His-Purkinje Conduction System Pacing in Atrioventricular Block: New Insights into Site of Conduction Block

Current role of Conduction System Pacing in Patients Requiring Permanent Pacing

His bundle pacing (HBP) and left bundle branch pacing (LBBP) are novel methods of pacing directly pacing the cardiac conduction system. HBP while developed more than two decades ago, only recently moved into the clinical mainstream. In contrast to conventional cardiac pacing, conduction system pacing including HBP and LBBP utilizes the native electrical system of the heart to rapidly disseminate the electrical impulse and generate a more synchronous ventricular contraction. Widespread adoption of conduction system pacing has resulted in a wealth of observational data, registries, and some early randomized controlled clinical trials. While much remains to be learned about conduction system pacing and its role in electrophysiology, data available thus far is very promising. In this review of conduction system pacing, the authors review the emergence of conduction system pacing and its contemporary role in patients requiring permanent cardiac pacing.

Conduction system pacing: how far are we from the "electrical" bypass?

Conduction system pacing is an alternative practice to conventional right ventricular apical pacing. It is a method that maintains physiologic ventricular activation, based on a correct pathophysiological basis, in which the pacing lead bypasses the lesion of the electrical fibers and the electrical impulse transmits through the intact adjacent conduction system. For this reason, it might be reasonably characterized by the term "electrical bypass" compared to the coronary artery bypass in revascularization therapy. In this review, reference is made to the sequence of events in which conventional right ventricular pacing may cause adverse outcomes. Furthermore, there is a reference to alternative strategies and pacing sites. Interest focuses on the modalities for which there are data from the literature, namely for the right ventricular (RV) septal pacing, the His bundle pacing (HBP), and the left bundle branch pacing (LBBP). A more extensive reference is about the HBP, for which there are the most updated data. We analyze the considerations that limit HBP-wide application in three axes, and we also present the data for the implantation and follow-up of these patients. The indications with their most important studies to date are then described in detail, not only in their undoubtedly positive findings but also in their weak aspects, because of which this pacing mode has not yet received a strong recommendation for implementation. Finally, there is a report on LBBP, focusing mainly on its points of differentiation from HBP.

His bundle pacing in nodal versus infranodal atrioventricular block: a mid-term follow-up study

INTRODUCTION

This study evaluated the feasibility of His bundle pacing (HBP) in consecutive, unselected patients with advanced atrioventricular block (AVB) over a medium-term follow-up period, comparing procedural characteristics between nodal and infranodal sites of the conduction block.

MATERIALS AND METHODS

Seventy-five consecutive patients with second-degree or third-degree AVB in which HBP was attempted were prospectively included in this study. The clinical and procedural-related characteristics of the patients were recorded at baseline and over a mid-term follow-up.

RESULTS

72% of the patients had normal QRS duration at baseline. Intracardiac electrograms revealed nodal AVB in 46 patients (61.3%). The permanent HBP procedural success was significantly higher in nodal AVB (84.8%) vs infranodal AVB (31%). There was no statistical difference between paced QRS duration, impedance, pacing and sensing thresholds and fluoroscopy time in the two groups. Infranodal block, baseline QRS duration, left bundle branch block morphology and ejection fraction were significantly associated with HBP procedural failure. The patients were followed for a period of 627.71±160.93 days. There were no significant differences in parameters at follow-up. An increase of >1 V in the His bundle (HB) capture threshold was encountered in one patient with infranodal AVB (11.1 %) and in four patients with nodal AVB (10.25%).

CONCLUSION

Permanent HBP is a feasible pacing technique in nodal AVB with a high success rate and stable thresholds in the medium term. Most infranodal blocks are located within the HB, so there is still the possibility to capture the conduction system, although with lower success rates.

