Cardiac resynchronization therapy (CRT) is a guideline-recommended therapy in patients with heart failure with mildly reduced ejection fraction (HFmrEF, 36%-50%) and left bundle branch block or indication for ventricular pacing. Conduction system pacing (CSP) using left bundle branch area pacing or His bundle pacing has been shown to be a safe and physiologic alternative to biventricular pacing (BVP).

The aim of this study was to compare the clinical outcomes between BVP and CSP for patients with HFmrEF undergoing CRT.

Consecutive patients who underwent BVP or CSP with HFmrEF between January 2018 and June 2023 at 16 international centers were included. The primary outcome was the composite end point of time to death or heart failure hospitalization (HFH). Secondary end points included change in left ventricular ejection fraction (LVEF) and individual end points of death and HFH.

A total of 1004 patients met inclusion criteria: BVP, 178; CSP, 826 (His bundle pacing, 154; left bundle branch area pacing, 672). Mean age was 73 ± 13 years; female, 34%; and LVEF, 42% ± 5%. Paced QRS duration in CSP was significantly narrower compared with BVP (129 ± 21 ms vs 144 ± 19 ms; P < .001). LVEF improved during follow-up in both groups (49% ± 10% vs 48% ± 10%; P = .32). CSP was independently associated with significant reduction in the primary end point of time to death or HFH compared with BVP (22% vs 34%; hazard ratio, 0.64; 95% confidence interval, 0.43-0.94; P = .025).

CSP was associated with improved clinical outcomes compared with BVP in this large cohort of patients with HFmrEF undergoing CRT. Randomized controlled trials comparing CSP with BVP will be necessary to confirm these results.

Paced QRS morphology may vary during left bundle branch area pacing (LBBAP) per the pacing location. It remains unclear whether electrocardiographic changes observed during LBBAP can predict clinical outcomes.

We aimed to assess correlation between characteristics of paced QRS on the electrocardiogram and clinical outcomes in heart failure patients with nonischemic cardiomyopathy.

Of 79 consecutive heart failure patients receiving LBBAP, 59 patients were included in this prospective study after exclusions. LBBAP was performed using Medtronic 3830 lead. Patients were assigned to various groups on the basis of paced QRS morphology in lead V1 (qR and Qr), QRS axis (normal, left, or right), and V6 R-wave peak time (RWPT, ≤80 ms or >80 ms) to compare echocardiographic outcomes.

RWPT was significantly shorter (75.7 ± 17.5 ms vs 85.3 ± 11.3 ms; P = .014), transition during threshold testing was more commonly observed (81.5% vs 53%; P = .02), and improvement in left ventricular ejection fraction (LVEF) was significantly greater in the qR group (21.4% ± 6.4% vs 16.4% ± 8.3%; P = .013) compared with the Qr group. RWPT or LVEF did not differ in patients with different paced QRS axis (P > .05). Whereas qR morphology and presence of transition during threshold testing independently predicted LVEF improvement, RWPT lacked predictive value. Nonresponders had greater incidence of loss of R' (P = .009) and prolonged RWPT (P = .003) on follow-up compared with average responders and superresponders.

Paced qR morphology and transition during threshold testing predicted greater improvement in LVEF, whereas RWPT lacked predictive value. Loss of terminal R in lead V1 and prolongation of RWPT on follow-up prognosticated nonresponse to LBBAP.

Cardiac conduction disease often necessitates permanent pacemaker implantation. While right ventricular pacing (RVP) effectively treats bradycardia, it may lead to adverse cardiac remodeling and heart failure. Left bundle branch area pacing (LBBAP) has emerged as an alternative, potentially preserving myocardial function. Non-invasive myocardial work (MW) assessment provides valuable insights into left ventricular systolic function, energetics, and efficiency. This study systematically reviewed and analyzed MW parameters, comparing LBBAP to RVP and His bundle pacing (HBP). A meta-analysis of 241 patients across five studies examined four MW parameters-Global Work Index (GWI), Global Constructive Work (GCW), Global Wasted Work (GWW), and Global Work Efficiency (GWE)-at baseline, post-implantation, and last follow-up (median: 180 days, IQR: 7-360 days). At baseline, MW parameters were similar between LBBAP and RVP. Post-implantation, LBBAP preserved MW more effectively, showing significantly higher GWI than RVP (2250.0 ± 400.0 vs. 1600.0 ± 300.0 mmHg%, p = 0.027), a difference that remained significant at follow-up (p = 0.035). GWE was also significantly higher at follow-up (p = 0.011), while GCW and GWW showed no significant differences. MW parameters did not differ significantly between LBBAP and HBP (all p-values >0.05). These findings suggest that LBBAP provides superior MW preservation compared to RVP, with significant benefits in GWI and GWE, while demonstrating comparable performance to HBP.

