Permanent, direct His-bundle pacing: a novel approach to cardiac pacing in patients with normal His-Purkinje activation

His Bundle Pacing – Stand-alone or adjunctive physiological pacing: a systematic review

His-bundle pacing (HBP) appears to be a viable stand-alone or adjunctive physiological pacing therapy in pacemaker dependent patients. It could also serve as an effective adjunct or alternative pacing therapy for heart failure patients who require cardiac resynchronization therapy or pacemaker upgrade. His-bundle pacing has demonstrated improvement of His-Purkinje conduction, left ventricular electrical / mechanical synchronization, and left ventricular ejection fraction (LVEF) compared with right ventricle pacing. Patients who have high pacing dependence and/or LVEF impairment would benefit most from HBP in terms of heart failure hospitalization and LVEF improvement. Mortality benefit has not been consistently demonstrated in latest meta-analysis. The long-term clinical benefit and safety profile of HBP remains to be explored in future studies.  Key words: His bundle pacing, physiologic pacing, upgrade pacing

Clinical outcomes of left bundle branch pacing compared to right ventricular apical pacing in patients with atrioventricular block

Background

Left bundle branch pacing (LBBP) can produce near normalization of QRS duration. This has recently emerged as alternative technique to right ventricular pacing and His bundle pacing.

Hypothesis

The purpose of this study is to evaluate clinical outcomes of LBBP compared to right ventricular apical pacing (RVAP).

Methods

A total of 70 AVB patients with indications for ventricular pacing were retrospectively studied. LBBP was attempted in 33 patients, classified as LBBP group. The other patients were classified as RVAP group. Pacing parameters, electrocardiogram and echocardiogram characteristics, heart failure hospitalization (HFH), and atrial fibrillation (AF) were evaluated perioperatively and at follow‐ups. Patients were followed in the device clinic for a minimum of 12 months and up to 24 months at a 3–6 monthly interval.

Results

LBBP was successful in 29 of 33(87.9%) patients while all 37 of the remaining patients successfully underwent RVAP. Paced QRS duration was significantly narrower in the LBBP group compare to RVAP(110.75 ± 6.77 ms vs. 154.29 ± 6.96 ms, p = .000) at implantation, and the difference persisted during follow‐ups. Pacing thresholds (at implantation: 0.68 ± 0.22 V in the LBBP group and 0.73 ± 0.23 V in the RVAP group, p = .620) remained low and stable during follow‐ups. The cardiac function in the LBBP group remained stable during follow‐ups (LVEF%:55.08 ± 4.32 pre‐operation and 54.17 ± 4.34 at the end of follow‐up, p = .609), and better than RVAP group (LVEF%: 54.17 ± 4.34 vs. 50.14 ± 2.14, p = .005). Less HFH was observed in the LBBP group (2/29,6.89%) compared to RVAP group (10/37,27.03%).

Conclusions

The present investigation demonstrates the safety and feasibility of LBBP that produces narrower paced QRS duration than RVAP. LBBP is associated with reduction in the occurrence of pacing‐induced left ventricular dysfunction and HFH compared to RVAP in patients requiring permanent pacemakers.

Innovations in Cardiac Implantable Electronic Devices

Cardiac implantable electronic devices (CIEDs) are essential for the management of a variety of cardiac conditions, including tachyarrhythmias, bradyarrhythmias, and medically refractory heart failure (HF). Recent advancements in CIED technology have led to innovative solutions that overcome shortcomings associated with traditional devices or address unmet needs. Leadless pacemakers, subcutaneous implantable cardioverter defibrillators (ICDs), and extravascular ICDs eliminate lead-related complications common with conventional pacemakers or ICDs. Conduction system pacing (His bundle pacing and left bundle branch pacing) is a more physiologic method of pacing and avoids the deleterious consequences associated with long-term right ventricular pacing. For HF-related devices, cardiac contractility modulation is an emerging therapy that bridges a gap for many patients ineligible for cardiac resynchronization therapy and has been shown to improve HF symptoms and decrease hospitalizations and mortality in select patients. Implantable pulmonary artery pressure monitors help guide HF management and reduce hospitalizations. Lastly, new phrenic nerve stimulating devices are being utilized to treat central sleep apnea, a common comorbidity associated with HF. While further long-term studies are still underway for many of these new technologies, it is anticipated that these devices will become indispensable therapeutics in the expanding cardiovascular armamentarium.

Efficacy of upgrading to left bundle branch pacing in patients with heart failure after right ventricular pacing

BACKGROUND

Chronic right ventricular (RV) pacing is associated with an increased incidence of heart failure and mortality. Left bundle branch (LBB) pacing could produce near-physiological electrical activation and mechanical synchrony. We aimed to report the effects of upgrading to LBB pacing in heart failure patients after chronic RV pacing.

METHODS

The indications included pacing-induced cardiomyopathy (PICM) in Group 1 and heart failure after RV pacing with left ventricular ejection fraction (LVEF) ≥ 50% in Group 2. LBB pacing was achieved by penetrating the pacing lead to the subendocardium of left-sided interventricular septum through the venous access. Left ventricular activation time (LVAT) was measured from the pacing stimulus to the ascending peak of lead V5 or V6. All patients underwent clinical and echocardiographic evaluations before and after upgrading.

