Clinical Outcomes of His Bundle Pacing Compared to Right Ventricular Pacing

Durability of output-dependent QRS transition and left bundle branch capture in left bundle branch area pacing

BACKGROUND

Although output-dependent QRS transition is a specific indicator that confirms left bundle branch (LBB) capture during left bundle branch area pacing (LBBAP), its durability remains unclear.

OBJECTIVE

The purpose of this study was to evaluate the presence of output-dependent QRS transition and capture thresholds of the LBB and left ventricular septal myocardium immediately and up to 1 year after the LBBAP procedure.

METHODS

We enrolled 129 patients with successful LBBAP who were available for 1-year follow-up postoperatively. Threshold testing was performed immediately after LBBAP on postoperative day 0 (POD-0) and after 3 days (POD-3), 6 months (POD-180), and 1 year (POD-360).

RESULTS

Output-dependent QRS transition persisted in 64 patients (88%) on POD-360, from among the 73 patients with output-dependent QRS transition on POD-0. In contrast, 55 of 56 patients without QRS transition on POD-0 (98%) did not exhibit QRS transition thereafter. LBB thresholds were slightly elevated on POD-360, albeit without statistical significance, compared with those on POD-0 (1.22 ± 1.00 V vs 1.43 ± 1.29 V at 0.4 ms; P = .26). The LBB thresholds increased by ≥1.5 V in 7 patients (11%). However, in 93% of patients with an LBB threshold of ≤2.5 V on POD-0, LBB capture was maintained at 2.5 V on POD-360. Left ventricular septal thresholds were similar on POD-0 and POD-360 (0.81 ± 0.36 V vs 0.83 ± 0.24 V; P > .99) and did not increase by ≥1.5 V in any patient.

CONCLUSION

Output-dependent QRS transitions were highly reproducible after implantation. Furthermore, LBB thresholds remained stable in most cases during the first postoperative year.

Hierarchical Physiologic Pacing to Enhance Clinical Outcomes in Conduction System Pacing

BACKGROUND

Left bundle branch area pacing (LBBAP) includes left bundle branch pacing (truncal or fascicular) and left ventricular septal pacing (LVSP). Studies show that LBBP provides better outcomes than LVSP in heart failure.

OBJECTIVES

We classified the lead placement with computed tomographic angiography (CTA) based method (CARA-Metis; CARA Medical Ltd.) into LBBP or LVSP and assessed the effect of pacing-lead location relative to the conduction tree hierarchy and the LV endocardium on clinical outcomes in patients with successful LBBAP.

METHODS

Two-center, non-randomized, observational study that included LBBAP patients undergoing CTA. The CTA parameters analyzed: 1) Distance between lead-tip and the anterior position of the floor of the membranous septum (LH) and 2) distance between lead-tip and LV endocardium (LE).

RESULTS

Among 264 patients analyzed, 172 (65%) with interpretable CTAs were included. Pacing lead-tip was categorized as LBBP in 153 (89%) and LVSP in 19 (11%) patients [Median (IQR) values were 27.7 [9.21] mm for LH and 0.80 [2.59] mm for LE]. Shorter LH was associated with greater improvement in left ventricular ejection fraction (LVEF) [each 1 mm shorter LH increased LVEF by 0.25% when adjusted for baseline LVEF (p=0.00637)]. Closer to the LV endocardium (Larger LE), increased LVEF response by 0.63% for each additional 1 mm (p=0.0133) in the entire cohort. Patients with depressed LVEF accrued significantly larger improvement in LVEF (p<0.0001 for both).

CONCLUSION

Hierarchical physiologic pacing with improved LVEF response is achieved with a closer position of the pacing lead to the His bundle and the LV-endocardium.

Novel technique and assessment of available 3-dimensional delivery sheath for endomyocardial biopsy during cardiac device implantation

BACKGROUND

Early cardiomyopathy diagnosis allows timely treatment and may help resolve problems that occur after cardiac implantable electronic device (CIED) implantation.

OBJECTIVE

This study aims to describe a novel technique for endomyocardial biopsy (EMB) using a 3-dimensional (3D) delivery sheath during CIED implantation. In addition, we investigated 3D delivery-sheath characteristics using sheath deflection during bioptome insertion.

METHODS

This study of 20 patients undergoing CIED implantation analyzed the EMB success rate and pathologic findings. Fluoroscopic images assessed 3D delivery sheath characteristics before and after bioptome insertion in 3 sheaths. CIEDs were implanted for sick sinus syndrome (n =3), atrioventricular conduction disorder (n = 16), and left ventricular dysfunction (n = 1). Fluoroscopic verification was performed using right anterior oblique (RAO) and left anterior oblique (LAO) views. EMB was performed with Selectra 3D (BIOTRONIK, Berlin, Germany), CSP Locator 3D (Abbott, Chicago, IL), and SSPC (Boston Scientific, Marlborough, MA) (12, 4, and 4 patients, respectively). The distance moved toward the right ventricular apex (RVA) in RAO was defined as Dis-RAO (mm) and that moved toward the RVA in LAO was defined as Dis-LAO (mm).

RESULTS

Among the 3 sheaths, only the CSP Locator 3D and Selectra 3D showed significant differences in Dis-RAO (13.2 ± 2.0 mm vs 19.8 ± 3.8 mm, P < .01) and Dis-LAO (8.1 ± 1.3 mm vs 15.3 ± 3.9 mm, P < .01). A total of 77 EMB samples from 20 patients were collected without any complication, and 4 patients (20%) were diagnosed with cardiac amyloidosis (CA) based on pathologic findings.

CONCLUSION

All 3D delivery sheaths were safe and effective for performing EMB from the RVS during CIED implantation, enabling early CA diagnosis in 20% of patients.

Lead Performance and Echocardiographic Outcomes for Delayed Bundle Capture Loss During Conduction System Pacing

BACKGROUND

Conduction system pacing (CSP) is increasingly recognized for mitigating the adverse hemodynamic effects commonly associated with conventional ventricular pacing. However, there is limited data on the lead performance and echocardiographic outcomes for delayed bundle capture loss during CSP.

OBJECTIVE

To evaluate the rate of complete loss of bundle capture/correction during CSP and assess the subsequent clinical outcomes.

METHOD

Patients who underwent successful CSP lead implantation with indications for ventricular pacing or cardiac resynchronization therapy (CRT) were screened. The reasons for complete loss of capture or failed LBBB correction were identified, and subsequent clinical outcomes were analyzed.

RESULT

Out of 2636 patients screened, nine experienced complete loss of bundle capture or LBBB correction during follow-up. Loss of capture was attributed to unexplained causes (n = 6), near-complete electrode dislodgement (n = 1), surgical damage (n = 1), and electrode malfunction (n = 1). The six patients with CRT indication and declining cardiac function underwent lead revision, with left ventricular ejection fraction (LVEF) improving from 40.6 ± 17.3% to 59.1 ± 6.0% at the last follow-up with the bundle capture threshold of 0.63 ± 0.14 V/0.5 ms. The remaining 3 atrioventricular block patients with stable cardiac function did not undergo lead revision and the local myocardium threshold of 0.58± 0.31 V/0.5 ms.

CONCLUSION

The incidence of complete capture loss during CSP is low recapturing/recorrecting the bundle significantly improves cardiac function in patients with CRT indications.

