Permanent His-bundle pacing: Long-term lead performance and clinical outcomes

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.

Safety and performance of conduction system pacing: real-world experience from a Product Surveillance Registry

BACKGROUND

Conduction system pacing (CSP) including His-bundle pacing (HBP) and left bundle branch area pacing (LBBAP), has been used as an alternative for pacemaker indicated patients requiring ventricular pacing.

OBJECTIVE

The purpose of this analysis was to characterize the safety and performance of HBP and LBBAP among patients enrolled in the Medtronic Product Surveillance Registry (PSR).

METHODS

This observational analysis included patients who underwent pacemaker implantations for HBP or LBBAP with a Model 3830 lead between January 2019 and December 2023 in the Medtronic PSR. The primary outcomes were lead-related complications and pacing capture threshold (PCT). Baseline characteristics, R-wave amplitude, impedance, and all-cause mortality were summarized.

RESULTS

A total of 2342 patients were included across 77 centers (mean age 74, 38.9% female). Of the patients implanted with a 3830 lead for CSP, 64.1% had LBBAP placement (n=1502) and 35.9% had HBP placement (n=840). The most commonly reported indications for CSP were sinus node dysfunction (67.0%) and AV block (57.2%). LBBAP had lower pacing thresholds, higher R-wave sensing and higher impedance (all p<0.001) through 30 months. At 36 months post-implant, the lead complication rate for LBBAP and HBP was 2.5% and 6.3%, respectively with no difference in all-cause mortality.

CONCLUSION

In a multi-center cohort of LBBAP and HBP patients treated with the catheter-delivered 3830 lead, lead-related complication rates were low and electrical parameters were stable through 30 months.

Enhancing cardiac pacing strategies: a review of conduction system pacing compared with right and biventricular pacing and their influence on myocardial function

Traditional right ventricular pacing (RVP) has been linked to the deterioration of both left ventricular diastolic and systolic function. This worsening often culminates in elevated rates of hospitalization due to heart failure, an increased risk of atrial fibrillation, and increased morbidity. While biventricular pacing (BVP) has demonstrated clinical and echocardiographic improvements in patients afflicted with heart failure and left bundle branch block, it has also encountered significant challenges such as a notable portion of non-responders and procedural failures attributed to anatomical complexities. In recent times, the interest has shifted towards conduction system pacing, initially, His bundle pacing, and more recently, left bundle branch area pacing, which are seen as promising alternatives to established methods. In contrast to other approaches, conduction system pacing offers the advantage of fostering more physiological and harmonized ventricular activation by directly stimulating the His-Purkinje network. This direct pacing results in a more synchronized systolic and diastolic function of the left ventricle compared with RVP and BVP. Of particular note is the capacity of conduction system pacing to yield a shorter QRS, conserve left ventricular ejection fraction, and reduce rates of mitral and tricuspid regurgitation when compared with RVP. The efficacy of conduction system pacing has also been found to have better clinical and echocardiographic improvement than BVP in patients requiring cardiac resynchronization. This review will delve into myocardial function in conduction system pacing compared with that in RVP and BVP.

Single-center experience of efficacy and safety of atrioventricular node ablation after left bundle branch area pacing for the management of atrial fibrillation

BACKGROUND

Atrioventricular node ablation (AVNA) with permanent pacing is an effective treatment of symptomatic atrial fibrillation (AF). Left bundle branch area pacing (LBBAP) prevents cardiac dyssynchrony associated with right ventricular pacing and could prevent worsening of heart failure (HF).

METHODS

In this retrospective monocentric study, all patients who received AVNA procedure with LBBAP were consecutively included. AVNA procedure data, electrical and echocardiographic parameters at 6 months, and clinical outcomes at 1 year were studied and compared to a matched cohort of patients who received AVNA procedure with conventional pacing between 2010 and 2023.

RESULTS

Seventy-five AVNA procedures associated with LBBAP were studied. AVNA in this context was feasible, with a success rate of 98.7% at first ablation, and safe without any complications. There was no threshold rise at follow-up. At 1 year, 6 (8%) patients were hospitalized for HF and 2 (2.7%) were deceased. Patients had a significant improvement in NYHA class and left ventricular ejection fraction (LVEF) (P ≤ 0.0001). When compared to a matched cohort of patients with AVNA and conventional pacing, AVNA data and pacing complications rates were similar. Patients with LBBAP had a better improvement of LVEF (+5.27 ± 9.62% vs. -0.48 ± 14%, P = 0.01), and a lower 1-year rate of composite outcome of hospitalization for HF or death (HR 0.39, 95% CI: 0.16-0.95, P = 0.037), significant on survival analysis (log-rank P-value = 0.03).

CONCLUSION

AVNA with LBBAP in patients with symptomatic AF is feasible, safe, and efficient. Hospitalization for HF or death rate was significantly lower and LVEF improvement was greater.

Caveats related to conduction system pacing utilizing a proprietary deflectable mapping catheter with a stylet-driven lead

BACKGROUND

Hitherto, lumen less leads (LLLs) were routinely utilized for conduction system pacing (CSP). We report the largest experience using stylet-driven leads (SDLs) with a deflectable mapping catheter for CSP.

METHODS

Patients were prospectively and sequentially enrolled for CSP with SDL between June, 2021 and November, 2022 to (i) a novel deflectable mapping catheter (AgilisHisProTM, Abbott) (Group A) or (ii) a fixed curve sheath (Selectra3D, Biotronik) (Group B) in a 1:1 non-randomized fashion. The primary aim was to evaluate safety, feasibility, and efficacy of the CSP using SDL and deflectable mapping catheter (Group A) while reporting procedural success and intermediate-term follow-up.

RESULTS

Seventy-nine patients (59.4%M, mean age 67.2+/-10.6 years) were allocated to either (i) Group A (n = 40) or (ii) Group B (n = 39). In Group A (n = 40, 50% M, mean age 67.2+/-9.5 years, follow-up 210.7 + 25.1days), His bundle pacing (HBP) was the default strategy with left bundle branch area pacing (LBBaP) for bailout. Procedural success with HBP was feasible in 17/40 (42.5%) patients with remaining 23/40 (57.5%) needing LBBaP bailout. After initial learning curve, a manual septal curve was introduced to successfully aid LBBaP in 6/23 (26.1%) cases. Procedural and follow-up parameters did not differ significantly in HBP vs. LBBaP. Head-to-head comparison was not performed between the groups owing to different default protocols (HBP-Group A, Discretionary-Group B).

CONCLUSIONS

Use of SDL with single-curve deflectable mapping catheter was safe, feasible and yielded moderate procedural success with HBP and frequently needed a LBBaP bailout strategy. In approximately one-fourth of the latter, an out-of-plane manual septal curve was needed to optimize LBBaP.

Success and complication rates of conduction system pacing: a meta-analytical observational comparison of left bundle branch area pacing and His bundle pacing

BACKGROUND

Left bundle branch area pacing (LBBAP) and His bundle pacing (HBP) are the main strategies to achieve conduction system pacing (CSP), but only observational studies with few patients have compared the two pacing strategies, sometimes with unclear results given the different definitions of the feasibility and safety outcomes. Therefore, we conducted a meta-analysis aiming to compare the success and complications of LBBAP versus HBP.