RESULTS

Totally 27 patients (13 in Group 1 and 14 in Group 2) were consecutively enrolled. The mean follow-up time after upgrade was 10.4 ± 6.1 months. Paced QRS duration was significantly shortened from 174.1 ± 15.8 milliseconds to 116.6 ± 11.7 milliseconds (p < .0001). The mean LVAT was 83.2 ± 11.7 milliseconds. LVEF increased from 40.3 ± 5.2% before upgrading to 48.1 ± 9.5% at follow-up in patients with PICM. Serum N-terminal probrain natriuretic peptide levels decreased and New York Heart Association classification improved in both groups. No upgrade-related complications were observed.

CONCLUSIONS

Upgrading to LBB pacing was feasible and effective with improved cardiac function in heart failure patients with both reduced and preserved LVEF after RV pacing.

Effects of Rhythm and Rate-Controlling Drugs in Patients With Permanent His-Bundle Pacing

Introduction: Antiarrhythmic drug therapy can affect pacemaker parameters in both the atrial and ventricular myocardium. It is not known whether antiarrhythmic drugs impact His bundle pacing/sensing parameters and His to ventricle (H-V) intervals following permanent His bundle pacing (HBP). The aims of the study were to prospectively determine the influence of rhythm and rate-controlling drugs on pacing parameters and H-V conduction after His bundle lead implantation and to assess the impact of rhythm and rate-controlling drugs on the safety of HBP.

Materials and Methods: Patients (N = 140) with QRS duration < 120 ms who met permanent pacing indications were prospectively enrolled. Propafenone, lidocaine, and adenosine were injected intravenously after implantation of 3,830 lead during the procedure. Metoprolol succinate, amiodarone, and digoxin were taken orally for 1 month. Pacing parameters before and after drug intervention was measured, including His capture threshold, sensing and impedance, H-V interval, and conduction.

Results: There were no statistically significant differences in His bundle pacing thresholds, impedance, and sensing after drug intervention at implantation or during a 2-month follow-up (P > 0.05). The HV interval was not affected except in the large-dose propafenone group where HV interval prolonged (P = 0.001). All patients maintained 1:1 H-V conduction following drug administration.

Conclusion: There was no adverse impact on the HBP parameters or H-V conduction after the administration of commonly used dosage of rhythm and rate-controlling drugs. The drugs were safe in patients with permanent His bundle pacing.

Impact of QRS morphology on response to conduction system pacing after atrioventricular junction ablation

Aims

His–Purkinje conduction system pacing (HPCSP) utilizing His (HBP) or left bundle branch pacing (LBBP) in patients with atrial fibrillation (AF) and wide QRS duration has not been well studied. We assessed the benefit of left bundle branch block (LBBB) correction during HPCSP in AF patients undergoing atrioventricular junction (AVJ) ablation with LBBB, compared with those with narrow QRS duration.

Methods and results

This is an observational study in consecutive patients with typical LBBB or narrow QRS duration in whom we attempted HPCSP after AVJ ablation for refractory AF with a left ventricular ejection fraction (LVEF) ≤ 50%. Echocardiographic responses and clinical outcomes were assessed at baseline and during 1 year of follow‐up. A total of 178 patients were enrolled, of which 170 achieved AVJ ablation + permanent HPCSP (age 69.3 ± 10.1 years; LVEF 34.3 ± 7.7%), 133 (78.2%) patients had a narrow QRS duration, and 37 (21.2%) had an LBBB. The QRS duration changed from a baseline of 159.7 ± 16.6 ms to a paced QRS duration of 110.4 ± 12.7 ms in the LBBB cohort and from 95.6 ± 10.4 to 100.8 ± 14.5 ms (both P < 0.001) in the narrow QRS cohort after AVJ ablation and pacing. Compared with the narrow QRS cohort, the LBBB cohort showed a greater absolute increase in LVEF (+22.3% vs. +14.2%, P < 0.001), higher super responder rate (71.4% vs. 49.2%, P = 0.011), and greater New York Heart Association (NYHA) class improvement (−1.9 vs. −1.4, P < 0.001) at 1 year.

Conclusion

Patients with LBBB have greater improvement in LVEF and NYHA class function than patients with narrow QRS from HPCSP after AVJ ablation.

Can permanent His bundle pacing be safely started by operators new to this technique? Data from a multicenter registry

BACKGROUND

Right ventricular pacing (RVP) induces ventricular asynchrony in patients with normal QRS and increases the risk of heart failure and atrial fibrillation in long term. His bundle pacing (HBP) is a physiological alternative to RVP, and could overcome its drawbacks. Recent studies assessed the feasibility and safety of HBP in expert centers with a vast experience of this technique. These results may not apply to less experienced centers. We aim to evaluate the feasibility and safety of permanent HBP performed by physicians who are new to this technique.

METHODS

We included all patients who underwent pacemaker implantation with attempt of HBP in three hospitals between September 2017 and January 2020. Indication for HBP was left to operators' discretion. All the operators were new for HBP. His bundle (HB) electrical parameters were recorded at implant, 3- and 12-month follow-up.