European Society of Cardiology (ESC) clinical consensus statement on indications for conduction system pacing, with special contribution of the European Heart Rhythm Association of the ESC and endorsed by the Asia Pacific Heart Rhythm Society, the Canadian Heart Rhythm Society, the Heart Rhythm Society, and the Latin American Heart Rhythm Society

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.

Left ventricular ejection fraction is a determinant of cardiac performance after long-term conduction system pacing in patients with left bundle branch block?

OBJECTIVE

This study aims to explore the feasibility, safety, and clinical performance of conduction system pacing (CSP) in patients with left bundle branch block (LBBB) and varying left ventricular ejection fraction (LVEF) values.

METHODS

We consecutively enrolled all patients with LVEF ≤ 35% and LBBB who met the criteria for cardiac resynchronization therapy (CRT) and underwent CSP from January 2018 to December 2021. We compared the differences in improvements in cardiac performance after CSP between patients with LVEF < 25% and those with LVEF between 25 to 35%.

RESULTS

CSP was successfully deployed in 74 out of 80 patients (92.50%), including 32 patients with LVEF < 25% and 42 patients with LVEF 25%-35%. The CSP response rates were similar between the two groups (71.90% vs. 90.50%, P = 0.076), as were the super-response rates (62.50% vs. 78.60%, P = 0.129) and the rates of left ventricular complete reverse remodeling (21.90% vs. 42.90%, P = 0.059) after a follow-up period of 40.81 ± 11.93 months. Significant improvements were observed in LVEF (20.50 ± 2.75% vs. 37.78 ± 13.04%, P < 0.001), left ventricular end-diastolic dimension (LVEDD) (69.56 ± 6.77 mm vs. 59.41 ± 11.00 mm, P < 0.001), left ventricular end-systolic volume (LVESV) (224.81 ± 50.65 ml vs. 134.00 ± 83.35 ml, P < 0.001), NYHA class (3.59 ± 0.48 vs. 1.78 ± 0.66, P < 0.001), and QRS duration (168.75 ± 21.52 ms vs. 117.81 ± 17.09 ms, P < 0.001) in patients with LVEF < 25%. Despite these improvements, the final LVEF (37.78 ± 13.04 vs. 46.19 ± 9.47, P = 0.003) and final LVESV (134.00 ± 83.35 vs. 70.89 ± 38.89, P = 0.001) after CSP were inferior in patients with LVEF < 25%, and the rate of rehospitalization for heart failure was higher in this group (46.90% vs. 21.40%, P = 0.021) compared to those with LVEF between 25 to 35%.

CONCLUSIONS

CSP is feasible and safe for improving clinical outcomes in patients with LVEF < 25%. Timely CSP intervention in patients with LBBB and HF may be beneficial for cardiac performance.

ACC/AHA/ASE/HFSA/HRS/SCAI/SCCT/SCMR 2025 Appropriate Use Criteria for Implantable Cardioverter-Defibrillators, Cardiac Resynchronization Therapy, and Pacing

This appropriate use criteria (AUC) document is developed by the American College of Cardiology along with key specialty and subspecialty societies. It provides a comprehensive review of common clinical scenarios where implantable cardioverter-defibrillator (ICD), cardiac resynchronization therapy (CRT), cardiac contractility modulation, leadless pacing, and conduction system pacing therapies are frequently considered. The 335 clinical scenarios covered in this document address ICD indications including those related to secondary prevention, primary prevention, comorbidities, generator replacement at elective replacement indicator, dual-chamber, and totally subcutaneous ICDs, as well as device indications related to CRT, conduction system pacing, leadless pacing, cardiac contractility modulation, and ICD therapy in the setting of left ventricular assist devices (LVADs).

The indications (clinical scenarios) were derived from common applications or anticipated uses, as well as from current clinical practice guidelines and results of studies examining device implantation. The indications in this document were developed by a multidisciplinary writing group and scored by a separate independent rating panel on a scale of 1 to 9 to designate care that is considered “Appropriate” (median 7 to 9), “May Be Appropriate” (median 4 to 6), and “Rarely Appropriate” (median 1 to 3). The final ratings reflect the median score of the 17 rating panel members.

In general, Appropriate designations were assigned to scenarios for which clinical trial evidence and/or clinical experience was available that supported device implantation. In contrast, scenarios for which clinical trial evidence was limited or device implantation seemed reasonable for extenuating or practical reasons were categorized as May Be Appropriate. Scenarios for which there were data showing harm, or no data were available, and medical judgment deemed device therapy was illadvised were categorized as Rarely Appropriate. For example, comorbidities including reduced life expectancy related to noncardiac conditions or severe cognitive dysfunction would negatively impact appropriateness ratings.

The appropriate use criteria for ICD, CRT, and pacing have the potential to enhance clinician decision making, healthcare delivery, and payment policy. Furthermore, recognition of clinical scenarios rated as May Be Appropriate facilitates the identification of areas where there may be gaps in evidence that would benefit from future research.

The American College of Cardiology (ACC) has a long history of developing documents (eg, expert consensus decision pathways, health policy statements, AUC documents) to provide members with guidance on both clinical and nonclinical topics relevant to cardiovascular care. In most circumstances, these documents have been created to complement clinical practice guidelines and to inform clinicians about areas where evidence is new and evolving or where sufficient data are more limited. Despite this, numerous gaps persist, highlighting the need for more streamlined and efficient processes to implement best practices in patient care.

Central to the ACC’s strategic plan is the generation of actionable knowledge —a concept that places emphasis on making clinical information easier to consume, share, integrate, and update. To this end, the ACC has shifted from developing isolated documents to creating integrated “solution sets.” These are groups of closely related activities, policy, mobile applications, decision-support tools, and other resources necessary to transform care and/or improve heart health. Solution sets address key questions facing care teams and attempt to provide practical guidance to be applied at the point of care. They use both established and emerging methods to disseminate information for cardiovascular conditions and their related management. The success of solution sets rests firmly on their ability to have a measurable impact on the delivery of care. Because solution sets reflect current evidence and ongoing gaps in care, the associated tools will be refined across time to match changing evidence and member needs.

AUC represent a key component of solution sets. They consist of common clinical scenarios associated with given disease states and ratings that define when it is reasonable to perform testing or provide therapies and, importantly, when it is not. AUC methodology relies on content development work groups, which create patient scenarios, and independent rating panels that employ a modified Delphi process to rate the relevant options for testing and intervention as Appropriate, May Be Appropriate, or Rarely Appropriate. AUC should not replace clinician judgment and practice experience but should function as tools to improve patient care and health outcomes in a cost-effective manner.

I extend sincere gratitude to the writing group for their invaluable contributions to the development of this document’s structure and clinical scenarios; to the rating panelists—a distinguished group of professionals with diverse expertise—for their thoughtful deliberation of the merits of device implantation across various clinical contexts; and to the reviewers for their thoughtful evaluation of the clinical scenarios and evidence mapping. Additionally, I am grateful to the members of the Solution Set Oversight Committee, which provided insight and guidance, and to ACC staff members María Velásquez and Lara Gold, for their support in bringing this document to fruition.

