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BACKGROUND: Electrocardiographic diagnosis of acute myocardial infarction in the setting of cardiac pacing represents diagnostic challenge. There are no focusing data, neither reporting about diagnostic sensitivity of 12­lead ECG with left bundle branch area pacing (LBBAP) during acute myocardial infarction (AMI). CASE SUMMARY: We present 12­lead ECG morphology in a patient with permanent LBBAP during AMI. DISCUSSION: Abnormal repolarization changes induced by ventricular pacing can lead to delay in diagnosis in patients with AMI. LBBAP and overall conduction system pacing may facilitate a timely diagnosis providing additional, still underestimated, advantages of physiological pacing of the heart.

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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.

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BACKGROUND: Conduction system pacing (CSP) by His bundle pacing or left bundle branch area pacing (LBBAP) is incorporated into Heart Rhythm Society guidelines for the management of bradycardia and cardiac resynchronization therapy. Despite increasing adoption with both lumenless leads and stylet-driven leads, concerns regarding the feasibility and safety of the extraction of CSP leads remain. OBJECTIVE: The aim of the study was to report on the safety, feasibility, and clinical outcomes of the extraction of CSP leads. METHODS: Patients undergoing the extraction of CSP leads from 10 international centers were enrolled in this retrospective study. Data regarding indications, lead location, lead type, extraction tools, procedural success, complications, and reimplantation in the conduction system were collected. RESULTS: Overall, 341 patients (age 69 ± 15 years; female 34%; cardiomyopathy 46%; lead dwell time 22 ± 26 months) underwent the extraction of 224 His bundle pacing and 117 LBBAP leads (lumenless leads 321; stylet-driven leads 20). Complete procedural success was achieved in 338 (99%), while clinical success was 100% with retained distal fragments in 3 patients (1%). Among patients with a lead dwell time of >6 months (6-193 months; n = 226), manual extraction was successful in 198 (87%), mechanical tools in 22 (10%), and laser in 6 (3%). Femoral tools were necessary in 3 patients. Minor complications occurred in 7 patients (2.1%). CSP reimplantation was successful in 233 of 244 patients attempted (95%). CONCLUSION: The overall success rates of the extraction of CSP leads were very high (although the LBBAP lead dwell time was <3 years), with a low need for extraction tools and minimal complication. Reimplantation in the conduction system is feasible and safe.

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Cardiac resynchronization therapy (CRT) significantly improves clinical outcomes in patients with ventricular systolic dysfunction and dyssynchrony. Biventricular pacing (BVP) has a class IA recommendation for patients with symptomatic heart failure with reduced ejection fraction (HFrEF) and left bundle branch block (LBBB). However, approximately 30% of patients have a poor therapeutic response and do not achieve real clinical benefit. Pre-implant imaging, together with tailored programming and dedicated device algorithms, have been proposed as possible tools to improve success rate but have shown inconsistent results. Over the last few years, conduction system pacing (CSP) is becoming a real and attractive alternative to standard BVP as it can restore narrow QRS in patients with bundle branch block (BBB) by stimulating and recruiting the cardiac conduction system, thus ensuring true resynchronization. It includes His bundle pacing (HBP) and left bundle branch area pacing (LBBAP). Preliminary data coming from small single-center experiences are very promising and have laid the basis for currently ongoing randomized controlled trials comparing CSP with BVP. The purpose of this review is to delve into the emerging role of CSP as an alternative method of achieving CRT. After framing CSP in a historical perspective, the pathophysiological rationale and available clinical evidence will be examined, and crucial technical aspects will be discussed. Finally, evidence gaps and future perspectives on CSP as a technique of choice to deliver CRT will be summarized.

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BACKGROUND: Left bundle branch area pacing (LBBAP) has swiftly emerged as a safe and effective alternative to right ventricular pacing. Limited data exist on the use of retractable-helix, stylet-driven leads for LBBAP. OBJECTIVE: The objective of this study was to prospectively evaluate the performance and safety of a stylet-driven pacing lead in a rigorously controlled multicenter trial to support US market application. METHODS: A multicenter, prospective, nonrandomized trial enrolled patients with standard pacing indications. Implant procedure and lead data, including threshold, sensing, impedance, and capture type, were collected through 3 months. Primary end points were freedom from LBBAP lead-related serious complications through 3 months and LBBAP implant success according to prespecified criteria. A blinded clinical events committee adjudicated all potential end point complications. RESULTS: A total of 186 patients were included from 14 US sites. LBBAP implants were successful in 95.7% (178 of 186; 95% confidence interval 91.7%-98.1%; P < .0001 for comparison to the performance goal of 88%). Through the 3-month follow-up visit, 3 patients (1.7%) experienced a serious LBBAP complication (all lead dislodgments), resulting in a LBBAP lead-related complication-free rate of 98.3%. A total of 13 patients (7.8%) experienced any system- or procedure-related complication. The mean threshold was 0.89 V at 0.4 ms, the sensing value was 10.8 mV, and impedance was 608 Ω. CONCLUSION: The short-term results from this prospective trial demonstrate both high implant success and freedom from LBBAP lead-related complications using this stylet-driven retractable helix lead. This trial supports the safety, use, and effectiveness of stylet-driven leads for performing contemporary physiologic pacing.