METHODS

We systematically searched the electronic databases for studies published from inception to March 22, 2023, and focusing on LBBAP versus HBP. The study endpoints were CSP success rate, device-related complications, CSP lead-related complications and non-CSP lead-related complications.

RESULTS

Fifteen observational studies enrolling 2491 patients met the inclusion criteria. LBBAP led to a significant increase in procedural success [91.1% vs 80.9%; RR: 1.15 (95% CI: 1.08-1.22); p < 0.00001] with a significantly lower complication rate [1.8% vs 5.2%; RR: 0.48 (95% CI: 0.29-0.78); p = 0.003], lead-related complications [1.1% vs 4.3%; RR: 0.38 (95% CI: 0.21-0.72); p = 0.003] and lead failure/deactivation [0.2% vs 3.9%; RR: 0.16 (95% CI: 0.07-0.35); p < 0.00001] than HBP. No significant differences were found between CSP lead dislodgement and non-CSP lead-related complications.

CONCLUSION

This meta-analysis of observational studies showed a higher success rate of LBBAP compared to HBP with a lower incidence of complications.

2024 HRS expert consensus statement on arrhythmias in the athlete: Evaluation, treatment, and return to play

Youth and adult participation in sports continues to increase, and athletes may be diagnosed with potentially arrhythmogenic cardiac conditions. This international multidisciplinary document is intended to guide electrophysiologists, sports cardiologists, and associated health care team members in the diagnosis, treatment, and management of arrhythmic conditions in the athlete with the goal of facilitating return to sport and avoiding the harm caused by restriction. Expert, disease-specific risk assessment in the context of athlete symptoms and diagnoses is emphasized throughout the document. After appropriate risk assessment, management of arrhythmias geared toward return to play when possible is addressed. Other topics include shared decision-making and emergency action planning. The goal of this document is to provide evidence-based recommendations impacting all areas in the care of athletes with arrhythmic conditions. Areas in need of further study are also discussed.

Transvenous extraction of conduction system pacing leads: An international multicenter (TECSPAM) study

BACKGROUND

Conduction system pacing (CSP) by His bundle pacing or left bundle branch area pacing (LBBAP) is incorporated into Heart Rhythm Society guidelines for the management of bradycardia and cardiac resynchronization therapy. Despite increasing adoption with both lumenless leads and stylet-driven leads, concerns regarding the feasibility and safety of the extraction of CSP leads remain.

OBJECTIVE

The aim of the study was to report on the safety, feasibility, and clinical outcomes of the extraction of CSP leads.

METHODS

Patients undergoing the extraction of CSP leads from 10 international centers were enrolled in this retrospective study. Data regarding indications, lead location, lead type, extraction tools, procedural success, complications, and reimplantation in the conduction system were collected.

RESULTS

Overall, 341 patients (age 69 ± 15 years; female 34%; cardiomyopathy 46%; lead dwell time 22 ± 26 months) underwent the extraction of 224 His bundle pacing and 117 LBBAP leads (lumenless leads 321; stylet-driven leads 20). Complete procedural success was achieved in 338 (99%), while clinical success was 100% with retained distal fragments in 3 patients (1%). Among patients with a lead dwell time of >6 months (6-193 months; n = 226), manual extraction was successful in 198 (87%), mechanical tools in 22 (10%), and laser in 6 (3%). Femoral tools were necessary in 3 patients. Minor complications occurred in 7 patients (2.1%). CSP reimplantation was successful in 233 of 244 patients attempted (95%).

CONCLUSION

The overall success rates of the extraction of CSP leads were very high (although the LBBAP lead dwell time was <3 years), with a low need for extraction tools and minimal complication. Reimplantation in the conduction system is feasible and safe.

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.

Outcomes of left bundle branch area pacing compared to His bundle pacing and right ventricular apical pacing in Japanese patients with bradycardia

Background

His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) emerge as better alternatives to right ventricular apical pacing (RVAP) in patients with bradycardia requiring permanent cardiac pacing. We aimed to compare the clinical outcomes of LBBAP, HBP, and RVAP in Japanese patients with bradycardia.

Methods

A total of 424 patients who underwent successful pacemaker implantation (HBP, n = 53; LBBAP, n = 75; and RVAP, n = 296) were retrospectively enrolled in this study. The primary study endpoint was the cumulative incidence of heart failure hospitalization (HFH) during the follow-up.

Results

The success rate for implantation was higher in the LBBAP group than in the HBP group (94.9% and 81.5%, respectively). Capture threshold increase >1V during the follow-up occurred in the HBP and RVAP groups (9.4% and 5.1%, respectively), while it did not in the LBBAP group. The cumulative incidence of HFH was significantly lower in the LBBAP group than the RVAP (adjusted hazard ratio, 0.12 [95% confidence interval: 0.02-0.86]; p = .034); it did not differ between the HBP and RVAP groups (adjusted hazard ratio, 0.48 [95% confidence interval: 0.17-1.34]; p = .16). Advanced age, mean percent right ventricular pacing (per 10% increase), left ventricular ejection fraction <50%, and RVAP were associated with HFH.

Conclusions

Compared to RVAP and HBP, LBBAP appeared more feasible and effective in patients with bradycardia requiring permanent cardiac pacing.

Prognostic benefits of His-Purkinje capture in physiological pacemakers for bradycardia

INTRODUCTION

Clinical outcomes of long-term ventricular septal pacing (VSP) without His-Purkinje capture remain unknown. This study evaluated the differences in clinical outcomes between conduction system pacing (CSP), VSP, and right ventricular pacing (RVP).

METHODS

Consecutive patients with bradycardia indicated for pacing from 2016 to 2022 were prospectively followed for the clinical endpoints of heart failure (HF)-hospitalizations and all-cause mortality at 2 years. VSP was defined as septal pacing due to unsuccessful CSP implant or successful CSP followed by loss of His-Purkinje capture within 90 days.

RESULTS

Among 1016 patients (age 73.9 ± 11.2 years, 47% female, 48% atrioventricular block), 612 received RVP, 335 received CSP and 69 received VSP. Paced QRS duration was similar between VSP and RVP, but both significantly longer than CSP (p < .05). HF-hospitalizations occurred in 130 (13%) patients (CSP 7% vs. RVP 16% vs. VSP 13%, p = .001), and all-cause mortality in 143 (14%) patients (CSP 7% vs. RVP 19% vs. VSP 9%, p < .001). The association of pacing modality with clinical events was limited to those with ventricular pacing (Vp) > 20% (pinteraction < .05). Adjusting for clinical risk factors among patients with Vp > 20%, VSP (adjusted hazard ratio [AHR]: 4.74, 95% confidence interval [CI]: 1.57-14.36) and RVP (AHR: 3.08, 95% CI: 1.44-6.60) were associated with increased hazard of HF-hospitalizations, and RVP (2.52, 95% CI: 1.19-5.35) with increased mortality, compared to CSP. Clinical endpoints did not differ between VSP and RVP with Vp > 20%, or amongst groups with Vp < 20%.

