His-bundle pacing as a standard approach in patients with permanent atrial fibrillation and bradycardia

Conduction System Pacing: Hope, Challenges, and the Journey Forward

PURPOSE OF THE REVIEW

Cardiac pacing has evolved in recent years currently culminating in the specific stimulation of the cardiac conduction system (conduction system pacing, CSP). This review aims to provide a comprehensive overview of the available literature on CSP, focusing on a critical classification of studies comparing CSP with standard treatment in the two fields of pacing for bradycardia and cardiac resynchronization therapy in patients with heart failure. The article will also elaborate specific benefits and limitations associated with CSP modalities of His bundle pacing (HBP) and left bundle branch area pacing (LBBAP).

RECENT FINDINGS

Based on a growing number of observational studies for different indications of pacing therapy, both CSP modalities investigated are advantageous over standard treatment in terms of narrowing the paced QRS complex and preserving or improving left ventricular systolic function. Less consistent evidence exists with regard to the improvement of heart failure-related rehospitalization rates or mortality, and effect sizes vary between HBP and LBBAP. LBBAP is superior over HBP in terms of lead measurements and procedural duration. With regard to all reported outcomes, evidence from large scale randomized controlled clinical trials (RCT) is still scarce. CSP has the potential to sustainably improve patient care in cardiac pacing therapy if patients are appropriately selected and limitations are considered. With this review, we offer not only a summary of existing data, but also an outlook on probable future developments in the field, as well as a detailed summary of upcoming RCTs that provide insights into how the journey of CSP continues.

Extraction of His Bundle Pacing Lead: More Difficult than Coronary Sinus Lead Extraction: An Analysis of 3897 Lead Extraction Procedures Including 27 His and 253 Coronary Sinus Lead Removals

BACKGROUND

Experience with the transvenous extraction of leads used for His bundle pacing (HBP) is limited.

METHODS

Analysis of 3897 extractions including 27 HBP and 253 LVP (left ventricular pacing) leads.

RESULTS

The main reason for HBP lead extraction was lead failure (59.26%). The age of HBP and LVP leads (54.52 vs. 50.20 months) was comparable, whereas procedure difficulties were related to the LVP lead dwell time. The extraction of HBP leads > 40 months old was longer than the removal of younger leads (8.57 vs. 3.87 min), procedure difficulties occurred in 14.29%, and advanced tools were required in 28.57%. There were no major complications. The extraction time of dysfunctional or infected leads was similar in the HBP and LVP groups (log-rank p = 0.868) but shorter when compared to groups with other leads. Survival after the procedure did not differ between HBP and LVP groups but was shorter than in the remaining patients.

CONCLUSIONS

1. HBP is used in CRT-D systems for resynchronisation of the failing heart in 33.33%. 2. Extraction of HBP leads is most frequently performed for non-infectious indications (59.26%) and most often because of lead dysfunction (33.33%). 3. The extraction of "old" (>40 months) HBP leads is longer (8.57 vs. 3.87 min) and more difficult than the removal of "young" leads due to unexpected procedure difficulties (14.29%) and the use of second line/advanced tools (28.57%), but it does not entail the risk of major complications and procedure-related death and is comparable to those encountered in the extraction of LVP leads of a similar age. 4. Survival after lead extraction was comparable between HBP and LVP groups but shorter compared to patients who underwent the removal of other leads.

Safety and efficacy of His-Purkinje system pacing in the treatment of patients with atrial fibrillation and heart failure: a systematic review and meta-analysis

Aim

To evaluate the safety and efficacy of the His-Purkinje system pacing (HPCSP) in the treatment of individuals with atrial fibrillation (AF) complicated by heart failure (HF).

Methods

The PubMed, Cochrane Library, Web of Science, and Embase databases were searched through September 1, 2022. The literature was initially screened based on the inclusion and exclusion criteria. The baseline characteristics of the subjects, implantation success rate, New York Heart Association (NYHA) classification, left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDd), QRS duration, pacing threshold, and impedance were extracted and summarized; statistical analysis was performed using RevMan 5.3 software.