RESULTS

HBP was successful in 141 of 170 patients (82.9%); selective HBP was obtained in 96 patients and nonselective HBP in 45. The mean procedure and fluoroscopy durations were 67.0 ± 28.8 min, and 7.3 ± 8.1 min (3.1 ± 4.1 Gy·cm² ), respectively. The mean HB paced QRS duration was 106 ± 18 ms. The mean HB capture threshold was 1.29 ± 0.77 V and did not increase at 3- and 12-month follow-up. The ventricular lead revision was required in five patients. Our results showed a rapid technical learning allowing a high procedure success rate (89.8%) after 15 procedures.

CONCLUSION

HBP performed by operators new to this technique appeared feasible and safe. This should encourage HBP to be performed in patients expected to experience high RVP burden.

Novel left ventricular cardiac synchronization: left ventricular septal pacing or left bundle branch pacing?

It is well recognized that a high burden of right ventricular pacing results in deleterious clinical outcomes over the long term. His bundle pacing can achieve optimal ventricular synchronization; however, relatively high pacing thresholds, low R-wave amplitudes, and the long-term performance have been concerns. Recently, left ventricular (LV) septal endocardium pacing (LVSP) has demonstrated improved acute haemodynamics. Another novel technique of intraseptal left bundle branch pacing (LBBP) via transvenous approach has been adopted rapidly and has demonstrated its feasibility and effectiveness. This article reviews the clinical application and differences between LVSP and LBBP. Compared with LVSP, LBBP has strict criteria for left conduction system capture and lead location. In addition to LV septal capture it also stimulates the proximal left bundle branch, resulting in rapid and physiological LV activation. With a uniformity and standardization of the implant procedure and definitions, it may be possible to achieve widespread application of this form of physiological pacing.

Safety of Distal His Bundle Pacing Via the Right Ventricle Backed Up by Adjacent Ventricular Capture

OBJECTIVES

This study investigated the differences between distal His bundle pacing (HBP) via the right ventricle and proximal HBP via the right atrium with regard to pacing and sensing parameters.

BACKGROUND

HBP preserves physiological ventricular activation. The capture threshold of the adjacent ventricle accompanying HBP has not been evaluated after implantation.

METHODS

Fifty patients with bradycardia (58% with atrioventricular block) underwent successful HBP and were followed for 1 year. Precise locations of the lead tips were confirmed using follow-up echocardiography.

RESULTS

HBP leads were fixed via the right atrium or right ventricle (25 patients each). Overall, the local ventricle and HBP thresholds were elevated during follow-up. The distal HBP thresholds did not significantly differ from the proximal HBP thresholds, although local ventricular thresholds of distal HBP were markedly lower than those of proximal HBP. At 6 months, the accepted ventricular threshold (≤2.5 V) was maintained in 39 patients (78%). An amplitude of ventricular electrogram post-fixation of ≥2.0 mV and a capture threshold of ≤1.1 V at implantation were determined to be optimal values for predicting the accepted threshold at 6 months, with areas under the curve of 0.86 and 0.84, respectively. Atrial oversensing was often detected in proximal HBP but not distal HBP.

CONCLUSIONS

Distal HBP via the right ventricle captured the His bundle, similar to proximal HBP via the right atrium, with a superior local ventricular threshold during follow-up. Anatomy and electrophysiological ventricular properties at implantation may be critical for maintaining adjacent ventricle capture to prevent lead revision (Evaluation of Electrophysiological Parameters related to His Bundle Pacing in Patients With Bradyarrhythmias; UMIN000031364).

Permanent His Bundle Pacing in Patients With Congenital Complete Heart Block: A Multicenter Experience

OBJECTIVES

This study retrospectively assessed the safety and efficacy of permanent His bundle pacing (HBP) in patients with congenital complete heart block (CCHB).

BACKGROUND

HBP has become an accepted form of pacing in adults. Its role in CCHB is not known.

METHODS

Seventeen patients with CCHB who underwent successful HBP were analyzed at 6 academic centers between 2016 and 2019. Nine patients had de novo implants, and 8 patients had previous right ventricular (RV) leads. Three RV paced patients had reduced left ventricular ejection fractions at the time of HBP. Implant/follow-up device parameters, New York Heart Association functional class, QRS duration, and left ventricular ejection fraction data were analyzed.

RESULTS

Patients' mean age was 27.4 ± 11.3 years, 59% were women, and mean follow-up was 385 ± 279 days. The following parameters were found to be statistically significant between implant and follow-up, respectively: impedance, 602 ± 173 Ω versus 460 ± 80 Ω (p < 0.001); and New York Heart Association functional class, 1.7 ± 0.9 versus 1.1 ± 0.3 (p = 0.014). In patients with previous RV pacing, HBP resulted in a significant decrease in QRS duration: 167.1 ± 14.3 ms versus 118.3 ± 13.9 ms (p < 0.0001). In de novo implants, HBP resulted in increases in QRS duration compared with baseline: 111.1 ± 19.4 ms versus 91.0 ± 4.8 ms (p = 0.016). Other parameters exhibited no statistically significant differences. During follow-up, 2 patients required lead revision due to elevated pacing thresholds.