CONCLUSION

Conduction system capture is associated with improved clinical outcomes. CSP should be preferred over VSP or RVP during pacing for bradycardia.

Does asymptomatic atrial fibrillation exist?

Atrial fibrillation (AF) is currently defined as symptomatic by asking patients if they are aware of when they are in AF and if they feel better in sinus rhythm. However, this approach of defining AF as symptomatic and asymptomatic fails to adequately consider the adverse effects of AF in patients who are unaware of their rhythm including progression from paroxysmal to persistent AF, and the development of dementia, stroke, sinus node dysfunction, valvular regurgitation, ventricular dysfunction, and heart failure. Labeling these patients as asymptomatic falsely suggests that their AF requires less intense therapy and puts into question the notion of truly asymptomatic AF. Because focusing on patient awareness ignores other important consequences of AF, clinical endpoints that are independent of symptoms are being developed. The concept of AF burden has more recently been used as a clinical endpoint in clinical trials as a more clinically relevant endpoint compared to AF-related symptoms or time to first recurrence, but its correlation with symptoms and other clinical outcomes remains unclear. This review will explore the impact of AF on apparently asymptomatic patients, the use of AF burden as an endpoint for AF management, and potential refinements to the AF burden metric. The review is based on a presentation by the senior author during the 2023 16th annual European Cardiac Arrhythmia Society (ECAS) congress in Paris, France.

Effect of His Bundle Pacing on Abnormal Myocardial Fatty Acid and Glucose Metabolism Induced by Right Ventricular Pacing

BACKGROUND

Metabolic disorder is noted for pacing-induced cardiomyopathy. The benefits of His bundle pacing over right ventricular (RV) pacing in preventing pacing-induced cardiomyopathy from a metabolic perspective are yet to be fully understood.

METHOD AND RESULTS

Three pig groups were established for this study: sham control, RV pacing (RV pacing for 6 months), and His pacing (RV pacing for 6 months, followed by His bundle pacing for 3 months). Complete atrioventricular block was created in the last 2 groups. Left ventricular function and dyssynchrony were assessed via echocardiography, while proteins linked to metabolism, endoplasmic reticulum stress, and inflammation in left ventricular myocardium were examined. The RV pacing group had significantly more left ventricular mechanical dyssynchrony compared with the other groups. The RV pacing group exhibited triglyceride and diacylglycerol accumulation in cardiomyocytes and higher expression of binding immunoglobulin protein and tumor necrosis factor-α than the other groups. Additionally, the expression of CD36 was activated, while the expression of hormone-sensitive lipase was downregulated in the RV pacing group compared with the His pacing and sham control groups. Furthermore, the expressions of GLUT4 and pyruvate dehydrogenase were higher in the RV pacing group than the sham control and His pacing groups. Notably, the abnormal fatty acid and glucose metabolic pathways in the left ventricular myocardium during RV pacing could be corrected by His bundle pacing.

CONCLUSIONS

His bundle pacing can mitigate the abnormal metabolism disorders, endoplasmic reticulum stress, and inflammation induced during RV pacing and may contribute to the superiority of conduction system pacing over RV pacing in reducing heart failure hospitalization.

Conduction System Pacing in Pediatrics and Congenital Heart Disease: A Case Report and Literature Review

Conduction system pacing involving either His bundle pacing (HBP) or left bundle branch pacing (LBBP) is a modality that has been introduced as a safe and effective alternative to right ventricular (RV) pacing to help prevent pacemaker-associated cardiomyopathy. While HBP has been employed in the pediatric and congenital populations, several small studies have shown LBBP to be safe and effective in the pediatric population. We present a patient with congenital atrioventricular block and postoperative ventricular septal defect repair cardiomyopathy with subsequent left ventricular function improvement following a transition from an RV epicardial pacemaker system to an LBBP system. This case report serves as a foundation for a review of the current state of LBBP in pediatrics and congenital heart disease.

Case Report: Left bundle branch pacing in an amyloid light-chain cardiac amyloidosis patient with atrioventricular block

Introduction

Amyloid light-chain cardiac amyloidosis is a progressive infiltrative disease characterized by the deposition of amyloid fibrils in the cardiac tissue, which can cause serious atrioventricular block requiring pacemaker implantation. Left bundle branch pacing has emerged as an alternative method for delivering physiological pacing to achieve electrical synchrony of the left ventricle. However, left bundle branch pacing in patients with amyloid light-chain cardiac amyloidosis has not been studied in detail. Therefore, in this study, we present a case of left bundle branch pacing in a patient with amyloid light-chain cardiac amyloidosis.

Case summary

A 66-year-old male patient with amyloid light-chain cardiac amyloidosis presented with syncope for 1 month. Holter monitoring revealed intermittent third-degree atrioventricular block. Left bundle branch pacing was performed successfully. During the 1-year follow-up, it was observed that the left bundle branch capture threshold remained stable without any pacemaker-related complications or left ventricle systolic dysfunction, and there was no recurrence of syncope.

Conclusion

Left bundle branch pacing appears to be a safe and feasible option for patients with amyloid light-chain cardiac amyloidosis experiencing atrioventricular block.

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.

Clinical outcomes of left bundle branch area pacing: Prognosis and specific applications

Cardiac pacing has become a widely accepted treatment strategy for bradyarrhythmia and heart failure. However, conventional right ventricular pacing (RVP) has been associated with electrical dyssynchrony, which may result in atrial fibrillation and heart failure. To achieve physiological pacing, Deshmukh et al. reported the first case of His bundle pacing (HBP) in 2000. This strategy was reported to have preserved ventricular synchronization by activating the conventional conduction system. Nonetheless, due to the anatomical location of the His bundle (HB), several issues such as high pacing thresholds, lead fixation, and early battery depletion may pose a challenge. Recently, left bundle branch area pacing (LBBAP) has emerged as a novel physiological pacing strategy to achieve conduction system pacing by capturing the left bundle branch through the deep septum. Additionally, several studies have investigated the clinical outcomes of LBBAP. In this paper, we describe the pacing parameters, QRS duration (QRSd), cardiac function, complications, and specific applications of LBBAP in recent years.

Autothreshold algorithm feasibility and safety in left bundle branch pacing

AIMS

Autothreshold algorithms enable remote monitoring of patients with conventional pacing, but there is limited information on their performance in left bundle branch pacing (LBBP). Our objective was to analyse the behaviour of the autothreshold algorithm in LBBP and compare it with conventional pacing and manual thresholds during initial device programming (acute phase), after 1-7 days (subacute), and 1-3 months later (chronic).

METHODS AND RESULTS

A prospective, non-randomized, single-centre comparative study was conducted. Consecutive patients with indication for cardiac pacing were enrolled. Implants were performed in the left bundle branch area or the right ventricle endocardium at the discretion of the operator. Left bundle branch pacing was determined according to published criteria. Autothreshold algorithm was activated in both groups whenever allowed by the device. Seventy-five patients were included, with 50 undergoing LBBP and 25 receiving conventional pacing. Activation of the autothreshold algorithm was more feasible in later phases, showing a favourable trend towards bipolar pacing. Failures in algorithm activation were primarily due to insufficient safety margins (82.8% in LBBP and 90% in conventional pacing). The remainder was attributed to atrial tachyarrhythmias (10.3% and 10%, respectively) and electrical noise (the remaining 6.9% in the LBBP group). In the LBBP group, there were not statistically significant differences between manual and automatic thresholds, and both remained stable during follow-up (mean increase of 0.50 V).