Left bundle branch (LBB) pacing (LBBP) demonstrates clinical potential but faces challenges in confirming selective capture via dynamic electrogram (EGM) criteria.

A 69-year-old male with a complete atrioventricular block underwent LBBP implantation. Real-time EGM monitoring (high-pass/low-pass filters: 200/500 Hz) revealed an abrupt shortening of stimulus-to-V6 R-wave peak time (Sti-V6 RWPT) from 87 to 69 ms during lead deployment, indicating a transition from septal pacing to LBBP. Output reduction (1.6 V → 1.5 V/0.5 ms) eliminated myocardial excitation notches, yielding isoelectric EGMs confirming selective LBB capture. Further output reduction (1.4 V → 1.3 V/0.5 ms) prolonged Sti-V6 RWPT to 90 ms with an isoelectric interval, suggesting fascicular-level conduction delay.

This case report illustrates the electrophysiological features of a diseased conduction system via dynamic EGM analysis, despite technical limitations such as signal artifacts. While EGM morphological patterns assist in differentiating pacing modalities, further validation of these electrophysiological observations is necessary.

Conduction system pacing (CSP), encompassing His-bundle pacing (HBP) and left bundle branch area pacing (LBBAP), revolutionizes cardiac pacing, allowing a more physiological left ventricular activation than conventional right ventricular (RV) pacing through electrode placed in RV apex, interventricular septum or right ventricular outflow tract. Echocardiography plays a pivotal role in patient assessment, primarily by measuring left ventricular ejection fraction (LVEF) to determine the pacing strategy in alignment with current guidelines. Clinical data, simulations and ongoing trials on CSP explore CSP viability across various LVEF conditions. CSP is supposed to defer pacing-induced cardiomyopathy (PiCM) associated with conventional right ventricular pacing (RVP). This paper aims to review the current literature regarding the use of echocardiography in CSP. Images from our experience in the echocardiographic lab were used throughout this document to show our proposals of imaging in CSP. Echocardiography may help to determine lead localization within the interventricular septum (IVS), customizing pacing to individual anatomy and electromechanical indices (like atro-ventricular delay) and evaluates often-overlooked valvular function, a potential PiCM contributor. Three-dimensional (3-D) echocardiography widens the knowledge of lead localization and valvular dysfunction, as well as dyssynchrony assessment. Dyssynchrony, crucial both to resynchronization per se and physiological stimulation is quantified via echocardiography, especially using speckle-tracking imaging. Baseline LVEF and follow-up observation of CSP effects: early in Global Longitudinal Strain (GLS), afterwards in LV volumes and LVEF may improve the future proper qualification of patients. Limited left atrial (LA) and right atrial (RA) strain assessments hold potential in the CSP qualification and response assessment context. Echocardiography complements other imaging modalities for comprehensive patient evaluation. Echocardiography is integral in the CSP clinical use, from patient selection (by showing subtle changes in myocardial function) to post-procedure follow-up (tricuspid regurgitation, LV and RV function, leads and synchrony assessment). GLS, assessed by speckle tracking imaging and profound 2D and 3D (lead placement, septum morphology and global heart function under CSP) analyses show promise in CSP outcome assessment, though standardization is needed.

Left bundle branch area pacing (LBBAP) is a technique suitable for treating both symptomatic bradycardia and cardiac resynchronization therapy (CRT). Our study aims to describe the first experience of LBBAP in a high-volume cardiac implantable electronic device (CIED) center.

This prospective single-center observational registry included consecutive patients who underwent pacemaker implantation with LBBAP technique for sinus node disease, bradycardia and CRT indications between January 2023 and January 2024. Procedural data, outcomes, and lead parameters were recorded at hospital discharge, at one and six months of follow-up.

A total of 164 consecutive patients undergoing LBBAP implantation were included, of whom 142 had a stylet-driven lead. LLBAP was achieved in 94.5% patients. Average QRS duration was 139.8±33.4 ms. Complete atrioventricular block was the most common indication (42.7%). CRT was performed in 24 (14.5%) patients. Mean procedural duration was 82.7±24.4 min and mean fluoroscopy time was 13.7±7.1 min. Average LVAT was 78.8±8.7 ms and paced QRS width 114.8±14.4 ms. Median acute R-wave amplitude was 14.0 mV, pacing threshold was 0.5 V and impedance 526 Ω. No relevant per-operative complications occurred. After one month of follow-up, median pacing threshold had significantly increased to 0.75 V (p<0.001) while R-wave amplitude and impedance remained unchanged (p=0.242 and p=0.101 respectively). During follow-up, no changes occurred in the evaluated parameters. Loss of left bundle branch capture occurred in five patients and macro-dislodgement in 2.

