Search

Introduction: A frequent complication after TAVI are postinterventional conduction abnormalities requiring permanent pacemaker implantation. In this study, we analyzed the characteristics of borderline conduction abnormalities leading to pacemaker implantation and the resulting ventricular pacing amounts., Methods and Results: All patients who underwent balloon-expandable TAVI between 2014 and 2019 in our tertiary center were analyzed in a retrospective manner. One hundred and sixty-five patients of 1083 TAVI-patients developed postinterventional conduction abnormalities leading to pacemaker implantation. Of these 19 (11.5%) did not represent a clear indication for cardiac pacing according to current European guidelines. Patient characteristics, underlying conduction abnormalities, and the temporal change of ventricular pacing percentages at 24 h and 6 weeks after pacemaker implantation were analyzed. The dominating borderline conduction abnormalities leading to pacemaker implantation were new-onset persisting bundle-branch-blocks and new first-degree AV-blocks with progression of AV-delay. While pacemaker implantation was safe and without severe complications in all cases, only 6 of 19 patients had high pacing amounts (95%-100%) after 24 h while 11 patients had low to no pacing amounts (0%-5%). After 6 weeks, 8 patients showed decreasing pacing amounts, no patient had an increasing amount of ventricular pacing and all patients had an intrinsic ventricular rhythm > 30/min., Conclusion: In our cohort of 1038 TAVI patients, 19 patients underwent PMI for borderline CAs (11.5% of all PMI). Of these, only 2 patients had high pacing amounts after 6 weeks. The risk of complete persisting heart block in these patients is very low. Furthermore, algorithms to reduce ventricular pacing are highly effective to avoid ventricular pacing whenever reasonable., (© 2024 The Author(s). Clinical Cardiology published by Wiley Periodicals LLC.)

Background: Despite growing clinical use of left bundle branch pacing (LBBP), data regarding the fundamentals of this pacing modality, including chronaxie and rheobase, are scarce., Objective: The purpose of this study was to calculate strength-duration curves with chronaxie and rheobase values for LBBP and left ventricular septal pacing (LVSP), and to analyze battery current drain and presence of selective LBBP at very short pulse duration (PD)., Methods: A group of 141 patients with permanent LBBP were studied. LBBP and LVSP capture thresholds were assessed at 6 different PDs to calculate the strength-duration curves. Battery current drain at these PDs and presence of selective LBBP were determined. For comparison of strength-duration curves between His-bundle pacing (HBP) and LBBP, source data from our previous work based on 127 patients with HBP were obtained., Results: The chronaxies for LBBP and LVSP were very similar (0.38 vs 0.39 ms), and the rheobases were identical (0.27 V). The chronaxie for LBBP was lower than for HBP (0.38 vs 0.53 ms; P <.001), whereas rheobases were similar (0.27 vs 0.26 V). A narrow zone of selective capture was present in 19% and 41% of patients at PD of 0.06 and 0.03 ms, respectively. When pacing with the safety margin of +1 V, the lowest battery current drain was achieved with PD of 0.2 ms., Conclusion: The obtained strength-duration curves for LBBP and LVSP provide insights to optimal programming of left bundle branch area pacing devices with regard to PD, voltage amplitude, battery longevity, and selective capture., Competing Interests: Disclosures Dr Kiełbasa reports consultant fees from Medtronic and Biotronik. Dr Jastrzebski reports consultant fees from Medtronic, Abbott, and Biotronik. Dr Moskal reports consultant fees from Medtronic and Biotronik. Dr Vijayaraman reports honoraria, consultant, research, and fellowship support from Medtronic; and being a consultant for Abbott and Eaglepoint. All other authors have no conflicts of interest to disclose., (Copyright © 2024. Published by Elsevier Inc.)