Results

In all, 22 articles were included, involving 1,445 patients. Compared to biventricular pacing (BiVP), HPCSP resulted in improved cardiac function, including increased ejection fraction (MD = 5.69, 95% CI: 0.78-10.60, P = 0.02) and decreased LVEDd (MD = -3.50, 95% CI: -7.05-0.05, P = 0.05). It was also correlated with shorter QRS duration (MD = -38.30, 95% CI: -60.71--15.88, P < 0.01) and reduced all-cause mortality and rehospitalization events (RR = 0.72, 95% CI: 0.57-0.91, P < 0.01) in patients. Left bundle branch pacing (LBBP) lowered the pacing threshold (MD = 0.47; 95% CI: 0.25-0.69; P < 0.01), and there was no statistical difference in the rate of endpoint events when comparing these two physiologic pacing modalities (RR = 1.56, 95% CI: 0.87-2.80, P = 0.14).

Conclusion

The safety and efficacy of HPCSP in patients with AF and HF were verified in this meta-analysis. HPCSP can reverse cardiac remodeling and has great clinical application value. Relatively speaking, His-bundle pacing (HBP) can maintain better ventricular electro-mechanical synchronization, and the pacing parameters of LBBP are more stable.

Systematic Review Registration

PROSPERO (CRD42022336109).

Hemodynamic Effects of Permanent His Bundle Pacing Compared to Right Ventricular Pacing Assessed by Two-Dimensional Speckle-Tracking Echocardiography

We compared the effects of right ventricular (RVP; n = 26) and His bundle (HBP; n = 24) pacing in patients with atrioventricular conduction disorders and preserved LVEF. Postoperatively (1D), and after six months (6M), the patients underwent global longitudinal strain (GLS) and peak systolic dispersion (PSD) evaluation with 2D speckle-tracking echocardiography, assessment of left atrial volume index (LAVI) and QRS duration (QRSd), and sensing/pacing parameter testing. The RVP threshold was lower than the HBP threshold at 1D (0.65 ± 0.13 vs. 1.05 ± 0.20 V, p < 0.001), and then it remained stable, while the HBP threshold increased at 6M (1.05 ± 0.20 vs. 1.31 ± 0.30 V, p < 0.001). The RVP R-wave was higher than the HBP R-wave at 1D (11.52 ± 2.99 vs. 4.82 ± 1.41 mV, p < 0.001). The RVP R-wave also remained stable, while the HBP R-wave decreased at 6M (4.82 ± 1.41 vs. 4.50 ± 1.09 mV, p < 0.02). RVP QRSd was longer than HBP QRSd at 6M (145.0 ± 11.1 vs. 112.3 ± 9.3 ms, p < 0.001). The absolute value of RVP GLS decreased at 6M (16.32 ± 2.57 vs. 14.03 ± 3.78%, p < 0.001), and HBP GLS remained stable. Simultaneously, RVP PSD increased (72.53 ± 24.15 vs. 88.33 ± 30.51 ms, p < 0.001) and HBP PSD decreased (96.28 ± 33.99 vs. 84.95 ± 28.98 ms, p < 0.001) after 6 months. RVP LAVI increased (26.73 ± 5.7 vs. 28.40 ± 6.4 mL/m², p < 0.05), while HBP LAVI decreased at 6M (30.03 ± 7.8 vs. 28.73 ± 8.7 mL/m², p < 0.01). These results confirm that HBP does not disrupt ventricular synchrony and provides advantages over RVP.

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.

Deep septal deployment of a thin, lumenless pacing lead: a translational cadaver simulation study

AIMS

The recently introduced technique of direct transseptal pacing of the left bundle branch is poorly characterized with many questions with regard to the optimal implantation strategy and safety concerns largely left unanswered. We developed a cadaver model for deep septal lead deployment in order to investigate the depth of penetration in relation to lead behaviour, lead tip position, and the number of rotations.