Leadless pacing: a comprehensive review

Over the past decade, leadless pacing has undergone a rapid evolution, resulting in multiple leadless pacemaker (LPM) devices that offer advancements such as atrioventricular synchronized pacing in VDD mode, atrial stimulation, dual-chamber pacing, and longer battery longevity. Studies comparing LPMs with transvenous pacemakers (TVPMs) show a lower rate of device-related complications with LPMs. In the near future, LPMs could be combined with other devices such as non-transvenous implantable cardioverter-defibrillators to provide anti-tachycardia pacing or bradycardia pacing. Future prospectives for leadless cardiac resynchronization therapy and leadless conduction system pacing are being investigated. As LPMs continue to improve, their applications are anticipated to expand further improving patient outcome, promising a bright future for leadless pacing. In this review, the past, present, and future of leadless pacing are discussed with a focus on cutting-edge implantation techniques, clinical outcomes, and modern advancements of LPMs.

Long-Term Complications Related to Cardiac Implantable Electronic Devices

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.

Conduction system pacing in heart failure: Time for a paradigm shift?

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.

Conduction system pacing associated with reduced heart failure hospitalizations and all-cause mortality compared with traditional right ventricular pacing in the Medicare population

BACKGROUND

Conduction system pacing (CSP) has emerged as an alternative therapy to traditional right ventricular (RV) pacing. However, most CSP studies reflect small cohorts or single-center experience.

OBJECTIVE

This analysis compared CSP with dual-chamber (DC) RV pacing in a large, population-based cohort using data from the Micra Coverage with Evidence Development study.

METHODS

Medicare administrative claims data were used to identify patients implanted with a DC RV pacemaker. Lead placement data from Medtronic's device registration system identified patients treated with CSP (n = 6197) using a 3830 catheter-delivered lead or DC RV (non-3830 lead, non-CSP placement; n = 16,989) at the same centers. CSP patients were stratified into left bundle branch area pacing (LBBAP; n = 4738) and His bundle pacing (HBP; n = 1459). Incident heart failure hospitalizations, all-cause mortality, complication rates, and reinterventions at 6 months were analyzed.

RESULTS

CSP patients with a 3830 catheter-delivered lead experienced significantly lower rates of incident heart failure hospitalization (hazard ratio [HR], 0.70; P = .02) and all-cause mortality at 6 months compared with DC RV patients (HR, 0.66; P < .0001). There was no difference in chronic complications (HR, 0.97; P = .62) or need for reintervention (HR, 0.95; P = .63) with CSP compared with DC RV, although LBBAP patients experienced significantly lower rates of complications (HR, 0.71; P = .001) compared with HBP.

CONCLUSION

DC pacemaker patients treated with CSP using a 3830 catheter-delivered lead experienced significant all-cause mortality and heart failure hospitalization benefits compared with DC RV pacing. LBBAP had lower complications compared with HBP. These real-world results align with findings in small clinical studies demonstrating the benefits of CSP.

The advantages of physiological pacing

The evidence that conventional right ventricular pacing can result in the development of cardiomyopathy and heart failure over time has prompted the search for alternative pacing sites. Conduction system pacing (CSP) represents an attempt to overcome the limitations of conventional pacing and to provide an alternative for patients with reduced EF and various degrees of dyssynchrony for whom resynchronization therapy is not feasible for technical or anatomical reasons. In particular, His bundle pacing and left bundle branch area pacing (LBBAP), with their advantages and disadvantages, have been shown to meet the criteria of physiological pacing. The former, although technically more challenging and less satisfactory in terms of electrical parameters, allows to obtain a QRS complex that is identical to the spontaneous one. The latter produces a wider paced QRS and although the technical complexity at the time of implantation is significantly reduced, is subject to a series of mechanical complications related to the trans-septal positioning of the lead. Careful patient selection along with an adequate learning curve for the operators make CSP a safe and effective procedure, although burdened by a higher complication rate compared with conventional pacing. Future studies will clarify its role, which is currently limited by current ESC guidelines to His Pacing only as an alternative procedure in case of failure of resynchronization therapy (class of recommendation IIa), after the 'ablate and pace' procedure or as an alternative to right ventricular pacing in patients with AV block, left ventricular ejection fraction <40% and an expected right ventricular pacing percentage >20% (class of recommendation IIb).

Gender Differences for His Bundle Pacing Long-Term Performance in the Elderly Population

BACKGROUND AND AIMS

His bundle pacing (HBP) is considered the most physiological form of cardiac pacing. Although feasibility studies have included older patients, specific data for HBP in this population are scarce. This study aimed to evaluate gender differences in HBP long-term performance in elderly patients with atrioventricular (AV) block.

METHODS

This retrospective study included 73 patients aged over 65 years with successful HBP and at least 2 years of follow-up. The patients' baseline and follow-up clinical and procedural characteristics were recorded.

RESULTS

The mean age of the cohort was 72.8 ± 6.3 years, with 43 males and 30 females. The paced QRS complex was significantly narrower than the baseline value for both genders. Females had a narrower-paced QRS complex without differences in detection, type of His bundle capture, impedance, or fluoroscopy time. The pacing threshold increased progressively, reaching statistical significance compared to the baseline values at the two-year follow-up. The pacing threshold increased by more than 1 V over the follow-up period in twenty-four patients (32.9%) and by more than 2 V in six patients (8.2%), with no significant difference between genders. The pacing threshold increase occurred within the first year for most patients, without gender differences. Multivariate Cox regression analysis demonstrated that the paced QRS duration, left ventricular ejection fraction, and ischemic cardiomyopathy were significantly associated with the pacing threshold increase over time.

CONCLUSION

In elderly patients with AV block, HBP remains a feasible pacing method, without significant gender differences, over a long-term follow-up period. Pacing threshold increases are expected in up to one-third of the patients, requiring regular follow-ups to adjust the programmed parameters and optimize battery longevity.

Lead fracture in stylet driven left bundle area pacing following exercise: Coincidence!

Lumen less leads (LLLs) and stylet-driven leads (SDL) are widely used for left bundle branch area pacing (LBBAP) and has become standard practice. The incidence of lead fracture is very rare with both leads. We report a case of delayed fracture in stylet driven lead producing syncope following exercise.

Electrical and mechanical interventricular dyssynchrony coupling in patients with bradycardia: A UHF-ECG validation trial

BACKGROUND

Ultra-high-frequency electrocardiography (UHF-ECG) is a noninvasive tool visualizing the ventricular activation sequence. It was never compared with other methods of dyssynchrony assessment in patients with bradycardia.

OBJECTIVE

We aimed to compare UHF-ECG interventricular electrical dyssynchrony (e-DYS) with interventricular mechanical delay (IVMD) measured by echocardiography in patients receiving right ventricular pacing (RVP) or conduction system pacing (CSP).

METHODS

Fifty-three patients with advanced atrioventricular conduction disease and preserved ventricular systolic function were prospectively assigned to RVP (n=32 [60 %]) or CSP (n=21 [40 %]). IVMD was measured as the time difference between left ventricular and right ventricular preejection periods. Interventricular e-DYS was calculated by software as the time difference between activation in V1 and V7 chest electrodes using UHF-ECG.