Background: Infranodal Wenckebach is rare and not well characterized., Objective: We prospectively studied clinical and electrophysiologic characteristics of patients with atrioventricular (AV) Wenckebach with an indication for permanent ventricular pacing., Methods: During a 2-year period, all patients with an indication for permanent ventricular pacing underwent targeted preimplantation electrophysiologic study. Clinical and electrophysiologic characteristics at presentation and ventricular pacing percentage at 6-month follow-up were evaluated., Results: A total of 163 patients (median age, 68 [interquartile range, 60-74] years; male, 59%; median QRS duration, 110 [90-130] ms; complete AV block in 123 [75.5%]) were included. AV Wenckebach was noted in 22 (13.4%) patients (median age, 70 [63-76.5] years; male, 54%; median QRS duration, 120 [110-140] ms) and classified as infranodal (12/163 [7.3%]) vs AV nodal (10/163 [6.1%]). Patients with infranodal Wenckebach (infrahisian in all), compared with AV nodal Wenckebach, demonstrated higher frequency with left ventricular ejection fraction ≤40% (41.7% vs 0%; P = .04), longer median HV interval (90 vs 49 ms; P = .005), lower frequency of isolated first-degree AV block (8.3% vs 60%; P = .02), higher frequency of right bundle branch block with left anterior fascicular block (75% vs 10%; P = .003), lesser PR increment at onset of AV Wenckebach (20.5 vs 80 ms; P = .002), and onset of 2:1 AV block at longer cycle lengths (91.7% vs 20%; P = .002)., Conclusion: Of patients referred for pacemaker implantation, infranodal Wenckebach was present in 27.5% (11/40) without complete AV block. It was as frequent as AV nodal Wenckebach and associated with characteristic electrophysiologic findings., Competing Interests: Disclosures The authors have no conflicts of interest to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: The impact of left bundle branch area pacing (LBBAP) on right ventricular (RV) function and tricuspid regurgitation (TR) remains unclear., Objective: We aimed to assess the long-term effects of LBBAP on RV performance and on TR., Methods: RV function was evaluated using RV free wall strain, tricuspid annular plane systolic excursion, fractional area changing, and systolic velocity of the lateral tricuspid annulus. The presence of reverse septal flash (RSF) and basal bulge (BB) was used to assess RV motion pattern. The distance between the lead entry site on the interventricular septum and the septal leaflet of the tricuspid annulus (lead-TV distance) was measured., Results: The analysis included 122 subjects [62 men (50.8%); mean age 76.5 ± 11.4 years] with a median follow-up of 21 months (18-24.5 months). During follow-up, RV free wall strain improved significantly (15.2 ± 5.8 vs 16.4 ± 5.5; P < .001) while tricuspid annular plane systolic excursion, systolic, and fractional area changing remained unchanged. Left ventricular ejection fraction was an independent predictor of improved RV function (B = 3.51; 95% confidence interval 1.39-8.9; P = .01). With LBBAP, RSF disappeared in 22 of 23 patients (96%) and BB in 15 of 22 patients (68%) in whom RSF and BB were present at baseline, respectively. RV function improvement was significantly higher when RSF was present at baseline (14 patients vs 11 patients; P = .02). At follow-up, no significant deterioration in TR occurred for the overall group. However, a lead-TV distance of <24.5 mm was associated with TR progression., Conclusion: LBBAP has a favorable impact on RV function. A basal LBBAP position is associated with worsening TR., Competing Interests: Disclosures Dr Burri has received institutional research and fellowship support and speaker fees from and serves on the advisory boards of Abbott, Biotronik, Boston Scientific, Medtronic, and MicroPort. Drs Jastrzębski and Moskal have received speaker and consultancy fees from Medtronic and Biotronik. The rest of the authors report no conflicts of interest., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

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., Competing Interests: Disclosures Dr Liu reports serving as a consultant for Biotronik. Dr Prasad reports having received consultation fees and honoraria from Biotronik. Dr Vijayaraman reports serving as a speaker and consultant for and receives research and fellowship support from Medtronic; he is also a consultant for Abbott and received honoraria from Biotronik and Boston Scientific and owns a patent on a His bundle pacing delivery tool. Dr Zanon reports speaker fees (modest) from Abbott, Biotronik, Boston Scientific, Medtronic, and MicroPort. Dr Gleva reports consultancy fees from Abbott, Biotronik, and Medtronic. Dr De Pooter reports speaker honoraria and consultancy fees from Medtronic, Biotronik, Abbott, and Boston Scientific. Dr Chinitz reports a speaker honoraria engagement with Abbott, Biotronik, Medtronic, and Biosense Webster. Dr Moretta reports no conflict of interest., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: One common mode of lead failure is insulation breach, which may result in myopotential noise and device malfunction. "Pseudo-unipolarization" of bipolar pacing stimuli, as observed from a routine 12-lead electrocardiogram (ECG) due to stimulus current leak, has been observed with insulation breaches., Objective: We sought to characterize this electrocardiographic finding to detect this type of lead malfunction., Methods: A total of 138 transvenous leads were analyzed, including 88 with known malfunction and 50 normal leads. The amplitude of a bipolar pacing stimulus on the ECG was recorded and compared with a control data set of newly implanted leads with bipolar stimuli normalized for output., Results: The malfunction group consisted of 61% right atrium and 39% right ventricle leads with mean pacing output of 2.74 V at 0.5 ms. There was a significant difference in ECG bipolar stimulus amplitudes at time of identification of failure (7.89 ± 7.56 mm/V; P < .001) compared with those of normal leads (0.86 ± 0.41 mm/V). Receiver operating characteristic curve for the prediction of lead malfunction based on absolute ECG amplitude displayed an area under the curve of 0.93 (95% CI, 0.891-0.969). When normalized for programmed stimulus output, a cutoff of 5 mm/V demonstrated a sensitivity of 91% and a specificity of 92% (area under the curve, 0.967; 95% CI, 0.938-0.996)., Conclusion: The maximum amplitude of a bipolar pacing stimulus on the ECG is significantly lower in normal functioning leads compared with those with known malfunction. This simply derived variable demonstrated good accuracy at identifying lead failure due to insulation breach., Competing Interests: Disclosures The authors have no conflicts of interest to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: A heart positioned on the right side of the thorax can be more a complex situation than it seems, also the potentially associated congenital cardiopathies are variable. In this regard, patients with dextrocardia presenting with complete atrioventricular block require a thorough anatomical investigation to map the veno-arterial system and potential cardiovascular defects before proceeding with a permanent pacing procedure., Case Presentation: A 73-year-old Caucasian woman with no significant medical history presented with syncope. Physical examination showed regular heart sounds with an average heart rate of 35-40 beats per minute and no other relevant physical findings. Chest X-rays revealed a heart positioned in the right hemithorax. A standard electrocardiogram revealed complete atrioventricular block with junctional escape rhythm at nearly 35-40 beats per minute. A transthoracic echocardiogram showed a mirror image dextrocardia without any other remarkable abnormalities. Venogram performed using the left peripheral cephalic vein showed normal venous return into the right atrium positioned on the left side. Surgical intervention consisted of permanent dual chamber pacemaker implantation using the left subclavian vein. Discussion is provided based on the relevant medical literature outlining different potential scenarios with associated cardiac and major vessels abnormalities., Conclusion: This case highlights an atypical presentation of atrioventricular block in a patient with dextrocardia and situs inversus, for whom a successful dual-pacemaker implantation procedure was performed., (© 2024. The Author(s).)