CONCLUSIONS

HBP seems to be safe and effective, with improvement in clinical outcomes in patients with CCHB. Larger studies with longer follow-up periods are required to confirm our findings.

The Footprints of Pacing Lead Position Using the 12-Lead Electrocardiograph

The 12-lead resting electrocardiograph (ECG) of a patient with an implanted cardiac pacemaker is a snapshot of cardiac electrical activity at the time of recording and may provide valuable information on both pacemaker function and malfunction, as well as identifying the position of pacing leads in the heart. The traditional site for atrial pacing is within or adjacent to the right atrial appendage and paced P waves on the ECG have a normal frontal plane axis, whereas the traditional site for ventricular pacing is at the right ventricular apex with the ECG demonstrating a left bundle branch block configuration and a left axis. More recently, ventricular leads and to a lesser extent, atrial leads have been positioned in alternate non-traditional sites resulting in 12-lead ECG appearances which have characteristic features, that are generally poorly recognised. Left ventricular pacing results in a right bundle branch block configuration and an axis dependent on the position of the lead in the ventricle. This review will describe the ECG patterns of pacing lead positions in the right atrium and ventricle as well as positions in the left ventricle, whether intentional or unintentional.

His bundle pacing for cardiac resynchronization therapy: a systematic literature review and meta-analysis

BACKGROUND

Permanent His bundle pacing has been to shown to be an alternative for the patients with CRT indications and more recently has been evaluated for feasibility as a first-line strategy. Data on His bundle pacing (HBP) for cardiac resynchronization therapy are largely limited to small single-center reports, and clinical benefits and risks have not been systematically examined. The purpose of this study was to systematically review published studies of HBP for cardiac resynchronization therapy and evaluate the feasibility and efficacy of the therapy.

METHODS

PubMed, Cochrane Library, Embase, CNKI, and WANFANG databases were searched up to December 2019 to identify relevant studies. Clinical outcomes of interest include implant success rate; Q wave, R wave, and S wave QRS duration; pacing thresholds; left ventricular ejection fraction (LVEF); left ventricular end-diastolic dimension (LVEDD); and New York Heart Association (NYHA) status, complications, and mortality. Extract and summarize the data. Using Revman5.3 software to perform the meta-analysis.

RESULTS

A total of 13 studies involving 503 patients were included. The average implant success rate was 79.8% (95% CI 72.4-87.2%). Permanent HBP resulted in a significant narrow of mean QRS duration from 165.5 ± 8.7 to 122.9 ± 12.0 ms (MD = 43.5, 95%Cl: 36.34 ~ 50.56, p < 0.001). A trend of increase was observed in capture thresholds at follow-up compared with that in the baseline threshold (MD = - 0.24, 95% Cl: - 0.38 ~ - 0.10, p = 0.001). Average NYHA functional class (MD = 1.2, 95% CI: 1.09 ~ 1.31, p < 0.001), LVEF (MD = - 12.60, 95% Cl: - 14.32 ~ - 10.87, p < 0.001), LVEDD (MD = 4.30, 95% Cl: 3.05 ~ 5.55, p < 0.001) significantly improved at > 3 months follow-up compared with that of the baseline (p < 0.001). Ten studies reported safety information and the most commonly reported complication was the increase in HB capture threshold.

CONCLUSIONS

HBP is feasible with a reasonable success rate in patients requiring CRT. HBP could achieve significant narrow of QRS duration and improve left ventricular function during follow-up. Randomized controlled trials are needed to further assess the efficacy of HBP compared with that of biventricular pacing (BVP) in achieving CRT. Graphical abstract Schematic representation of detecting ofloxacin (OFL) by differential pulse voltammetry approach based on the laser modified glassy carbon electrode (LGCE), which increased the active functional groups and surface area compared to GCE.

His-Purkinje Conduction System Pacing: State of the Art in 2020

Conduction system pacing involves directly stimulating the specialised His-Purkinje cardiac conduction system with the aim of activating the ventricles physiologically, in contrast to the dyssynchronous activation produced by conventional myocardial pacing. Since the first report of permanent His bundle pacing (HBP) in 2000, the stylet-driven technique of its earliest incarnation has been superseded by a more successful stylet-less approach. Widespread uptake has led to a much greater evidence base. Single-centre observational studies have now been supported by large multicentre, international registries, mechanistic studies and the first randomised controlled trials. New evidence has elucidated mechanisms of HBP and illustrated the nature and magnitude of its potential benefits for preventing pacing-induced cardiomyopathy and correcting bundle branch block. Left bundle branch pacing (LBBP) is a newer technique in which the lead is fixed deep into the left side of the intraventricular septum to allow capture of the left bundle, distal to the His bundle. LBBP holds promise as a method for physiological pacing that overcomes some of the fixation, threshold and sensing challenges of HBP. In this state-of-the-art review of His-Purkinje conduction system pacing, the authors assess recent evidence and current practice and explore emerging and future directions in this rapidly evolving field.

