (Global Longitudinal Strain)%, -28.88 ± 4.94 versus -29.82 ± 5.35, p = .114; Myo-GLS%, -25.72 ± 4.75 versus -25.72 ± 5.21, p = .559; Free Wall St%, 27.40 ± 8.03 versus -28.71 ± 7.34, p = .304] between the native-conduction and LBBP capture modes, while the RVSP capture mode was associated with a significant reduction in the above parameters compared with the native-conduction mode (p < .0001). The interventricular synchrony in the LBBP group was also superior to the RVSP group significantly.

Conclusion: LBBP is a pacing technique that seems to associate with a positive and protective impact on RV performance.

Keywords: cardiac mechanical synchrony; echocardiography; left bundle branch pacing; physiological pacing; right ventricular function; right ventricular septum pacing; sick sinus syndrome.

Figure 1

Representative examples of right ventricular parameters analysis and QRSd in both groups. Paced QRS duration of LBBP (B, left) was slightly wider than that of that in native‐conduction mode (A, left). While QRSd of RVSP (D, left) mode was obvious wider than that in native‐conduction mode (C, left). As for right ventricular parameters analysis, superimposed end‐diastolic (ED; green) and end‐systolic (ES; yellow) endocardial borders for the right ventricle, and speckle‐tracking analysis of the RV is performed in the RV‐focused apical four‐chamber view, from which dimension, function, global and segmental longitudinal strain were derived. A comprehensive array of data can be visualized. Similar RV‐GLS and time of peak strain in the RV segments was relatively concentrated in native‐conduction (A, right) and LBBP capture modes (B, right) by speckle‐tracking analysis of the RV in a patient with SSS. Poorer RV‐GLS and time of peak strain in the RV segments was discrete showed in RVSP capture mode (D, right) compared with native‐conduction mode (C, right) in another patient with SSS. EDA, right ventricular end diastolic area; EDDmid, right ventricular end diastolic diameter‐mid; EDL, right ventricular end diastolic length; ESA, right ventricular end systolic area; ESL, right ventricular end systolic length; EDDbas, right ventricular end diastolic diameter‐basal; EndoGLS, endocardial global longitudinal strain; ESDbas, right ventricular end systolic diameter‐basal; ESDmid, right ventricular end systolic diameter‐mid; FreeWallSt, strain of right ventricular free wall; MyoGLS, myocardial global longitudinal strain; RV, right ventricle; RV‐FAC, fractional area change.

Figure 2

Comparison of RV and interventricular mechanical synchrony between LBBP and RVSP groups. Smaller means of IVMD during LBBP indicates mechanical contraction of LV earlier than RV (A). LBBP maintained a similar IVSA to native conduction, and was significantly better than that of RVSP (B). There were no significant differences on RV Ts‐6 (C), or RV‐SD4 (D) between pacing mode or native conduction mode in both groups. RV Ts‐6, the standard deviation of the time from QRS onset to peak systolic velocity in six right ventricular lateral wall and interventricular septal segments. IVMD, interventricular mechanical delay; IVSA, the time difference from the onset of the QRS complex to the peak systolic velocities between left ventricle and right ventricle; LBBP, left bundle branch pacing; NCM, native conduction mode; PCM, paced capture mode; RVSP, right ventricular septum pacing; RV‐SD4, the standard deviation of the times to peak‐systolic strain for the four mid‐basal right ventricular segments corrected to the R‐R interval between two QRS complexes.

Figure 3

Comparison of RV function between LBBP and RVSP groups. RVSP manifested significant worsening in RV‐FAC (A) and RV‐GLS (B–D) compared with intrinsic conduction. On the contrary, LBBP is similar to native conduction in all indexes relating to RV hemodynamic effect. EndoGLS, endocardial global longitudinal strain; FreeWallSt, strain of right ventricular free wall; LBBP, left bundle branch pacing; NCM, native conduction mode; PCM, paced capture mode; RVSP, right ventricular septum pacing; RV‐FAC, fractional area change; MyoGLS, myocardial global longitudinal strain.

Figure 4

Comparison of TR and RV function between LBBP subgroups of different pacing sites. AIVS, anterior interventricular septum; E‐T distance, the distance from the electrode fixation site to the tricuspid annulus; EndoGLS, endocardial global longitudinal strain; NCM, native conduction mode; PIVS, posterior interventricular septum; PCM, paced capture mode; RAA, right atrial area; RV‐FAC, fractional area change; TR, tricuspid regurgitation.