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For many years, cardiac pacing has been based on the stimulation of right ventricular common myocardium to correct diseases of the conduction system. The birth and the development of cardiac resynchronization have led to growing interest in the correction and prevention of pacing-induced dyssynchrony. Many observational studies and some randomized clinical trials have shown that conduction system pacing (CSP) can not only prevent pacing-induced dyssynchrony but can also correct proximal conduction system blocks, with reduction of QRS duration and with equal or greater effectiveness than biventricular pacing. Based on these results, many Italian electrophysiologists have changed the stimulation target from the right ventricular common myocardium to CSP. The two techniques with greater clinical impact are the His bundle stimulation and the left bundle branch pacing. The latter, in particular, because of its easier implantation technique and better electric parameters, is spreading like wildfire and is representing a real revolution in the cardiac pacing field. However, despite the growing amount of data, until now, the European Society of Cardiology guidelines give a very limited role to CSP.

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Background: Conduction system pacing (CSP), either as His bundle pacing (HBP) or as left bundle branch area pacing (LBBAP), may be superior to right ventricular apical or septal pacing. Objective: The study sought to present acute results for a new guiding catheter (Biotronik Selectra 3D) designed for CSP implantations of a retractable screw-in lead (Biotronik Solia S). Methods: The primary endpoint of the prospective, international nonrandomized BIO|MASTER.Selectra 3D study was freedom from catheter-related serious adverse device effects (SADEs) within 1 week of lead implantation. Results: Of 157 enrolled patients, CSP was achieved in 147 (93.6%) patients. No SADEs occurred within 7 days. LBBAP was achieved in 82 patients (45 as crossover from an HBP attempt) and HBP in 65 (44.2%) patients. In centers considering both HBP and LBBAP, the CSP implantation success approached 99%. Successful CSP implantations lasted on average ∼50 minutes (fluoroscopy ∼6 minutes). Most procedures (87.9%) needed only 1 catheter, even after switch from HBP to LBBAP. The catheter's handling was rated largely positive. In patients without bundle branch block, mean QRS duration increased from 106 ms (intrinsic) to 122 ms (CSP) (P = .001). In patients with bundle branch block, mean QRS duration decreased from 151 ms (intrinsic) to 137 ms (CSP) (P = .004). Conclusion: The Selectra 3D catheter is a valuable tool for HBP and LBBAP implantations of the stylet-supported pacemaker leads. When implanters considered both HBP and LBBAP, the success rate was ∼99%. Flexibility to change between different approaches may be advisable in heterogeneous and challenging areas, such as CSP implantations.

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BACKGROUND: Cardiac resynchronization therapy (CRT) using biventricular pacing (BVP) has been associated with greater clinical improvement in women than men. Recently, left bundle branch area pacing (LBBAP) has been shown to be an alternative form of CRT. OBJECTIVES: The purpose of this study was to investigate sex-specific outcomes for death and heart failure events in a large, international, multicenter, cohort of patients undergoing CRT with BVP or LBBAP. METHODS: In this international study of 1,778 patients (575 female and 1203 male), sex-specific survival analysis was performed to compare the effect of LBBAP-CRT relative to BVP-CRT on the combined endpoint of death or heart failure hospitalization (HFH), and secondary endpoints of HFH only, and death alone. RESULTS: Female patients were more likely to have nonischemic cardiomyopathy and left bundle branch block (LBBB) and less likely to have hypertension, diabetes, or coronary artery disease than were male patients. Overall, female patients had a better result with LBBAP compared with BVP than did male patients, with a significant 36% reduction in death or HFH (HR: 0.64; 95% CI: 0.43 to 0.97; P = 0.03) and a significant 60% reduction in HFH alone (HR: 0.4; 95% CI: 0.24 to 0.69, P < 0.01). Women had a greater reduction in death or HFH among those with nonischemic cardiomyopathy (HR: 0.45 95% CI: 0.26 to 0.79; P < 0.01) and LBBB (HR: 0.49; 95% CI: 0.27 to 0.87; P < 0.01). Sex-specific echocardiographic outcomes were better in women than in men. CONCLUSIONS: Women obtained significantly greater reductions in the combined endpoint of death or HFH (primarily driven by reduction in HFH) with LBBAP compared with BVP among patients requiring CRT than did men.