Sensitivity analysis of an electrophysiology model for the left ventricle

Modelling the cardiac electrophysiology entails dealing with the uncertainties related to the input parameters such as the heart geometry and the electrical conductivities of the tissues, thus calling for an uncertainty quantification (UQ) of the results. Since the chambers of the heart have different shapes and tissues, in order to make the problem affordable, here we focus on the left ventricle with the aim of identifying which of the uncertain inputs mostly affect its electrophysiology. In a first phase, the uncertainty of the input parameters is evaluated using data available from the literature and the output quantities of interest (QoIs) of the problem are defined. According to the polynomial chaos expansion, a training dataset is then created by sampling the parameter space using a quasi-Monte Carlo method whereas a smaller independent dataset is used for the validation of the resulting metamodel. The latter is exploited to run a global sensitivity analysis with nonlinear variance-based indices and thus reduce the input parameter space accordingly. Thereafter, the uncertainty probability distribution of the QoIs are evaluated using a direct UQ strategy on a larger dataset and the results discussed in the light of the medical knowledge.

Cardiac resynchronization therapy in heart failure patients: tough road but clear future

Cardiac resynchronization therapy (CRT) based on biventricular pacing (BVP) is an invaluable intervention currently used in heart failure (HF) patients. The therapy involves electromechanical dyssynchrony, which can not only improve heart function and quality of life but also reduce hospitalization and mortality rates. However, approximately 30% to 40% of patients remain unresponsive to conventional BVP in clinical practice. In the recent years, extensive research has been employed to find a more physiological approach to cardiac resynchronization. The His-Purkinje system pacing (HPSP) including His bundle pacing (HBP) and left bundle branch area pacing (LBBaP) may potentially be the future of CRT. These technologies present various advantages including offering an almost real physiological pacing, less complicated procedures, and economic feasibility. Additionally, other methods, such as isolated left-ventricular pacing and multipoint pacing, may in the future be important but non-mainstream alternatives to CRT because currently, there is no strong evidence to support their effectiveness. This article reviews the current situation and latest progress in CRT, explores the existing technology, and highlights future prospects in the development of CRT.

Novel bradycardia pacing strategies

The adverse effects of ventricular dyssynchrony induced by right ventricular (RV) pacing has led to alternative pacing strategies, such as biventricular, His bundle (HBP), LV septal (LVSP) and left bundle branch pacing (LBBP). Given the overlap, LVSP and LBBP are also collectively referred to as left bundle branch area pacing (LBBAP). Although among these alternative pacing sites HBP is theoretically the ideal strategy as it maintains a physiological ventricular activation, its application requires more skills and is associated with the most complications. LBBAP, where the ventricular pacing lead is advanced through the interventricular septum to its left side, creates ventricular activation that is only slightly more dyssynchronous. Preliminary studies have shown that LBBAP is feasible, safe and encounters less limitations than HBP. Further studies are needed to differentiate between LVSP and LBBP with regard to acute functional and long-term clinical outcome.

Permanent His Bundle Pacing Implantation Facilitated by Visualization of the Tricuspid Valve Annulus

Background:

His bundle pacing (HBP) is the most physiological pacing modality. However, HBP has longer procedure times with frequent high capture thresholds, which likely contributes to the low adoption of this approach. The aim of this study is to compare HBP implantation with a novel imaging technique versus the standard implantation technique.

Methods:

This study included 50 patients with standard pacing indications randomized to HBP with visualization of the tricuspid valve annulus (N=25, the visualization group) or with the standard method (N=25, the control group). In the visualization group, the tricuspid valve annulus was imaged by contrast injection in the right ventricle during fluoroscopy. The site for HBP was identified in relationship to the tricuspid septal leaflet and interventricular septum.

Results:

Permanent HBP was successful in 92% in the visualization group and 88% in the control group. The fluoroscopic time for HBP lead placement was significantly shorter in the visualization group (7.1±3.3 minutes) compared with the control group (10.1±5.6 minutes, P =0.03). Total procedural and fluoroscopic times were also significantly shorter in the visualization group (91.0±15.7 and 9.6±3.8 minutes) than the control group (104.4±17.8 and 12.7±6.2 minutes, P =0.01 and 0.04, respectively). There was no significant difference in capture threshold between groups. In the visualization group, there was a quantitative association between the HBP site and the tricuspid valve annulus.

Conclusions:

The visualization technique shortens the procedural and fluoroscopic times for HBP implantation. Moreover, anatomic localization of HBP sites is strongly associated with physiological characteristics of pacing, which can help guide optimal lead placement.

Registration:

URL: https://www.chictr.org.cn/index.aspx . Unique identifier: ChiCTR2000029834.

The Emerging Role of Cardiac Conduction System Pacing as a Treatment for Heart Failure

PURPOSE OF REVIEW

The aim of cardiac resynchronization therapy (CRT) is to improve cardiac function by delivering more physiological cardiac activation to patients with heart failure and conduction abnormalities. Biventricular pacing (BVP) is the most commonly used method for delivering CRT; it has been shown in large randomized controlled trials to significantly improve morbidity and mortality in patients with heart failure. However, BVP delivers only modest reductions in ventricular activation time and is only beneficial in patients with prolonged QRS duration. In this review, we explore conduction system pacing as a method for delivering more effective ventricular resynchronization and to extend pacing therapy for heart failure to patients without left bundle branch block (LBBB).