Aims: Conduction system pacing (CSP) and atrioventricular junction ablation (AVJA) improve outcomes in patients with symptomatic, refractory atrial fibrillation (AF). Superior approach (SA) from the pocket, via the axillary or subclavian vein, has been recently proposed as an alternative to the conventional femoral access (FA) to perform AVJA. In this study, we compare the impact of these alternative approaches on nurse workload (NWL) and patient satisfaction., Methods and Results: This was a prospective, observational study enrolling consecutive patients undergoing simultaneous CSP and AVJA. Electrophysiology laboratory (EP Lab) NWL was calculated by using a self-developed model. Ward NWL was calculated using the MIDENF® validated scale. Patient satisfaction was collected using the Hospital Consumer Assessment of Healthcare Provider Systems questionnaire. A total of 119 patients were enrolled: in 50, AVJA was primarily attempted with SA, and in 69 with FA. Compared with FA, SA was associated with a lower EP Lab NWL (169.8 ± 26.7 vs. 202.7 ± 38.9 min; P < 0.001) and a lower Ward NWL (474.5 ± 184.8 vs. 808.6 ± 289.9 min; P < 0.001). Multivariate analysis identified SA as an independent predictor of lower EP Lab NWL [hazard ratio (HR) 4.60; P = 0.001] and of lower Ward NWL (HR 45.13; P < 0.001). Compared with FA, SA was associated with a higher patient-reported rating regarding their experience during hospital stay (P = 0.035) and the overall hospital evaluation (P = 0.026)., Conclusion: In patients undergoing simultaneous CSP and AVJA, the use of an SA for ablation is a valid alternative to conventional FA. Compared with FA, this approach significantly reduces NWL and is associated with greater patient satisfaction., Registration: ClinicalTrials.gov: NCT03612635., Competing Interests: Conflict of interest: None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Background: The subcutaneous implantable cardioverter-defibrillator (ICD) is associated with fewer lead-related complications than a transvenous ICD; however, the subcutaneous ICD cannot provide bradycardia and antitachycardia pacing. Whether a modular pacing-defibrillator system comprising a leadless pacemaker in wireless communication with a subcutaneous ICD to provide antitachycardia and bradycardia pacing is safe remains unknown., Methods: We conducted a multinational, single-group study that enrolled patients at risk for sudden death from ventricular arrhythmias and followed them for 6 months after implantation of a modular pacemaker-defibrillator system. The safety end point was freedom from leadless pacemaker-related major complications, evaluated against a performance goal of 86%. The two primary performance end points were successful communication between the pacemaker and the ICD (performance goal, 88%) and a pacing threshold of up to 2.0 V at a 0.4-msec pulse width (performance goal, 80%)., Results: We enrolled 293 patients, 162 of whom were in the 6-month end-point cohort and 151 of whom completed the 6-month follow-up period. The mean age of the patients was 60 years, 16.7% were women, and the mean (±SD) left ventricular ejection fraction was 33.1±12.6%. The percentage of patients who were free from leadless pacemaker-related major complications was 97.5%, which exceeded the prespecified performance goal. Wireless-device communication was successful in 98.8% of communication tests, which exceeded the prespecified goal. Of 151 patients, 147 (97.4%) had pacing thresholds of 2.0 V or less, which exceeded the prespecified goal. The percentage of episodes of arrhythmia that were successfully terminated by antitachycardia pacing was 61.3%, and there were no episodes for which antitachycardia pacing was not delivered owing to communication failure. Of 162 patients, 8 died (4.9%); none of the deaths were deemed to be related to arrhythmias or the implantation procedure., Conclusions: The leadless pacemaker in wireless communication with a subcutaneous ICD exceeded performance goals for freedom from major complications related to the leadless pacemaker, for communication between the leadless pacemaker and subcutaneous ICD, and for the percentage of patients with a pacing threshold up to 2.0 V at a 0.4-msec pulse width at 6 months. (Funded by Boston Scientific; MODULAR ATP ClinicalTrials.gov NCT04798768.)., (Copyright © 2024 Massachusetts Medical Society.)