LBBAP is a feasible pacing technique which reduces QRS duration and improves LV synchrony and can be adopted at most centers, with favorable success rates and safety profile.

Cardiac conduction disorders can manifest in young adults in isolated forms, associated with myocardial diseases or as part of a multiorgan disorder. Underlying causes of cardiac conduction disorders may be genetically determined or acquired. Cardiac conduction disorder in young adults is a complex and often underestimated and underrecognized disease that may need of a multidisciplinary team for the diagnosis, treatment, and long-term management of these patients. Therefore, it is crucial to raise clinicians' awareness of this condition. In this review, we provide a comprehensive update on the cause, diagnosis, and treatment of young adults with cardiac conduction disorders, also suggesting potential strategies to improve the current clinical management of these patients.

Right ventricular apex (RVA) pacing has been reported to induce pacing-induced cardiomyopathy (PICM), with biventricular pacing being the standard cardiac resynchronization therapy (CRT) for RVA-PICM. However, recent studies suggest that left bundle branch area pacing (LBBAP) may provide even better outcomes as a CRT. In this case, we observed a dynamic alteration in the left ventricular (LV) activation pattern when transitioning from RVA-PICM to LBBAP, including changes in the functional block line.

A female patient with dilated-phase hypertrophic cardiomyopathy (d-HCM), septal, and apical myocardial damage caused by cardiomyopathy, and prior ventricular tachycardia ablations experienced worsening heart failure due to dyssynchronous LV activation from RVA pacing (paced QRS duration of 250 ms). She underwent an upgrade to LBBAP (paced QRS duration of 160 ms) as CRT. Six months later, three-dimensional LV activation mapping was performed during both RVA pacing and LBBAP. During RVA pacing, a functional conduction block was observed in the anterior wall, resulting in unidirectional excitation propagation in a counterclockwise direction from the septum and a significant delay in the basal-mid anterior wall. In contrast, with LBBAP, the functional conduction block shifted to the septal-apical region, enabling bidirectional excitation propagation to the basal-mid lateral wall and facilitating synchronized excitation in vertically opposing LV segments.

The change in LV activation is specific to this d-HCM case with damaged septum and apex; however, it provides one of the insights into the mechanisms by which LBBAP exerts its beneficial effects when upgrading from RVA-PICM.

An electrophysiology (EP) recording system is recommended throughout the left bundle branch area pacing (LBBaP) procedure. However, the requirement of an EP recording system limits the wide adoption of LBBaP in non-EP laboratory settings. Thus, in this study, we proposed a novel set-up in non-EP laboratories using manufacturer pacing system analyzer (PSA)-derived electrogram guidance and fluoroscopy of the angiography system for LBBaP.

Our study prospectively enrolled consecutive patients who underwent LBBaP for bradyarrhythmia indications. LBBaP was performed using a stylet-driven lead (SDL) delivered through a dedicated delivery sheath. Procedural characteristics were recorded at the implant. The agreement of measurements on the modified 3-lead ECG of PSA and standard 12-lead ECG was analyzed.

A total of 83 patients were enrolled (mean age 65.4 ± 11.8 years, 55.4% male). The LBBaP with an SDL was successful for all patients. The pacing response was observed as LBBP in 69.9% of cases, while 30.1% were classified as left ventricular septal pacing. The mean paced QRS duration (pQRSd) and the stimulus to left ventricular activation time (LVAT) were measured at 117.6 ± 11.4 ms and 68 ± 17 ms using a modified 3-lead ECG of PSA, compared to 118.5 ± 11.8 ms and 70 ± 13 ms using the standard 12-lead ECG, with agreements of 0.89 and 0.93, respectively. SDL-LBBaP resulted in low unipolar and bipolar pacing thresholds (0.7 ± 0.2 V at 0.4 ms and 0.8 ± 0.2 V at 0.4 ms), which remained stable at a median 12-month follow-up (p > 0.05). An atrial lead revision was needed for one (1.2%) patient during the first-month visit. Acute interventricular septal perforation occurred in two (2.4%) patients as a specific complication of LBBaP.

Our novel setting in non-EP laboratories, utilizing fluoroscopy from the angiography system and manufacturer-modified 3-lead ECG and EGM of PSA during LBBaP, is feasible, reliable, and widely available. LBB capture was confirmed by both the standard EP recording system and new modified PSA 3-lead ECG measurements, which showed good agreement. Further large-scale data is needed to validate our findings.

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.

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.

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).

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.