Left Bundle Branch Pacing: A Paradigm Shift in Physiological Pacing for Patients With Atrioventricular Block and Preserved Left Ventricular Systolic Function, A Systematic Review and Meta-analysis

His-Purkinje conduction system pacing (HPCSP) via His bundle pacing (HBP) and Left Bundle Branch Pacing (LBBP) offer a physiological approach to pacing by restoring normal ventricular activation. This meta-analysis compares the feasibility, outcomes, and success rates of HBP and LBBP in patients with atrioventricular block (AVB) and preserved left ventricular function. A systematic search identified studies comparing LBBP with HBP in AVB patients with preserved systolic function. Primary outcomes included QRS duration, success rates, pacing threshold, and improvement in R-wave amplitudes. Secondary outcomes were procedure time and fluoroscopy time. Random-effects models calculated odds ratios (OR) and mean differences (MD) with 95% confidence intervals (CI). Methodological quality was assessed using the Newcastle-Ottawa scale. Among 382 screened articles, seven observational studies involving 1035 patients were analyzed. The mean age was 69.9 years, the mean LVEF was 59.3%, and the average follow-up duration was 8.7 months. LBBP showed higher R-wave amplitudes (MD 7.88, 95% CI 7.26 to 8.50, P < 0.0001) and lower pacing thresholds (MD -0.64, 95% CI -0.81 to -0.47, P < 0.0001) compared to HBP. LBBP had shorter procedure time (MD -17.81, 95% CI -30.44 to -5.18, P = 0.006) and reduced fluoroscopy time (MD -5.39, 95% CI -8.81 to -1.97, P = 0.002). No significant differences were observed in QRS duration or success rates. LBBP offers advantages over HBP, including improved electrical activation, lower pacing thresholds, and shorter procedure and fluoroscopy times. Success rates and QRS duration reductions were comparable between LBBP and HBP. These findings support LBBP as a feasible and effective alternative to HBP in AVB patients with preserved systolic function.

Conduction system pacing for ventricular pacing requirement is feasible and effective on patients with hypertrophic cardiomyopathy and cardiac dysfunction

Objective

We aimed to evaluate the feasibility and safety of his-bundle pacing (HBP) and left bundle branch pacing (LBBP) in patients with hypertrophic cardiomyopathy (HCM) and heart failure (HF).

Methods

Patients with HF and interventricular septal thickness (IVST) ≥ 13 mm resulted from HCM, who accepted conduction system pacing (CSP) with a percentage of ventricular pacing > 40% from May 2018 to April 2022 were consecutively enrolled in our center. LBBP was preferred and HBP was the alternative therapy unless IVST ≥ 16 mm or LBBP failed, whereas LBBP would be the alternative therapy if HBP failed in patients with IVST ≥ 16 mm. All patients were followed up for at least one year. Data including clinical, echocardiographic parameters and electrocardiogram measurements, were collected and evaluated in patients with and without left ventricular ejection fraction (LVEF) < 50%.

Results

A total of 27 patients (65.93 ± 9.09 years old) were enrolled and only 3 patients failed in CSP (11.11%) via LBBP (6/13) and HBP (18/21) procedures. LVEF (P = 0.521), left ventricular end-diastolic diameter (LVEDD) (P = 0.816), and QRS duration (P = 0.928) did not worsen after CSP, and left atrial diameter (LAD) (49.58 ± 8.99 mm vs.47.04 ± 9.82 mm, P = 0.045) tended to improve slightly after 19.19 ± 7.71 months follow-up. Of note, LVEF (39.22%±7.51% vs. 45.22%±9.59%, P = 0.015), LVEDD (52.11 ± 10.10 mm vs. 48.33 ± 9.07 mm, P = 0.037), LAD (50.33 ± 8.93 mm vs. 46.11 ± 5.97 mm, P = 0.013) and New York Heart Association (NYHA) grade (2.67 ± 0.5 vs. 1.38 ± 1.02, P = 0.029) improved in 9 patients with LVEF < 50%, whereas LVEF (P = 0.372), LVEDD (P = 0.665), LAD (P = 0.093) and NYHA grade (P = 0.452) did not deteriorate in patients with preserved ejection fraction.

Conclusion

CSP was safe and feasible in patients with HCM and cardiac dysfunction, and did not worsen cardiac performance especially in patients with LVEF < 50%. HBP might be an effective alternative to LBBP in patients with significantly thickened interventricular septum.