RESULTS

The median age of patients was 75 (interquartile range 72-80) years, and both groups had similar clinical characteristics. Baseline IVMD and interventricular e-DYS were similar in the entire population (-2 [-8 to 5] ms vs-1 [-6 to 5] ms, respectively; P=.52). Both methods showed the same dyssynchrony trends after pacemaker implantation; that is, while both IVMD and interventricular e-DYS increased in the RVP group (IVMD 28 [23-33] ms vs interventricular e-DYS 26 [19-33] ms; P=.99), they remained low in the CSP group (IVMD -7 [-16 to 2] ms vs interventricular e-DYS -5 [-12 to 2] ms; P=.91). There was a moderate overall correlation between IVMD and interventricular e-DYS for all studied ventricular rhythms (R=0.74).

CONCLUSION

UHF-ECG noninvasively expresses interventricular dyssynchrony from V7-V1 chest leads with similar results to echocardiography. RVP increases interventricular dyssynchrony, while CSP preserves synchronous ventricular activation.

High-resolution 3D visualization of human hearts with emphases on the cardiac conduction system components-a new platform for medical education, mix/virtual reality, computational simulation

Introduction

High-resolution digitized cardiac anatomical data sets are in huge demand in clinical, basic research and computational settings. They can be leveraged to evaluate intricate anatomical and structural changes in disease pathology, such as myocardial infarction (MI), which is one of the most common causes of heart failure and death. Advancements in high-resolution imaging and anatomical techniques in this field and our laboratory have led to vast improvements in understanding cardiovascular anatomy, especially the cardiac conduction system (CCS) responsible for the electricity of the heart, in healthy/aged/obese post-mortem human hearts. However, the digitized anatomy of the electrical system of the heart within MI hearts remains unexplored.

Methods

Five post-mortem non-MI and MI human hearts were obtained by the Visible Heart® Laboratories via LifeSource, Minneapolis, MN, United States (with appropriate ethics and consent): specimens were then transported to Manchester University with an material transfer agreement in place and stored under the HTA 2004, UK. After performing contrast-enhanced micro-CT, a visualization tool (namely Amira) was used for 3D high-resolution anatomical visualizations and reconstruction. Various cardiovascular structures were segmented based on the attenuation difference of micro-CT scans and tissue traceability. The relationship between the CCS and surrounding tissues in MI and non-MI human hearts was obtained. 3D anatomical models were further explored for their use in computational simulations, 3D printing and mix/virtual reality visualization.

Results

3D segmented cardiovascular structures in the MI hearts elicited diverse macro-/micro- anatomical changes. The key findings are thickened valve leaflets, formation of new coronary arteries, increased or reduced thicknesses of pectinate and papillary muscles and Purkinje fibers, thinner left bundle branches, sinoatrial nodal atrophy, atrioventricular conduction axis fragmentation, and increased epicardial fat in some hearts. The propagation of the excitation impulses can be simulated, and 3D printing can be utilized from the reconstructed and segmented structures.

Discussion

High-resolution digitized cardiac anatomical datasets offer exciting new tools for medical education, clinical applications, and computational simulation.

Atrioventricular Block Treatment: Pacing Site, AV Synchrony, or Both?

Background/Objectives: Right ventricular pacing (RVP), leadless pacing (LL), and conduction system pacing (CSP) are treatment options for atrioventricular block (AVB), each with distinct characteristics. However, the long-term outcomes of these pacing strategies remain insufficiently compared. This study evaluates clinical and echocardiographic outcomes of patients with AVB treated with dual chamber RVP, His bundle pacing (HBP), or LL. Methods: This single-center observational registry study included 22 consecutive patients receiving LL with atrioventricular resynchronization functionality (October 2020 to October 2022), matched with 66 control patients receiving either RVP (33 patients) or HBP (33 patients) using propensity score matching (2:3:3 ratio). Primary and secondary endpoints included all-cause mortality, cardiovascular mortality, heart failure, and echocardiographic outcomes. Atrioventricular synchrony in the LL group was assessed. Results: At two years, all-cause mortality was significantly higher in the LL group compared to RVP (36.4% vs. 6.1%, p = 0.002) and HBP (36.4% vs. 12.1%, p = 0.03), but LL had a more severe clinical profile. Cardiovascular mortality and heart failure incidence showed no significant differences. Patients receiving RVP showed a significant decrease in left ventricular ejection fraction and an increase in ventricular volumes. In contrast, HBP patients exhibited favorable cardiac remodeling. Stratification based on atrial sensing showed that LL patients with >66% AV synchrony had a lower mortality (p = 0.02). Conclusions: CSP offers superior results compared to other pacing methods in terms of ventricular function owing to a physiological ventricular activation and maintenance of AV synchrony. However, LL may be a viable alternative for frail and high-risk patients, as the suboptimal AV synchrony is traded off with lesser ventricular dyssynchrony.

Early Improvement in Cardiac Function and Dyssynchrony After Physiological Upgrading in Pacing-Induced Cardiomyopathy

BACKGROUND

Interventricular dyssynchrony derived from the classic non-physiological stimulation (n-PS) of the right ventricle (RV) is a known cause of left ventricular dysfunction (LVDys).

METHODS

This was a prospective descriptive single-center study. We analyzed patients who develop LVDys with n-PS, and the results after upgrading to conduction system pacing (CSP). Ultra-high frequency electrocardiogram (UHF-ECG) was performed pre and post-implantation of the last patients included. ECG recordings in 16 frequency bands (150-1000 Hz) were used to create maps of ventricular depolarization. The maximum time difference between the centers of mass of the complex UHF QRS of leads V1-V6 (electrical dyssynchrony [DYS-e] 16) and V1-V8 (DYS-e 18) defined ventricular dyssynchrony. Data were expressed as mean ± standard deviation.

RESULTS

27 patients were upgraded to CSP from January 2022 to January 2024 after developing LVDys. Permanent His bundle pacing (p-HBP) was achieved in 63% (n = 17); in the other 10 patients left bundle branch area pacing (LBBAp) was performed. The average baseline LVEF improved from 34.5% (27-42) to 47.6% (38.2-57), p < 0.001. Telediastolic left ventricle diameter as well as QRS width also decreased. Thresholds remained stable at 6-month follow-up. The last eight patients included were studied in terms of ventricular synchrony parameters by UHF-ECG (VDI Technologies), both His bundle pacing (HBP) and the LBBAp achieved significant improvement with respect to baseline parameters.

CONCLUSIONS

LVEF improved in patients with previous n-PS-induced cardiomyopathy after upgrading to CSP. LVDys due to dyssynchronopathy is frequent and probably underdiagnosed. UHF-ECG provides useful new information about ventricular activation and will likely improve patient selection for cardiac resynchronization therapy (CRT).

Mid-term comparison of new-onset AHRE between His bundle and left bundle branch area pacing in patients with AV block

Background

Atrial high-rate episodes (AHRE) detected by cardiac implanted electronic devices are known markers for adverse cardiac events. Previous studies have shown that the incidence of new-onset AHREs in patients with right ventricular pacing reaches 50%. At the same time, His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) were associated with significantly fewer AHRE. This study aimed to compare the incidence of new-onset AHRE between HBP and LBBAP in patients with atrioventricular block and no history of atrial fibrillation.

Methods

One hundred and forty-two patients, fifty-nine with HBP and eighty-three with LBBAP for advanced atrioventricular block, were prospectively followed for new-onset AHRE.