CONCLUSION

The autothreshold algorithm is feasible in LBBP, with a favourable trend towards bipolar pacing. Automatic thresholds are similar to manual in patients with LBBP, and they remain stable during follow-up.

Conventional biventricular pacing is still preferred to conduction system pacing for atrioventricular block in patients with reduced ejection fraction and narrow QRS

It is well established that right ventricular pacing is detrimental in patients with reduced cardiac function who require ventricular pacing (VP), and alternatives nowadays are comprised of biventricular pacing (BiVP) and conduction system pacing (CSP). The latter modality is of particular interest in patients with a narrow baseline QRS as it completely avoids, or minimizes, ventricular desynchronization associated with VP. In this article, experts debate whether BiVP or CSP should be used to treat these patients.

Spontaneous Sinus Rhythm Restoration in Patients With Refractory, Permanent Atrial Fibrillation Who Underwent Conduction System Pacing and Atrioventricular Junction Ablation

Ablate and pace (A&P) with conduction system pacing (CSP) improves outcomes in patients with symptomatic permanent atrial fibrillation (AF). Data on spontaneous sinus rhythm restoration (SSRR) in this setting are lacking. This study aimed to assess the incidence and the predictors of SSRR in a population of patients with permanent AF who underwent A&P with CSP. Prospective, observational study, enrolling consecutive patients with symptomatic permanent AF (of documented duration >6 months) and uncontrolled, drug-refractory high ventricular rate, who underwent A&P with CSP. The incidence and predictors of SSRR were prospectively assessed. A total of 107 patients (79.0 ± 9.1 years, 33.6% male, 74.8% with New York Heart Association class ≥III, 56.1% with ejection fraction <40%) were enrolled: 40 received His' bundle pacing, 67 left bundle branch area pacing. During a median follow-up of 12 months SSRR was observed in 14 patients (13.1%), occurring a median of 3 months after A&P (interquartile range 1 to 6; range 0 to 17). Multivariable analysis identified a duration of permanent AF <12 months (hazard ratio 7.7, p = 0.040) and a left atrial volume index <49 ml/m2 (hazard ratio 14.8, p = 0.008) as independent predictors of SSRR. In patients with coexistence of both predictors the incidence of SSRR was of 41.4%. In a population of patients with symptomatic, permanent AF, treated with A&P with CSP, SSRR was observed in 13% of patients during follow-up. A duration of permanent AF <12 months and a left atrial volume index <49 ml/m2 were independent predictors of this phenomenon.

Result of the Physiologic Pacing Registry, an international multicenter prospective observational study of conduction system pacing

BACKGROUND

Conduction system pacing (CSP), including both left bundle branch area pacing (LBBAP) and His-bundle pacing (HBP) has been proposed as an alternative therapy option for patients with indication for cardiac pacing to treat bradycardia or heart failure.

OBJECTIVE

The purpose of this study was to evaluate implant success, safety, and electrical performances of HBP and LBBAP in the multinational Physiological Pacing Registry.

METHODS

The international prospective observational registry included 44 sites from 16 countries globally between November 2018 and May 2021.

RESULTS

Of 870 subjects enrolled, CSP lead implantation was attempted in 849 patients. Subjects with successful CSP lead implantation were followed for 6 months (5 ± 2 months). CSP lead implantation was successful in 768 patients (90.4%). Implant success was 95.2% (239/251) for LBBAP and 88.5% (529/598) for HBP (P = .002). Procedural duration and fluoroscopy duration were comparable between LBBAP and HBP (P = .537). Capture threshold at implant was 0.69 ± 0.39 V at 0.46 ± 0.15 ms in LBBAP and 1.44 ± 1.03 V at 0.71 ± 0.33 ms in HBP (P <.001). Capture threshold at 6 months was 0.79 ± 0.33 V at 0.44 ± 0.13 ms in LBBAP and 1.59 ± 0.97 V at 0.67 ± 0.31 ms in HBP (P <.001). Pacing threshold rise ≥1 V was observed at 6 months in 3 of 208 (1.4%) of LBBAP and 55 of 418 (13.2%) of HBP (P <.001). Serious adverse events related to implant procedure or CSP lead occurred in 5 of 251 (2.0%) with LBBAP and 25 of 598 (4.2%) with HBP (P = .115).

CONCLUSION

This large prospective multicenter study demonstrates that CSP is technically feasible in most patients with relatively higher implant success and suggests that, with current technology, LBBAP may have better pacing parameters than HBP.

Superior approach from the pocket for atrioventricular junction ablation performed at the time of conduction system pacing implantation

BACKGROUND

Conduction system pacing (CSP) and atrioventricular junction ablation (AVJA) improve outcomes in patients with symptomatic, refractory atrial fibrillation (AF). Superior approach (SA) from the pocket via axillary or subclavian vein has been proposed as an alternative to the conventional femoral venous access (FA) to perform AVJA.

OBJECTIVE

To assess the feasibility and safety of SA for AVJA performed simultaneously with CSP, and to compare this approach with FA.

METHODS

A prospective, observational study, enrolling consecutive patients with symptomatic, refractory AF undergoing simultaneous CSP and AVJA.

RESULTS

A total of 107 patients were enrolled: in 50, AVJA was primarily attempted with SA, in 69 from FA. AVJA with SA was successful in 38 patients (76.0%), while in 12 patients, a subsequent FA was required. AVJA from FA was successful in 68 patients (98.5%), while in one patient, a left-sided approach via femoral artery was required. Compared with FA, SA was associated with a significantly longer duration of ablation (238.0 ± 218.2 vs. 161.9 ± 181.9 s; p = .035), a significantly shorter procedure time (28.1 ± 19.8 vs. 19.8 ± 16.8 min; p = .018), an earlier ambulation (2.7 ± 3.2 vs. 19.8 ± 0.1 h; p < .001), and an earlier discharge from procedure completion (24.0 ± 2.7 vs. 27.1 ± 5.1 h; p < .001). After a median follow-up of 12 months, the rate of complications was similar in the two groups (2.0% in SA, 4.3% in FA; p = .483).

CONCLUSION

Simultaneous CSP and AVJA with SA is feasible, with a safety profile similar to FA. Compared to FA, this approach reduces the procedure times and allows earlier ambulation and discharge.

Lead Management in Patients with Congenital Heart Disease

Pediatric patients with congenital heart disease present unique challenges when it comes to cardiac implantable electronic devices. Pacing strategy is often determined by patient size/weight and operator experience. Anatomic considerations, including residual shunts, anatomic obstructions and barriers, and abnormalities in the native conduction system, will affect the type of CIED implanted. Given the young age of patients, it is important to have an "eye on the future" when making pacemaker/defibrillator decisions, as one can expect several generator changes, lead revisions, and potential lead extractions during their lifetime.