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BACKGROUND: Left bundle branch area pacing (LBBAP) may be associated with greater improvement in left ventricular ejection fraction and reduction in death or heart failure hospitalization compared with biventricular pacing (BVP) in patients requiring cardiac resynchronization therapy. We sought to compare the occurrence of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) and new-onset atrial fibrillation (AF) in patients undergoing BVP and LBBAP. METHODS: The I-CLAS study (International Collaborative LBBAP Study) included patients with left ventricular ejection fraction ≤35% who underwent BVP or LBBAP for cardiac resynchronization therapy between January 2018 and June 2022 at 15 centers. We performed propensity score-matched analysis of LBBAP and BVP in a 1:1 ratio. We assessed the incidence of VT/VF and new-onset AF among patients with no history of AF. Time to sustained VT/VF and time to new-onset AF was analyzed using the Cox proportional hazards survival model. RESULTS: Among 1778 patients undergoing cardiac resynchronization therapy (BVP, 981; LBBAP, 797), there were 1414 propensity score-matched patients (propensity score-matched BVP, 707; propensity score-matched LBBAP, 707). The occurrence of VT/VF was significantly lower with LBBAP compared with BVP (4.2% versus 9.3%; hazard ratio, 0.46 [95% CI, 0.29-0.74]; P<0.001). The incidence of VT storm (>3 episodes in 24 hours) was also significantly lower with LBBAP compared with BVP (0.8% versus 2.5%; P=0.013). Among 299 patients with cardiac resynchronization therapy pacemakers (BVP, 111; LBBAP, 188), VT/VF occurred in 8 patients in the BVP group versus none in the LBBAP group (7.2% versus 0%; P<0.001). In 1194 patients with no history of VT/VF or antiarrhythmic therapy (BVP, 591; LBBAP, 603), the occurrence of VT/VF was significantly lower with LBBAP than with BVP (3.2% versus 7.3%; hazard ratio, 0.46 [95% CI, 0.26-0.81]; P=0.007). Among patients with no history of AF (n=890), the occurrence of new-onset AF >30 s was significantly lower with LBBAP than with BVP (2.8% versus 6.6%; hazard ratio, 0.34 [95% CI, 0.16-0.73]; P=0.008). The incidence of AF lasting >24 hours was also significantly lower with LBBAP than with BVP (0.7% versus 2.9%; P=0.015). CONCLUSIONS: LBBAP was associated with a lower incidence of sustained VT/VF and new-onset AF compared with BVP. This difference remained significant after adjustment for differences in baseline characteristics between patients with BVP and LBBAP. Physiological resynchronization by LBBAP may be associated with lower risk of arrhythmias compared with BVP.

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BACKGROUND: The Medtronic SelectSecure Model 3830 lumenless lead (Medtronic, Inc., Minneapolis, MN) is commonly used for conduction system pacing (CSP). However, with this increased use, the potential need for transvenous lead extraction (TLE) also will increase. While extraction of endocardial 3830 leads is rather well described especially in pediatric and adult congenital heart disease population, there is very limited data on extraction of CSP leads. In the present study, we reported our preliminary experience on TLE of CSP leads and provided technical considerations. METHODS: The study population comprised 6 consecutive patients (67% male; mean age 70 ± 22 years) with CSP leads (3830 leads), including left bundle branch pacing (LBBP) lead (n = 3) and His pacing lead (n = 3) undergoing TLE. Overall target leads were 17. The mean implant duration time of CSP leads was 97 ± 90 months [range 8-193). RESULTS: Manual traction was successful in 2 cases and mechanical extraction tools were required in the remaining cases. Sixteen leads (94%) were completely extracted, whereas incomplete removal was observed in one lead (6%) among 1 patient. Of note, in the only lead incompletely removed, we observed retention of < 1-cm remnant of lead material consisting of the screw of 3830 LBBP lead into the interventricular septum. No failure of lead extraction was reported and no major complications occurred. CONCLUSIONS: Our findings demonstrated that at an experienced center the success of TLE of chronically implanted CSP leads is high in the absence of major complications also when mechanical extraction tools are needed.

