Most initial experience with Left bundle branch are pacing (LBBAP) has involved lumenless leads (LLLs). Recently, stylet-driven leads (SDLs) have also been introduced for LBBAP. This study examined the clinical success rates, outcomes, and complication rates between SDLs and LLLs.

A systematic review of randomized clinical trials and observational studies comparing LLL and SDL up to November 30, 2024, was conducted. Random- and fixed-effects meta-analyses assessed the impact of implant technology on outcomes, including pacing metrics, lead complications, and procedural parameters. In total, 11 studies with 12,916 patients (SDLs: 3920; LLLs: 8996) were included. Implant success rates were comparable between SDL and LLL (RR 1.00, 95% CI 0.96-1.04, P = 0.96). SDL was associated with shorter procedure time (MD - 11.94 min, 95% CI - 19.48 to - 4.40, P = 0.002) and shorter fluoroscopy times, though this differences was not statistically significant (MD - 1.27 min, 95% CI - 2.92 to 0.39, P = 0.13). Pacing metrics, including impedance, pacing threshold, and R-wave amplitude, also showed no significant differences during follow-up (up to 28 months). However, SDLs were associated with a significantly higher risk of lead-related complications compared to LLLs (RR 1.89, 95% CI 1.47-2.41, P < 0001).

LBBAP using SDL is feasible and demonstrates comparable success rates with a shorter procedure duration. A higher incidence of lead-related complications was observed in the SDL group; however, due to potential confounding factors and the absence of randomized head-to-head comparisons, no definitive conclusions can be drawn regarding causality. Further prospective studies are warranted to clarify this association.

Left bundle branch block (LBBB), initially described in the early 20th century, has become increasingly recognized as one of the leading causes of advanced heart failure (HF). In addition to rapidly growing data on guideline-directed medical therapy, cardiac resynchronization therapy (CRT) via transvenous coronary sinus lead has been the gold-standard therapy, but one-third of the indicated patients do not receive the expected benefits. Recently, cardiac conduction system pacing (CSP) was identified as an alternative to traditional CRT strategy, and multiple data have been published during the last few years. This review will discuss the diagnostic criteria of LBBB and its relation to the development of HF and review available data for traditional CRT as well as CSP in depth.

Conduction system pacing started with His bundle pacing (HBP) and then rapidly switched gears into left bundle branch pacing (LBBP). We describe our center's experience with LBBP using either lumenless leads (LLLs) or stylet-driven leads (SDLs). Patients who were admitted to two tertiary centers between 1 April 2021 and 30 June 2024 and met the guidelines for pacing were recruited and prospectively followed up. A total of 124 patients underwent permanent pacemaker (PPM) implantation using the LBBP technique with a mean follow-up of 19.7 ± 13.3 months. In total, 90 patients were implanted with LLLs and 34 with SDLs. There was no significant difference in the procedural time and final paced QRS duration, but fluoroscopy time was significantly longer in the SDLs (26.2 ± 17.7 min vs. 17.5 ± 13.0 min, respectively, p = 0.026). The on-table impedance values were also significantly higher in the LLLs, and this persisted throughout the follow-up. There were no differences in the rates of complications. The success of conduction system pacing implantation with SDLs and LLLs is comparable with reasonable safety and reliable outcomes. Good pre-implant patient selection will contribute to improved outcomes.

The Right Ventricular (RV) apex has been the standard site for pacing in symptomatic bradyarrhythmias, but chronic RV pacing can cause adverse effects such as atrial arrhythmias and left ventricular dysfunction. Physiological pacing, including His bundle and left bundle pacing, offers alternatives with fewer complications. We present a 66-year-old male with a dextroposed heart and fibrotic right lung requiring left bundle branch pacing due to a high RV pacing burden. The procedure involved modified lead placement and a medial subclavian vein puncture, successfully achieving good electrical parameters and post-procedural device function, highlighting left bundle branch pacing's feasibility in complex anatomical conditions.

Prior studies have established the safety and efficacy of conduction system pacing (CSP) in improving echocardiographic parameters and clinical outcomes. This meta-analysis aimed to investigate whether CSP could reduce the occurrence of new-onset atrial fibrillation (AF) in comparison to traditional right ventricular pacing (RVP) therapy.

A literature search was performed in PubMed, Embase, and the Cochrane Library to identify relevant clinical studies comparing CSP with RVP from January 2000 to June 2024. The study outcome was new-onset AF after pacemaker implantation. Estimated risk ratios (RR), odds ratio (OR) with 95% confidence intervals (CI) were evaluated.

Our analysis included 8 observational studies comprising a total of 2033 patients. The results indicated that 20% (406/2033) of study patients experienced new-onset AF, and CSP was associated with a significantly lower risk of new-onset AF when compared with RVP (RR: 0.44, 95% CI: 0.36-0.54, p < 0.00001, I2 = 11%; OR: 0.34, 95% CI: 0.27-0.44, p < 0.0001, I2 = 0). In the subgroup analysis, patients with atrioventricular block (AVB) tended to benefit more from CSP than those with sinus node dysfunction (SND) or AVB (p = 0.06 for RR; p = 0.12 for OR). Publication bias was observed and confirmed by the Egger's test (p = 0.0125 for RR and 0.0345 for OR). Trim and fill analysis was performed, and the overall summary effect size (RR: 0.51, 95% CI: 0.40-0.64; OR: 0.40, 95% CI: 0.31-0.52) remained significant after adjusting for publication bias.