A Personalized Approach to the Management of Congestion in Acute Heart Failure

Heart failure (HF) is the common final pathway of several conditions and is characterized by hyperactivation of numerous neurohumoral pathways. Cardiorenal interaction plays an essential role in the progression of the disease, and the use of diuretics is a cornerstone in the treatment of hypervolemic patients, especially in acute decompensated HF (ADHF). The management of congestion is complex and, to avoid misinterpretations and errors, one must understand the interface between the heart and the kidneys in ADHF. Congestion itself may impair renal function and must be treated aggressively. Transitory elevations in serum creatinine during decongestion is not associated with worse outcomes and diuretics should be maintained in patients with clear hypervolemia. Monitoring urinary sodium after diuretic administration seems to improve the response to diuretics as it allows for adjustments in doses and a personalized approach. Adequate assessment of volemia and the introduction and titration of guideline-directed medical therapy are mandatory before discharge. An early visit after discharge is highly recommended, to assess for residual congestion and thus avoid readmissions.

Clinical, procedural and lead outcomes associated with different pacing techniques: a network meta-analysis

BACKGROUND

His- Purkinje system pacing (HPSP) techniques have been proposed as alternative to biventricular pacing (BVP) and right ventricular pacing (RVP).

OBJECTIVE

To compare data regarding clinical, procedural and lead outcomes associated with different pacing techniques.

METHODS

An accurate search of online scientific libraries (from inception to May, 12,022) was performed. Thirty-three studies were included in the meta-analysis involving 4386 patients, of whom 1324 receiving RVP, 1032 patients receiving BVP, 1069 patients receiving his-bundle pacing (HBP) and 968 patients receiving left bundle branch pacing (LBBP).

RESULTS

LBBP provided a statistically significant increase in LVEF relative to HBP (0.4473 [0.0584; 0.8361] p = 0.0242) and BVP (0.6733 [0.4734; 0.8732] p < 0.0001) in patients with cardiac resynchronization therapy indication. LBBP and HBP significantly decreased QRS duration as compared to BVP, with largest QRS narrowing obtained by LBBP (-0.4951 [-0.9077; -0.0824] p = 0.0187). As compared to LBBP, HBP was associated with a significant increase of pacing threshold (p = 0.0369) and significant reduction of R-wave amplitude over time (p = 0.027). LBBP was associated with significant reduction in RR of hospitalization for HF (HFH) as compared to both BVP (p = 0.0343) and HBP (p = 0.0476), whereas, as compared to RVP, the risk of lead issues was significantly higher with BVP (p = 0.0424) and HBP (p = 0.0298), but not for LBBP (p = 0.425).

CONCLUSIONS

As compared to other pacing techniques, LBBP significantly improved LVEF, narrowed QRS duration and reduced HFHs, with steadily lower capture thresholds and higher R-wave amplitude, and without increasing lead issues.

[Arrhythmias : Update on ablations and devices]

The field of invasive electrophysiology is technically evolving and especially the catheter ablation treatment of symptomatic atrial fibrillation (AF). The technically innovative method of so-called electroporation (pulsed field ablation, PFA) is characterized by a rapid and effective treatment of AF. The current study data confirm a high success rate for ablation and a good safety profile in the treatment of paroxysmal and persistent AF. In the field of radiofrequency ablation (RF) of AF the modified form of energy transfer, the very high-power short-duration (vHPSD) protocols, show good results and can reduce the procedural time. There are also technical innovations in other single-shot devices. There is a device based on the RF technique that could show good clinical results in an initial study and can combine the targeted delivery of RF energy with the advantages of a single-shot device. For ventricular tachycardia (VT) there are innovations in the diagnostics and clarification in the new European guidelines that were presented in August 2022. These make individual recommendations for different types of cardiomyopathy. There are also technical developments in the field of active rhythm implants. In cardiac pacemaker treatment and specifically for conduction system pacing (CSP) there is evidence for a targeted stimulation of the bundle of His or left bundle branch pacing (LBBP). This form of stimulation is particularly advantageous for patients with heart failure and a broad QRS complex. For leadless pacemakers (leadless pacing) there are now good long-term results and also a two-chamber approach.

A Continuous Pacing and Recording Technique for Differentiating Left Bundle Branch Pacing From Left Ventricular Septal Pacing: Electrophysiologic Evidence From an Intrapatient-Controlled Study

BACKGROUND

Left bundle branch pacing (LBBP) is a promising approach for achieving near-physiologic pacing. However, differentiating LBBP from left ventricular septal endocardial pacing (LVS(e)P) remains a challenge. This study aimed to establish a simple and effective method for differentiating LBBP from LVS(e)P and to evaluate their electrophysiologic characteristics.

