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.

Comparisons of long-term clinical outcomes with left bundle branch pacing, left ventricular septal pacing, and biventricular pacing for cardiac resynchronization therapy

BACKGROUND

Left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP) are referred to as left bundle branch area pacing.

OBJECTIVE

This study investigated whether long-term clinical outcomes differ in patients undergoing LBBP, LVSP, and biventricular pacing (BiVP) for cardiac resynchronization therapy (CRT).

METHODS

Consecutive patients with reduced left ventricular ejection fraction (LVEF <50%) undergoing CRT were prospectively enrolled if they underwent successful LBBP, LVSP, or BiVP. The primary composite end point was all-cause mortality or heart failure hospitalization. Secondary end points included all-cause mortality, heart failure hospitalization, and echocardiographic measures of reverse remodeling.

RESULTS

A total of 259 patients (68 LBBP, 38 LVSP, and 153 BiVP) were observed for a mean duration of 28.8 ± 15.8 months. LBBP was associated with a significantly reduced risk of the primary end point by 78% compared with both BiVP (7.4% vs 41.2%; adjusted hazard ratio [aHR], 0.22 [0.08-0.57]; P = .002) and LVSP (7.4% vs 47.4%; aHR, 0.22 [0.08-0.63]; P = .004]. The adjusted risk of all-cause mortality was significantly higher in LVSP than in BiVP (31.6% vs 7.2%; aHR, 3.19 [1.38-7.39]; P = .007) but comparable between LBBP and BiVP (2.9% vs 7.2%; aHR, 0.33 [0.07-1.52], P = .155). Propensity score adjustment also obtained similar results. LBBP showed a higher rate of echocardiographic response (ΔLVEF ≥10%: 60.0% vs 36.2% vs 16.1%; P < .001) than BiVP or LVSP.

CONCLUSION

LBBP yielded long-term clinical outcomes superior to those of BiVP and LVSP. The role of LVSP for CRT needs to be reevaluated because of its high mortality risk.

Left bundle branch pacing vs ventricular septal pacing for cardiac resynchronization therapy

Background

The outcomes of left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP) in patients with heart failure remain to be learned.

Objective

The objective of this study was to assess the echocardiographic and clinical outcomes of LBBP, LVSP, and deep septal pacing (DSP).

Methods

This retrospective study included patients who met the criteria for cardiac resynchronization therapy (CRT) and underwent attempted LBBP in 5 Mayo centers. Clinical, electrocardiographic, and echocardiographic data were collected at baseline and follow-up.

Results

A total of 91 consecutive patients were included in the study. A total of 52 patients had LBBP, 25 had LVSP, and 14 had DSP. The median follow-up duration was 307 (interquartile range 208, 508) days. There was significant left ventricular ejection fraction (LVEF) improvement in the LBBP and LVSP groups (from 35.9 ± 8.5% to 46.9 ± 10.0%, P < .001 in the LBBP group; from 33.1 ± 7.5% to 41.8 ± 10.8%, P < .001 in the LVSP group) but not in the DSP group. A unipolar paced right bundle branch block morphology during the procedure in lead V1 was associated with higher odds of CRT response. There was no significant difference in heart failure hospitalization and all-cause deaths between the LBBP and LVSP groups. The rate of heart failure hospitalization and all-cause deaths were increased in the DSP group compared with the LBBP group (hazard ratio 5.10, 95% confidence interval 1.14-22.78, P = .033; and hazard ratio 7.83, 95% confidence interval 1.38-44.32, P = .020, respectively).

Conclusion

In patients undergoing CRT, LVSP had comparable CRT outcomes compared with LBBP.

An individualized criterion for left bundle branch capture in patients with a narrow QRS complex

BACKGROUND

Left bundle branch (LBB) pacing (LBBP) is a physiological pacing; however, the accuracy of current electrocardiographic criteria for LBBP remains inadequate.

OBJECTIVE

The purpose of this study was to establish a novel individualized criterion to improve the accuracy of LBBP determination in patients with a narrow QRS complex.

METHODS

Patients in whom both LBBP and left ventricular septal pacing (LVSP) were acquired during operation were enrolled. LBB conduction time (LBBCT) was measured from LBB potential (LBBpo) to intrinsic QRS onset. LBBpo-V6RWPT, Native-V6RWPT, and Paced-V6RWPT were respectively measured from LBBpo, intrinsic QRS onset, and stimulus to R-wave peak in V6. ΔV6RWPT was the difference value between Paced-V6RWPT and Native-V6RWPT. The accuracy of ΔV6RWPT criterion for determining LBBP was evaluated.