Results

The mean follow-up period was 624 ± 148.6 days for the HBP patients and 663.4 ± 157.4 days for the LBBAP patients. New-onset AHRE was encountered in 8 of 59 patients (13.5%) with HBP and 14 of 83 (16.8%) with LBBAP (hazard ratio-0.91, log rank p = .84). In the multivariate Cox regression model, HBP and LBBAP had similar predictive values, while only age and diabetes mellitus were significantly associated with new-onset AHRE occurrence.

Conclusion

HBP and LBBAP were associated with a similar incidence of device-detected new-onset AHRE during a medium-term follow-up period in patients with atrioventricular block and no history of atrial fibrillation.

Left bundle branch area pacing from the iliac approach in a patient without superior access: a case report

Background

Left bundle branch area pacing (LBBAP) emerges as an alternative to traditional right ventricular pacing, demonstrating safety and feasibility through superior access for implantation.

Case summary

An 89-year-old female, with a prior history of pacemaker pocket infection and a tricuspid endocarditis during follow-up, was referred to our hospital for management due to a sinus arrest. The patient underwent pacemaker removal due to a pocket infection in the right subclavian area, necessitating tricuspid valvuloplasty for infective endocarditis. Venography revealed occlusion in the left brachiocephalic vein. Subsequently, LBBAP pacemaker implantation via the right iliac vein was performed, with follow-up indicating proper functioning of the pacing system.

Discussion

The feasibility of the right iliac vein access for LBBAP implantation is highlighted, demonstrating good stability and offering a practical alternative. This approach mitigates unnecessary risks associated with thoracotomy and epicardial lead placement, providing a safer and effective option for cardiac pacing.

Mid-term clinical outcomes of left bundle branch area pacing compared to accurate right ventricular septal pacing

BACKGROUND

Although left bundle branch area pacing (LBBAP) reportedly results in fewer adverse outcomes after implantation than conventional stylet-guided right ventricular septal pacing (RVSP), previous studies have not compared LBBAP with accurate RVSP using a delivery catheter. The aim of this study was to compare clinical outcomes between LBBAP and accurate RVSP among patients with atrioventricular block (AVB).

METHODS

This single-center observational study enrolled 160 patients requiring RV pacing due to symptomatic AVB between September 2018 and December 2021. Primary composite outcomes included all-cause death, hospitalization due to heart failure (HF), and upgrading to biventricular pacing. Secondary composite outcomes included any procedural and postprocedural complications.

RESULTS

Overall, 160 patients were analyzed (LBBAP, n = 81; RVSP, n = 79). No significant differences in baseline characteristics were observed between the two groups. The RV pacing burden at 1 year after implantation was 90.8% ± 20.4% and 86.2% ± 22.6%, respectively (p = 0.21). During a mean follow-up of 840 ± 369 days, the incidence of the primary outcome was significantly lower with LBBAP (4.9%) compared to RVSP (22.8%) (Log-rank p = 0.02). There was no significant difference in the incidence of the secondary outcome between the two groups (3.7% vs. 5.1%, p = 0.65). In the multivariate analysis, baseline QRS duration, RV pacing burden, and LBBAP were independently associated with the primary outcome (baseline QRS duration: hazard ratio [HR], 1.01; 95% confidence interval [CI], 1.00-1.02; p < 0.001; RV pacing burden: HR, 1.01; 95% CI, 1.00-1.02; p < 0.001; LBBAP: HR, 0.45; 95% CI, 0.31-0.64; p < 0.001).

CONCLUSION

In patients requiring frequent RV pacing, LBBAP was associated with reduced adverse clinical outcome compared to accurate RVSP using a delivery catheter.

Outcomes with physiologic His bundle pacing in patients with narrow QRS complex

BACKGROUND

In patients with narrow QRS complex, both ventricular and biventricular pacing is associated with increased cardiac morbidity and mortality. This risk is not decreased by ventricular pacing avoidance algorithms, which cause nonphysiologic atrioventricular (AV) delays.

OBJECTIVE

This study aimed to report outcomes in patients with narrow QRS complex when the paced complex is in normal range and physiologic AV delays are programmed.

METHODS

In 196 patients with QRS duration of 92 ± 10 ms, permanent pacing was done at the site of the His bundle electrogram. The pacemakers were then programmed to maintain physiologic AV delays and to increase heart rates in response to exercise. Patients received usual care and were observed for 3 years.

RESULTS

The paced complex exhibited a delta wave, and the ventricular activation time, QRS axis, and lead I voltage remained in normal range. Physiologic programming resulted in His bundle pacing burden of 92%. In patients with decreased ejection fraction, there was significant improvement in left ventricular function, left ventricular dilation, and mitral regurgitation (P < .003). In patients with normal ejection fraction, left ventricular function remained normal without new valvular abnormalities. The 3-year all-cause mortality was 10%, and there was no increase in heart failure admissions.

CONCLUSION

In patients with narrow QRS complex, when paced QRS morphology is maintained in normal range and AV dyssynchrony is avoided, His bundle pacing is associated with low all-cause mortality and improvement in abnormal echocardiographic parameters. The paced QRS morphology and physiologic AV delays may be important factors to evaluate in future trials of conduction system pacing.

Concomitant ablation of atrial fibrillation: New pacemakers and early rhythm recovery

OBJECTIVE

New permanent pacemaker (PPM) implantation after concomitant atrial fibrillation (AF) ablation has been associated with surgical ablation (SA). We sought to determine factors for PPM use as well as early rhythm recovery.

METHODS

From 2004 through 2019, 6135 patients underwent valve surgery and were grouped: No AF (n = 4584), AF no SA (n = 346), and AF with SA (n = 1205) to evaluate predischarge PPM and 3-month rhythm recovery (intrinsic heart rate >40 beats per minute).

RESULTS

Overall, 282 (4.6%) patients required a predischarge PPM: atrioventricular node dysfunction in 75.3%, sick sinus syndrome in 19.1%, both (5%), and indeterminate (0.7%). Patients with AF had more PPMs: AF with SA (7.9%) versus AF no SA (6.9%) versus No AF (3.6%) (P < .001). For patients with AF, PPM rates were not significantly higher for ablation patients (7.6% SA vs 6.9% AF no SA; P = .56). There were differences in PPM by SA lesion set (biatrial 12.8%; left atrial only 6.1%; pulmonary vein isolation 3.0%; P < .001). Among patients with AF treated with 3-month PPM follow-up, rhythm recovery was common (35 out of 62 [56.5%]) and did not differ by lesion set. Rhythm recovery was seen in 63 out of 141 (44.7%) in the atrioventricular node dysfunction group versus 24 out of 35 (68.6%) in the sick sinus syndrome group (P = .011). In propensity score-matched groups, late survival was similar (P = .63) for new PPM patients.

CONCLUSIONS

Avoiding conduction system trauma and delaying implantation reduces the need for postoperative PPM. Rhythm recovery within 3 months is frequent, especially for patients with sick sinus syndrome. A conservative approach to the implantation of a new PPMs is warranted.

Physiological Pacing for the Prevention and Treatment of Heart Failure: a State-of-the-Art Review

Permanent pacing from the right ventricular apex can reduce quality of life and increase the risk of heart failure and death. This review summarizes the milestones in the evolution of pacemakers toward physiological pacing with biventricular pacing systems and lead implantation into the cardiac conduction system to synchronize cardiac contraction and relaxation. Both approaches aim to reproduce normal cardiac activation and help to prevent and treat heart failure. This review introduces the basic concepts and clinical evidence and discusses the practical uses of physiological pacing.