METHODS AND RESULTS

Five fresh human hearts and five lumenless, 4.1-Fr pacing leads were used for deep septal deployment simulations. The leads were positioned with the use of a dedicated delivery sheath and screwed into the interventricular septum at several sites progressively more distal from the atrioventricular ring with a predetermined number of lead rotations. During each lead deployment, the depth of tip penetration was measured and the lead behaviour was noted. Four distinct lead behaviours were observed: (i) helix only penetration, no matter how many rotations were performed, due to the 'endocardial entanglement effect' (43.1% cases) or (ii) 'endocardial barrier effect' (19.6% cases), (iii) shallow/moderate penetration, with ensuing 'drill effect' when more rotations were added (9.8% cases), and (iv) deep progressive penetration with each additional rotation, occurring when the 'screwdriver effect' was present (27.4% cases, including three septal perforations). These different lead behaviours seemed to be determined by the lead position-mainly the strength of the initial endocardial layer-and the number of fully transmitted rotations.

CONCLUSION

New insights into deep septal lead deployment technique were gained with regard to safe and successful implantation.

Safety and efficacy of His-bundle pacing/left bundle branch area pacing versus right ventricular pacing: a systematic review and meta-analysis

BACKGROUND

Recent studies have demonstrated that right ventricular pacing (RVP) has deleterious effects on non-synchronized ventricular contraction, while His-bundle pacing (HBP) or left bundle branch area pacing (LBBaP) contribute to improvements in patients' mid- and long-term outcomes. This meta-analysis aimed to compare the safety and efficacy of physiologic pacing (HBP/LBBaP) versus those of RVP.

METHODS

A systematic search of PubMed, Cochrane Library, and Embase was conducted for studies that compared the effects of physiologic pacing and RVP. All eligible studies were published before January 1, 2021 and were conducted in humans. STATA software version 15.0 was used for all the data analyses.

RESULTS

Twenty articles (n = 2787 patients) were included in this meta-analysis. Compared to RVP, physiologic pacing was associated with a significantly shorter QRS duration and better cardiac function. Physiologic pacing was also correlated with lower rates of mitral regurgitation, pacing-induced cardiomyopathy, death, heart failure hospitalization, and atrial fibrillation, although the above results were not statistically significant. In addition, RVP led to the achievement of higher success rates than physiologic pacing, a shorter fluoroscopic time and mean procedure duration, a lower pacing threshold: the results were statistically significant. Compared with HBP, LBBaP appeared to have some advantages in R wave amplitudes, pacing threshold, fluoroscopic time, procedure time, and success rate, with statistically significant differences. Whereas HBP was associated with fewer surgical complications and shorter QRS duration, the results were not statistically significant.

CONCLUSION

Physiologic pacing (HBP/LBBaP) might be a better strategy than RVP and improve long-term clinical outcomes like cardiac function. Although LBBaP appears to have some advantages over HBP, the long-term benefits are still controversial. More large-scale randomized clinical trials are needed for further verification.

Long-Term Safety and Feasibility of Left Bundle Branch Pacing in a Large Single-Center Study

BACKGROUND

Left bundle branch pacing (LBBP) is a novel pacing method and has been observed to have low and stable pacing thresholds in prior small short-term studies. The objective of this study was to evaluate the feasibility and safety of LBBP in a large consecutive diverse group of patients with long-term follow-up.

METHODS

This study prospectively enrolled 632 consecutive pacemaker patients with attempted LBBP from April 2017 to July 2019. Pacing parameters, complications, ECG, and echocardiographic measurements were assessed at implant and during follow-up of 1, 6, 12, and 24 months.