CSP could reduce the occurrence of new-onset AF compared with RVP, and this benefit appeared to be more pronounced in patients with AVB than those with SND or AVB. However, large scale randomized controlled trials are needed to validate our findings.

Registration number: CRD42024569052; registration date: July 25, 2024; https://www.crd.york.ac.uk/PROSPERO/view/CRD42024569052.

Conduction system pacing (CSP) is being increasingly adopted as a more physiological alternative to right ventricular and biventricular pacing. Since the 2021 European Society of Cardiology pacing guidelines, there has been growing evidence that this therapy is safe and effective. Furthermore, left bundle branch area pacing was not covered in these guidelines due to limited evidence at that time. This Clinical Consensus Statement provides advice on indications for CSP, taking into account the significant evolution in this domain.

Cardiac implantable electronic devices (CIEDs) are commonly used for a number of cardiac-related conditions, and it is estimated that over 300,000 CIEDs are placed annually in the US. With advances in technology surrounding these devices and expanding indications, CIEDs can remain implanted in patients for long periods of time. Although the safety profile of these devices has improved over time, both the incidence and prevalence of long-term complications are expected to increase. This review highlights pertinent long-term complications of CIEDs, including lead-related issues, device-related arrhythmias, inappropriate device therapies, and device-related infections. We also explore key clinical aspects of each complication, including common presentations, patient-specific and non-modifiable risk factors, diagnostic evaluation, and recommended management strategies. Our goal is to help spread awareness of CIED-related complications and to empower physicians to manage them effectively.

Heart failure (HF) is a major clinical challenge characterized by significant morbidity and mortality. Electrical conduction abnormalities play a critical role in HF pathophysiology and progression, often leading to suboptimal outcomes with conventional pacing techniques. Con-duction system pacing (CSP), encompassing His bundle pacing and left bundle branch area pacing, has emerged as a novel approach. Despite data come from observational studies, recent guidelines recommend that a specific population may benefit from CSP. However, significant practical considerations and challenges need to be clarified before CSP can be routinely implemented in clinical practice. The reliance on observational studies means that long-term clinical outcomes for HF patients remain uncertain until data from randomized controlled trials (RCTs) become available. Current CSP practices face challenges with lead implantation, mechanical stress on leads, and the need for more advanced tools and artificial intelligence integration to improve procedure efficacy and safety. Future large-scale RCTs are essential to identify optimal candidates and address these technical challenges, potentially leading to a paradigm shift in HF management.

For many years, the apex of the right ventricle (RV) seemed to be a sufficiently good site for ventricular pacing, effectively protecting both the health and life of patients with atrioventricular conduction disorders. However, the studies have demonstrated that this is not an optimal site, since it leads to electrical and mechanical interventricular asynchrony, which in some cases (15-20 ​%) results in the development of pacing-induced cardiomyopathy (PICM). The introduction of biventricular cardiac resynchronization therapy (BiV-CRT) into clinical practice was a real breakthrough in the development of modern electrotherapy, and conduction system pacing (CSP) has heralded even greater hopes. The CSP-optimized CRT is the most complex modality of CRT, involving the simultaneous pacing of His bundle or its left branch, and additionally, epicardial pacing of the left ventricle. This modality of pacing may represent the most optimal method for spreading the ventricle depolarization wave in severely damaged cardiac muscle and may represent a real hope for patients who do not adequately respond to other forms of CRT.

Atrioventricular nodal ablation (AVNA) represents a critical intervention in the management of refractory atrial fibrillation (AF) and heart failure (HF). When combined with biventricular pacing or conduction system pacing, particularly His bundle pacing and left bundle branch area pacing, this strategy offers distinct and complementary benefits. While each pacing modality presents unique advantages and potential limitations, their combination with AVNA offers a comprehensive and individualized treatment strategy for addressing associated HF. This integrated approach can enhance symptom control, improve hemodynamic performance, and contribute to better long-term outcomes in patients with advanced HF and AF.

This review provides a history of physiological pacing from inception to current practice and into the future. This review stems from personal experience and is not formally systematic. Physiological cardiac pacing is covered from 1960s to date. Concepts, and major milestones with their practical applications are reviewed including possible applications in the future. Huge strides have been made in the last 50 years, but consequences of developments have not always been well considered resulting in important adverse effects. The future requires deep electrophysiological thinking to achieve further benefits for our patients.