Aims: We report our single-centre experience of mid-term to long-term retrieval and reimplantation of a tine-based leadless pacemaker [Micra transcatheter pacing system (TPS)]. The TPS is a clinically effective alternative to transvenous single-chamber ventricular pacemakers. Whereas it is currently recommended to abandon the TPS at the end of device life, catheter-based retrieval may be favourable in specific scenarios., Methods and Results: We report on nine consecutive patients with the implanted TPS who subsequently underwent transcatheter retrieval attempts. The retrieval system consists of the original TPS delivery catheter and an off-the-shelf single-loop 7 mm snare. The procedure was guided by fluoroscopy and intracardiac echocardiography. After an implantation duration of 3.1 ± 2.8 years (range 0.4-9.0), the overall retrieval success rate was 88.9% (8 of 9 patients). The mean procedure time was 89 ± 16 min, and the fluoroscopy time was 18.0 ± 6.6 min. No procedure-related adverse device events occurred. In the one unsuccessful retrieval, intracardiac echocardiography revealed that the TPS was partially embedded in the ventricular tissue surrounding the leadless pacemaker body in the right ventricle. After retrieval, three patients were reimplanted with a new TPS device. All implantations were successful without complications., Conclusion: A series of transvenous late retrievals of implanted TPS devices demonstrated safety and feasibility, followed by elective replacement with a new leadless pacing device or conventional transvenous pacing system. This provides a viable end-of-life management alternative to simple abandonment of this leadless pacemaker., Competing Interests: Conflict of interest: P.N and V.Y.R. are consultants for Medtronic, Abbott, and Boston Scientific, manufactures of leadless pacemakers, and unrelated to this manuscript; V.Y.R. has served as a consultant for and has equity in Ablacon, Acutus Medical, Affera-Medtronic, Anumana, Apama Medical-Boston Scientific, APN Health, Append Medical, AquaHeart, AtaCor, Autonomix, Axon Therapies, Backbeat, BioSig, CardiaCare, CardioFocus, CardioNXT/AFTx, Circa Scientific, CoRISMA, Corvia Medical, Dinova-Hangzhou DiNovA EP Technology, East End Medical, EP Frontiers, Farapulse-Boston Scientific, Field Medical, Focused Therapeutics, HRT, InterShunt, Javelin, Kardium, Laminar Medical, LuxMed, Medlumics, Neutrace, Nuvera-Biosense Webster, Oracle Health, Pulse Biosciences, Restore Medical, Sirona Medical, and SoundCath and unrelated to this work; V.Y.R. has served as a consultant for Abbott, Adagio Medical, AtriAN, Biosense Webster, BioTel Heart, Biotronik, Boston Scientific, Cairdac, Cardionomic, CoreMap, Fire1, Gore & Associates, Impulse Dynamics, Novartis, Novo Nordisk, and Philips and unrelated to this work, V.Y.R. has equity in Atraverse, DRS Vascular, Manual Surgical Sciences, Newpace, Nyra Medical, Surecor, and Vizaramed. The other authors have no conflicts of interest related to this manuscript., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Competing Interests: Disclosures The author has no conflicts of interest to disclose.

Background: The impact of varying rates of pacemapping (PM) rates on QRS morphology and PM score matching in patients with scar-related ventricular tachycardia (VT) has not been systematically assessed., Objectives: In this study, the authors sought to assess the variability in PM score matching at different pacing rates., Methods: During substrate mapping for VT ablation, PM was performed at cycle lengths (CLs) of 600 ms, 500 ms, 400 ms, 300 ms, and VT CL. PM scores were compared for the entire QRS, the first half (H1) of QRS, and the second half (H2) of QRS to examine the influence of the preceding T-wave superimposed into the onset of paced QRS complex (TR fusion)., Results: A total of 269 PMs in 40 patients undergoing scar-related VT ablation were systematically analyzed. The PM score improved at rates closer to VT with a median difference of 6% (Q1-Q3: 4%-10%; range: 0%-33%) between the lowest and the highest PM scores at a given site. Greater slurring of the QRS onset was observed at faster-paced CL, corresponding to a superimposition of the preceding T-wave into QRS onset, with significant differences in H1 but not H2 of the QRS complex. At faster PM rates, 32% of overall sites developed pseudo delta wave and 69% of endocardial pacing sites fulfilled epicardial criteria., Conclusions: The rate of pacemapping can significantly alter morphologic score matching, with the most optimal match observed closest to VT CL. The onset of QRS complex morphology is influenced by superimposition of the preceding T-wave at faster rates, resulting in an underrecognized TR fusion phenomenon that may confound epicardial electrocardiographic criteria predicated upon the initial QRS slope and vector., Competing Interests: Funding Support and Author Disclosures Dr Tung has received speaking honoraria from Abbott, Medtronic, Boston Scientific, and Biotronik. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

The authors report for the first time to their knowledge, implantation of a standard implantable cardioverter-defibrillator lead for permanent delivery of left bundle branch area pacing. Implantation was successful and safe in 11 of 12 patients, with adequate defibrillation testing, good electrical and electrocardiographic parameters, and uneventful device-related short-term follow-up., Competing Interests: Funding Support and Author Disclosures Dr Imnadze is an advisory board member for Abbott and Medtronic. Dr Sommer is an advisory board member for Abbott and Medtronic. Dr Burri has received institutional research grants, fellowship support, and speaker fees from Abbott, Biotronik, Boston Scientific, Medtronic, and MicroPort. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

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., (© 2024 Wiley Periodicals LLC.)

A larger left bundle branch (LBB) potential or LBB current of injury (COI) indicates a low LBB capture threshold in LBB pacing. During LBB pacing in an 85-year-old woman, achieving a low LBB capture threshold did not initially present with a larger LBB potential or LBB COI, but rather with a new initial negative deflection in a ventricular electrogram. LBB COI gradually developed over 7 min thereafter, which suggested that the lead tip had reached the left ventricular subendocardium. Therefore, this negative deflection may be the first sign to avoid further lead rotation., (© 2024 Wiley Periodicals LLC.)