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

The initial criterion to achieve conduction system area pacing (CSP) is the presence of a terminal R wave in lead V1. Different configurations were used to determine that placing V1 in lower right intercostal spaces results in a greater amplitude of the terminal R waves when the CSP lead is placed deep in the mid-septal or antero-septal locations. Easily identified terminal R wave in V1 will be more practical and potentially reduce the number of sites attempted for left bundle branch area pacing (LBBaP), resulting in faster procedures and reducing potential complications such as septal perforation.

Left bundle branch pacing (LBBP) is a novel physiological pacing modality. However, whether it delivers comparable efficacy with different capture sites in patients with heart failure remains unclear.

This study aimed to assess the association between different pacing sites and the response of LBBP.

Forty-three consecutive patients with heart failure, referred for successful LBBP implantation, were prospectively recruited in this study. Patients were assigned to 3 subgroups according to the paced QRS complex morphology (left bundle branch trunk pacing [LBTP], left posterior fascicular pacing, or left anterior fascicular pacing groups). Echocardiograms and electrocardiograms were recorded and analyzed at baseline and 6-month follow-up.

The response rate was 95.0%, 88.2%, and 83.3% in LBTP, left posterior fascicular pacing, and left anterior fascicular pacing groups, respectively. All subgroups were efficient in narrowing the QRS complex (QRS complex narrowing: 38.1 ± 10.8 ms, 36.4 ± 12.6 ms, and 40.8 ± 10.8 ms) and improving cardiac function (LVEF improvement： 25.7% ± 8.1%, 15.3% ± 8.1%, and 18.8% ± 4.4%). Compared with left fascicular pacing, LBTP resulted in longer peak left ventricular activation time (76.5 ± 10.2 ms vs 82.3 ± 6.5 ms; P = .037) and shorter duration from intrinsicoid deflection in V1 or V2 to QRS end (128.0 ± 6.0 ms vs 113.3 ± 5.2 ms; P＜.0001), along with better improvement in septal systolic longitudinal strain (P = .007) and lateral-septal myocardial loading inhomogeneity (P = .036). Linear regression analysis further revealed that left bundle branch capture sites were strongly associated with the improvement in peak strain dispersion (model R2 = 0.586; P = .042) and LVEF (model R2 = 0.425; P < .0001).

Different left bundle branch capture sites led to a subtle difference in mechanical synchrony, which may, in turn, affect LVEF improvement in patients with heart failure.

The interrupted technique of left bundle branch pacing (LBBP) limits the continuous monitoring of paced electrocardiogram and intracardiac electrogram (EGM) transitions, which may result in overlooked or misinterpreted subtle transitions.

This study aimed to explore the electrophysiological characteristics of lead position-dependent EGM continuous transitions to evaluate lead depth and to investigate the clinical significance of transseptal pacing modalities.

A continuous pacing and recording technique enabled by a rotatable connector was used to allow the real-time monitoring of progressive changes in paced EGM and electrocardiographic morphology. Careful observations were conducted to evaluate whether there were significant changes in the amplitude and morphology of the ventricular current of injury (COI), R-wave peak times in leads V1 and V6, QRS duration, and impedance at different interventricular septal depths.

The study included 105 patients. Nonselective LBBP was achieved in 94 patients (89.5%), of whom 88 (83.8%) achieved selective LBBP (SLBBP). Left ventricular septal pacing was confirmed in 11 patients (11.5%). The amplitude of ventricular EGM predictably changed with radial septum depth and peaked in the interventricular septum (26.3±11.3 mV). As the lead was inserted into the left ventricular subendocardium, the ventricular COI declined to a level approximating that of the right septum (11.7 ± 6.3 mV for SLBBP vs 10.4 ± 5.8 mV for right ventricular septal pacing). When selective left bundle branch capture occurred, significant morphological transitions in the ventricular COI were observed in the unfiltered EGM.

The continuous recording technique provides a more detailed understanding of pacing lead radial depth throughout implantation. COI amplitude and morphology variations can identify different pacing modalities, particularly in recognizing SLBBP.

Left bundle branch area pacing (LBBAP) leverages the strengths of His bundle pacing (HBP) and traditional myocardial pacing. While automatic threshold (AT) algorithms are often not suitable for HBP leads, their function in LBBAP remains uncertain.

Data from the LATITUDE remote monitoring system were evaluated retrospectively comparing LBBAP leads to a sample of right ventricular (RV) placed leads. AT accuracy was assessed comparing the nearest in-office (IO) pacing capture threshold (PCT) ± 7 days at 1 and/or 3 months at 0.4 ms pulse width. Methodology from a previous trial (CAPTIVATE, NCT02097290) used for regulatory approval of an AT algorithm for standard RV apical leads was employed, comparing percent of accurate tests, with an accurate test defined as: |AT - IO | ≤ 0.6 V (or ≤ 1 V if IO > 3.5 V). Secondary analysis assessed the percentage of devices with AT turned off during 6 mo follow-up. Statistical comparisons were made using Chi-square tests.