METHODS

LBBP, using continuous uninterrupted pacing and real-time monitoring of electrocardiograms along with intracardiac electrograms, was performed in 97 consecutive patients. We evaluated the electrophysiologic characteristics observed during LBBP using 6 modalities: right ventricular septal pacing (RVSP), intraventricular septal pacing (IVSP 1 and 2), LVS(e)P, nonselective LBBP (NSLBBP), and selective LBBP (SLBBP).

RESULTS

Of the 97 patients, 87 (89.7%) met the criteria (abrupt change in paced QRS morphology with a transition from Qr to QR/qR in lead V1 and shortening of stimulus to V6 R-wave peak time [Stim-V6RWPT] of ≥ 10 ms with constant output while rather than after lead screwing) for nonselective left bundle branch (LBB) capture. Selective LBB capture was observed in 82 patients (84.5%). The Stim-V6RWPT of NSLBBP and SLBBP were significantly shorter than LVS(e)P (respectively, 67.1 ± 8.7 ms, 67.0 ± 9.3 ms, and 82.1 ± 10.9 ms). Stim-QRSend was the narrowest in IVSP2 (136.6 ± 15.2 ms) instead of NSLBBP (140.0 ± 17.1 ms).

CONCLUSIONS

The uninterrupted pacing technique for differentiating LBBP from LVS(e)P in the same group of patients is feasible. Electrophysiologic evidence from our intrapatient-controlled study shows that LBBP and LVS(e)P differ in ventricular electrical synchronization.

A systematic review and Bayesian network meta-analysis comparing left bundle branch pacing, his bundle branch pacing, and right ventricular pacing for atrioventricular block

BACKGROUND

Although right ventricular pacing (RVP) is recommended by most of the guidelines for atrioventricular block, it can cause electrical and mechanical desynchrony, impair left ventricular function, and increase the risk of atrial fibrillation. Recently, the His-Purkinje system pacing, including His bundle pacing (HBP) and left bundle branch pacing (LBBP), has emerged as a physiological pacing modality. However, few studies have compared their efficacy and safety in atrioventricular block (AVB).

METHODS AND RESULTS

The PubMed, Web of Science, Cochrane Library, and ScienceDirect databases were searched for observational studies and randomized trials of patients with atrioventricular block requiring permanent pacing, from database inception until 10 January 2022. The primary outcomes were complications and heart failure hospitalization. The secondary outcomes included changes in left ventricular ejection fraction (LVEF) and left ventricular end-diastolic diameter (LVEDD), pacing parameters, procedure duration, and success rate. After extracting the data at baseline and the longest follow-up duration available, a pairwise meta-analysis and a Bayesian random-effects network meta-analysis were performed. Odds ratios (ORs) with 95% confidence intervals (CIs) or 95% credible intervals (CrIs) were calculated for dichotomous outcomes, whereas mean differences (MDs) with 95% CIs or 95% CrIs were calculated for continuous outcomes. Seven studies and 1,069 patients were included. Overall, 43.4% underwent LBBP, 33.5% HBP, and 23.1% RVP. Compared with RVP, LBBP and HBP were associated with a shorter paced QRS duration and a more preserved LVEF. HBP significantly increased the pacing threshold and reduced the R-wave amplitude. There was no difference in the risk of complications or the implant success rate. The pacing threshold remained stable during follow-up for the three pacing modalities. The pacing impedance was significantly reduced in HBP, while a numerical but non-significant pacing impedance decrease was observed in both LBBP and RVP. LBBP was associated with an increased R-wave amplitude during follow-up.

CONCLUSION

In this systematic review and network meta-analysis, HBP and LBBP were superior to RVP in paced QRS duration and preservation of LVEF for patients with atrioventricular block. LBBP was associated with a lower pacing threshold and a greater R-wave amplitude than HBP. However, the stability of the pacing output of LBBP may be a concern. Further investigation of the long-term efficacy in left ventricular function and the risk of heart failure hospitalization is needed.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=315046], identifier [CRD42022315046].