Soon after the rapid growth of the popularity of His bundle pacing (HBP), the use of this conduction system pacing modality was overshadowed by left bundle branch area pacing (LBBAP). This focused review on HBP addresses whether there are any advantages of HBP over LBBAP and what the current uses of HBP may be. We conclude that HBP must be considered as an alternative physiological pacing method with several potential applications, undoubtedly at least as a rescue option for failed CRT/LBBAP. For wider application of HBP, prospective studies are needed to document a reduction in the incidence of late threshold rise with modern implantation techniques. Nevertheless, HBP should be available in every modern pacing laboratory. This requires an active HBP program to maintain and develop the ability of operators to deliver HBP when it is most needed.

There are many factors contributing to the failure of conventional CRT with biventricular pacing, including coronary anatomy and an inability to stimulate diseased tissue. In this paper, we review evolving conduction system pacing (CSP), a physiological alternative to conventional CRT. CSP allows correction of bundle branch block and provides new opportunities to address multiple limitations of conventional CRT. Further studies are required to determine how the techniques are best applied in specific clinical situations.

Right ventricular (RV) pacing, particularly from the RV apex, causes bilateral ventricular dyssynchrony, reducing systolic and diastolic function, by delayed activation of the lateral left ventricle, resulting in a wide QRS with a left bundle branch block (LBBB) morphology. Alternative pacing strategies, such as His-bundle pacing and LBB area pacing, tend to be more physiological, avoiding this problem. The feasibility of attaining a narrow paced QRS from the RV septum has not been methodically examined. This study aimed to test the hypothesis that, through pacing at select RV septal sites by careful mapping, it is possible to achieve a narrow "paced QRS," facilitating physiological pacing. The underlying assumption is that a narrow paced QRS prevents long-term deterioration of cardiac function. During dual-chamber pacemaker implantation with standard active fixation leads, the RV septum was mapped carefully before fixing the lead. A characteristic spike potential was identified at some sites which, on stimulation, yielded a narrow paced QRS. The paced QRS duration was measured at different mapping sites; the narrowest paced complex was chosen for long-term pacing. Sixteen consecutive patients underwent pacemaker implantation using this mapping technique. A narrow paced QRS was achieved in 12 patients, whereas narrow paced complexes could not be achieved in 4 patients. Among the 12 narrow paced QRS patients (mean age, 81.5 ± 8.2 years), the indication for pacing was atrioventricular block in 6 patients and sick sinus syndrome in 6 patients. Two patients showed a negative paced QRS in leads 1 and aVL, suggesting an early left-sided septal activation. In the 12 narrow paced QRS patients, the post-pacing mean QRS duration (121.5 ± 14.9 ms) was not significantly different from the pre-pacing mean QRS duration (118.2 ± 23.5 ms) (P > .5); the QRS morphology was normal in seven patients, while four patients had LBBB and one patient had right bundle branch block. In all 12 patients, the narrowest paced complex was associated with a characteristic potential in the endocardial electrogram. Detailed RV septal mapping can yield a narrow paced QRS associated with a characteristic endocardial potential in the pre-pacing electrogram, suggesting possible direct native conduction system access.

There is a paucity of data comparing conduction system pacing (CSP) to biventricular pacing (BiVP) in patients with heart failure (HF) with mid-range left ventricular ejection fraction (LVEF).

Compare the clinical outcomes of patients with mid-range LVEF undergoing CSP versus BiVP.

Patients with mid-range LVEF (> 35 to 50%) undergoing CSP or BiVP were retrospectively identified. Lead performance, LVEF, HF hospitalization, and clinical composite outcome including upgrade to cardiac resynchronization therapy and mortality were compared.

A total of 36 patients (20 BiVP, 16 CSP--14 His bundle pacing, 4 left bundle branch area pacing) were analyzed. The mean age was 73 ± 15, 44% were female, and the mean LVEF was 42 ± 5%. Procedural and fluoroscopy time was comparable between the two groups. QRS duration was significantly shorter for the CSP group compared to the BiVP group (P < 0.001). During a mean follow-up of 47 ± 36 months, no significant differences were found in thresholds or need for generator change due to early battery depletion. LVEF improved in both groups (41.5 ± 4.5% to 53.9 ± 10.9% BiVP, P < 0.001; 41.6 ± 5.3% to 52.5 ± 8.3% CSP, P < 0.001). There were no significant differences in HF hospitalizations (P = 0.71) or clinical composite outcomes (P = 0.07).

Among patients with HF with moderately reduced ejection fraction, CSP appears associated with similar improvements in LVEF and had similar clinical outcomes as BiVP in mid-term follow-up.

His-bundle pacing (HBP) is a pacing mode that provides near-physiological pacing and has more advantages over standard right ventricle (RV) septum pacing in positive clinical results. However, traditional HBP cannot accurately and stably place the lead tip into the His-Purkinje system. Hence, this study aimed to establish a novel strategy for HBP to strike a balance between an excellent pacing threshold and minor injuries to the conduction system.

HBP, using continuous and real-time monitoring of unipolar His-bundle (HB) electrograms along with electrocardiograms, was performed in 29 consecutive atrial fibrillation patients. We analyzed the unipolar HB intracardiac electrogram (EGM) and electrophysiological characteristics during HBP using John Jiang's connecting cable and an electrophysiology recording system. All patients were followed up for 12 months.