LOCAlizaTion and clinical corrElation of Left Bundle Branch Pacing lead: Insights from a computed tomographic angiography (LOCATE LBBP) study

BACKGROUND

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.

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Sex differences outcomes in conduction system pacing for patients with typical left bundle branch block

BACKGROUND

Biventricular pacing (BVP) appears to confer more pronounced advantages in women, yet the impact of conduction system pacing (CSP) remains insufficiently characterized. This investigation seeks to elucidate sex-specific disparities in clinical outcomes among patients with typical left bundle branch block (LBBB) undergoing CSP, with a particular focus on assessing contributory factors.

METHODS

Consecutive patients diagnosed with nonischemic cardiomyopathy, exhibiting left ventricular ejection fraction (LVEF) ≤ 40%, and manifesting typical LBBB as Strauss criteria, underwent CSP. Subsequent longitudinal monitoring assessed improvements in LVEF and the composite endpoint of mortality or heart failure hospitalization (HFH).

RESULTS

Among the included 176 patients, women (n = 84, mean age: 69.5 ± 8.8 years) displayed smaller heart size (LVEDd, 62.0 ± 8.3 mm vs. 64.8 ± 7.9 mm, P = 0.023) and shorter baseline QRSd (163.5 ± 17.7 ms vs. 169.7 ± 15.1 ms; P = 0.013) than men. Of the 171 patients who completed the follow-up, super-response was observed in 120 (70%), with a higher occurrence in women than men (78.3% vs. 62.5%, P = 0.024). The incidence of death or HFH was numerically lower in women (7.1% Vs 13%, Log-rank P = 0.216). Notably, the super-response showed a significant difference in women compared to men at the same electrocardiography and/or echocardiographic parameters value. Mediation analysis between sex and super-response revealed that LVEDd and pQRSd play an intermediary role, with the mediation proportion of 26.07% and 27.98%, respectively.

CONCLUSIONS

Women may derive more benefits from CSP, and pQRSd and LVEDd partly drive this difference.

Conduction System Pacing in Children and Congenital Heart Disease

Permanent cardiac pacing in children with congenital complete atrioventricular block (CCAVB) and/or congenital heart disease (CHD) is challenging. Conduction system pacing (CSP) represents a novel pacing strategy aiming to preserve physiological ventricular activation. Patients with CCAVB or CHD are at high risk of developing pacing-induced cardiomyopathy with chronic conventional right ventricular myocardial pacing. CSP may be a valuable pacing modality in this particular setting because it can preserve ventricular synchrony. In this review, we summarise implantation techniques, the available clinical evidence and future directions related to CSP in CCAVB and CHD.

Left ventricular volumes and function in successful and failed His-BundLe Pacing. A comparative prospective study

INTRODUCTION

Initial data suggest that His Bundle Pacing (HBP) could preserve long-term cardiac structure and function better than Right Ventricular Pacing (RVP), but evidence is limited.

METHODS

We studied consecutive patients with baseline ejection fraction (EF) ≥ 50% who underwent HBP attempt, either successful (HBP group) or failed (RVP group). Two-dimensional (2D) and three-dimensional (3D) echocardiography were carried out at baseline and after 6 months of ventricular pacing burden > 20%.

RESULTS

Among 68 patients, 40 underwent successful HBP, and 28 RVP. The HBP and RVP groups did not differ for age, sex and pacing indication. At baseline, the HBP and RVP groups did not differ for 2D EF (62% vs. 62%), 3D EF (60% vs. 63%), 2D (-19% vs. -19%) and 3D global longitudinal strain (GLS) (-15% vs. -16%). After 6 months, 2D EF (-3.86%) and 3D EF (-5.71%) significantly decreased in the RVP group and did not change in the HBP group (p for interaction .006 and <.001, respectively). 2D GLS (3.08%) and 3D GLS (2.22%) significantly increased in the RVP group, but did not change in the HBP group (p for interaction .013 and <.016, respectively). Pacing induced cardiomyopathy (PICM) (EF drop ≥ 10% and EF < 50%) occurred in 14% (RVP) versus 0% (HBP) of patients (p = .025).

CONCLUSIONS

Successful HBP was superior to RVP in preserving LV systolic function despite a high ventricular pacing burden, and was less frequently associated with PICM.

New-Onset Left Ventricular Dysfunction After Left Bundle Branch Pacing

BACKGROUND

Left bundle branch pacing (LBBP) provides stable pacing parameters and has been suggested as an alternative for right ventricular pacing and cardiac resynchronization therapy.

OBJECTIVES

The aim of the study was to assess the incidence and etiology of new-onset left ventricular dysfunction (NOLVD) following LBBP in patients with baseline normal left ventricular (LV) function and cardiomyopathy patients with normalized LV function.

METHODS

Patients undergoing successful LBBP for symptomatic bradyarrhythmia or as an alternative to cardiac resynchronization therapy were included. Normalization of LV function was defined as improvement in LV ejection fraction to ≥50%. Patients with baseline normal LV function and those with recovered LV function after LBBP constituted the study group. Loss of conduction system capture (LOCSC) was defined as complete or partial loss of right bundle branch delay pattern along with inability to demonstrate capture transition during threshold assessment.

RESULTS

A total of 426 patients were included; 59% (n = 250) had baseline normal LV function (group I) and 41% (n = 176) had recovered LV function after LBBP (group II). Mean follow-up duration of 28.3 ± 16.7 months. NOLVD was noted in 3.75% (n = 16; group I, n = 5, and group II, n = 11) of patients. The etiologies for NOLVD were LOCSC in 62.5% (n = 10), suboptimal atrioventricular (AV) delay in 18.7% (n = 3), atrial fibrillation in 6.3% (n = 1), and idiopathic in 12.5% (n = 2). LOCSC occurred at a mean interval of 9.2 ± 6.4 months after the initial implantation. Reinterventions (n = 6) including lead repositioning, AV delay optimization, and AV junction ablation resulted in renormalization of LV function in all 6 patients.

CONCLUSIONS

Periodic assessment in device clinic is required because NOLVD from reversible causes can occur during follow-up in patients after LBBP.

Electrophysiologic characteristics and clinical correlation of right ventricular activation during left bundle branch area pacing (RV-LBBAP study)

BACKGROUND

Left bundle branch area pacing (LBBAP) results in a right bundle branch (RBB) delay pattern because of preexcitation of the left bundle. The mechanism of right ventricular (RV) activation during LBBAP is largely unknown.

OBJECTIVE

The aim of the study was to analyze the electrophysiologic characteristics of RV activation by mapping the RBB during LBBAP and its clinical correlation.

METHODS

Consecutive patients who underwent successful LBBAP were included. RBB block, RV paced rhythm, and suboptimal intracardiac electrograms were excluded. LBBAP was performed with continuous recording of His bundle (HB) and RBB electrograms. RV activation was classified into 3 types based on the intracardiac electrogram: type I, RBB mediated; type II, transseptal activation; and type III, fusion pattern.

