A Comparison of the Electrophysiological and Anatomic Characteristics of Pacing Different Branches of the Left Bundle Conduction System

Left bundle fascicular versus left bundle trunk pacing: A comparison of their electrical synchrony parameters

BACKGROUND

Variation in human left bundle branch (LBB) anatomy has a significant effect on the sequence of left ventricular depolarization. However, little is known regarding the electrophysiological characteristics of pacing different LBB fascicles.

OBJECTIVE

We aimed to analyse the different electrocardiographic characteristics of LBB pacing (LBBP) attending to the site of pacing at the LBB system.

METHODS

In 200 consecutive patients with confirmed LBBP, we distinguished left bundle trunk capture (LBTP) from any LB fascicular pacing (LBFP) based on the presence of LB potentials and paced QRS morphologies. We compared them regarding procedure, LBBP criteria and electrical synchrony parameters.

RESULTS

One hundred and seventy-three patients with LBFP were compared to 25 patients with LBTP. Left septal and posterior fascicles were significantly more prevalent than left anterior in LBFP (46.8 %, 41.0 % and 12.2 % respectively). QRS transition criteria (80.0 % vs 61.8 %; p = 0.077), selective LBBP (40.0 vs 21.5 %; p = 0.101), paced QRS width (110.3 ± 16.8 ms vs 115.4 ± 14.9 ms; p = 0.117), V6-RWPT (79.2 ± 10.7 ms vs 75.3 ± 9.7 ms; p = 0.068) and interpeak interval (42.5 ± 19.1 ms vs 45.7 ± 12.9 ms; p = 0.282) were not significantly different between LBTP and LBFP. All short-term complications occurred in LBFP, mainly driven by septal perforations (n = 23), without any difference in the pacing parameters. Among the LBFP subgroups, only aVL-RWPT was longer when the posterior fascicle was paced.

CONCLUSIONS

LBFP is much more prevalent than LBTP in unselected consecutive patients with LBBP. LBFP seems more feasible, and as good as LBTP in terms of electrical synchrony and pacing safety.

Comparison of electrocardiogram parameters and echocardiographic response between distinct left bundle branch area pacing modes in heart failure patients

Background

Left bundle branch area pacing (LBBAP) has become an alternative method for cardiac resynchronization therapy. Various modes of LBBAP have been determined, including left bundle trunk pacing (LBTP), left anterior branch pacing (LAFP) and left posterior branch pacing (LPFP). However, whether the outcomes of various pacing modes differ in heart failure (HF) patients is still unclear. This study aimed to compare the electrophysiological characteristics and echocardiographic response rate among those distinct modes of LBBAP.

Methods

HF patients undergoing successful LBBAP were retrospectively included. Distinct modes of pacing were determined based on paced QRS morphology. The fluoroscopic images were collected to compare the lead tip position between the groups. The electrocardiograms (ECG) before and after LBBAP were used to measure the depolarization (QRS duration [QRSd] and the interventricular delay [IVD]), and the repolarization parameters [QTc, TpeakTend(TpTe), and TpTe/QTc]. The left ventricular ejection fraction (LVEF) and left ventricular end-diastolic diameter (LVEDD) of patients were also recorded. In addition, the lead parameters and certain complications were compared.

Results

A total of 64 HF patients were finally included, consisting of 16 (25.0%) patients in the LBTP group, 22 (34.4%) patients in the LAFP group, and 26 (40.6%) patients in the LPFP group. The distribution features of LBBAP lead tips were significantly related to pacing modes: LBTP was more likely to be in zone 4 while LAFP or LPFP was prone to locate in zone 5. After LBBAP, the ventricular ECG parameters were significantly improved, regardless of pacing modes. Besides, the LVEF of the patients was significantly increased (P < 0.001), and LVEDD was significantly decreased (P < 0.001). There was no difference in the response rate and super-response rate among groups (P > 0.05). In addition, the lead parameters remained stable and no significant difference was observed among groups.

Conclusion

LPFP was the main pacing mode among HF patients after LBBAP. The paced QRS morphology was significantly related to the position of lead tips. After LBBAP, the ventricular depolarization synchronization and repolarization stability were both significantly improved, regardless of pacing modes. There was no significant difference in the echocardiographic response rate among distinct LBBAP modes.

His bundle pacing versus left bundle branch area pacing in patients undergoing atrioventricular node ablation: A prospective and comparative study

BACKGROUND

Pacemaker implantation combined with atrioventricular node ablation (AVNA) is a well-established strategy for uncontrolled atrial arrhythmias. Limited data are available regarding His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) in this setting.

AIM

To compare the outcomes of HBP and LBBAP in patients undergoing pacemaker implantation combined with AVN in routine clinical practice.

METHODS

We prospectively included all patients who underwent AVNA after successful conduction system pacing (CSP) in two hospitals between September 2017 and May 2023. The primary outcome was the 1-year composite of first episode of heart failure hospitalization, symptomatic atrioventricular node reconduction requiring a second AVNA procedure, lead revision or death from any cause.