Conduction System Pacing for Patients with Congenital Heart Disease

For patients with congenital heart disease (CHD), chronic ventricular pacing may lead to progressive cardiomyopathy owing to electromechanical dyssynchrony. Cardiac conduction system pacing (CSP) has been proposed as a physiologic pacing strategy-directly engaging the His-Purkinje system and preserving electromechanical synchrony. CSP may be indicated for a wide variety of children and adults with CHD and has emerged as an important tool in the armamentarium for cardiac implantable electronic device operators. This review provides the rationale, background, and supportive evidence for CSP in patients with CHD and discusses implant strategies and outcomes in the context of dominant ventricular morphologic categories.

The Emerging Role of Left Bundle Branch Area Pacing for Cardiac Resynchronisation Therapy

Cardiac resynchronisation therapy (CRT) reduces the risk of heart failure-related hospitalisations and all-cause mortality, as well as improving quality of life and functional status in patients with persistent heart failure symptoms despite optimal medical treatment and left bundle branch block. CRT has traditionally been delivered by implanting a lead through the coronary sinus to capture the left ventricular epicardium; however, this approach is associated with significant drawbacks, including a high rate of procedural failure, phrenic nerve stimulation, high pacing thresholds and lead dislodgement. Moreover, a significant proportion of patients fail to derive any significant benefit. Left bundle branch area pacing (LBBAP) has recently emerged as a suitable alternative to traditional CRT. By stimulating the cardiac conduction system physiologically, LBBAP can result in a more homogeneous left ventricular contraction and relaxation, thus having the potential to improve outcomes compared with conventional CRT strategies. In this article, the evidence supporting the use of LBBAP in patients with heart failure is reviewed.

Outcomes of left bundle branch area pacing compared to His bundle pacing as a primary pacing strategy: Systematic review and meta-analysis

BACKGROUND

Novel pacing technologies, such as His bundle pacing (HBP) and left bundle branch area pacing (LBBaP), have emerged to maintain physiological ventricular activation. We investigated the outcomes of LBBP with HBP for patients requiring a de novo permanent pacing.

METHODS AND RESULTS

Systematic review of randomized clinical trials and observational studies comparing LBBaP with HBP until March 01, 2023 was performed. Random and fixed effects meta-analyses of the effect of pacing technology on outcomes were performed. Study outcomes included pacing metrics, QRS duration, lead revision, procedure parameters, all-cause mortality and heart failure hospitalization (HFH). Overall, 10 studies with 1596 patients were included. Implant success rate was higher in LBBaP compared with HBP (RR 1.24, 95% CI: 1.08 to 1.42, p = .002). LBBaP was associated with lower capture threshold at implantation (mean difference (MD) -0.62 V, 95% CI: -0.74 to -0.51 V, p < .0001) and at follow-up (MD -0.74 V, 95% CI: -0.96 to -0.53, p < .0001), shorter procedure duration (MD -14.66 min, 95% CI: -23.54 to -5.78, p = .001) and shorter fluoroscopy time (MD -4.2 min, 95% CI: -8.4 to -0.0, p = .05). Compared with HBP, LBBaP was associated with a decreased risk of all-cause mortality (RR: 0.50, 95% CI: 0.33 to 0.77, p = .002) and HFH (RR: 0.57, 95% CI: 0.33 to 1.00, p = .05). No statistical differences were found in lead revisions and QRS duration before and after pacing.

CONCLUSION

This meta-analysis found that LBBaP was superior to HBP regarding pacing metrics and implant success rate as an initial pacing strategy, although absence of head-to-head randomized comparison warrants caution in interpretation of the results.

Implant, assessment, and management of conduction system pacing

His bundle pacing and left bundle branch pacing, together referred to as conduction system pacing, have (re)gained considerable interest over the past years as it has the potential to preserve and/or restore a more physiological ventricular activation when compared with right ventricular pacing and may serve as an alternative for cardiac resynchronization therapy. This review manuscript dives deeper into the implantation techniques and the relevant anatomy of the conduction system for both pacing strategies. Furthermore, the manuscript elaborates on better understanding of conduction system capture with its various capture patterns, its potential complications as well as appropriate follow-up care. Finally, the limitations and its impact on clinical care for both His bundle pacing and left bundle branch pacing are being discussed.

Long-term follow-up of selective and non-selective His bundle pacing leads in patients with atrioventricular block

BACKGROUND

His bundle pacing (HBP) is a novel treatment with limited knowledge on long-term outcome. We aimed to assess long-term safety and effectiveness of HBP in patients with atrioventricular block treated with HBP and a back-up right ventricular pacing (RVP) lead.

METHODS

We included 38 patients from a completed single-center, randomized controlled cross-over trial designed to compare left ventricular (LV) function after 12 months of HBP vs. RVP conducted between September 2007 and August 2011. Lead performance beyond the 2-year study period was assessed based on a retrospective review of capture thresholds, sensing, impedance, energy consumption, and rate of HBP interruption.

RESULTS

Patients were followed for a mean of 7 ± 4 years. Both at baseline and during follow-up, HBP leads displayed significantly higher capture thresholds than RVP leads (P < 0.001), multifold higher energy consumption (P < 0.001), and lower sensing amplitudes (P < 0.001). During follow-up, 17 (53%) HBP leads were deactivated or abandoned. The principal cause for HBP interruption was high pacing thresholds in patients with preserved LVEF during RVP. Device longevity was shorter than that of contemporary cohorts treated with dual-chamber pacing or CRT, and time to first device exchange was 6.8 ± 1.5 years. No lead dislodgements occurred, but four patients (10%) developed device-related infections requiring device extraction.

CONCLUSION

HBP was interrupted in > 50% of patients during long-term follow-up. The principal cause was unacceptably high capture thresholds and no significant difference in LV function with HBP compared with RVP. Device longevity was shorter, and infection rates were higher than anticipated.

Left bundle branch pacing with and without anodal capture: impact on ventricular activation pattern and acute haemodynamics

AIMS

Left bundle branch pacing (LBBP) can deliver physiological left ventricular activation, but typically at the cost of delayed right ventricular (RV) activation. Right ventricular activation can be advanced through anodal capture, but there is uncertainty regarding the mechanism by which this is achieved, and it is not known whether this produces haemodynamic benefit.

METHODS AND RESULTS

We recruited patients with LBBP leads in whom anodal capture eliminated the terminal R-wave in lead V1. Ventricular activation pattern, timing, and high-precision acute haemodynamic response were studied during LBBP with and without anodal capture. We recruited 21 patients with a mean age of 67 years, of whom 14 were males. We measured electrocardiogram timings and haemodynamics in all patients, and in 16, we also performed non-invasive mapping. Ventricular epicardial propagation maps demonstrated that RV septal myocardial capture, rather than right bundle capture, was the mechanism for earlier RV activation. With anodal capture, QRS duration and total ventricular activation times were shorter (116 ± 12 vs. 129 ± 14 ms, P < 0.01 and 83 ± 18 vs. 90 ± 15 ms, P = 0.01). This required higher outputs (3.6 ± 1.9 vs. 0.6 ± 0.2 V, P < 0.01) but without additional haemodynamic benefit (mean difference -0.2 ± 3.8 mmHg compared with pacing without anodal capture, P = 0.2).