RESULTS

LBBP was successful in 618/632 (97.8%) patients according to strict criteria for LBB capture. Mean follow-up time was 18.6±6.7 months. Two hundred thirty-one patients had follow-up over 2 years. LBB capture threshold at implant was 0.65±0.27 mV at 0.5 ms and 0.69±0.24 mV at 0.5 ms at 2-year follow-up. A significant decrease in QRS duration was observed in patients with left bundle branch block (167.22±18.99 versus 124.02±24.15 ms, P<0.001). Postimplantation left ventricular ejection fraction improved in patients with QRS≥120 ms (48.82±17.78% versus 58.12±13.04%, P<0.001). The number of patients with moderate and severe tricuspid regurgitation decreased at 1 year. Permanent right bundle branch injury occurred in 55 (8.9%) patients. LBB capture threshold increased to >3 V or loss of bundle capture in 6 patients (1%), 2 patients of them had a loss of conduction system capture. Two patients required lead revision due to dislodgement.

CONCLUSIONS

This large observational study suggests that LBBP is feasible with high success rates and low complication rates during long-term follow-up. Therefore, LBBP appears to be a reliable method for physiological pacing for patients with either a bradycardia or heart failure pacing indication.

Electrocardiographic characterization of non-selective His-bundle pacing: validation of novel diagnostic criteria

AIMS

Permanent His-bundle (HB) pacing is usually accompanied by simultaneous capture of the adjacent right ventricular (RV) myocardium-this is described as a non-selective (ns)-HB pacing. It is of clinical importance to confirm HB capture using standard electrocardiogram (ECG). Our aim was to identify ECG criteria for loss of HB capture during ns-HB pacing.

METHODS AND RESULTS

Patients with permanent HB pacing were recruited. Electrocardiograms during ns-HB pacing and loss of HB capture (RV-only capture) were obtained. Electrocardiogram criteria for loss/presence of HB capture were identified. In the validation phase, these criteria and the 'HB ECG algorithm' were tested using a separate, sizable set of ECGs. A total of 353 ECG (226 ns-HB and 128 RV-only) were obtained from 226 patients with permanent HB pacing devices. QRS notch/slur in left ventricular leads and R-wave peak time (RWPT) in lead V6 were identified as the best features for differentiation. The 'HB ECG algorithm' based on these features correctly classified 87.1% of cases with sensitivity and specificity of 93.2% and 83.9%, respectively. The criteria for definitive diagnosis of ns-HB capture (no QRS slur/notch in Leads I, V1, V4-V6, and the V6 RWPT ≤ 100 ms) presented 100% specificity.

CONCLUSION

A novel ECG algorithm for the diagnosis of loss of HB capture and criteria for definitive confirmation of HB capture were formulated and validated. The algorithm might be useful during follow-up and the criteria for definitive confirmation of ns-HB capture offer a simple and reliable ancillary procedural endpoint during HB device implantation.

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.

Short-term and intermediate-term performance and safety of left bundle branch pacing

Introduction

Left bundle branch pacing (LBBP) is a promising new method for patients with pacing indications. This study aims to evaluate the safety and feasibility of LBBP in a relatively longer time span.

Methods and Results

A total of 164 patients were recruited for LBBP in this study. Among these patients, 148 patients had pacing indications due to symptomatic bradycardia while the other 16 patients had indications for cardiac resynchronization therapy (CRT). LBBP was successful in 89.0% (146/164) of all recruited patients. Intracardiac and surface electrographic parameters and image data were documented during the LBBP procedure. The mean paced QRS duration (pQRSD) and the mean stimulus to left ventricular activation time (stim‐LVAT) was 106.0 ± 12.9 ms and 64.4 ± 13.7 ms respectively. Left bundle branch (LBB) potentials were recorded in 89 patients. Forty‐three of whom had sick sinus syndrome (SSS), and 46 had atrioventricular block (AVB). The presence of LBB potential was more common in patients with SSS (82.7% vs 57.5%, P = .002). No significant differences in pQRSD, stim‐LVAT, or capture threshold were detected between patient groups with or without LBB potential. Patients were followed up at 1 month, 3 months, 6 months, and 1 year after the procedure. Pacing parameters and the echocardiographic data remained stable within a mean follow‐up period of 8.6 ± 4.3 months. No serious complication caused by this procedure was found in this study.