Of the 29 patients, 28 (96.55%) successfully received HBP. Twenty-one (75%) patients were confirmed to have the negative deflection of His potential with a negative amplitude of ≥ 0.1 mV in HB EGM. The subgroup with a deep negative deflection was recorded with an HBP threshold (0.71 ± 0.41 V), significantly lower than those thresholds with no deep negative deflection (1.83 ± 0.76 V) (p < 0.05). The selective HBP rate was significantly different between the two groups: 20 (95.24%) in the deep negative deflection group and three (42.86%) in the non-deep negative deflection group (p < 0.05); five (17.24%) patients presented right bundle branch block (RBBB) during the lead placement.

This study supports the safety and feasibility of using an uninterrupted real-time monitoring technique for HBP. An uninterrupted real-time monitoring technique can guide the accurate placement of the HB lead and may provide a balance between an excellent pacing threshold and minor injury to the conduction system.

In patients with symptomatic, refractory atrial fibrillation the ablate and pace (A&P) strategy (pacemaker implantation followed by atrio-ventricular junction ablation (AVJA)) is superior to medical therapy in improving quality of life and prognosis. Despite its well-proven benefits, this invasive therapeutic option is still underutilized in clinical practice. The choice of pacing modality (right ventricular pacing, biventricular pacing, BVP, or conduction system pacing, CSP) is crucial and can have significant clinical implications. In particular, in recent years CSP is emerging as an alternative to BVP, showing a good effectiveness and safety profile. Other important aspects are the timing of ablation, the approach used for AVJA, and the correct device programming after AVJA.

This article reviews the currently available evidence on this therapeutic strategy with a particular focus on its impact on patient outcome, recognized indications, technical considerations, and future perspectives.

With the availability of more robust evidence confirming the better effectiveness and safety profile of CSP compared to conventional pacing modalities, in the next few years CSP will become the standard pacing modality in candidates for A&P. The routine adoption of this pacing modality could lead to a wider use of A&P in clinical practice.

To evaluate systematically the feasibility and effectiveness of His Bundle Pacing (HBP) for cardiac resynchronization therapy.

A comprehensive search was conducted in PubMed, EMbase, WOS, Cochrane Library, Medline, and SinoMed for studies published between December 2003 and December 2023. Primary clinical outcomes included implantation success, QRS wave duration, pacing threshold, left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD), New York Heart Association (NYHA) cardiac function class, and complications. Data were extracted and summarized, and meta-analysis was performed by Revman 5.3 software.

Fourteen studies involving a total of 555 patients were included. The overall success rate for HBP implantation was 83.2% (462/555). Compared to baseline values, QRS duration was significantly reduced (MD=48.29, 95% CI: 45.20 to 51.38, P<0.01, I2=85%), LVEF was significantly increased (MD=-13.62, 95% CI: -15.46 to -11.79, P<0.01, I2=74%), LVEDD was smaller (MD=5.83, 95% CI: 4.44-7.22, P<0.01, I2=78.2%), and NYHA showed significant improvement (MD=1.24, 95% CI: 1.14-1.35, P<0.01, I2=97.2%). At follow-up, pacing threshold increased (MD=-0.28, 95% CI: -0.43 to -0.12, P<0.01, I2=0%), and pacing impedance decreased (MD=51.62, 95% CI: 23.67 to 79.56, P<0.01, I2=56%).

HBP is effective for cardiac resynchronization therapy. HBP significantly reduces QRS duration and improves LVEF in heart failure patients.

Despite key advances in catheter-based treatments, the management of persistent atrial fibrillation (AF) remains a therapeutic challenge in a significant subset of patients. While success rates have improved with repeat AF ablation procedures and the concurrent use of antiarrhythmic drugs, the likelihood of maintaining sinus rhythm during long-term follow-up is still limited. Atrioventricular node ablation (AVNA) has returned as a valuable treatment option given the recent developments in cardiac pacing. With the advent of conduction system pacing, AVNA has seen a revival where pacing-induced cardiomyopathy after AVNA is felt to be overcome. This review will discuss the role of permanent pacemaker implantation and AVNA for AF management in this new era of conduction system pacing. Specifically, this review will discuss the haemodynamic consequences of AF and the mechanisms through which 'pace-and-ablate therapy' enhances outcomes, analyse historical and more recent literature across various pacing methods, and work to identify patient groups that may benefit from earlier implementation of this approach.

Existing techniques for pacing the right ventricle and providing cardiac resynchronization therapy through biventricular pacing are not effective in restoring damage to the conduction system. Therefore, the need for new pacing modalities and techniques with more sensible designs and algorithms is justified. Although the benefits of conduction system pacing (CSP), which mainly include His bundle pacing (HBP) and left bundle branch area pacing (LBBAP), are evident in patients who require conduction system recuperation, the critical criteria for left CSP remain unclear, and the roles of different pacing modalities of CSP for cardiac resynchronization are not definite. In this review, we aimed to highlight the advantages of different CSP options, current advancement in the surgical devices, and future directions.

Left bundle branch pacing (LBBP) provides physiological activation with stable pacing parameters. However, there is a paucity of data on direct assessment of lead stability.