CONCLUSION

Left bundle branch pacing with anodal capture advances RV activation by stimulating the RV septal myocardium. However, this requires higher outputs and does not improve acute haemodynamics. Aiming for anodal capture may therefore not be necessary.

Ablate and pace: Comparison of outcomes between conduction system pacing and biventricular pacing

BACKGROUND

Conduction system pacing (CSP), including His-bundle pacing (HBP) and left bundle branch area pacing (LBBAP), have been proposed as alternatives to biventricular pacing (BVP) in patients scheduled for ablate and pace (A&P) strategy. The aim of this study was to compare the clinical outcomes, including the rate and nature of device-related complications, between BVP and CSP in a cohort of patients undergoing A&P.

METHODS

Prospective, multicenter, observational study, enrolling consecutive patients undergoing A&P. The risk of device-related complications and of heart failure (HF) hospitalization was prospectively assessed.

RESULTS

A total of 373 patients (75.3 ± 8.7 years, 53.9% male, 68.9% with NYHA class ≥III) were enrolled: 263 with BVP, 68 with HBP, and 42 with LBBAP. Baseline characteristics of the three groups were similar. Compared to BVP and HBP, LBBAP was associated with the shortest mean procedural and fluoroscopy times and with the lowest acute capture thresholds (all p < .05). At 12-month follow-up LBBAP maintained the lowest capture thresholds and showed the longest estimated residual battery longevity (all p < .05). At 12-months follow-up the three study groups showed a similar risk of device-related complications (5.7%, 4.4%, and 2.4% for BVP, HBP, and LBBAP, respectively; p = .650), and of HF hospitalization (2.7%, 1.5%, and 2.4% for BVP, HBP, and LBBAP, respectively; p = .850).

CONCLUSIONS

In the setting of A&P, CSP is a feasible pacing modality, with a midterm safety profile comparable to BVP. LBBAP offers the advantage of reducing procedural times and obtaining lower and stable capture thresholds, with a positive impact on the device longevity.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

Conduction system pacing on track to replace CRT? Review of current evidence and prospects of conduction system pacing

Conduction system pacing (CSP) has been emerging over the last decade as a pacing option instead of conventional right ventricular (RV) pacing and biventricular (BiV) pacing. Numerous case reports, some observational studies and a few randomized control trials have looked at optimum pacing strategies for heart failure (HF) with left bundle branch block (LBBB) or cases where left ventricular (LV) dysfunction is anticipated due to chronic RV pacing (RVP). Evolution of pacing strategies from standard RVP to septal RVP, BiV pacing and now CSP have shown improving hemodynamic responses and possible ease of implantation of CSP systems. In this review article, we review the literature on the evolution of CSP and common scenarios where it might be beneficial.

Cardiac Resynchronisation with Conduction System Pacing

To date, biventricular pacing (BiVP) has been the standard pacing modality for cardiac resynchronisation therapy. However, it is non-physiological, with the activation spreading between the left ventricular epicardium and right ventricular endocardium. Up to one-third of patients with heart failure who are eligible for cardiac resynchronisation therapy do not derive benefit from BiVP. Conduction system pacing (CSP), which includes His bundle pacing and left bundle branch area pacing, has emerged as an alternative to BiVP for cardiac resynchronisation. There is mounting evidence supporting the benefits of CSP in achieving synchronous ventricular activation and repolarisation. The aim of this review is to summarise the current options and outcomes of CSP when used for cardiac resynchronisation in patients with heart failure.

Pacing of Specialized Conduction System

Right ventricular pacing for bradycardia remains the mainstay of pacing therapy. Chronic right ventricular pacing may lead to pacing-induced cardiomyopathy. We focus on the anatomy of the conduction system and the clinical feasibility of pacing the His bundle and/or left bundle conduction system. We review the hemodynamics of conduction system pacing, the techniques to capture the conduction system and the electrocardiogram and pacing definitions of conduction system capture. Clinical studies of conduction system pacing in the setting of atrioventricular block and after AV junction ablation are reviewed and the evolving role of conduction system pacing is compared with biventricular pacing.

Left Bundle Branch Area Pacing Versus Biventricular Pacing as Initial Strategy for Cardiac Resynchronization

BACKGROUND

Left bundle branch area pacing (LBBAP) for cardiac resynchronization therapy (CRT) is an alternative to biventricular pacing (BiVp).

OBJECTIVES

The purpose of this study was to compare the outcomes between LBBAP and BiVp as an initial implant strategy for CRT.

METHODS

In this prospective multicenter, observational, nonrandomized study, first-time CRT implant recipients with LBBAP or BiVp were included. The primary efficacy outcome was a composite of heart failure (HF)-related hospitalization and all-cause mortality. The primary safety outcomes were acute and long-term complications. Secondary outcomes included postprocedural New York Heart Association functional class and electrocardiographic and echocardiographic parameters.

RESULTS

A total of 371 patients (median follow-up of 340 days [IQR: 206-477 days]) were included. The primary efficacy outcome occurred in 24.2% in the LBBAP vs 42.4% in the BiVp (HR: 0.621 [95% CI: 0.415-0.93]; P = 0.021) group, driven by a reduction in HF-related hospitalizations (22.6% vs 39.5%; HR: 0.607 [95% CI: 0.397-0.927]; P = 0.021) without significant difference in all-cause mortality (5.5% vs 11.9%; P = 0.19) or differences in long-term complications (LBBAP: 9.4% vs BiVp: 15.2%; P = 0.146). LBBAP resulted in shorter procedural (95 minutes [IQR: 65-120 minutes] vs 129 minutes [IQR: 103-162 minutes]; P < 0.001) and fluoroscopy times (12 minutes [IQR: 7.4-21.1 minutes] vs 21.7 minutes [IQR: 14.3-30 minutes]; P < 0.001), shorter QRS duration (123.7 ± 18 milliseconds vs 149.3 ± 29.1 milliseconds; P < 0.001), and higher postprocedural left ventricular ejection fraction (34.1% ± 12.5% vs 31.4% ± 10.8%; P = 0.041).

CONCLUSIONS

LBBAP as an initial CRT strategy resulted in a lower risk of HF-related hospitalizations compared to BiVp. A reduction in procedural and fluoroscopy times, shorter paced QRS duration, and improvements in left ventricular ejection fraction compared with BiVp were observed.

Comparison of Pacing Performance and Clinical Outcomes Between Left Bundle Branch and His Bundle Pacing

BACKGROUND

Left bundle branch (LBBP) and His-bundle pacing (HBP) provide physiological ventricular activation.

OBJECTIVES

This study investigated differences in feasibility, device performance, and clinical outcomes between LBBP and HBP.

METHODS

Consecutive patients with LBBP and HBP from 2018 to 2021 in 2 centers were prospectively studied. The primary endpoint was optimal device performance during follow-up, defined as the presence of pacing thresholds <2.5 V, R-wave amplitude ≥5 V, and absence of conduction system pacing (CSP)-related complications. The secondary endpoint was the composite of heart failure hospitalizations or all-cause mortality.