RESULTS

Overall, 86 patients (94% left bundle branch pacing [LBBP]; 6% left ventricular septal pacing) were included. The mean age was 59.6 ± 12.8 years. Nonselective to selective capture transition was noted in 85% (n = 73). In patients with baseline normal QRS (n = 47), during selective LBBP (S-LBBP; n = 39), the most common pattern was type I (n = 34 [87%]), whereas during nonselective LBBP (NS-LBBP; n = 44), type III pattern (n = 40 [91%]) was common. In patients with left bundle branch block (n = 39), type III pattern was common during both S-LBBP and NS-LBBP. Type I pattern was noted only in patients with retrograde HB activation during S-LBBP. Left ventricular septal pacing showed type II activation in both groups. Patients without retrograde HB activation had higher left ventricular end-diastolic diameter, lower left ventricular ejection fraction, and prolonged HV interval compared with those with retrograde HB activation.

CONCLUSION

Physiologic RBB-mediated (type I) activation of the right ventricle was the most common pattern observed during S-LBBP in patients with intact retrograde HB activation. Type III pattern was the most common pattern observed during NS-LBBP with fusion of multiple wavefronts from anterograde RBB activation, myocardial, and transverse interbundle connections.

His Bundle Pacing and Left Bundle Branch Pacing in Patients with Heart Failure

BACKGROUND

His bundle pacing (HBP) and left bundle branch pacing (LBBP) are emerging therapies for patients with heart failure and conduction disorders, offering potential advantages over traditional pacing methods. These approaches aim to restore physiological conduction and improve cardiac function more effectively.

OBJECTIVE

This study aims to evaluate the efficacy and safety of HBP and LBBP in patients with heart failure and conduction disturbances, comparing these techniques to conventional pacing.

METHODS

A comprehensive review of recent studies and clinical trials was conducted, focusing on the performance of HBP and LBBP in improving cardiac function, reducing QRS duration, and enhancing overall patient outcomes. The analysis includes data on clinical efficacy, procedural safety, and long-term benefits associated with these pacing modalities.

RESULTS

Both HBP and LBBP have demonstrated significant improvements in cardiac function and clinical outcomes compared to conventional pacing. HBP effectively restores physiological conduction with improved synchronization and a reduction in QRS duration. LBBP has shown enhanced left ventricular activation, leading to better overall cardiac performance. Both techniques have been associated with a lower incidence of complications and a higher success rate in achieving optimal pacing thresholds.

CONCLUSIONS

HBP and LBBP offer promising alternatives to traditional pacing for patients with heart failure and conduction disorders. These advanced pacing strategies provide superior clinical outcomes and improved cardiac function with reduced risk of complications. Further research and clinical trials are needed to fully establish the long-term benefits and safety profiles of these techniques in diverse patient populations.

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 117 (34%); cardiomyopathy 157 (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%). Reimplantation in the conduction system 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.

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.

Comparison of clinical and echocardiographic outcomes between left bundle branch area pacing and right ventricular pacing in older patients

BACKGROUND

Left bundle branch area pacing (LBBAP) is safe and effective, but studies in older patients are lacking. This study compared the clinical and echocardiographic outcomes of LBBAP and right ventricular pacing (RVP) in patients aged ≥75 years.

METHODS

This prospective observational study included older patients with symptomatic bradycardia who underwent LBBAP or RVP between 2019 and 2022. Clinical data, including pacing and electrophysiological characteristics, echocardiographic measurements, and device-related complications were collected. The primary endpoint was a composite of all-cause mortality, heart failure hospitalization, and upgrade to biventricular pacing. Secondary outcomes included changes in left ventricular ejection fraction (LVEF).

RESULTS

Of 267 included patients, 110 underwent LBBAP and 157 underwent RVP. LBBAP was successful in 109 patients (success rate: 99.1%), with one patient eventually undergoing RVP. The pacing parameters of LBBAP were similar to those of RVP, except for a significantly narrower paced QRS duration (112.8 ± 11.6 vs. 138.3 ± 23.9 ms, p < .001). Ventricular lead implanting procedural duration was longer for LBBAP than RVP (14.0 vs. 6.0 min, p < .001), as was the fluoroscopy time (4.0 vs. 2.0 min, p < .001). During a mean follow-up period of 31.0 ± 16.8 months, the primary outcome incidence was significantly lower following LBBAP than RVP (15.1% vs. 21.1%; hazard ratio, 0.471; 95% confidence interval, 0.215-1.032; p = .036) in 149 patients (55.8%) with ventricular pacing burden > 20%. RVP reduced LVEF from 62.7 ± 4.1% at baseline to 59.8 ± 7.8% at the final follow-up (p = .001), whereas LBBAP preserved LVEF (61.4 ± 6.3% vs. 60.1 ± 7.4%, p = .429).

CONCLUSION

LBBAP demonstrated improved clinical outcomes compared with RVP and maintained LVEF in older patients with high ventricular pacing burdens.

Predictors of success in left bundle branch area pacing with stylet-driven pacing leads: a multicenter investigation

Purpose

Although left bundle branch area pacing (LBBAP) is an emerging conduction system pacing modality, it is unclear which parameters predict procedural success and how many implant attempts are acceptable. This study aimed to assess predictors of successful LBBAP, left bundle branch (LBB) capture, and factors associated with the number of LBBAP implant attempts.

Methods

This retrospective observational multicenter study was conducted in Korea. LBBAP was attempted in 119 patients; 89.3% of patients had bradyarrhythmia (atrioventricular block 82.4%), and 10.7% of patients had heart failure (cardiac resynchronization therapy) indication. Procedural success and electrophysiological and echocardiographic parameters were evaluated.

Results

The acute success rate of lead implantation in LBBAP was 95.8% (114 of 119 patients) and that of LBB capture was 82.4% (98 of 119 patients). Fewer implant attempts were associated with LBBAP success (three or fewer vs. over three times, p = 0.014) and LBB capture (three or fewer vs. over three times, p = 0.010). In the multivariate linear regression, the patients with intraventricular conduction delay (IVCD) required a greater number of attempts than those without IVCD [estimates = 2.33 (0.35-4.31), p = 0.02], and the larger the right atrial (RA) size, the more the attempts required for LBBAP lead implantation [estimates = 2.08 (1.20-2.97), p < 0.001].

Conclusion

An increase in the number of implant attempts was associated with LBBAP procedural failure and LBB capture failure. The electrocardiographic parameter IVCD and the echocardiographic parameter RA size may predict the procedural complexity and the number of lead implant attempts for LBBAP.

Stylet-driven Leads or Lumenless Leads for Conduction System Pacing

Stylet-driven leads have been recently introduced for conduction system pacing, while most of the previous experience has been obtained with lumenless leads. Design and structural characteristics of both lead types are significantly different, resulting in different implant techniques and independent learning curves. Lead performance appears to be comparable, whereas data on direct comparison of clinical outcomes are scarce. Currently, there are no specific clinical scenarios favouring the use of one lead type over another and the decision should rely on the individual experience of the implanter.

Risk factors and incidence of new-onset heart failure with conventional pacemaker implant: A nationwide study

Background

Studies have shown that the risk of new-onset heart failure (HF) is higher postimplantation for patients receiving right ventricular pacing.

Objective

This study aimed to investigate incidence, risk factors, and implications for long-term prognosis of new-onset HF in patients after pacemaker implantation.