The purpose of this study was to assess the stability of an LBBP lead using computed tomographic angiography (CTA) during medium-term follow-up and to correlate the anatomic location of the lead and electrophysiological characteristics of LBBP.

Consecutive patients with successful LBBP using a lumenless lead were included. Patients without LBB capture, contrast allergy, and renal dysfunction were excluded. CTA was performed postimplantation and at 6 months. Primary endpoint was defined as consistent left bundle branch (LBB) capture with helix tip separated from the left ventricular (LV) blood pool by <2 mm by CTA at 6 months. Secondary endpoints were defined as loss of conduction system capture (LOCSC) or perforation with complete capture loss at 6 months.

Overall, 67 of 105 patients who underwent CTA after successful LBBP were included. Mean follow-up was 33.8 ± 4.4 months. Nonselective to selective capture transition was noted in 82% (n = 55). The lead remained stable at 6 months, with no difference in mean distance between LV blood pool and helix tip (-0.5 ± 1.8 mm vs -0.1 ± 2.1 mm; P = .23). Primary endpoint was achieved in 89.5% (n = 60). Consistent LBB capture (group I) at 6 months was noted in 94% (n = 63). LOCSC (group 2) was noted in 6% (n = 4) at 6 months. No perforation into the LV cavity with complete loss of capture was seen. Lead displacement by >2 mm away from the LV blood pool (sensitivity 100%; specificity 95%) and lack of nonselective to selective capture transition during implantation (odds ratio 18.0; 95% confidence interval 1.7-192.7; P = .01) were LOCSC predictors.

Deep septal deployment of the lead in the LV subendocardium for LBB capture is safe, with 94% of patients showing consistent conduction system capture during follow-up.

Background Ventricular septal pacing has long been performed using a stylet during pacemaker implantation, but with the availability of guiding catheters, His bundle pacing and left bundle branch area pacing have also been performed. However, it is not known to what extent the tip load of the ventricular lead differs when a guiding catheter is used compared with a stylet alone. In this study, the tip load was measured for different stylet stiffness and guiding catheter geometries at sites where His bundle pacing and left bundle branch area pacing were assumed. Method A small weighing instrument was placed in the right ventricular septal portion of the silicone heart model to measure the apical load of the ventricular lead when using two types of guiding catheters and three different types of stylets according to stiffness at the site where His bundle pacing and left bundle branch area pacing were assumed. Results The guiding catheter group had by far the highest tip load compared to the stylet group (Site Selective Pacing Catheter (SSPC) multipurpose group 17.9 ± 1.6 g, SSPC extended hook group 3.6 ± 0.8 g). There was no significant difference in tip load between His bundle pacing site and the left bundle branch area pacing site for the normally used stiffness stylet. Conclusions Guiding catheters are used for conduction system pacing but must be used with great care as they apply a much greater tip load than conventional lead placement with a stylet alone.

His bundle pacing (HBP) could replace failed biventricular pacing (BVP) in guidelines (IIa Indication), but the high capture thresholds and backup lead pacing requirements limit its development. We assessed the efficacy and safety of HBP combined with atrioventricular node ablation (AVNA) for atrial fibrillation (AF) and compared with BVP and left bundle branch pacing (LBBP).

We reviewed PubMed, Embase, Web of Science, and Cochrane Library databases on left ventricular ejection fraction (LVEF), New York Heart Association (NYHA) score, QRS duration (QRSd), and pacing threshold.

Thirteen studies included 1115 patients (639 with HBP, 338 with BVP, and 221 with LBBP). Compared with baseline, HBP improved LVEF (mean difference [MD]: 9.24 [6.10, 12.37]; p < 0.01), reduced NYHA score (MD: -1.12 [-1.34, -0.91]; p < 0.01), increased QRSd (MD: 10.08 [4.45, 15.70]; p < 0.01), and rose pacing threshold (MD: 0.16 [0.05, 0.26]; p < 0.01). HBP had comparable efficacy to BVP and LBBP and lower QRSd (p < 0.05). HBP had a lower success rate (85.97%) and more complications (16.1%).

HBP combined with AVNA is effective for AF, despite having a lower success rate and more complications. Further trials are required to determine whether HBP is superior to BVP and LBBP.

Left bundle branch area pacing (LBBAP) is a novel physiological pacing method for treating left ventricular dyssynchrony. LBBAP is often delivered using lumenless leads (LLL). However, recent studies have also reported the use of style-driven leads (SDL). This study is the first systematic review comparing the outcomes of LBBAP with SDL vs. LLL.

The review and meta-analysis included all available comparative studies published on Embase, PubMed, Web of Science, CENTRAL, and Scopus up to 6th March 2024.

Eight observational studies were included in the review. Meta-analysis showed that success rates of LBBAP performed with LLL and SDL were comparable (OR: 1.72 95% CI: 0.94, 3.17 I2 = 38%). Duration of implantation and total procedural duration were significantly lower in LBBAP performed with SDL. The pacing threshold was significantly higher, while pacing impedance was significantly lower in the SDL compared to the LLL group. Pacing QRS interval, R-wave amplitude, and stimulus to peak left ventricular activation time were similar in the two groups. Intra-operative and post-operative dislodgement were significantly higher in the SDL group, but no difference was noted in intra-operative perforation and pneumothorax risk.