RESULTS

Among 338 patients, 282 underwent successful CSP (119 HBP, 163 LBBP). Success rates, CSP-related complications, and need for reoperations did not differ between LBBP and HBP (P > 0.05). Pacing thresholds were lower, whereas R-wave amplitudes and lead impedance were higher in LBBP (P < 0.05). The primary endpoint was more frequent in LBBP than HBP (79% vs 34%; P < 0.001), with LBBP independently associated with 9-fold increased odds of optimal device performance (adjusted OR: 9.31; 95% CI: 5.14-16.86). LBBP was less likely to have increased pacing thresholds by >1 V (1% vs 19% HBP, P < 0.001). The secondary outcome was less frequent in LBBP than HBP (9% vs 24%, P = 0.001), with LBBP trending towards higher event-free survival (HR: 0.62; 95% CI: 0.31-1.23). The secondary outcome was independent of pacing burden or pacing indication.

CONCLUSIONS

Despite similar feasibility and safety profiles, LBBP confers additional benefits in pacing performance and reliability, shows trends towards improved survival compared to HBP, and should be the preferred first-line CSP modality of choice.

Beyond Conventional Cardiac Resynchronisation Therapy: A Review of Electrophysiological Options in the Management of Chronic Heart Failure

The incidence of heart failure (HF) continues to grow and burden our health care system. Electrophysiological aberrations are common amongst patients with heart failure and can contribute to worsening symptoms and prognosis. Targeting these abnormalities with cardiac and extra-cardiac device therapies and catheter ablation procedures augments cardiac function. Newer technologies aimed to improvement procedural outcomes, address known procedural limitations and target newer anatomical sites have been trialled recently. We review the role and evidence base for conventional cardiac resynchronisation therapy (CRT) and its optimisation, catheter ablation therapies for atrial arrhythmias, cardiac contractility and autonomic modulation therapies.

Pacing-Induced Cardiomyopathy

Right ventricular (RV) pacing-induced cardiomyopathy (PICM) is typically defined as left ventricular systolic dysfunction resulting from electrical and mechanical dyssynchrony caused by RV pacing. RV PICM is common, occurring in 10-20% of individuals exposed to frequent RV pacing. Multiple risk factors for PICM have been identified, including male sex, wider native and paced QRS durations, and higher RV pacing percentage, but the ability to predict which individuals will develop PICM remains modest. Biventricular and conduction system pacing, which better preserve electrical and mechanical synchrony, typically prevent the development of PICM and reverse left ventricular systolic dysfunction after PICM has occurred.

Risk Factors, Management, and Avoidance of Conduction System Disease after Transcatheter Aortic Valve Replacement

Transcatheter valve replacement (TAVR) is a rapidly developing modality to treat patients with aortic stenosis (AS). Conduction disease post TAVR is one of the most frequent and serious complications experienced by patients. Multiple factors contribute to the risk of conduction disease, including AS and the severity of valve calcification, patients' pre-existing conditions (i.e., conduction disease, anatomical variations, and short septum) in addition to procedure-related factors (e.g., self-expanding valves, implantation depth, valve-to-annulus ratio, and procedure technique). Detailed evaluation of risk profiles could allow us to better prevent, recognize, and treat this entity. Available evidence on management of conduction disease post TAVR is based on expert opinion and varies widely. Currently, conduction disease in TAVR patients is managed depending on patient risk, with minimal-to-no inpatient/outpatient observation, inpatient monitoring (24-48 h) followed by ambulatory monitoring, or either prolonged inpatient and outpatient monitoring or permanent pacemaker implantation. Herein, we review the incidence and risk factors of TAVR-associated conduction disease and discuss its management.

Cardiovascular imaging in conduction system pacing: What does the clinician need?

Permanent pacemakers are used for symptomatic bradycardia and biventricular pacing (BVP)-cardiac resynchronization therapy (BVP-CRT) is established for heart failure (HF) patients traditionally. According to guidelines, patients' selection for CRT is based on QRS duration (QRSd) and morphology by surface electrocardiogram (ECG). Cardiovascular imaging techniques evaluate cardiac structure and function as well as identify pathophysiological substrate changes including the presence of scar. Cardiovascular imaging helps by improving the selection of candidates, guiding left ventricular (LV) lead placement, and optimization devices during the follow-up. Conduction system pacing (CSP) includes His bundle pacing (HBP) and left bundle branch pacing (LBBP) which is screwed into the interventricular septum. CSP maintains and restores ventricular synchrony in patients with native narrow QRSd and left bundle branch block (LBBB), respectively. LBBP is more feasible than HBP due to a wider target area. This review highlights the role of multimodality cardiovascular imaging including fluoroscopy, echocardiography, cardiac magnetic resonance (CMR), myocardial scintigraphy, and computed tomography (CT) in the pre-procedure assessment for CSP, better selection for CSP candidates, the guidance of CSP lead implantation, and the optimization of devices programming after the procedure. We also compare the different characteristics of multimodality imaging and discuss their potential roles in future CSP implantation.

Optimization of the atrioventricular delay in conduction system pacing

INTRODUCTION

In patients receiving conduction system pacing (CSP), it is not well established how to program the sensed atrioventricular delay (sAVD), with respect to the type of capture obtained (selective, nonselective His-bundle [HB] capture or left bundle branch [LBB] capture). The aim of this study was to acutely assess the effectiveness of an electrophysiology (EP)-guided method for sAVD optimization by comparing it with the echocardiogram-guided optimization.

METHODS AND RESULTS

Consecutive patients undergoing HB or LBB pacing were enrolled. The EP-guided sAVD was defined as the sAVD leading to a PR interval of 150 ms on surface electrocardiogram (ECG). In HB pacing patients, EP-guided sAVD was obtained subtracting the time from the onset of the P wave on ECG to the local atrial electrogram (EGM) recorded by the atrial lead (right atrial sensing latency, RASL) and the His-ventricular interval from 150 ms; in LBB pacing patients, subtracting RASL from 150 ms. Transmitral flow assessment by pulsed wave Doppler was used to find the echo-optimized sAVD by a modified iterative method. The discordance between the EP-guided and the echo-optimized sAVD was recorded.

RESULTS

Seventy-one patients were enrolled: 12 with selective, 32 nonselective HB capture, and 27 LBB capture. Overall, the rate of concordance between the EP-guided and the echo-optimized sAVD was 71.8%, with no significant differences between the three groups.

CONCLUSION

In CSP patients, an optimal sAVD can be programmed, in more than 70% of cases, considering only simple EGM intervals to obtain a physiological PR interval on surface ECG.

Left Bundle Branch Area Pacing over His Bundle Pacing: How Far Have We Come?

Implantable cardiac pacemakers have greatly evolved during the few past years, focusing on newer modalities of physiologic cardiac pacing [...].

Paradigm Shifts in Cardiac Pacing: Where Have We Been and What Lies Ahead?

The history of cardiac pacing dates back to the 1930s with externalized pacing and has evolved to incorporate transvenous, multi-lead, or even leadless devices. Annual implantation rates of cardiac implantable electronic devices have increased since the introduction of the implantable system, likely related to expanding indications, and increasing global life expectancy and aging demographics. Here, we summarize the relevant literature on cardiac pacing to demonstrate the enormous impact it has had within the field of cardiology. Further, we look forward to the future of cardiac pacing, including conduction system pacing and leadless pacing strategies.