Although ventricular capture during the atrial threshold test is possible, there are rare reports on the insulation defect and inactive leads thereof. In this case, we present a pacemaker-dependent patient with a history of pacemaker generator replacements. The patient experienced ventricular capture induced by atrial pacing due to adhesion of the atrial and ventricular leads with an insulation defect. The atrial lead was abandoned and a new lead was implanted. However, there was a significant decrease in ventricular impedance detected shortly after the new lead was implanted. When observing the phenomenon of atrial pacing-induced ventricular depolarization, one uncommon reason to consider is lead adhesive wear. It is important to pay attention to the contact and bending sites of the leads., (© 2024 Wiley Periodicals LLC.)

We present a case of a neonate who presented with worsening heart failure due to congenital complete atrioventricular (AV) block, secondary to maternal anti Ro/SSA and anti-LA/SSB antibodies. The patient was implanted a temporary pacemaker in view of hemodynamic deterioration and subsequently was weaned off ionotropic support and referred for permanent epicardial pacemaker implantation. We report temporary pacemaker implantation in a neonate with hemodynamic instability as a stabilizing measure and discuss technical challenges for the same., (© 2024 Wiley Periodicals LLC.)

Background: The first dual-chamber leadless pacemaker (DC-LP) system consists of 2 separate atrial and ventricular devices that communicate to maintain synchronous atrioventricular pacing and sensing. The initial safety and efficacy were previously reported., Objective: The purpose of this study was to evaluate the chronic electrical performance of the DC-LP system., Methods: Patients meeting standard dual-chamber pacing indications were enrolled and implanted with the DC-LP system (Aveir DR, Abbott), including right atrial and ventricular helix-fixation LPs (atrial leadless pacemaker [ALP], ventricular leadless pacemaker [VLP]). Pacing capture threshold, sensed amplitude, and pacing impedance were collected using the device programmer at prespecified timepoints from 0-6 months postimplant., Results: De novo devices were successfully implanted in 381 patients with complete 6-month data (62% male; age 69 ± 14 years; weight 82 ± 20 kg; 65% sinus nodal dysfunction, 30% atrioventricular block). ALPs were implanted predominantly in the right atrial appendage anterior base and VLPs primarily at the mid-to-apical right ventricular septum. From implant to 1 month, pacing capture thresholds (0.4-ms pulse width) improved in both ALPs (2.4 ± 1.5 V to 0.8 ± 0.8 V; P <.001) and VLPs (0.8 ± 0.6 V to 0.6 ± 0.4 V; P <.001). Sensed amplitudes improved in both ALPs (1.8 ± 1.3 mV to 3.4 ± 1.9 mV; P <.001) and VLPs (8.8 ± 4.0 mV to 11.7 ± 4.2 mV; P <.001). Impedances were stable in ALPs (334 ± 68 Ω to 329 ± 52 Ω; P = .17) and reduced in VLPs (789 ± 351 Ω to 646 ± 190 Ω; P <.001). Electrical measurements remained relatively stable from 1-6 months postimplant. No differences in electrical metrics were observed among ALP or VLP implant locations., Conclusion: This first in-human evaluation of the new dual-chamber leadless pacemaker system demonstrated reliable electrical performance throughout the initial 6-month evaluation period., Competing Interests: Disclosures Dr Rahul Doshi, Dr Derek V. Exner, Dr Vivek Y. Reddy, Dr Reinoud E. Knops, Dr Petr Neužil, Dr Thomas Callahan, Dr Sri Sundaram, and Dr James E. Ip report Abbott consulting fees. Dr Pascal Defaye, Dr Derek V. Exner, and Dr Reinoud E. Knops report Abbott research grants. Dr Derek V. Exner, Dr Thomas Callahan, and Dr Sri Sundaram report Abbott honoraria. Dr Gerhard Hindricks, Dr Rahul Doshi, Dr Reinoud E. Knops, Dr Morio Shoda, Dr Maria Grazia Bongiorni, and Dr James E. Ip serve as Abbott steering committee members. Dr Nima Badie is an Abbott employee. Additional Disclosures unrelated to this manuscript: Dr Petr Neužil reports research grants from Boston Scientific and Medtronic. Dr Derek V. Exner serves as a consultant for Boston Scientific, Medtronic, and GE Healthcare; and has equity in Clarius, CorVista eMurmur, HelpWear, and ProtonIntel. Dr Vivek Y. Reddy serves as a consultant for and has equity in Ablacon, Acutus Medical, Affera-Medtronic, Apama Medical-Boston Scientific, Anumana, APN Health, Aquaheart, Atacor, Autonomix, Axon Therapies, Backbeat, BioSig, CardiaCare, CardioNXT/AFTx, Circa Scientific, CoRISMA, Corvia Medical, Dinova-Hangzhou DiNovA EP Technology, East End Medical, EPD-Philips, EP Frontiers, Epix Therapeutics-Medtronic, EpiEP, Eximo, Farapulse-Boston Scientific, Field Medical, Focused Therapeutics, HRT, Intershunt, Javelin, Kardium, Keystone Heart, Laminar Medical, LuxMed, Medlumics, Middlepeak, Neutrace, Nuvera-Biosense Webster, Oracle Health, Restore Medical, Sirona Medical, SoundCath, Valcare. Dr Vivek Y. Reddy has served as a consultant for Adagio Medical, AtriAN, Biosense-Webster, BioTel Heart, Biotronik, Boston Scientific, Cairdac, Cardiofocus, Cardionomic, CoreMap, Fire1, Gore & Associates, Impulse Dynamics, Medtronic, Novartis, Philips, Pulse Biosciences; and has equity in DRS Vascular, Manual Surgical Sciences, Newpace, Nyra Medical, Surecor, and Vizaramed. Dr Reinoud E. Knops reports research grants, consulting fees, and serves as a steering committee member of Boston Scientific; and reports speaking fees from Medtronic. Dr Robert Canby reports consulting fees from Medtronic. Dr Thomas Callahan reports speaking and consulting feeds from Medtronic, Philips, Boston Scientific, and ShockWave. Dr Sri Sundaram holds an unrelated patent with Abbott. Dr James E. Ip reports consulting fees from Medtronic and serves as a data safety monitoring committee member of Boston Scientific. All other authors have no conflicts of interest