RESULTS

In all 71 enrolled patients, ΔV6RWPT was <30 ms during LBBP (21.3 ± 4.6 ms; range 9.3-28.3 ms) but was >30 ms during LVSP (38.5 ± 4.6 ms; range 31.1-47.0 ms). The probability distribution of ΔV6RWPT was well separated between LBBP and LVSP. Sensitivity and specificity of the novel criterion of "ΔV6RWPT <30 ms" for determining LBBP both were 100%. However, the optimal cutoff value of Paced-V6RWPT for validation of LBBP was 64.2 ms, and sensitivity and specificity were 84.5% and 97.2%, respectively. Paced-V6RWPT during LBBP was equivalent to LBBpo-V6RWPT in all patients. There was a strong linear correlation between Native-V6RWPT and LBBpo-V6RWPT (r = 0.796; P <.001).

CONCLUSION

ΔV6RWPT could be an accurate individualized criterion for determining LBB capture with high sensitivity and specificity and was superior over the fixed Paced-V6RWPT criterion.

Conduction system pacing: overview, definitions, and nomenclature

Pacing from the right ventricle is associated with an increased risk of development of congestive heart failure, increases in total and cardiac mortality, and a worsened quality of life. Conduction system pacing has become increasingly realized as an alternative to right ventricular apical pacing. Conduction system pacing from the His bundle and left bundle branch area has been shown to provide physiologic activation of the ventricle and may be an alternative to coronary sinus pacing. Conduction system pacing has been studied as an alternative for both bradycardia pacing and for heart failure pacing. In this review, we summarize the clinical results of conduction system pacing under a variety of different clinical settings. The anatomic targets of conduction system pacing are illustrated, and electrocardiographic correlates of pacing from different sites in the conduction system are defined. Ultimately, clinical trials comparing conduction system pacing with standard right ventricular apical pacing and cardiac resynchronization therapy pacing will help define its benefit and risks compared with existing techniques.

Diverse QRS morphology reflecting variations in lead placement for left bundle branch area pacing

AIMS

Left bundle branch area pacing (LBBAP) is a potential alternative to His bundle pacing. This study aimed to investigate the impact of different septal locations of pacing leads on the diversity of QRS morphology during non-selective LBBAP.

METHODS AND RESULTS

Non-selective LBBAP and left ventricular septal pacing (LVSP) were achieved in 50 and 21 patients with atrioventricular block, respectively. The electrophysiological properties of LBBAP and their relationship with the lead location were investigated. QRS morphology and axis showed broad variations during LBBAP. Echocardiography demonstrated a widespread distribution of LBBAP leads in the septum. During non-selective LBBAP, the qR-wave in lead V1 indicated that the primary location for pacing lead was the inferior septum (93%). The non-selective LBBAP lead was deployed deeper than the LVSP lead in the inferior septum. The Qr-wave in lead V1 with the inferior axis in aVF suggested pacing lead placement in the anterior septum. The penetration depth of the non-selective LBBAP lead in the anterior septum was significantly shallower than that in the inferior septum (72 ± 11 and 87 ± 8%, respectively). In lead V6, the deep S-wave indicated the time lag between the R-wave peak and the latest ventricular activation in the coronary sinus trunk, with pacemaker leads deployed closer to the left ventricular apex.

CONCLUSION

Different QRS morphologies and axes were linked to the location of the non-selective LBBAP lead in the septum. Various lead deployments are feasible for LBBAP, allowing diversity in the conduction system capture in patients with atrioventricular block.

Conduction system pacing: Current status and prospects

Conduction system pacing (CSP), including His bundle pacing (HBP) and left bundle branch area pacing (LBBAP), is the most physiological of all pacing modalities for ventricular capture and a potential alternative to right ventricular pacing. It induces electrical and mechanical dyssynchrony, resulting in left ventricular dysfunction, heart failure hospitalization, and atrial arrhythmia. CSP activates the normal conduction system and restores ventricular synchrony. In 2000, HBP was first performed as permanent ventricular pacing, which improved left ventricular systolic dysfunction. The feasibility of permanent HBP has already been demonstrated in patients with bradycardia, although a high capture threshold and limited efficacy for infra-Hisian conduction diseases remain critical issues. The LBBAP is an alternative pacing form that overcomes the limitations of the HBP. A lower capture threshold was obtained at implantation and preserved during the follow-up period in patients with LBBAP. Cardiac resynchronization therapy with HBP or LBBAP may provide better synchronization than the traditional biventricular pacing. Hybrid therapy utilizing HBP or LBBAP in combination with left ventricular pacing has been introduced to treat patients with heart failure. In this review, we have focused on the clinical implications, limitations, and a literature review on CSP.