Clinical Outcomes Of Left Bundle Branch Area Pacing Compared To His Bundle Pacing

BACKGROUND

His bundle pacing (HBP) is the most physiologic form of pacing and has been associated with reduced risk for heart failure hospitalization (HFH) and mortality compared to right ventricular pacing. Left bundle branch area pacing (LBBAP) is a safe and effective alternative option for patients needing ventricular pacing.

OBJECTIVE

The aim of this study was to compare the clinical outcomes between LBBAP and HBP among a large cohort of patients undergoing permanent pacemaker implantation.

METHODS

This observational registry included consecutive patients with AV block/AV node ablation who underwent de novo permanent pacemaker implantations with successful LBBAP or HBP between April 2018 to October 2020. The primary outcome was the composite endpoint of time to death from any cause or HFH. Secondary outcomes included the composite endpoint among patients with prespecified ventricular pacing burden and individual outcomes.

RESULTS

The study population included 359 patients who met the inclusion criteria (163 in the HBP and 196 in the LBBAP group). Paced QRSd during LBBAP was similar to HBP (125 ± 20.2 vs 126 ± 23.5 ms, p=0.643). There were no statistically significant differences in the primary composite outcome in LBBAP (17.3%) compared to HBP (24.5%) (HR 1.15, CI 0.72-1.82, p = 0.552). Secondary outcomes of death (10 vs 17%; HR 1.3, CI 0.73-2.33, p=0.38) and HFH (10 vs 12%; HR 1.02,CI 0.54-1.94, p=0.94) were not different among both groups.

CONCLUSIONS

There were no statistically significant differences in the clinical outcomes of death or HFH in LBBAP when compared to HBP. This article is protected by copyright. All rights reserved.

The Physiologic Mechanisms of Paced QRS Narrowing During Left Bundle Branch Pacing in Right Bundle Branch Block Patients

Left bundle branch pacing (LBBP) is a physiological pacing technique that captures the left bundle branch (LBB) directly, causing the left ventricle (LV) to be excited earlier than the right ventricle (RV), resulting in a “iatrogenic” right bundle branch block (RBBB) pacing pattern. Several studies have recently shown that permanent LBBP can completely or partially narrow the wide QRS duration of the intrinsic RBBB in most patients with bradycardia, although the mechanisms by which this occurs has not been thoroughly investigated. This article presents a review of the LBBP in patients with intrinsic RBBB mentioned in current case reports and clinical studies, discussing the technique, possible mechanisms, future clinical explorations, and the feasibility of eliminating the interventricular dyssynchronization accompanied with LBBP.

Clinical Outcomes Associated With His-Purkinje System Pacing vs. Biventricular Pacing, in Cardiac Resynchronization Therapy: A Meta-Analysis

Aims

His-Purkinje system pacing has recently emerged as an alternative to biventricular pacing (BIVP) in cardiac resynchronization therapy (CRT). The aim of this study was to conduct a meta-analysis comparing the clinical outcomes associated with His-Purkinje system pacing (HPSP) vs. BIVP in patients with heart failure. There is also a comparison of clinical outcomes of His-bundle pacing (HBP) and left bundle branch pacing (LBBP) in the His-Purkinje system.

Methods

We searched the Cochrane Library, Embase, and PubMed, for studies published between January 2010 and October 2021 that compared the clinical outcomes associated with HPSP vs. BIVP and HBP vs. LBBP in HPSP in patients who underwent CRT. The pacing threshold, R-wave amplitudes, QRS duration, New York Heart Association functional (NYHA), left ventricular ejection fraction (LVEF), and LV end-diastolic diameter (LVEDD) of heart failure, at follow-up, were extracted and summarized for meta-analysis.

Results

A total of 18 studies and 1517 patients were included in our analysis. After a follow-up period of 9.3 ± 5.4 months, the HPSP was found to be associated with shorter QRS duration in the CRT population compared to that in the BIVP (SMD, −1.17; 95% CI, −1.56 to −0.78; P &lt; 0.00001; I2 = 74%). No statistical difference was verified between HBP and LBBP on QRS duration (SMD, 0.04; 95% CI, −0.32 to 0.40; P = 0.82; I2 = 84%). In the comparison of HPSP and BIVP, the LBBP subgroup showed improved LVEF (SMD, 0.67; 95% CI, 0.42–0.91; P &lt; 0.00001; I2 = 0%), shorter LVEDD (SMD, 0.59; 95% CI, 0.93–0.26; P = 0.0005; I2 = 0%), and higher New York Heart Association functional class (SMD, −0.65; 95% CI, −0.86 to −0.43; P &lt; 0.00001; I2 = 45%). In terms of pacing threshold and R-wave amplitude clinical outcomes, LBBP has a lower pacing threshold (SMD, 1.25; 95% CI, 1.12–1.39; P &lt; 0.00001; I2 = 47%) and higher R-wave amplitude (MD, −7.88; 95% CI, −8.46 to −7.31; P &lt; 0.00001; I2 = 8%) performance compared to HBP.