Data from 1288 devices (798 LBBAP, 490 RV) were evaluated, limited by the in-office visit requirement for comparison. Among LBBAP patients, 677 had an INGEVITY+ lead, 121 FINELINE II. Generators were 668 PM, 128 CRT-D/P, 2 ICD; 694 in RV port, 96 LV, 8 RA. Compared to IO PCT, the AT algorithm accuracy was 96.9% in LBBAP leads and 97.6% in RV leads, (LBBAP vs. RV p = 0.47, Figure 1), both exceeding the 90% target. The median (IQR) difference between AT and IO PCTs for LBBAP leads was 0.1 V (0.0, 0.2 V); 59%, 81% and 91% of AT values were within 0.1, 0.2 and 0.3 V of IO, respectively (Figure 2). The AT feature was turned off at similar rates for LBBAP and RV leads in first 6 mo (LBBA 1.8%, RV 0.9%; p = 0.18; Figure 3).

AT algorithms' accuracy was high and similar for RV and LBBAP leads in this analysis. Future research is needed to determine if current algorithms are sufficient for achieving conduction system capture when the conduction system threshold is greater than the myocardial threshold.

Cardiac resynchronization therapy (CRT) using biventricular (BiV) pacing is the standard treatment for heart failure (HF) patients with reduced left ventricular ejection fraction (LVEF) and electrical dyssynchrony. However, one in three patients remains a non-responder. Left bundle branch area pacing (LBBAP) could represent a more physiological alternative, but its effectiveness is limited in cases of atypical left bundle branch block (LBBB) or intraventricular conduction delay (IVCD). Left Bundle Branch Pacing Optimized cardiac resynchronization therapy (LOT-CRT) integrates LBBAP with coronary sinus (CS) lead pacing to improve electrical synchrony and clinical outcomes. This review evaluates the feasibility, advantages, disadvantages, and clinical outcomes of LOT-CRT. Additionally, we describe our center's experience and propose an evidence-based implantation algorithm. A review of published studies investigating LOT-CRT was conducted, comparing its effectiveness with BiV-CRT and LBBAP alone using QRS narrowing, LVEF improvement, left ventricular remodeling, New York Heart Association (NYHA) class changes and NT-proBNP levels. It was found that LOT-CRT outperforms BiV-CRT or LBBAP alone in selected populations, at the cost of higher clinical skills, longer procedural times, and specific device setups. Randomized trials are underway to further define its role in clinical practice.

Conduction system pacing (CSP), encompassing His bundle pacing and left bundle branch area pacing, has emerged as a physiological pacing technique designed to activate the heart's intrinsic conduction system. CSP is a promising alternative to traditional right ventricular pacing for bradycardia and to biventricular pacing for cardiac resynchronization therapy. This article outlines key considerations for achieving successful CSP implantation, including procedural techniques, available tools, and programming strategies.

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.

Patients with chronic right ventricular (RV) pacing are at risk for developing pacing-induced cardiomyopathy (PICM). Data regarding the incidence of PICM when pacing the RV septum using a leadless pacemaker (LP) are limited. Left bundle branch area pacing (LBBAP) has emerged as a viable alternative to RV pacing with a low incidence of PICM.

All patients who received either a LP capable of providing atrioventricular (AV) synchronous pacing or a permanent pacemaker (PPM) with a LBBAP lead (lumenless or stylet-driven leads) for AV block between January 2021 and January 2023 at a single center were screened. Patients were included in the final analysis if they had both a pre- and post-operative transthoracic echocardiogram, pre- and post-operative electrocardiograms, and a pacing burden of ≥ 20%. The incidence of PICM, defined as a decrease in the left ventricular ejection fraction (LVEF) by ≥ 20% and to a value < 50% after a follow-up of at least six months, was compared between LBBAP and LP groups.

Over the study period, 533 PPMs were implanted for AV block. Of these, 95 patients met the inclusion criteria; 70 underwent LBBAP and 25 received LPs. The average age of the population was 75 ± 13 years; 64 (63%) were men. There was no difference in the mean pre-operative LVEF (57% ± 16% vs. 61% ± 10%; p = 0.25) or QRS duration (123 ± 33ms vs. 130 ± 29ms) between the LBBAP and LP groups. There was a high burden of ventricular pacing in both groups (90% ± 19% vs. 92% ± 13%; p = 0.52). After a follow-up of 14 ± 8 months, the incidence of PICM was significantly lower in the LBBAP group compared to the LP group (4.3% vs. 24%; p = 0.0039).

In patients who are not candidates for cardiac resynchronization, who require a high burden of ventricular pacing, LBBAP may lead to a lower incidence of PICM than right ventricular septal pacing with a LP.