New criterion to determine left bundle branch capture on the basis of individualized His bundle or right ventricular septal pacing

BACKGROUND

Left bundle branch pacing (LBBP) is an emerging physiological pacing modality. How to differentiate LBBP from left ventricular septal pacing (LVSP) remains challenging.

OBJECTIVE

We aimed to develop a new personalized intraoperative criterion to confirm left bundle branch (LBB) capture in patients with or without heart failure (HF).

METHODS

Patients were enrolled if 12-lead surface electrocardiograms of LBBP, LVSP, temporary His bundle pacing (HBP), and right ventricular septal pacing (RVSP) were recorded during the procedure, with the leads placed in the basal midseptal region. Left ventricular activation time (LVAT) was measured during different pacing modalities. ΔLVAT1 was defined as the difference in LVAT between HBP and LBBP/LVSP. ΔLVAT2 was estimated by the difference in LVAT between RVSP and LBBP/LVSP. ΔLVAT1% and ΔLVAT2% were calculated as the percent reduction of ΔLVAT1 and ΔLVAT2, respectively.

RESULTS

A total of 105 consecutive patients were included, of whom 80 (76.2%) had normal cardiac function (65 LBBP and 15 LVSP) and 25 had HF. Patients with LBBP showed significantly shorter LVAT than did those with LVSP. In patients with normal cardiac function, a cutoff value of ΔLVAT1 > 12.5 ms showed 73.9% sensitivity and 93.3% specificity to confirm LBB capture. In patients with HF, a cutoff value of ΔLVAT1% > 9.8% exhibited great accuracy for LBB capture (sensitivity 92.0%; specificity 92.3%). The optimal value of ΔLVAT2% for differentiating LBBP from LVSP was 21.2%.

CONCLUSION

Temporary HBP and RVSP can serve as references to confirm LBB capture in an individualized fashion in patients with or without HF.

Left bundle branch area pacing outcomes: the multicentre European MELOS study

Aims

Permanent transseptal left bundle branch area pacing (LBBAP) is a promising new pacing method for both bradyarrhythmia and heart failure indications. However, data regarding safety, feasibility and capture type are limited to relatively small, usually single centre studies. In this large multicentre international collaboration, outcomes of LBBAP were evaluated.

Methods and results

This is a registry-based observational study that included patients in whom LBBAP device implantation was attempted at 14 European centres, for any indication. The study comprised 2533 patients (mean age 73.9 years, female 57.6%, heart failure 27.5%). LBBAP lead implantation success rate for bradyarrhythmia and heart failure indications was 92.4% and 82.2%, respectively. The learning curve was steepest for the initial 110 cases and plateaued after 250 cases. Independent predictors of LBBAP lead implantation failure were heart failure, broad baseline QRS and left ventricular end-diastolic diameter. The predominant LBBAP capture type was left bundle fascicular capture (69.5%), followed by left ventricular septal capture (21.5%) and proximal left bundle branch capture (9%). Capture threshold (0.77 V) and sensing (10.6 mV) were stable during mean follow-up of 6.4 months. The complication rate was 11.7%. Complications specific to the ventricular transseptal route of the pacing lead occurred in 209 patients (8.3%).

Conclusions

LBBAP is feasible as a primary pacing technique for both bradyarrhythmia and heart failure indications. Success rate in heart failure patients and safety need to be improved. For wider use of LBBAP, randomized trials are necessary to assess clinical outcomes.

Physiologic Pacing Targeting the His Bundle and Left Bundle Branch: a Review of the Literature

PURPOSE OF REVIEW

Conduction system pacing (CSP) has emerged as a means to preserve or restore physiological ventricular activation via pacing at the His bundle or at more distal targets in the conduction system, including the left bundle branch area. This review examines strengths, weaknesses, and clinical applications of CSP performed via these approaches.