Limited evidence from observational studies with inherent selection bias shows that success rates for LBBAP may not differ between SDL and LLL. While implantation of SDL may be significantly faster, it carries a higher risk of lead dislodgement. Both SDL and LLL are associated with comparable pacing characteristics except for reduced pacing impedance with SDL.

Left bundle branch block (LBBB) is frequently associated with structural heart disease, and predicts higher rates of morbidity and mortality. In patients with cardiomyopathy (ejection fraction <35%) and LBBB, current guidelines recommend cardiac resynchronisation therapy (CRT) after 3 months of medical therapy. However, studies have suggested that medical therapy alone would be less effective, and the majority of patients would still need CRT at the end of 3 months. Conversely, CRT trials have shown better results and favourable clinical outcomes in patients with LBBB. In the absence of any other known aetiology, LBBB-associated cardiomyopathy represents a potentially reversible form of cardiomyopathy, with the majority of the patients having reverse remodelling after CRT by left bundle branch pacing. This review provides the mechanism, published evidence and role of conduction system pacing for patients with LBBB-associated cardiomyopathy.

Permanent left bundle branch area pacing (LBBAP) has been established as an effective means to correct left bundle branch block. Right bundle branch block (RBBB), emerge as a distinct form of cardiac conduction abnormality, can be seen in the context of LBBAP procedure. However, the correction potential of LBBAP in patients with RBBB remains largely unexplored.

The objective of this study was to evaluate the efficacy and safety of permanent LBBAP in patients with RBBB.

Ninety-two consecutive patients who underwent successful permanent LBBAP were recruited from May. 2019 to Dec. 2022 in Fuwai Central China Cardiovascular Hospital. Among them, 20 patients with RBBB were included in our analysis. These patients were followed up at 1, 3, 6 and 12 months post-LBBAP. The QRS duration (QRSd) on the V1 lead of the 12-lead elctrocardiogram was measured and compared before and after the LBBAP procedure. Additionally, mitral regurgitation, tricuspid regurgitation and cardiac function were assessed using transthoracic echocardiography, specifically focusing on left ventricular ejection fraction (LVEF) and mitral regurgitation severity. The acute pitfills and delayed complications associated with the LBBAP procedure were recorded to evaluate its safety. SPSS 23.0 was used to perform statistical analysis with Student's t test or one way ANOVA or nonparametric tests (paired Wilcoxon test). A p value less than 0.05 was defined as significant.

The demographic breakdown of the RBBB cohort revealed a mean age of 66.35 ± 11.55 years, 60% being male. Comorbidities were prevalent, including severe atrioventricular block (AVB) in 75%, sick sinus syndrome (SSS) in 20%, heart failure in 25%, atrial fibrillation in 30%, coronary heart diseases in 45%, hypertension in 35%, and diabetes mellitus in 15%. Regarding the LBBAP procedure, the average operation time was 106.53 ± 2.72 min, with 45% of patients (9 individuals) requiring temporary cardiac pacing during the surgery. Notably, the LBBAP procedure significantly narrow the QRS duration in RBBB patients, from 132.60 ± 31.49ms to 119.55 ± 18.58 ms (P = 0.046). Additionally, at the 12-month follow-up, we observed a marked improvement in LVEF, which increased significantly from 55.15 ± 10.84% to 58.5 ± 10.55% (P = 0.018). Furthermore, mitral regurgitation severity improved, with a median reduction from 4.46 (0.9, 7.3) to 2.29 (0, 3.49) cm2 (P = 0.033). Importantly, no cases of ventricular septum perforation or pericardial effusion were reported during the LBBAP procedure or during the follow-up period.

LBBAP provides an immediate reduction in QRS duration for patients suffering from RBBB, accompanied by improvements in mitral regurgitation and cardiac function as evident in the 12-month follow-up period.

With the advancement of pacing technologies, His-Purkinje conduction system pacing (HPCSP) has been increasingly recognized as superior to conventional right ventricular pacing (RVP) and biventricular pacing (BVP). This method is characterized by a series of strategies that either strengthen the native cardiac conduction system or fully preserve physical atrioventricular activation, ensuring optimal clinical outcomes. Treatment with HPCSP is divided into two pacing categories, His bundle pacing (HBP) and left bundle branch pacing (LBBP), and when combined with atrioventricular node ablation (AVNA), can significantly improve left ventricular (LV) function. It effectively prevents tachycardia and regulates ventricular rates, demonstrating its efficacy and safety across different QRS wave complex durations. Therefore, HPCSP combined with AVNA can alleviate symptoms and improve the quality of life in patients with persistent atrial fibrillation (AF) who are unresponsive to multiple radiofrequency ablation, particularly those with concomitant heart failure (HF) who are at risk of further deterioration. As a result, this "pace and ablate" strategy could become a first-line treatment for refractory AF. As a pacing modality, HBP faces challenges in achieving precise localization and tends to increase the pacing threshold. Thus, LBBP has emerged as a novel approach within HPCSP, offering lower thresholds, higher sensing amplitudes, and improved success rates, potentially making it a preferable alternative to HBP. Future large-scale, prospective, and randomized controlled studies are needed to evaluate patient selection and implantation technology, aiming to clarify the differential clinical outcomes between pacing modalities.