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The field of cardiac pacing has changed rapidly in the last several years. Since the initial description of His bundle pacing targeting the conduction system, recent advances in pacing the left bundle branch and its fascicles have evolved. The field and investigators' knowledge of conduction system pacing including relevant anatomy and physiology has advanced significantly. The aim of this review is to provide a comprehensive update on recent advances in conduction system pacing.

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INTRODUCTION: Restoring physiological cardiac electrical activity in patients with conduction disease can be crucial for the survival and quality of life. Conduction system pacing (CSP) is a valuable option, although it is limited by technical challenges in difficult anatomies. 3D electroanatomical mapping (3D-EAM) can support CSP ensuring high electro-anatomical precision and low fluoroscopy. OBJECTIVES: We evaluated the feasibility and effectiveness of a systematic 3D-EAM use to guide CSP in difficult anatomical scenarios (highly dilated atria, congenital cardiomyopathies, failed biventricular implants (BiV) and pacing-induced cardiomyopathy (PICM)). METHODS: Forty-three consecutive patients (27 males, 75 ± 10 years old) with standard pacing indications and difficult anatomical scenarios were included. The right atrium, His cloud, and atrio-ventricular septum were reconstructed by 3D-EAM. The His bundle (HB) was the initial target, while left bundle branch area pacing (LBBAP) was aimed at in case of unsatisfactory parameters, sub-optimally paced QRS, or impossibility of reaching the HB. RESULTS: CSP was successful in 37 (86%) patients (15 HBP; 22 LBBAP). Mean mapping, fluoroscopy, and procedural times were 18 ± 7 min, 7 ± 5 min, 98 ± 47 min, respectively. The mean pacing threshold, R wave sensing, and pacing impedance of CSP lead were 1.2 ± 0.5V@0.5ms, 11.4 ± 6.2 mV, 736 ± 306 Ω, respectively. Baseline and paced QRS were 139 ± 38 ms and 114 ± 23 ms, respectively. No procedural complications were observed. CONCLUSIONS: 3D-EAM allowed the accurate definition of the His cloud and high ventricular septum and effectively guided CSP. It facilitated CSP in complex anatomies, with a procedural success rate of 86%. The results were satisfactory and reproducible, with acceptable fluoroscopy and procedural times.

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Patients with symptomatic heart failure (HF) and left bundle branch block (LBBB) are currently treated with biventricular pacing (BiV) which has a Class IA recommendation. Given the possibility to re-establish the inter and intra-ventricular synchrony, BiV is commonly referred to as cardiac resynchronization therapy (CRT). This wording is widely utilized and over time the terms BiV and CRT have become interchangeable. Conduction system pacing (CSP) is emerging as a valid therapeutic opportunity to obtain CRT restoring the native conduction via the Purkinje network. Therefore the acronym CRT is no longer synonymous with BiV only but could also refer to CSP. A terminology update is needed to include the resource of CSP to ensure better communication among all the stakeholders involved in managing recipients of cardiac devices and should be a fundamental step in advancing the quality of patient care. Making use of the NBG code to describe the implantable cardiac device would ease such terminology update, since only the first three positions of the five letters NBG code are commonly utilized, while the last two are rarely used.

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BACKGROUND: Conduction system pacing (CSP), including both left bundle branch area pacing (LBBAP) and His-bundle pacing (HBP) has been proposed as an alternative therapy option for patients with indication for cardiac pacing to treat bradycardia or heart failure. OBJECTIVE: The purpose of this study was to evaluate implant success, safety, and electrical performances of HBP and LBBAP in the multinational Physiological Pacing Registry. METHODS: The international prospective observational registry included 44 sites from 16 countries globally between November 2018 and May 2021. RESULTS: Of 870 subjects enrolled, CSP lead implantation was attempted in 849 patients. Subjects with successful CSP lead implantation were followed for 6 months (5 ± 2 months). CSP lead implantation was successful in 768 patients (90.4%). Implant success was 95.2% (239/251) for LBBAP and 88.5% (529/598) for HBP (P = .002). Procedural duration and fluoroscopy duration were comparable between LBBAP and HBP (P = .537). Capture threshold at implant was 0.69 ± 0.39 V at 0.46 ± 0.15 ms in LBBAP and 1.44 ± 1.03 V at 0.71 ± 0.33 ms in HBP (P <.001). Capture threshold at 6 months was 0.79 ± 0.33 V at 0.44 ± 0.13 ms in LBBAP and 1.59 ± 0.97 V at 0.67 ± 0.31 ms in HBP (P <.001). Pacing threshold rise ≥1 V was observed at 6 months in 3 of 208 (1.4%) of LBBAP and 55 of 418 (13.2%) of HBP (P <.001). Serious adverse events related to implant procedure or CSP lead occurred in 5 of 251 (2.0%) with LBBAP and 25 of 598 (4.2%) with HBP (P = .115). CONCLUSION: This large prospective multicenter study demonstrates that CSP is technically feasible in most patients with relatively higher implant success and suggests that, with current technology, LBBAP may have better pacing parameters than HBP.