RECENT FINDINGS

The aim of conduction system pacing is to provide physiological ventricular activation by directly stimulating the conduction system. Current modalities include His bundle and left conduction system pacing. His bundle pacing is the most established method; it has the potential to correct left bundle branch block and deliver more effective ventricular resynchronization than BVP. This translates into greater acute haemodynamic improvements and observational data suggests that His-CRT results in improvements in cardiac function and symptoms. AV-optimized His bundle pacing is being investigated in patients with heart failure and long PR interval without LBBB, to see if this improves exercise capacity. More recently, a technique for pacing the left bundle branch has been developed. Early studies show potential advantages including low and stable capture thresholds. Conduction system pacing can deliver more effective ventricular resynchronization than BVP, which has the potential to deliver greater improvements in cardiac function. It may also provide the opportunity to extend pacing therapy for heart failure to patients who do not have LBBB. Further data is required from randomized trials to assess these promising pacing techniques.

Imaging-Based Localization of His Bundle Pacing Electrodes: Results From the Prospective IMAGE-HBP Study

OBJECTIVES

This study sought to evaluate the correlation between His bundle (HB) pacing (HBP) implantation characteristics, lead-tip location, and association of intraprocedural His recordings with approximated HB anatomic landmarks using computed tomography (CT) imaging.

BACKGROUND

HBP continues to grow in clinical practice due to offering true physiological pacing. However, a clear understanding of HB anatomy and the lead-tip location's influence on pacing characteristics is lacking.

METHODS

The IMAGE-HBP study (Imaging Study of Lead Implant for His Bundle Pacing) was a prospective, multicenter study designed to assess implantation characteristics of the SelectSecure Model 3830 lead placed at the HB, evaluate protocol-specified HBP success (His recording present on electrogram and HBP threshold ≤2.5 V at 1 ms), and correlation between lead-tip location by CT imaging and HBP characteristics as well as lead-related complications through 12 months.

RESULTS

Sixty-nine patients underwent a lead implantation attempt at the HB. Of these, 61 patients (88%) had a lead successfully implanted at the HB, and 52 patients (75%) met the pre-specified definition of successful HBP. In 51 patients with CT imaging, 11 leads (22%) were placed in the atrial aspect of the HB region (36% selective HBP), and 40 leads (78%) were placed in the ventricular aspect (28% selective HBP). Four of the 51 patients had P-wave oversensing, all with leads in the atrium. Freedom from lead-related complication at 12 months was 93%.

CONCLUSIONS

Successful HBP could be achieved at lead-tip locations in the atrium or ventricle but is preferable in the ventricle to eliminate risk of oversensing. The IMAGE-HBP study offers better insight into approximated HB anatomic landmarks, lead-tip location, and correlation with pacing characteristics. (Imaging Study of Lead Implant for His Bundle Pacing [IMAGE-HBP]; NCT03294317).

Clinical outcomes of His-Purkinje conduction system pacing

His-Purkinje conduction system pacing (HPCSP) in the form of His bundle pacing (HBP) and left bundle branch pacing (LBBP) allows normal left ventricular activation, thereby preventing the adverse consequences of right ventricular pacing. HBP has been established for several years with centers from China, Europe, and North America reporting their experience. There is international guidance as to how to implant such systems with the differing patterns of His bundle capture clearly described. LBBP is a more recent innovation with potential advantages including improved pacing parameters. HPCSP has been extensively studied in a variety of indications including cardiac resynchronization therapy, atrioventricular node ablation, and bradycardia pacing. This review will focus on the clinical outcomes of HPCSP including mortality and morbidity of heart failure hospitalization and symptoms.

[Indications for His bundle and left bundle branch pacing]

His bundle pacing (HBP) allows ventricular excitation through the entire cardiac conduction system, resulting in a better synchronicity and efficacy of contraction compared to myocardial pacing. Due to better, dedicated implantation tools and exact practical implantation recommendations, HBP has developed into a form of stimulation that can be successfully applied with reasonable time and effort in >90% of patients. The rate of lead dislodgement and threshold increase is similar to conventional pacemaker systems. Despite a rather weak data base and a paucity of randomized trials, HBS represents an alternative to conventional right or biventricular pacing in the following conditions: (1) high-degree atrioventricular (AV) block with expected ventricular pacing >20% of the time, (2) AV block 1st degree with long PQ (alone or in combination with intermittent 2nd to 3rd degree AV block or sick sinus syndrome), (3) AV node ablation due to refractory atrial fibrillation, and (4) upgrade in pacing-induced cardiomyopathy. Moreover, HBP may be useful in context with cardiac resynchronization therapy (CRT). Left bundle branch block below the level of His represents a limitation of HBP. Therefore, more recently left bundle branch pacing (LBBP) has been introduced to correct left bundle branch block. LBBP seems to be possible in a wider anatomic area and may be easier to implant. However, LBBP requires active screw-in of the lead deep into the ventricular septum. Experience with this new technique is limited, particularly regarding long-term performance.

Left bundle branch pacing improved heart function in a 10-year-old child after a 3-month follow-up

AIMS

As a physiological pacing strategy, left bundle branch pacing (LBBP) were used to correct left bundle branch block (LBBB), however, there is no relevant report in children. We aimed to evaluate the feasibility of LBBP in children.