Outcomes in patients with relatively high His-bundle (HB) capture thresholds at implantation are unknown. This study aimed to compare changes in the HB capture threshold and prognosis between patients with a relatively high threshold and those with a low threshold.

Forty-nine patients who underwent permanent HB pacing (HBP) were divided into two groups: low (<1.25 V at 1.0 ms; n=35) and high (1.25-2.49 V; n=14) baseline HB capture threshold groups. The HB capture threshold was evaluated at implantation, and after 1 week, 1, 3, and 6 months, and every 6 months thereafter. HB capture threshold rise was defined as threshold rise ≥1.0 V at 1.0 ms compared with implantation measures. We compared outcomes between the groups. During a mean follow-up period of 34.6 months, the high-threshold group showed a trend toward a higher incidence of HB capture threshold of ≥2.5 V (50% vs. 14%; P=0.023), HBP abandonment (29% vs. 8.6%; P=0.091), lead revision (21% vs. 2.9%; P=0.065), and clinical events (all-cause death, heart failure hospitalization, and new-onset or progression of atrial fibrillation; 50% vs. 23%; P=0.089) than the low-threshold group. A baseline HB capture threshold of ≥1.25V was an independent predictor of clinical events.

A relatively high HB capture threshold is associated with increased risk of HBP abandonment, lead revision, and poor clinical outcomes.

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).

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.

Left bundle branch area pacing is an alternative to biventricular pacing. In this study, we aim to summarize the available evidence on the feasibility, efficacy, and safety of left bundle branch block area pacing (LBBAP).

The study summarizes the available evidence on the feasibility, efficacy, and safety of left bundle branch block area pacing (LBBAP).

Cardiac resynchronization therapy (CRT) reduced mortality and hospitalizations in heart failure (HF) patients with a left ventricular ejection fraction (LVEF) ≤ 35% and concomitant LBBB. Recently LBBAP has been studied as a more physiological alternative to achieve CRT.

A search of PubMed, EMBASE, and Cochrane databases were performed to identify studies examining the role of LBBAP for CRT in heart failure. Comprehensive meta-analysis version 4 was used for meta-regression to examine variables that contribute to data heterogeneity.

Eighteen studies, 17 observational and one randomized controlled trial (RCT) were examined. A total of 3906 HF patients who underwent CRT (2036 LBBAP vs. 1870 biventricular pacing [BVP]) were included. LBBAP was performed successfully in 90.4% of patients. Compared to baseline, LBBAP was associated with a reduction in QRS duration (MD: -47.23  ms 95% confidence interval [CI]: -53.45, -41.01), an increase in LVEF (MD: 15.22%, 95% CI: 13.5, 16.94), and a reduction in NYHA class (MD: -1.23, 95% CI: -1.41, -1.05). Compared to BVP, LBBAP was associated with a significant reduction in QRS duration (MD: -20.69 ms, 95% CI: -25.49, -15.88) and improvement in LVEF (MD: 4.78%, 95% CI: 3.30, 6.10). Furthermore, LBBAP was associated with a significant reduction in HF hospitalization (odds ratio [OR]: 0.44, 95% CI: 0.34, 0.56) and all-cause mortality (OR: 0.67, 95% CI: 0.52, 0.86) compared to BVP.

LBBAP was associated with improved ventricular electrical synchrony compared to BVP, as well as better echocardiographic and clinical outcomes.

In patients with a reduced left ventricular (LV) systolic function (ejection fraction < 35%) and a left bundle branch block with a QRS duration > 130 ms, cardiac resynchronization therapy (CRT) can contribute to an improvement in the quality of life and a reduction in mortality. The resynchronization is mostly achieved by pacing via an epicardial LV lead in the coronary sinus; however, this approach is often limited by the patient's venous anatomy and an increase in the stimulation threshold over time. In addition, up to 30% of patients do not respond to the intervention. New treatment approaches involve direct stimulation of the conduction system by pacing of the bundle of His or left bundle branch. This enables a more physiological propagation of the stimulus. Pacing of the left bundle branch is achieved by advancing the lead into the right ventricle and screwing it deep into the interventricular septum. Due to the relatively large target area of the left bundle branch the success rate is very high (currently > 90%). Observational studies have shown a greater reduction in the QRS duration, a more pronounced improvement in systolic function and a lower hospitalization rate for heart failure associated with conduction system pacing compared to CRT using a coronary sinus lead. These findings have been confirmed in small randomized trials. Therefore, the use of left bundle branch pacing should be considered not only as a bail out in the case of failed resynchronization using coronary sinus lead placement but increasingly also as an initial pacing strategy. The results of the first large randomized trials are expected to be released in late 2024.