to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Left bundle branch area pacing includes left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP), which is effective in patients with dyssynchronous heart failure (DHF). However, the basic mechanisms are unknown., Objectives: This study aimed to compare LBBP with LVSP and explore potential mechanisms underlying the better clinical outcomes of LBBP., Methods: A total of 24 beagles were assigned to the following groups: 1) control group; 2) DHF group, left bundle branch ablation followed by 6 weeks of AOO pacing at 200 ppm; 3) LBBP group, DHF for 3 weeks followed by 3 weeks of DOO pacing at 200 ppm; and 4) LVSP with the same interventions in the LBBP group. Metrics of electrocardiogram, echocardiography, hemodynamics, and expression of left ventricular proteins were evaluated., Results: Compared with LVSP, LBBP had better peak strain dispersion (44.67 ± 1.75 ms vs 55.50 ± 4.85 ms; P < 0.001) and hemodynamic effect (dP/dtmax improvement: 27.16% ± 7.79% vs 11.37% ± 4.73%; P < 0.001), whereas no significant differences in cardiac function were shown. The altered expressions of proteins in the lateral wall vs septum in the DHF group were partially reversed by LBBP and LVSP, which was associated with the contraction and adhesion process, separately., Conclusions: The animal study demonstrated that LBBP offered better mechanical synchrony and improved hemodynamics than LVSP, which might be explained by the reversed expression of contraction proteins. These results supported the potential superiority of left bundle branch area pacing with the capture of the conduction system in DHF model., Competing Interests: Funding Support and Author Disclosures This work was financially supported by the National Natural Science Foundation of China (No. 82100325, 82000325, 82070349), the Beijing Gold-bridge project (No. ZZ21055), Young Elite Scientists Sponsorship Program by Beijing Association for Science and Technology (No. BYESS2023392), the Peking University First Hospital Seed Foundation (No. 2020SF19), and the National High Level Hospital Clinical Research Funding (No. 2022-GSP-GG-11, 2023-GSP-GG-22, 2023-GSP-QN-40). The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Roughly one in six patients receiving conventional transvenous pacemaker systems experience significant complications within 1 year of implant, mainly due to the transvenous lead and subcutaneous pocket. A new helix-fixation single-chamber ventricular leadless pacemaker (LP) system capable of pre-deployment exploratory electrical mapping is commercially available. Such an LP may mitigate complications while streamlining the implantation. In this study, the initial real-world implant experience of the helix-fixation LP was evaluated following its commercial release., Methods: In patients indicated for single-chamber right ventricular pacing, helix-fixation Aveir VR LPs (Abbott, Abbott Park, IL) were implanted using the dedicated loading tool, introducer, and delivery catheter. Implant procedural characteristics, electrical parameters, and any 30-day procedure-related adverse events of consecutive implant attempts were retrospectively evaluated., Results: A total of 167 patients with Class I indication for permanent pacing received implants in four North American centers (57% male, 70 years old). Pre-fixation electrical mapping of potential sites allowed repositioning to be avoided in 95.7% of patients. Median [interquartile range] LP procedure and fluoroscopy durations were 25.5 min [20.0, 35.0] and 5.7 min [4.0, 9.2], respectively. Pacing capture threshold, sensed R-wave amplitude, and impedance were 0.8 V [0.5, 1.3], 9.0 mV [6.0, 12.0], and 705 Ω [550, 910], respectively. Implantation was successful in 98.8% of patients, with 98.2% free from acute adverse events., Conclusions: The initial, real-world experience of the helix-fixation ventricular leadless pacemaker demonstrated safe and efficient implantation with minimal repositioning, viable electrical metrics, and limited acute complications., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Aims: The MicraVR™ transcatheter pacing system (TPS) has been implemented into clinical routine for several years. The primary recipients are patients in need for VVI pacing due to bradycardia in the setting of atrial fibrillation (AF). Implantation safety and acute success have been proven in controlled studies and registries. So far only few long-term real-life data on TPS exist. We report indication, procedure and outcome data from two high-volume implanting German centers., Methods: Between 2016 and 2019, 188 (of 303) patients were included. During follow-up (FU), TPS interrogation was performed after 4 weeks and thereafter every 6 months., Results: Indication for TPS implantation in 159/188 (85%) patients was permanent or intermittent AV block III° in the setting of atrial fibrillation. The mean procedure duration was 50 min [35.0-70.0]. The average acute values after system release were: thresholds: 0.5V [0.38-0.74]/0.24ms; R-wave sensing: 10.0mV [8.1-13.5]; impedance: 650 Ohm [550-783]; RV-pacing demand: 16.9% [0.9-75.9]; and battery status: 3.15 V [3.12-3.16]. During FU of 723.4 ± 597.9 days, neither pacemaker failure nor infections were reported. Long-term FU revealed: thresholds: 0.5V [0.38-0.63]/0.24 ms; sensing: 12.3mV [8.9-17.2]; impedance: 570 Ohm [488-633]; RV-pacing demand: 87.1% [29.5-98.6]; and battery status 3.02 V [3.0-3.1]. Forty-three patients died from not-device-related causes., Conclusion: This to date largest German long-term dataset for MicraVR™ TPS implantation revealed stable device parameter. Foremost, battery longevity seems to fulfill predicted values despite a significant increase in RV-pacing demand over time and even in patients with consecutive AV-node ablation. Of note, no infections or system failure were observed., (© 2023. The Author(s).)