Conclusions

Successful LBBP carried an aspect of short pQRSD and stim‐LVAT while the LBB potential was not the prerequisite and necessary feature. The LBBP procedure had a high success rate with satisfied and stable lead parameters during short and intermediate‐term observations.

Programmed His Bundle Pacing: A Novel Maneuver for the Diagnosis of His Bundle Capture

BACKGROUND

During permanent nonselective His bundle (ns-HB) pacing, it is crucial to confirm HB capture/exclude that only right ventricle (RV) myocardial septal pacing is present. Because the effective refractory period (ERP) of the working myocardium is different than the ERP of the HB, we hypothesized that it should be possible to differentiate ns-HB capture from RV myocardial capture using programmed extrastimulus technique.

METHODS

In consecutive patients during HB pacemaker implantation, programmed HB pacing was delivered from the screwed-in HB pacing lead. Premature beats were introduced at 10-ms steps during intrinsic rhythm and also after a drive train of 600 ms. The longest coupling interval that resulted in an abrupt change of QRS morphology was considered equal to ERP of HB or RV myocardium.

RESULTS

Programmed HB pacing was performed from 50 different sites in 32 patients. In 34 of 36 cases of ns-HB pacing, the RV myocardial ERP was shorter than HB ERP (271.8±38 versus 353.0±30 ms; P<0.0001). Programmed HB pacing using a drive train resulted in a typical abrupt change of paced QRS morphology: from ns-HB to RV myocardial QRS (34 of 36 cases) or to selective HB QRS (2 of 36 cases). Programmed HB pacing delivered during native conduction resulted in obtaining selective HB QRS in 20 of 34 and RV myocardial QRS in 14 of 34 of the ns-HB cases. In RV myocardial-only pacing cases (false ns-HB pacing, n=14), such responses were not observed-the QRS morphology remained stable. Therefore, the programmed HB pacing correctly diagnosed all ns-HB cases and all RV myocardial pacing cases.

CONCLUSIONS

A novel maneuver for the diagnosis of HB capture, based on the differences in ERP between HB and myocardium, was formulated, assessed, and found as diagnostically valuable. This method is unique in enabling to visualize selective HB QRS in patients with otherwise obligatory ns-HB pacing (RV myocardial capture threshold <HB capture threshold).

His bundle pacing, learning curve, procedure characteristics, safety, and feasibility: Insights from a large international observational study

Background

His‐bundle pacing (HBP) provides physiological ventricular activation. Observational studies have demonstrated the techniques’ feasibility; however, data have come from a limited number of centers.

Objectives

We set out to explore the contemporary global practice in HBP focusing on the learning curve, procedural characteristics, and outcomes.

Methods

This is a retrospective, multicenter observational study of patients undergoing attempted HBP at seven centers. Pacing indication, fluoroscopy time, HBP thresholds, and lead reintervention and deactivation rates were recorded. Where centers had systematically recorded implant success rates from the outset, these were collated.

Results

A total of 529 patients underwent attempted HBP during the study period (2014‐19) with a mean follow‐up of 217 ± 303 days. Most implants were for bradycardia indications.

In the three centers with the systematic collation of all attempts, the overall implant success rate was 81%, which improved to 87% after completion of 40 cases.

All seven centers reported data on successful implants. The mean fluoroscopy time was 11.7 ± 12.0 minutes, the His‐bundle capture threshold at implant was 1.4 ± 0.9 V at 0.8 ± 0.3 ms, and it was 1.3 ± 1.2 V at 0.9 ± 0.2 ms at last device check.

HBP lead reintervention or deactivation (for lead displacement or rise in threshold) occurred in 7.5% of successful implants.

There was evidence of a learning curve: fluoroscopy time and HBP capture threshold reduced with greater experience, plateauing after approximately 30‐50 cases.

Conclusion

We found that it is feasible to establish a successful HBP program, using the currently available implantation tools. For physicians who are experienced at pacemaker implantation, the steepest part of the learning curve appears to be over the first 30‐50 cases.