Conclusion

Our meta-analysis showed that the HPSP produced higher LVEF, shorter QRS duration, and higher NYHA functional class in the CRT population than the BIVP as observed on follow-up. LBBP has a lower pacing threshold and higher R-wave amplitude. HPSP may be a new and promising alternative to BIVP in the future.

Conduction System Pacing Following Septal Myectomy: Insights into Site of Conduction Block

INTRODUCTION

Septal myectomy for obstructive hypertrophic cardiomyopathy (HCM) is associated with conduction block; however, the electrophysiological characteristics of conduction block have not been well characterized. The aim of study was to assess the feasibility and safety of His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) in patients with septal myectomy-associated conduction block.

METHODS AND RESULTS

Patients with HCM and indications for pacing or cardiac resynchronization therapy after septal myectomy were included. Electrophysiological mapping was performed to identify the site of block. The success rates and pacing characteristics of HBP and LBBAP were also recorded. The echocardiographic data and complications were documented and tracked during follow-up. Ten patients with atrioventricular block (AVB) or left bundle branch block (LBBB) post-myectomy were included in the study. The site of block was infranodal in the nine patients with AVB. HBP failed due to the lack of distal His bundle capture (N=7) or LBBB correction (N=3). LBBAP was successful in nine patients and failed in one. QRS duration narrowed from 163.3 ± 16.6 ms after surgery to 123.6 ± 15.8 ms during LBBAP (P<0.001). The mean depth of the leads was 13.3 ± 4.0 mm (range from 10 to 20 mm). At a mean follow-up of 5.3 ± 3.9 months, pacing parameters and left ventricular ejection fraction remained stable.

CONCLUSIONS

Electrophysiological mapping revealed that the site of block was infra-Hisian and not correctable with HBP in patients with HCM post-myectomy. LBBAP appears to be a more feasible physiological strategy for these patients. This article is protected by copyright. All rights reserved.

His-Purkinje conduction system pacing: A systematic review and network meta-analysis in bradycardia and conduction disorders

BACKGROUND

His-Purkinje conduction system pacing (HPCSP) has emerged as an effective alternative to overcome the limitations of right ventricular pacing (RVP) via physiological left ventricular activation, but there remains a paucity of comparative information for His bundle pacing (HBP) and left bundle branch pacing (LBBP).

METHODS

A Bayesian random-effects network analysis was conducted to compare the relative effects of HBP, LBBP, and RVP in patients with bradycardia and conduction disorders. PubMed, Embase, Cochrane Library, and Web of Science were systematically searched from database inception until September 21, 2021.

RESULTS

Twenty-eight studies involving 4160 patients were included in this meta-analysis. LBBP significantly improved success rate, pacing threshold, pacing impedance, and R-wave amplitude compared with HBP. LBBP also demonstrated a nonsignificant trend towards superior outcomes of lead complications, heart failure hospitalization, atrial fibrillation, and all-cause death. However, HBP was associated with significantly shorter paced QRS duration relative to LBBP. Despite higher success rates, shorter procedure/fluoroscopy duration, and fewer lead complications, patients receiving RVP were more likely to experience reduced left ventricular ejection fraction, longer paced QRS duration, and higher rates of heart failure hospitalization than those receiving HPCSP. No statistical differences were observed in the remaining outcome measures.

CONCLUSIONS

This network meta-analysis demonstrates the efficacy and safety of HPCSP for the treatment of bradycardia and conduction disorders, with differences in pacing parameters, electrophysiology characteristics, and clinical outcomes between HBP and LBBP. Larger-scale, long-term comparative studies are warranted for further verification.