METHODS AND RESULTS

Left bundle branch pacing was performed in a 10-year-old girl with a second-degree atrioventricular and LBBB. Under the guide of fluoroscopy, the pacing lead was deeply screwed into the interventricular septum to gain right bundle branch block (RBBB) pattern of paced QRS. Selective LBBP was achieved with a typical RBBB pattern of paced morphology and a discrete component between stimulus and ventricular activation in intracardiac electrogram and reached the standard of the stimulus to left ventricular activation time of 56 ms. At a 3-month follow-up, the LBBP acquired the reduction of left ventricular size and enhancement of left ventricular ejection fraction.

CONCLUSION

The application of LBBP in a child was first achieved with inspiring preliminary results. The LBBP can be carried out in children by cautiousness under the premise of strict grasp of indications.

Bilateral Bundle Branch Area Pacing to Achieve Physiological Conduction System Activation

Background:

Left bundle branch pacing (LBBP) is a technique for conduction system pacing, but it often results in right bundle branch block morphology on the ECG. This study was designed to assess simultaneous pacing of the left and right bundle branch areas to achieve more synchronous ventricular activation.

Methods:

In symptomatic bradycardia patients, the distal electrode of a bipolar pacing lead was placed at the left bundle branch area via a transventricular-septal approach. This was used to pace the left bundle branch area, while the ring electrode was used to pace the right bundle branch area. Bilateral bundle branch area pacing (BBBP) was achieved by stimulating the cathode and anode in various pacing configurations. QRS duration, delayed right ventricular activation time, left ventricular activation time, and interventricular conduction delay were measured. Pacing stability and short-term safety were assessed at 3-month follow-up.

Results:

BBBP was successfully performed in 22 of 36 patients. Compared with LBBP, BBBP resulted in greater shortening of QRS duration (109.3±7.1 versus 118.4±5.7 ms, P <0.001). LBBP resulted in a paced right bundle branch block configuration, with a delayed right ventricular activation time of 115.0±7.5 ms and interventricular conduction delay of 34.0±8.8 ms. BBBP fully resolved the right bundle branch block morphology in 18 patients. In the remaining 4 patients, BBBP partially corrected the right bundle branch block with delayed right ventricular activation time decreasing from 120.5±4.7 ms during LBBP to 106.1±4.2 ms during BBBP ( P =0.005).

Conclusions:

LBBP results in a relatively narrow QRS complex but with an interventricular activation delay. BBBP can diminish the delayed right ventricular activation, producing more physiological ventricular activation.

Graphic Abstract:

A graphic abstract is available for this article.

His bundle pacing insights from electroanatomical mapping: Topography and pacing targets

OBJECTIVES

To characterize 3D electroanatomical mapping (EAM) of the His bundle (HB) region.

BACKGROUND

Visualization of selective (S) and nonselective (NS) HB capture areas by EAM has not been described and may help guide HB pacing (HBP).

METHODS

EAM was performed via NavX system in 17 patients (pts) undergoing HBP. HB cloud, S-HB, NS-HB, and right bundle (RB) capture areas were mapped.

RESULTS

S-HBP areas were identified in 11, NS-HBP in 14, and RB in 11 pts. Two NS-HBP areas (upper and lower) either separated by S-HBP (8 pts) or almost contiguous (5 pts) were observed. S-HBP area measured: 1.1 ± 0.9 cm² , NS upper: -1.2 ± 0.9 cm² , NS lower: -1.2 ± 0.9 cm² , RB: -1.7 ± 1.3 cm² , total His cloud: -4.1 ± 2.7 cm² . Electrocardiogram (ECG) pacemaps were different between upper and lower NS-HBP areas in 13/14 pts (p = .006). ECG differences between NS clouds were present in inferior leads in 9 pts (more negative QRS complex from lower NS area) and in precordial leads in 5 pts. There was no correlation between HBP lead location and capture threshold. R-wave amplitude was higher at more distal locations on HB cloud (p = .02).

CONCLUSION

(1) Pacemapping identifies distinct regions that may correspond to HB anatomy. (2) A linear S-HBP area is typically surrounded by two separate NS areas. (3) Pace-map ECGs from upper and lower NS-HBP areas have different morphologies. (4) These EAM features and pace-mapping may be helpful to the implanter.

Mid-term feasibility, safety and outcomes of left bundle branch pacing-single center experience

BACKGROUND

His bundle pacing (HBP) has evolved as the most physiological form of pacing but associated with limitations. Recently, left bundle branch pacing (LBBP) is emerging as an effective alternative strategy for HBP.

OBJECTIVES

Our study was designed to assess the feasibility, efficacy, electrophysiological parameters, and mid-term outcomes of LBBP in Indian population.

METHODS

All patients requiring permanent pacemaker implantation for symptomatic bradycardia and heart failure were prospectively enrolled. Echocardiography, QRS duration, pacing parameters, left bundle (LB) potentials, paced QRS duration, and peak left ventricular activation time (pLVAT) were recorded.