Guidelines for management of heart failure with reduced ejection fraction (HFrEF) emphasize personalized care, patient engagement, and shared decision-making. Medications and cardiac rhythm management (CRM) devices are recommended with a high level of evidence. However, there are significant disparities: patients who could benefit from devices are frequently referred too late or not at all. Misconceptions about device therapy and the notion that the needs of patients (especially the prevention of sudden cardiac death) can now be met by expanding drug therapies may play a role in these disparities. This state-of-the-art review is produced by members of the DIRECT HF initiative, a patient-centred, expert-led educational programme that aims to advance guideline-directed use of CRM devices in patients with HFrEF. This review discusses the latest evidence on the role of CRM devices in reducing HFrEF mortality and morbidity, and provides practical guidance on patient referral, device selection, implant timing and patient-centred follow-up.

Left bundle branch pacing (LBBP) emerged as a novel physiological pacing modality that improves clinical outcomes. This study aimed to explore the impact of LBBP on QRS wave amplitude (RWA).

This prospective observational study included patients with complete left bundle branch block (CLBBB) and cardiac resynchronization therapy (CRT) indication, as well as patients with QRSd < 120 ms and pacemaker indication. During the procedure, when the LBBP lead reached the target site, 12-lead ECGs at baseline and 1, 2, 3, 4, and 5 times the pacing thresholds and 3.5 V (pacemaker default value) pacing were recorded, and RWA values were measured accordingly. The absolute values of I + aVL, II + III+ aVF, and V1 + V2 + V3 + V4 + V5 + V6 RWA were defined as X-, Y-, and Z-axis ΣRWA.

A total of 195 consecutive patients (50 CLBBB and 145 narrow QRS) were enrolled (69.7 ± 10.3 years, 52.3% male). Compared with the baseline, LBBP significantly increased X- and Y-axis ΣRWA independent of pacing voltage in CLBBB (ΔX/Y-axis 0.49 ± 0.78 mV, p < 0.0001/0.61 ± 1.24 mV, p = 0.001) and narrow QRS group (ΔX/Y-axis 0.88 ± 0.61 mV, p < 0.0001/0.91 ± 1.05 mV, p < 0.0001); LBBP significantly reduced Z-axis ΣRWA in CLBBB patients (ΔZ-axis -2.64 ± 3.67 mV, p < 0.0001) but not in narrow QRS group (ΔZ-axis -0.14 ± 1.87 mV, p = 0.36). LBBP significantly improved cardiac function at 1 week of follow-up.

LBBP significantly increased X/Y-axis ΣRWA independent of pacing voltage in CLBBB and narrow QRS patients. LBBP significantly reduced Z-axis ΣRWA in CLBBB but not in narrow QRS patients. Whether these ΣRWA changes, through enhancing whole myocardial contractility, have a synergistic effect with LBBP synchronization to further improve cardiac function remains to be investigated.

The majority of data on left bundle branch area pacing (LBBAP) are on a lumenless lead. Data on the safety and effectiveness of stylet driven leads are comparatively lacking.

We retrospectively analyzed 265 patients who underwent attempted LBBAP with an 7842 (Boston Scientific, Marlborough, MA) lead in the Duke University Health System between 1/1/2020 and 9/1/2023. Outcomes of interest included post-operative 7842 helix extension (≥2 helix rotations beyond the lead tip), complications, and lead parameters. A nested analysis of single and dual chamber LBBAP attempts was performed to compare outcomes among similar patients who underwent attempted LBBAP with the lumenless 3830 (Medtronic, Mineappolis, MN) lead.

LBBAP success with 7842 was 89.8%. Characteristics were similar among patients with (n = 238) and without (n = 27) successful implants. Helix extension was evaluable for 222 of 238 successful 7842 implants. Of evaluable leads, helix extension was complete for 174 leads (78%), and partial for 48 (21.6%). A trend towards lower dislodgement rates was observed in patients with full versus partial extension (2.9% vs. 8.3%, p = 0.0895) and the rate of full helix extension increased over time (64.1% over 24 months vs. 81.4% over 21 months, p = 0.0162). The success rate of 3830 LBBAP implants (n = 140) was 92.8% (p = 0.069 vs. 7842). At implant, R waves were similar for 7842 and 3830 leads but were greater for 7842 during follow-up (14.4 + /-0.77 vs. 11.3 + /-0.68, p = 0.004). Pacing impedances were higher with 7842 compared with 3830 at baseline (838 + /-10.44 ohms vs. 772 + /-14.58 ohms, p < 0.001) and during follow-up (652 + /-11.0 ohms vs. 513 + /-9.18 ohms, p < 0.001); similarly, 7842 pacing thresholds (@ 0.4 ms) were slightly higher at baseline (0.85 V + /-0.03 vs. 0.68 V + /-0.03, p < 0.001) and 6 months (0.95 V + /-0.03 vs. 0.80 V + /-0.03, p < 0.001) compared with those for the lumenless 3830.