Comparison of methods for delivering cardiac resynchronization therapy: an acute electrical and haemodynamic within-patient comparison of left bundle branch area, His bundle, and biventricular pacing

AIMS

Left bundle branch area pacing (LBBAP) is a promising method for delivering cardiac resynchronization therapy (CRT), but its relative physiological effectiveness compared with His bundle pacing (HBP) is unknown. We conducted a within-patient comparison of HBP, LBBAP, and biventricular pacing (BVP).

METHODS AND RESULTS

Patients referred for CRT were recruited. We assessed electrical response using non-invasive mapping, and acute haemodynamic response using a high-precision haemodynamic protocol. Nineteen patients were recruited: 14 male, mean LVEF of 30%. Twelve had time for BVP measurements. All three modalities reduced total ventricular activation time (TVAT), (ΔTVATHBP -43 ± 14 ms and ΔTVATLBBAP -35 ± 20 ms vs. ΔTVATBVP -19 ± 30 ms, P = 0.03 and P = 0.1, respectively). HBP produced a significantly greater reduction in TVAT compared with LBBAP in all 19 patients (-46 ± 15 ms, -36 ± 17 ms, P = 0.03). His bundle pacing and LBBAP reduced left ventricular activation time (LVAT) more than BVP (ΔLVATHBP -43 ± 16 ms, P < 0.01 vs. BVP, ΔLVATLBBAP -45 ± 17 ms, P < 0.01 vs. BVP, ΔLVATBVP -13 ± 36 ms), with no difference between HBP and LBBAP (P = 0.65). Acute systolic blood pressure was increased by all three modalities. In the 12 with BVP, greater improvement was seen with HBP and LBBAP (6.4 ± 3.8 mmHg BVP, 8.1 ± 3.8 mmHg HBP, P = 0.02 vs. BVP and 8.4 ± 8.2 mmHg for LBBAP, P = 0.3 vs. BVP), with no difference between HBP and LBBAP (P = 0.8).

CONCLUSION

HBP delivered better ventricular resynchronization than LBBAP because right ventricular activation was slower during LBBAP. But LBBAP was not inferior to HBP with respect to LV electrical resynchronization and acute haemodynamic response.

Approach to Left Bundle Branch Pacing

Cardiac pacing refers to the implantation tool serving as a treatment modality for various indications, the most common of which is symptomatic bradyarrhythmia. Left bundle branch pacing has been noted in the literature to be safer than biventricular pacing or His-bundle pacing in patients with left bundle branch block (LBBB) and heart failure, thereby becoming the focus of further research on cardiac pacing. A review of the literature was conducted using a combination of keywords, including "Left Bundle Branch Block," "Procedural techniques," "Left Bundle Capture," and "Complications." The following factors have been investigated as key criteria for direct capture: paced QRS morphology, peak left ventricular activation time, left bundle potential, nonselective and selective left bundle capture, and programmed deep septal stimulation protocol. In addition, complications of LBBP, inclusive of septal perforation, thromboembolism, right bundle branch injury, septal artery injury, lead dislodgement, lead fracture, and lead extraction, have also been elaborated on. Despite clinical implications based on clinical research comparing the use of LBBP with other forms such as right ventricular apex pacing, His-bundle pacing, biventricular pacing, and left ventricular septal pacing, a paucity in the literature on long-term effects and efficacy has been noted. LBBP can thus be considered to have a promising future in patients requiring cardiac pacing, assuming that additional research on clinical outcomes and the limitation of significant complications such as thromboembolism can be established.

Electrophysiological demonstration of nonselective His-Purkinje system capture with para-Hisian pacing

BACKGROUND

The adverse effects of conventional right ventricular (RV) apical pacing prompted the search for more physiological pacing sites, such as selective and nonselective His bundle pacing (HBP), a variant of nonselective HBP (para-Hisian pacing), and mid-septal pacing. However, knowledge of their true benefit on the physiology of ventricular activation, lead stability, and pacing thresholds is limited.

METHODS AND RESULTS

We included 152 consecutive patients (mean age 61 ± 24, 63% men) in this retrospective study. Of these, 137 patients with different bradyarrhythmias underwent active fixation lead implantation at the RV apex (n = 54), para-Hisian region (n = 66), or mid interventricular septum (n = 17). Fifteen patients with ventricular preexcitation due to an accessory pathway not undergoing pacing were included as controls. A 12‑lead ECG was recorded in all patients, and cardiac electrical synchrony was assessed using the Synchromax® cross-correlation cardiac synchrony index (CSI).

RESULTS

QRS duration was prolonged in all pacing sites: from 114 ± 28 to 160 ± 29 (RV apex), from 110 ± 28 to 122 ± 29 (para-Hisian), and from 121 ± 24 to 154 ± 30 (mid interventricular septum). The CSI was significantly improved only in patients undergoing para-Hisian pacing, despite a slight widening of the QRS interval. There was no difference in pacing thresholds and sensed R-wave voltage between pacing sites. Only 1 lead, implanted at the para-Hisian region (1.5%), was dislodged towards the mid septum 48 h after implantation but did not require repositioning.

CONCLUSIONS

QRS duration was not associated with changes in CSI, meaning that QRS width does not significantly affect electrical synchrony.

Rate and nature of complications of conduction system pacing compared with right ventricular pacing: results of a propensity-matched analysis from a multicentre registry

BACKGROUND

Conduction system pacing (CSP) using His-bundle pacing (HBP) or left bundle branch area pacing (LBBAP) has emerged as an alternative to right ventricular pacing (RVP). Comparative data on the risk of complications between CSP and RVP are lacking.

OBJECTIVE

Prospective, multicenter, observational study aimed to compare the long-term risk of device-related complications between CSP and RVP.

METHODS

A total of 1,029 consecutive patients undergoing pacemaker implantation with CSP (including HBP and LBBAP) or RVP were enrolled. Propensity matching for baseline characteristics yielded 201 matched pairs. Rate and nature of device-related complications occurring during follow-up were prospectively collected and compared between the two groups.

RESULTS

During a mean follow-up of 18 months, device-related complications were observed in 19 patients: 7 in RVP (3.5%), and in 12 in CSP (6.0%) (p=0.240). Dividing the matched cohort in three groups with similar baseline characteristics according to the pacing modality (RVP, n=201; HBP, n=128; LBBAP, n=73), HBP patients showed a rate of device-related complications significantly higher compared to RVP patients (8.6 vs. 3.5%; p=0.047), and to LBBAP patients (8.6 vs. 1.3%; p=0.034). LBBAP patients showed a rate of device-related complications similar to that of RVP patients (1.3 vs. 3.5%, p=0.358). Most of the complications observed in HBP patients (63.6%) were lead-related.

CONCLUSIONS

Globally, CSP was associated with a risk of complications similar to that of RVP. Considering separately HBP and LBBAP, HBP showed a significantly higher risk of complications than both RVP and LBBAP, whereas LBBAP showed a risk of complications similar to RVP.