RESULTS

LBBP was successful in 93 out of 99 patients (94% acute success). Mean age was 62.6 ± 13 years, male 59%, diabetes 69%, and coronary artery disease 65%. Follow-up duration was 4.8 months (range1-12 months). Indication for pacing included atrioventricular (AV) block 43%, cardiac resynchronization therapy 44%, and AV node ablation 4%. LB potential was noted in 37 patients (40%). QRS duration reduced from 144.38 ± 34.6 at baseline to 110.8 ± 12.4 ms after LBBP (p < 0.0001). Pacing threshold was 0.59 ± 0.22 V and sensed R wave 14.14 ± 7.19 mV, and it remained stable during follow-up. Lead depth in the septum was 9.62 mm. LV ejection fraction increased from 44.96 to 53.3% after LBBP (p < 0.0001). One died due to respiratory tract infection on follow up.

CONCLUSION

LBBP is a safe and effective strategy (94% acute success) of physiological pacing. The pacing parameters remained stable over a period of 12 months follow-up. LBBP can effectively overcome the limitations of HBP.

His bundle pacing using a simple stylet and a standard active fixation electrode

Conventionally, His bundle pacing (HBP) is achieved using specially designed pacing leads and delivery sheaths. This paper describes the feasibility of permanent HBP with a pre-shaped simple stylet and a standard active-fixation electrode, through axillary vein access, without using dedicated delivery tools. This method may be a feasible and safe alternative to the only commercially available system.

Value of surface electrocardiography in His bundle pacing

His bundle pacing (HBP) provides physiological ventricular activation and is frequently used to treat patients with bradyarrhythmias. HBP reduces the risk of developing heart failure and atrial fibrillation by preventing ventricular electromechanical dyssynchrony associated with conventional right ventricular pacing. There are two types of HBP, including selective (S-HBP) and non-selective HBP (NS-HBP). It is important to determine the type of HBP during implantation and follow-up. This review discusses the role of standard surface electrocardiography in differentiating S‑HBP and NS-HBP and diagnosing loss of His bundle capture.

[Echocardiographic assessment of myocardial function during His bundle and right ventricular pacing]

INTRODUCTION

In patients with pacemaker (PM) therapy, His bundle stimulation (HBS) may lead to a more synchronous activation of the left ventricle (LV) than conventional right ventricular stimulation (RVS). In this study, we investigated to which extent this effect can be objectified by means of contemporary echocardiographic functional imaging.

METHODS

In all, 15 RVS patients (6 women, mean age 76.6 ± 4.1 years) and 15 HBS patients (6 women, mean age 74.6 ± 3.7 years) underwent echocardiography with and without cardiac pacing. Besides LV end-diastolic volume (EDV), ejection fraction (EF), and global strain (GLS), we measured global and regional myocardial work and LV efficiency based on noninvasive pressure-strain loops.

RESULTS

In all HBS patients, optimization of PM settings resulted in immediate changes in myocardial function parameters. With pacing, RVS patients showed a higher decrease in EF and GLS than HBS patients. Global LV work and LV work efficiency decreased significantly only in RVS patients.

CONCLUSION

Changes in regional and global myocardial function can by proven and quantified by functional echocardiography. In patients under PM therapy, HBS shows functional advantages in comparison to conventional RVS.

His-Purkinje conduction system pacing and atrioventricular node ablation

His-Purkinje conduction system pacing (HPCSP) in the form of His bundle pacing and left bundle branch pacing allows normal ventricular activation, thereby preventing the adverse consequences of right ventricular pacing. One potential area where HPCSP could be used is in the field of atrioventricular (AV) node ablation in patients with atrial fibrillation refractory to medical therapy and/or catheter ablation. His bundle pacing has been established for several years, with centres from North America, Europe and China publishing their experience. The differing patterns of His bundle capture are clearly described with established guidance as to how to implant such systems. Left bundle branch pacing has only recently been reported, but there are several advantages with better pacing parameters and lower risk of threshold change after AV node ablation. Six studies have been identified in the literature which describe the experience of His bundle pacing in patients requiring AV node ablation. Overall the results are positive and favour this new technique; however, they are limited by low numbers of patients and non-randomised study design. An observational study was recently published demonstrating better outcomes with left bundle branch pacing in a small number of patients with left ventricular dysfunction and atrial fibrillation that underwent AV node ablation. HPCSP has the potential to be the primary pacing modality in patients with atrial fibrillation requiring AV node ablation. However, it is essential that this is confirmed in large randomised clinical trials.

Implantation technique of His bundle pacing

His bundle pacing (HBP) preserves physiological ventricular synchrony, with clinical benefits particularly evident when a high percentage of ventricular pacing is required. First experiences with standard leads and manually shaped stylets produced the impression that HBP is highly complex and time-consuming. However, with dedicated leads and sheaths, reliable HBP can be achieved in routine clinical practice. Implantation success in more than 90% of patients can be reached with current technology and has been shown to be reliable and effective, both at implantation and during long-term follow-up. At the same time, fluoroscopy and total procedural time can be reduced. New customized technologies will continue to improve the implant success rate and system performance. Large randomized trials will prove the long-term clinical benefits of HBP definitively and may render HBP the first choice in patients requiring ventricular pacing.