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.

The current gold standard in device therapy for advanced heart failure (HF), which has been firmly established in HF management for more than 25 years, is classical biventricular pacing (BiV-CRT). In the last decade, a new pacing modality called conduction system pacing (CSP) has emerged as a variant for advanced cardiac device therapy. It provides pacing with preserved intrinsic cardiac activation by direct stimulation of the specific cardiac conduction system. The term CSP integrates the modalities of HIS bundle pacing (HBP) and left bundle branch area pacing (LBBAP), both of which have provided convincing data in smaller randomized and big non-randomized studies for the prevention of pacemaker-induced cardiomyopathy and for providing effective cardiac resynchronization therapy in patients with classical CRT-indication (primary approach or after failed CRT). Recent American guidelines proposed the term "cardiac physiological pacing" (CPP), which summarizes CSP including left ventricular septal pacing (LVSP), a technical variant of LBBAP together with classical BiV-CRT. The terms HOT-CRT (HIS-optimized CRT) and LOT-CRT (LBBP-optimized CRT) describe hybrid technologies that combine CSP with an additional coronary-sinus electrode, which is sometimes useful in patients with advanced HF and diffuse interventricular conduction delay. If CSP continues providing promising data that can be confirmed in big, randomized trials, it is likely to become the new gold standard for patients with an expected high percentage of pacing (>20%), possibly also for cardiac resynchronization therapy. CSP is a sophisticated new treatment option that has the potential to raise the term "cardiac resynchronization therapy" to a new level. The aim of this review is to provide basic technical, anatomical, and functional knowledge of these new pacemaker techniques in order to facilitate the understanding of the different modalities, as well as to provide an up-to-date overview of the existing randomized and non-randomized evidence, particularly in direct comparison to right ventricular and classical biventricular pacing.

While supported by robust evidence and decades of clinical experience, right ventricular apical pacing for bradycardia is associated with a risk of progressive left ventricular dysfunction. Cardiac resynchronization therapy for heart failure with reduced ejection fraction can result in limited electrical resynchronization due to anatomical constraints and epicardial stimulation. In both settings, directly stimulating the conduction system below the atrio-ventricular node (either the bundle of His or the left bundle branch area) has potential to overcome these limitations. Conduction system pacing has met with considerable enthusiasm in view of the more physiological electrical conduction pattern, is rapidly becoming the preferred option of pacing for bradycardia, and is gaining momentum as an alternative to conventional biventricular pacing.

This article provides a review of the current efficacy and safety data for both people requiring treatment for bradycardia and the management of heart failure with conduction delay and discusses the possible future roles for conduction system pacing in routine clinical practice.

Conduction system pacing might be the holy grail of pacemaker therapy without the disadvantages of current approaches. However, hypothesis and enthusiasm are no match for robust data, demonstrating at least equivalent efficacy and safety to standard approaches.

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.

The results of clinical trials show that up to one-third of patients who are eligible for cardiac resynchronization therapy (CRT) do not benefit from biventricular pacing. The reasons vary, including technical problems related to left ventricle pacing lead placement in the appropriate branch of the coronary sinus. Herein, we present a case report of a patient with heart failure with reduced ejection fraction and left bundle branch block, in whom a poor coronary sinus bed made implantation of classic biventricular CRT impossible, but in whom, alternatively, rescue-performed left bundle branch area pacing allowed effective electrical and mechanical cardiac resynchronization. The report confirms that left bundle branch area pacing may be a rational alternative in such cases.

Atrioventricular block (AVB) is a frequent complication in patients undergoing transcatheter aortic valve implantation (TAVI). Right apex ventricular pacing (RVP) represents the standard treatment but may induce cardiomyopathy over the long term. Left bundle branch area pacing (LBBAP) is a promising alternative, minimizing the risk of desynchrony. However, available evidence with LBBAP after TAVI is still low.

To assess the feasibility and safety of LBBAP for AVB post-TAVI compared with RVP.

Consecutive patients developing AVB early after TAVI were enrolled between 1 January 2022 and 31 December 2022 at three high-volume hospitals and received LBBAP or RVP. Data on procedure and at short-term follow-up (at least 3 months) were collected.

A total of 38 patients (61% men, mean age 83 ± 6 years) were included; 20 patients (53%) received LBBAP. Procedural success was obtained in all patients according to chosen pacing strategy. Electrical pacing performance at implant and after a mean follow-up of 4.2 ± 2.8 months was clinically equivalent for both pacing modalities. In the LBBAP group, procedural time was longer (70 ± 17 versus 58 ± 15 min in the RVP group, P  = 0.02) and paced QRS was shorter (120 ± 19 versus 155 ± 12 ms at implant, P  < 0.001; 119 ± 18 versus 157 ± 9 ms at follow-up, P  < 0.001). Complication rates did not differ between the two groups.

In patients with AVB after TAVI, LBBAP is feasible and safe, resulting in a narrow QRS duration, either acutely and during the follow-up, compared with RVP. Further studies are needed to evaluate if LBBAP reduces pacing-induced cardiomyopathy in this clinical setting.