Methods

Patients without pre-existing HF who received a pacemaker in Sweden during the period of 2005 to 2020 were identified via the nationwide Pacemaker Registry. Data were crossmatched with the population registry and national disease registries. The primary outcome was new-onset HF within 5 years, and a risk score for this was developed and validated.

Results

In all, 65,579 patients met the inclusion criteria (10,351 single-chamber ventricular and 55,228 dual-chamber pacemakers). A total of 13,792 (21.0%) patients were diagnosed with HF within 5 years postimplantation. Of these, 6244 (45.3%) were hospitalized for HF. Patients with new-onset HF were more likely to die within 5 years (41.2% vs 19.7%, P < .0001). Risk factors for new-onset HF included increasing age, male sex, hypertension, diabetes, atrial fibrillation, chronic lung and kidney disease, ischemic heart disease, and atrioventricular block. In a combined score using these variables, patients in the highest risk-score quartile had a hazard ratio of 5.36 (95% CI 4.91-5.86, P < .001) and an absolute risk of 32% for developing HF.

Conclusion

Pacemaker therapy is associated with >20% risk of new-onset HF within 5 years, and we identified 9 risk factors associated with the diagnosis of new-onset HF. The proposed score based on these variables can be used to identify patients at high risk for new-onset HF.

Case Report: Extraction of a stylet-driven lead for left bundle branch area pacing >2 years after implantation

Left bundle branch pacing has recently emerged as a significant alternative to right ventricular pacing. The rate of implanted stylet-driven septal leads is expected to increase substantially in the coming years, along with the need to manage long-term complications. Experience in extracting these leads is currently very limited; however, the number of complex extractions is anticipated to increase in the future. We report a complex case involving the extraction of a long-dwelling Solia lead used for left bundle branch pacing in a 21-year-old man. The lead was extracted through the implant vein 27 months after implantation, using a methodology that involved a locking stylet and compression coil. The new lead insertion was challenging due to venous occlusion but after successful venoplasty, the His lead was successfully implanted. The postoperative course was uneventful, demonstrating the feasibility of extraction without complications.

Feasibility, safety and outcomes of conduction system pacing for bradycardia amongst the very elderly

The impact of age (≥ 85 vs < 85 years) on clinical outcomes and pacemaker performance of conduction system pacing (CSP) compared to right ventricular pacing (RVP) were examined. Consecutive patients from a prospective, observational, multicenter study with pacemakers implanted for bradycardia were studied. The primary endpoint was a composite of heart failure (HF)-hospitalizations, pacing-induced cardiomyopathy requiring cardiac resynchronization therapy or all-cause mortality. Secondary endpoints were acutely successful CSP, absence of pacing-complications, optimal pacemaker performance defined as pacing thresholds < 2.5 V, R-wave amplitude ≥ 5 V and absence of complications, threshold stability (no increases of > 1 V) and persistence of His-Purkinje capture on follow-up. Among 984 patients (age 74.1 ± 11.2 years, 41% CSP, 16% ≥ 85 years), CSP was independently associated with reduced hazard of the primary endpoint compared to RVP, regardless of age-group (< 85 years: adjusted hazard ratio [AHR] 0.63, 95% confidence interval [CI] 0.40-0.98; ≥ 85 years: AHR 0.40, 95% CI 0.17-0.94). Among patients with CSP, age did not significantly impact the secondary endpoints of acute CSP success (86% vs 88%), pacing complications (19% vs 11%), optimal pacemaker performance (64% vs 69%), threshold stability (96% vs 96%) and persistent His-Purkinje capture (86% vs 91%) on follow-up (all p > 0.05). CSP improves clinical outcomes in all age-groups, without compromising procedural safety or pacemaker performance in the very elderly.

Long-Term Outcomes in Patients With Relatively High His-Bundle Capture Threshold After Permanent His-Bundle Pacing - A Multicenter Clinical Study

Background

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.

Methods and Results

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.

Conclusions

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

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.

Result of the left bundle branch area pacing data collection registry, an international multicenter study of conduction system pacing with a Tendril STS 2088 stylet-driven lead

INTRODUCTION

Left bundle branch area (LBBA) pacing (LBBAP) has been proposed as an alternative therapy option in patients indicated for cardiac pacing to treat bradycardia or heart failure. The aim of the study was to evaluate the safety and effectiveness of LBBAP in patients implanted with a Tendril 2088 stylet-driven lead.

METHODS

The international retrospective data collection registry included 11 sites from 5 countries globally. Patients with attempted implants of the Tendril lead in the LBBA were followed for at least 6 months post the implant attempt. The primary safety and efficacy endpoints were freedom from LBBAP lead-related serious adverse events and the composite of LBBA capture threshold of ≤2.0 V and R-wave amplitudes ≥5 mV (or ≥value at implant), respectively.

RESULTS

Of 221 patients with attempted implants of the Tendril 2088 lead in the LBBA, 91.4% (202/221) had successful implants for LBBAP. Regardless of the LBBAP implant success, all patients were followed for at least 6 months (8.7 ± 7.3 months). Baseline characteristics: 44% female, 84% ≥65 years old, 34% coronary artery disease, and 86% of primary indications for pacemaker implant. Both primary safety and effectiveness endpoints were met (freedom from LBBAP lead-related serious adverse device effects of 99.5% and electrical performance composite success rate of 93%). The capture thresholds in LBBAP at implant and 6 months were 0.8 ± 0.3 V@0.4 ± 0.1 ms and 0.8 ± 0.3 V@0.4 ± 0.1 ms. The rate of patients with capture threshold rise ≥1 V was 1.5% through 6 months. The R-wave amplitudes in LBBAP at implant and 6 months were 9.3 ± 3.2 mV and 10.6 ± 3.0 mV.

CONCLUSIONS

This large multicenter study demonstrates that the stylet-driven Tendril™ STS 2088 lead is safe and effective for LBBAP with high success and low complication rates.

Is conduction system pacing a panacea for pacemaker therapy?

INTRODUCTION

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.

AREAS COVERED

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.

EXPERT OPINION

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.

Significant Mitral Regurgitation After Permanent Right Ventricular Pacemaker Implantation: Prognostic Implications

The underlying mechanisms leading to the development of mitral regurgitation (MR) after right ventricular (RV) pacemaker (PM) implantation and its prognostic value have yet to be fully understood. The purpose of this study was to evaluate the prevalence and clinical variables associated with the development of MR after RV pacing and its association with outcomes. A total of 451 patients (mean age 69 ± 15 years, 61% male) who underwent de novo RV PM implantation were included. The development of significant MR, defined as ≥moderate from mild or none/trace at baseline, occurred in 131 (29%) patients at a median of 2.4 years (interquartile range: 1.0 to 3.8 years) after PM implantation. Multivariate logistic regression analysis demonstrated that implantation of a single-chamber PM, left ventricular end-systolic volume index, and the presence of mild MR (vs no MR) at baseline were independently associated with the development of significant MR post-implant. Cardiac events, defined as the composite of all-cause mortality or heart failure hospitalization, occurred in 143 patients (31.7%) during a median follow-up of 5.4 years (interquartile range: 3.0 to 8.1 years). Multivariate Cox regression analysis demonstrated that the development of significant MR was independently related to the occurrence of cardiac events. In conclusion, the development of significant MR after PM implantation is seen in about one-third of recipients and is independently associated with adverse cardiac events.

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.