LBBAP implant success rates, complications, and pacing parameters using the 7842 lead are stable over time, and appeared overall similar to the 3830 lead. Incomplete 7842 helix extension is a modifiable risk factor for lead dislodgement.

The QRS morphology in left bundle branch area pacing (LBBAP) is utilized to assess procedural success and to confirm left bundle branch (LBB) capture.

We present a case in which the QRS morphology of the left bundle branch pacing (LBBP) changed during the procedure despite the maintenance of LBB capture throughout.

This case highlights the necessity for operators to be aware of this pitfall and raises potential questions regarding the determination of LBB capture.

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.

Septal perforation, defined as partial or complete protrusion of a lead helix, is a potential complication of left bundle branch area pacing, theoretically increasing risks of pacing failure and thromboembolism. However, no studies have examined the long-term prognosis of patients with partial perforations (PPs).

This study aimed to elucidate the incidence, outcomes, and electrophysiological characteristics of PP in clinical and experimental swine studies.

Patients requiring pacing who underwent successful left bundle branch area pacing were retrospectively included. PP was identified using postoperative echocardiography. Clinical outcomes, including all-cause mortality, thromboembolism, and lead-related complications, were compared between the PP and non-PP groups. Waveforms from the nonfiltered unipolar electrogram (NF-EGM) recorded at the lead tip were evaluated to identify morphology specific to PP.

Of the 95 patients, PP was confirmed in 25 (26.3%), occurring only in patients with left bundle branch capture, with an incidence rate of 41.7%. Event-free survival rates were comparable between the PP and non-PP groups at a median follow-up of 24 months (log rank, P = 0.298). No thromboembolisms or lead-related complications occurred in the PP group. The type-QS and type-R morphologies of NF-EGM reliably identified and excluded PP, respectively, as validated in swine heart experiments.

This study found that PP is not associated with an increased risk of adverse clinical outcomes. Deep septal lead deployment utilizing the NF-EGM morphology would be useful in recognizing and avoiding PP intraoperatively.

Determining capture type and septal lead location during left bundle branch area pacing (LBBAP) relies on criteria obtained during implantation. However, during follow-up, the interpretation of left bundle branch (LBB) capture largely depends on QRS morphology, which is not so straightforward in LBBAP.

This study aimed to investigate the inter- and intraobserver agreement, as well as the accuracy of clinical judgment of the electrocardiogram (ECG) in determining LBB-capture and septal lead position in patients undergoing LBBAP implantation. In addition, the role of vectorcardiographic QRS-area in determining LBB-capture was evaluated.

Unipolar paced ECGs during LBBAP implantation from 50 patients with baseline narrow QRS were collected. LBB-capture was attempted in all patients and assessed using MELOS (Multicentre European Left Bundle Branch Area Pacing Outcomes Study) criteria and the European Heart Rhythm Association (EHRA) consensus statement. Eight blinded cardiologists classified 100 ECGs for capture type and septal location.

The interobserver and intraobserver agreement for capture type had a Light's kappa of 0.43 and 0.62, respectively. Concordance between clinical judgment and intraprocedural confirmation averaged 72%. Interobserver and intraobserver agreement for septal lead position had a Light's kappa of 0.43 and 0.77 respectively. QRS-area was significantly higher for left ventricular septal pacing (LVSP) than nsLBBP, whereas QRS duration was not. A QRS-area cutoff of 26 mV.ms had 77% accuracy in distinguishing LVSP from nsLBBP. Clinical judgment accuracy averaged 72%.

Interobserver agreement and correlation with intraprocedural confirmation (gold standard) are only moderate, whereas intraobserver agreement on ECG-based differentiation of capture type and septal lead location is substantial. Vectorcardiographic QRS-area slightly outperforms clinical judgment in distinguishing capture types and may be a useful objective alternative.

Permanent implantation of a DF-4 implantable cardiac defibrillator (ICD) lead in the left bundle branch area (LBBA-ICD) is the next paradigm in amalgamating cardiac resynchronization therapy (CRT) and defibrillation. We systematically investigated feasibility/success rate, procedural caveats, and complications associated with a permanent DF-4 LBBA ICD implant and pertinent data at short-term follow-up.

We prospectively attempted implantation of 7 Fr Durata (Abbott, Chicago, IL, USA) single coil DF-4 ICD lead at the LBBA using a fixed-curve non-deflectable CPS locator delivery sheath. Standard criteria defined LBBA capture. Relevant sensing/pacing, defibrillation, radiographic, and echocardiographic parameters testing were recorded at implant, discharge and 5-month follow-up.