RECENT FINDINGS

His bundle pacing (HBP) has been successfully utilized for standard bradyarrhythmia indications and for QRS correction among patients receiving devices for cardiac resynchronization therapy (CRT). Limitations of HBP pacing have included implant complexity and rising pacing thresholds over time. Left bundle branch area pacing (LBBAP) appears to deliver similar physiological benefits with shorter implant times and more stable thresholds. More recently, hybrid systems utilizing HBP or LBBAP in combination with left ventricular leads have been used to treat heart failure (HF) patients, and may be useful in multilevel or mixed conduction blocks. There is growing interest in CSP for bradycardia and HF indications, although high quality data with randomized controlled trials are needed to help guide future treatment paradigms.

Physiology of Left Ventricular Septal Pacing and Left Bundle Branch Pacing

Following the recognition of the adverse effects of right ventricular pacing, alternative permanent pacing strategies aiming to maintain a synchronous ventricular contraction have been sought. The quest for the optimal pacing site has recently led to several promising and rapidly emerging new pacing strategies, such as left ventricular septal pacing and left bundle branch pacing. In both animal and human studies, these pacing strategies seem to maintain electrical and mechanical activation of the left ventricle to a (near)physiologic level. However, more studies on the long-term effects of both strategies are needed.

What Intracardiac Tracings Have Taught Us About Left Bundle Branch Block

Current electrocardiogram (ECG) criteria for left bundle branch block (LBBB) are largely based on early work in animal models or on mathematical models of cardiac activation. The resulting criteria have modest specificity, and up to one-third of patients who meet current ECG criteria for LBBB may have intact conduction through their His-Purkinje systems. Intracardiac tracings offer the ability to accurately discriminate between LBBB and other causes of delayed activation, which may facilitate the development of more accurate ECG criteria. Assessing these distinctions are particularly salient to applications for conduction system pacing.

Is the pacing site closer to the left ventricular septal endocardium in left bundle branch pacing or in left ventricular septal pacing?

PURPOSE

Distinguishing between left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP) is challenging. This study aimed to compare the echocardiographic distance from the pacing lead tip to the left ventricular (LV) septal endocardium between patients who underwent LBBP and those who underwent LVSP successfully.

METHODS

Fifty-nine consecutive patients (age 71.9 ± 12.0 years, 35.6% male) with traditional indications for permanent cardiac pacing were included (LBBP group, n = 46; LVSP group, n = 13). Unipolar pacing from the final pacing sites generated narrow QRS complexes with a right bundle branch block pattern in all patients. After the procedure, a physician blinded to the group allocation performed echocardiographic measurements of the distance between the lead tip and the LV septal endocardium.

RESULTS

The mean paced QRS duration was comparable between the LBBP group and the LVSP group (105.3 ± 15.6 ms vs. 109.2 ± 9.6 ms, P = 0.287). In the LBBP group, the interval from the left bundle branch potential to QRS onset was 28.7 ± 9.0 ms. During diastole, the mean distance between the lead tip and the LV septal endocardium was 0.6 ± 0.9 mm in the LBBP group and 3.0 ± 1.6 mm in the LVSP group (P < 0.001). During systole, the distance was 1.5 ± 1.4 mm in the LBBP group and 4.3 ± 2.6 mm in the LVSP group (P < 0.001).

CONCLUSIONS

The landing zone of the lead tip was closer to the LV septal endocardium in the patients who underwent LBBP. There is a need for real-time intraprocedural monitoring of the distance between the lead tip and the LV septal endocardium when performing LBBP.

Physiology and Practicality of Left Ventricular Septal Pacing

Left ventricular septal pacing (LVSP) and left bundle branch pacing (LBBP) have been introduced to maintain or correct interventricular and intraventricular (dys)synchrony. LVSP is hypothesised to produce a fairly physiological sequence of activation, since in the left ventricle (LV) the working myocardium is activated first at the LV endocardium in the low septal and anterior free-wall regions. Animal studies as well as patient studies have demonstrated that LV function is maintained during LVSP at levels comparable to sinus rhythm with normal conduction. Left ventricular activation is more synchronous during LBBP than LVSP, but LBBP produces a higher level of intraventricular dyssynchrony compared to LVSP. While LVSP is fairly straightforward to perform, targeting the left bundle branch area may be more challenging. Long-term effects of LVSP and LBBP are yet to be determined. This review focuses on the physiology and practicality of LVSP and provides a guide for permanent LVSP implantation.