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The conduction system of the human heart is composed of specialized cardiomyocytes that initiate and propagate the electric impulse with consequent rhythmic and synchronized contraction of the atria and ventricles, resulting in the normal cardiac cycle. Although the His-Purkinje system (HPS) was already described more than a century ago, there has been a recent resurgence of conduction system pacing (CSP), where pacing leads are positioned in the His bundle region and left bundle branch area to provide physiological cardiac activation as alternatives to the unnatural myocardial stimulation obtained with conventional right ventricular and biventricular pacing. In this review, we describe the fundamental anatomical and pathophysiological aspects of the specialized HPS along with the CSP technique's nuts and bolts to highlight its potential benefits in everyday clinical practice.

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BACKGROUND: Cardiac resynchronization therapy (CRT) with biventricular pacing (BVP) is a well established therapy in patients with reduced left ventricular ejection fraction (LVEF), heart failure, and wide QRS or expected frequent ventricular pacing. Left bundle branch area pacing (LBBAP) has recently been shown to be a safe alternative to BVP. OBJECTIVES: The aim of this study was to compare the clinical outcomes between BVP and LBBAP among patients undergoing CRT. METHODS: This observational study included patients with LVEF ≤35% who underwent BVP or LBBAP for the first time for Class I or II indications for CRT from January 2018 to June 2022 at 15 international centers. The primary outcome was the composite endpoint of time to death or heart failure hospitalization (HFH). Secondary outcomes included endpoints of death, HFH, and echocardiographic changes. RESULTS: A total of 1,778 patients met inclusion criteria: 981 BVP, 797 LBBAP. The mean age was 69 ± 12 years, 32% were female, 48% had coronary artery disease, and mean LVEF was 27% ± 6%. Paced QRS duration in LBBAP was significantly narrower than baseline (128 ± 19 ms vs 161 ± 28 ms; P < 0.001) and significantly narrower compared to BVP (144 ± 23 ms; P < 0.001). Following CRT, LVEF improved from 27% ± 6% to 41% ± 13% (P < 0.001) with LBBAP compared with an increase from 27% ± 7% to 37% ± 12% (P < 0.001) with BVP, with significantly greater change from baseline with LBBAP (13% ± 12% vs 10% ± 12%; P < 0.001). On multivariable regression analysis, the primary outcome was significantly reduced with LBBAP compared with BVP (20.8% vs 28%; HR: 1.495; 95% CI: 1.213-1.842; P < 0.001). CONCLUSIONS: LBBAP improved clinical outcomes compared with BVP in patients with CRT indications and may be a reasonable alternative to BVP.

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Conduction system pacing (CSP) has emerged as a more physiological alternative to right ventricular pacing and is also being used in selected cases for cardiac resynchronization therapy. His bundle pacing was first introduced over two decades ago and its use has risen over the last five years with the advent of tools which have facilitated implantation. Left bundle branch area pacing is more recent but its adoption is growing fast due to a wider target area and excellent electrical parameters. Nevertheless, as with any intervention, proper technique is a prerequisite for safe and effective delivery of therapy. This document aims to standardize the procedure and to provide a framework for physicians who wish to start CSP implantation, or who wish to improve their technique.

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Conduction system pacing (CSP) has emerged as a more physiological alternative to right ventricular pacing and is also being used in selected cases for cardiac resynchronization therapy. His bundle pacing was first introduced over two decades ago and its use has risen over the last years with the advent of tools which have facilitated implantation. Left bundle branch area pacing is more recent but its adoption is growing fast due to a wider target area and excellent electrical parameters. Nevertheless, as with any intervention, proper technique is a prerequisite for safe and effective delivery of therapy. This document aims to standardize the procedure and to provide a framework for physicians who wish to start CSP implantation, or who wish to improve their technique. A synopsis is provided in this print edition of EP-Europace. The full document may be consulted online, and a 'Key Messages' App can be downloaded from the EHRA website.

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