We enrolled 12 consecutive cardiac device-naïve patients (median age 67.5 years, male 91.7%, median LVEF 30%, median septal thickness 9 mm, median QRS duration 140 ms, class I CRT indication 58.3%, primary prevention ICD indication 75%). Minor complications (two transeptal perforations and one micro-dislodgment) were noted in 3/12 (25%) patients. Successful permanent LBBA ICD implant with adequate sensing/pacing was achieved in 9/12 (75%) subjects. Sustained ventricular fibrillation (VF) was inducible in 7/9 patients with successful implants with effective sensing and defibrillation in all. Follow-up device-related and echocardiographic parameters were similar at discharge and 5-month follow-up.

Permanent DF-4 LBBA ICD implant is feasible and successful in 75% of patients with an indication for ICD. With dedicated toolkits, higher volumes, and an obligate learning curve, the higher-than-expected frequency (25%) of minor complications may be ameliorated. Short-term data regarding lead and selected RV parameters remained favorable.

Left bundle branch area pacing is currently the most common form of physiological pacing prior to His bundle pacing. It is intended to prevent or correct the development of pacemaker-induced cardiomyopathy and is being used more and more frequently. In order to be able to perform this successfully, knowledge regarding the specific anatomy and radiological anatomy as well as the ECG criteria for left bundle branch pacing is required in addition to knowledge of the tools. In this article, the technical requirements and steps for successful implantation are summarized and pitfalls are highlighted.

Left bundle branch area pacing (LBBAP) has become the procedure of choice for various indications including atrioventricular block and considered to be physiologic modality of pacing compared with right ventricular apex pacing.

The purpose of this study was to assess ventricular activation and synchrony in patients with an LBBAP device using electrocardiographic imaging (ECGI).

A total of 25 consecutive patients underwent an LBBAP device implantation were included in the study. Electrocardiography (ECG) and ECGI analyses have been performed the day after implantation. Native and paced QRS, left ventricular activation time, right ventricular activation time, and V1-V6 activation delay were calculated using ECG. Total ventricular activation time, left ventricular activation time, intrinsic left ventricular activation time, right ventricular activation time, intrinsic right ventricular activation time, and intraventricular dyssynchrony were calculated based on ECGI. All patients have been followed up to 12 months.

All patients were divided in 2 groups (wide and narrow QRS) based on intrinsic ECG and then based on paced ECG parameters. The study showed that for initially narrow QRS group activation time and synchrony during pacing was comparable to native. In wide QRS group these parameters were significantly improved. For paced rhythm analysis classic ECG LBBAP parameters (paced QRS and left ventricular activation time) were not sufficient to properly evaluate the ventricular activation for paced rhythm. Discordance between classic ECG parameters and ECGI analysis was identified. Two additional 12-lead ECG parameters predicting the ECGI measurements were found. Follow-up did not show any worsening of ejection fraction, paced QRS, or pacing parameters.

ECG imaging can bring a significant value into assessing the efficacy of new pacing modalities and provide much more data for precise determination of implantation outcome including detailed activation assessment and comparison with intrinsic conduction. Key ECGI values confirming proper ventricular activation have been defined, and corresponding 12-lead parameters were also identified, which allows to predict ventricular activation by using 12-lead ECG only.

Transthyretin Cardiac amyloidosis (ATTR-CA) is an increasingly recognised cause of heart failure in our elderly patients with preserved ejection fraction. Patients with ATTR-CA who require permanent pacemaker implantation often have preserved ejection fraction and do not meet the clinical indication for cardiac resynchronization therapy (CRT). In these patients, left bundle branch area pacing (LBBAP) can be a reasonable option to maximise physiological activation of the left ventricle. We describe a series of three patients with cardiac amyloidosis who have undergone LBBAP with the use of lumenless leads and successful capture of the myocardium and left bundle branch region.

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).

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.

The cornerstone of heart failure treatment consists of a four pillar drug therapy. Patients with existing heart failure and complete left bundle branch block, or patients with an indication for pacemaker therapy for bradycardia and heart failure, benefit from physiological stimulation. For patients with left bundle branch block and severely impaired left ventricular systolic pump function (HFrEF), cardiac resynchronisation therapy (CRT) has so far been the gold standard. However, it is now increasingly possible to stimulate the conduction system directly using new forms of stimulation and to achieve similar clinical results. At present, left bundle branch area pacing (LBBAP) is the form of stimulation most frequently investigated in clinical studies. A special situation arises in the case of pacemaker-induced cardiomyopathy with right ventricular apical pacing. Here, LBBAP is certainly a beacon of hope.