RESULTS

A total of 164 patients underwent AVNA following successful CSP (68 HBP and 96 LBBAP). Mean pacemaker implantation and AVNA procedure times were shorter in the LBBAP group than the HBP group (46±18 vs 59±23min; P<0.001 and 31±12 vs 43±22min, respectively; P<0.001). Complete atrioventricular block was more frequently obtained in the LBBAP group (88/96 patients [92%] vs 54/68 patients [79%]; P=0.04). One-year freedom from the composite outcome was more frequent in the LBBAP group (89.7% vs 72.9%; hazard ratio 0.32, 95% confidence interval 0.14-0.72; P=0.01). The strategy was similarly effective in both groups with a significant improvement in NYHA class and left ventricular ejection fraction. A secondary pacing threshold elevation >1V occurred only in the HBP group (11%).

CONCLUSION

In this prospective, comparative study, LBBAP provided better 1-year outcomes than HBP.

Difference of ventricular synchrony between LBBP, LBFP and LVSP: A speckle tracking echocardiographic study

PURPOSE

Left bundle branch area pacing (LBBAP) has emerged as a physiological and stable form of pacing. We aim to compare the mechanical ventricular synchrony of LBBP, LBFP, and LVSP.

METHODS

Proximal Left bundle branch pacing (LBBP), left bundle fascicular pacing (LBFP) and left ventricular septal pacing (LVSP) were identified in patients with bradycardia who successfully underwent LBBAP. Patients with left ventricular ejection fraction (LVEF) < 50% or QRS duration (QRSd) ≥ 120 ms were excluded. By using electrocardiograms, the left ventricular activation time (LVAT) and QRS duration (QRSd) were measured to examine electrophysiological synchrony. As indications of mechanical synchrony, global longitudinal strain (GLS), global circumferential strain (GCS), global radial strain (GRS), and peak strain dispersion (PSD) were evaluated by using 2-dimensional speckle tracking echocardiography (2D-STE).

RESULTS

In 56 patients, data were collected during LBBP (n = 18), LBFP (n = 16), and LVSP (n = 22). LVSP resulted in a longer LVAT (91.3 ± 14.9 ms) than LBBP (77.1 ± 10.8 ms, P < 0.05) and LBFP (72.1 ± 9.6 ms, P < 0.05), but all three groups had similar QRSd. There were no differences in GLS, GCS, GRS, or PSD between LBBP, LBFP, and LVSP.

CONCLUSIONS

In patients with normal cardiac function and narrow QRS, though LBBAP with LBB capture resulted in better electrophysiological synchrony than without, the mechanical synchrony of the three groups was comparable.

Exploring QRS Area beyond Patient Selection in CRT-Can It Guide Left Ventricular Lead Placement?

Vectorcardiographic QRS area is a promising tool for patient selection and implantation guidance in cardiac resynchronization therapy (CRT). Research has mainly focused on the role of QRS area in patient selection for CRT. Recently, QRS area has been proposed as a tool to guide left ventricular lead placement in CRT. Theoretically, vector-based electrical information of ventricular fusion pacing, calculated from the basic 12-lead ECG, can give real-time insight into the extent of resynchronization at any LV lead position, as well as any selected electrode on the LV lead. The objective of this review is to provide an overview of the background of vectorcardiographic QRS area and its potential in optimizing LV lead location in order to optimize the benefits of CRT.

Redefining QRS transition to confirm left bundle branch capture during left bundle branch area pacing

Background

QRS transition criteria during dynamic manoeuvers are the gold-standard for non-invasive confirmation of left bundle branch (LBB) capture, but they are seen in <50% of LBB area pacing (LBBAP) procedures.

Objective

We hypothesized that transition from left ventricular septal pacing (LVSP) to LBB pacing (LBBP), when observed during lead penetration into the deep interventricular septum (IVS) with interrupted pacemapping, can suggest LBB capture.

Methods

QRS transition during lead screwing-in was defined as shortening of paced V6-R wave peak time (RWPT) by ≥10 ms from LVSP to non-selective LBBP (ns-LBBP) obtained during mid to deep septal lead progression at the same target area, between two consecutive pacing manoeuvres. ECG-based criteria were used to compared LVSP and ns-LBBP morphologies obtained by interrupted pacemapping.

Results

Sixty patients with demonstrated transition from LVSP to ns-LBBP during dynamic manoeuvers were compared to 44 patients with the same transition during lead screwing-in. Average shortening in paced V6-RWPT was similar among study groups (17.3 ± 6.8 ms vs. 18.8 ± 4.9 ms for transition during dynamic manoeuvres and lead screwing-in, respectively; p = 0.719). Paced V6-RWPT and aVL-RWPT, V6-V1 interpeak interval and the recently described LBBP score, were also similar for ns-LBBP morphologies in both groups. LVSP morphologies showed longer V6-RWPT and aVL-RWPT, shorter V6-V1 interpeak interval and lower LBBP score punctuation, without differences among the two QRS transition groups. V6-RWPT < 75 ms or V6-V1 interpeak interval > 44 ms criterion was more frequently achieved in ns-LBBP morphologies obtained during lead screwing-in compared to those obtained during dynamic manoeuvres (70.5% vs. 50%, respectively p = 0.036).

Conclusions

During LBBAP procedure, QRS transition from LVSP to ns-LBBP can be observed as the lead penetrates deep into the IVS with interrupted pacemapping. Shortening of at least 10 ms in paced V6-RWPT may serve as marker of LBB capture.