The pacing threshold is important for leadless pacemakers, as the pacing output has a significant impact on battery longevity. Acute pacing rate-dependent threshold increases have also been reported with leadless pacemakers. In the present case, we experienced a case in which the threshold, which had been raised in the acute phase, once showed a tendency to improve, but then worsened again. And, as in previous reports, thresholds improved completely in the chronic phase. Repeated retrieval and reimplantation of leadless pacemakers increases the likelihood of fatal complications, so being aware of such phenomenon may prevent unnecessary procedure and complications., (© 2024 Wiley Periodicals LLC.)

Competing Interests: Disclosures Abbott: consulting fees, steering committee; Medtronic: consulting fees; Boston Scientific: data safety monitoring committee.

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., Competing Interests: Disclosures Dr Vijayaraman has received honoraria and research support from and is a consultant and serves on the advisory board for Medtronic, serves on the advisory board of and is a consultant for Abbott, and has received honoraria from Biotronik and Boston Scientific. He owns a patent for His bundle pacing delivery tool. Dr Koneru has received honoraria from Medtronic and Biotronik and has received fellowship support from Boston Scientific, Biosense Webster, Medtronic, and Abbott Medical. Dr Sharma has received honoraria from Medtronic and is a consultant for Medtronic, Abbott, and Biotronik. Dr De Pooter has received speaker honoraria and consultancy fees from Medtronic, Biotronik, Abbott, and Boston Scientific. Dr Schaller has received honoraria from Medtronic, Cook Medical, and Phillips. Dr Cano has received honoraria from and is a consultant for Medtronic, Biotronik, and Boston Scientific. Dr Whinnett has received honoraria from Medtronic and Boston Scientific and is a consultant for Medtronic and Abbott. Dr Migliore is a consultant for and has received research support from Boston Scientific and Cook Medical. Dr Ponnusamy has received honoraria from Medtronic. Dr Zanon has received honoraria from Abbott, Biotronik, Boston Scientific, Medtronic, and MicroPort. Dr Heuverswyn has received honoraria from Abbott and Boston Scientific. Dr Ellenbogen is a consultant for Medtronic, Boston Scientific, Abbott, and Biotronik and has received honoraria from Medtronic, Boston Scientific, and Biotronik. Dr Herweg is a speaker and consultant for Abbott and is a speaker for and has received fellowship support from Medtronic. The rest of the authors report no conflicts of interest., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Intraoperative implantation of leadless cardiac pacemakers (LCPs) under direct visualization during cardiac surgery is a novel strategy to provide pacing to patients with an elevated risk of postoperative conduction disorders or with a preexisting pacing indication undergoing valve surgery., Objectives: This study sought to evaluate the long-term safety and efficacy of intraoperative LCP implantation in 100 consecutive patients., Methods: Retrospective single-center cohort study of consecutive patients (n = 100) who underwent intraoperative LCP implantation during valve surgery. Safety and efficacy were assessed at implantation and follow-up visits., Results: A total of 100 patients (age 68 ± 13 years, 47% female) underwent intraoperative LCP implantation. The surgery involved the tricuspid valve in 99 patients (99%), including tricuspid valve repair in 59 (59%) and tricuspid valve replacement in 40 (40%). Most of the patients (78%) underwent multivalve surgery. The indication for LCP implantation was elevated risk of postoperative atrioventricular block in 54% and preexisting bradyarrhythmias in 46%. LCP implantation was successful in all patients. During a median of 10.6 months (IQR: 2.0-22.7 months) of follow-up, no device-related complications occurred. At 12-month follow-up, the pacing thresholds were acceptable (≤2.0 V at 0.24 milliseconds) in 95% of patients., Conclusions: Intraoperative LCP implantation under direct visualization is a safe strategy to provide permanent pacing in patients undergoing valve surgery, with a postoperative electrical performance comparable to percutaneously placed LCPs., Competing Interests: Funding Support and Author Disclosures Dr Reddy has received research grants and served as a consultant for Medtronic, the manufacturer of the leadless pacemaker used in this series. Dr Miller has served as a consultant for Medtronic. Dr Adams declares that The Icahn School of Medicine at Mount Sinai receives royalty payments from Medtronic for intellectual property related to the development of 2 tricuspid valve repair rings. Medtronic is the manufacturer of the leadless pacemaker used in this study. Dr Breeman has received an unrestricted research grant from Medtronic and funding from the KNAW Medical Sciences Fund, Royal Netherlands Academy of Arts & Sciences. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Advances in leadless pacemaker technology have enabled accelerometer-based atrioventricular (AV) synchronous pacing by sensing atrial mechanical contraction., Objective: The purpose of this study was to report the performance of the Micra AV leadless pacemaker from the worldwide Micra AV post-approval registry (PAR) through 12 months., Methods: The Micra AV PAR is a prospective, single-arm, observational registry designed to assess the safety and effectiveness of Micra AV in a real-world setting. For the present interim analysis, major complications and system revisions through 12 months were summarized and compared to a historical cohort of 2667 patients implanted with a transvenous dual-chamber pacing system., Results: The device was successfully implanted in 796 of 801 patients (99.4%) at 97 centers in 19 countries. Micra AV patients were older (74.1 years vs 71.1 years; P < .0001) with a higher incidence of renal disease (22.3% vs 9.8%; P < .0001) compared with transvenous dual-chamber patients. Through 12 months, the major complication rate was 3.7% in Micra AV patients compared with 8.8% in transvenous dual-chamber patients (hazard ratio 0.42; 95% confidence interval 0.28-0.61; P < .001). The system revision rate was 1.5% in Micra AV patients compared with 5.5% for transvenous dual-chamber patients (hazard ratio 0.25; 95% confidence interval 0.13-0.47; P < .001); this reduction was largely driven by the absence of lead dislodgments requiring revision. The median AV synchrony index was 79.4% (interquartile range 65.2%-86.4%) in patients paced >90%., Conclusion: The Micra AV leadless pacemaker was implanted with a high rate of success in patients with multiple comorbidities, with a significantly lower rate of complications and system revisions through 12 months compared to a historical cohort of patients with transvenous dual-chamber pacemakers., Competing Interests: Disclosures Dr Garweg has received consultant/speaker fees and research grants from Abbott, Biotronik, and Medtronic. Dr Chinitz has received consulting fees from Medtronic, Boston Scientific, and Biosense Webster and speaking/teaching honorarium fees from Boston Scientific and Biotronik. Dr Marijon has received consulting fees from Medtronic, Abbott, and Boston Scientific. Dr Haeberlin has received travel fees/educational grants from Medtronic, Biotronik, Abbott, and Philips/Spectranetics without impact on personal remuneration and works as a proctor for Medtronic. Dr El-Chami serves as a consultant for Medtronic, Boston Scientific, and Biotronik. Dr Roberts has received honoraria from Medtronic, Boston Scientific, and Abbott and research funding from Boston Scientific. Dr Piccini has received clinical research grants from Abbott and Philips and serves as a consultant for Abbott, Boston Scientific, Medtronic, and Philips. Drs Stromberg and Fagan are employees/shareholders of Medtronic. Dr Clementy has received consulting fees from Medtronic. The remaining authors have nothing to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Functional mitral regurgitation (FMR) and its severity are associated with adverse outcomes in heart failure patients. This study aims to analyze the predictors of FMR improvement after successful left bundle branch area pacing (LBBAP) in patients with LVEF < 50% and complete left bundle branch block (CLBBB)., Methods: Consecutive patients with LVEF < 50% and CLBBB who underwent successful LBBAP from July 2018 to July 2023 were retrospectively identified. Significant MR was defined as regurgitation of moderate severity or greater. Patients with significant FMR were included in the analysis. FMR improvement (FMRI) was defined as a reduction of at least one grade in regurgitation severity compared to baseline at 3 months or longer follow-up., Results: Among the 81 identified patients, 42 patients with significant FMR preoperatively were included. After LBBAP, QRS duration significantly shortened from 170.6 ± 18.8 ms to 114.5 ± 20.2 ms (p < .001). Significant FMR improves in approximately 76.2%, and the patients were divided into an FMRI group (n = 32) and a non-FMRI group (n = 10). Univariate analysis showed that absence of persistent atrial fibrillation, typical CLBBB, and left atrium diameter at baseline were associated with improvement of FMR after LBBAP. Of these variables, only absence of persistent atrial fibrillation remains an independent predictor in the multivariate model (OR 12.436, p = .009)., Conclusion: LBBAP is able to improve FMR in heart failure patients who had CLBBB with LVEF < 50%. Meanwhile, the absence of persistent atrial fibrillation is an independent predictor of FMR improvement., (© 2024 Wiley Periodicals LLC.)

Asymptomatic paroxysmal atrial fibrillation (AF) is often found in patients implanted with cardiac implantable electronic devices (CIEDs). Second-generation atrial antitachycardia pacing (A-ATP) is effective in managing AF in patients implanted with CIEDs. The purpose of this study was to evaluate the efficacy and safety of A-ATP in patients implanted with CIEDs. This was a single-center retrospective study involving 91 patients (male 46 patients, mean age 74 ± 9 years) implanted with Reactive A-ATP equipped devices (84 patients with pacemakers, 6 with ICDs, and 1 with a CRT-D). The AF burden, rate of AF termination, and details of the activation of the A-ATP were analyzed in each patient. During a mean follow-up period of 21 ± 13 months, A-ATP was activated in 45 of 91 patients (49.5%). No patients had adverse events. Although the efficacy of the A-ATP varied among the patients, the median rate of AF termination was 44%. In comparison to the A-ATP start time, "0 min" had a higher AF termination rate by the A-ATP (39.4% vs. 24.4%, P = 0.011). The rate of termination by the A-ATP was high for AF with a long cycle length and a relatively regular rhythm. A-ATP successfully terminated AF episodes in some patients implanted with CIEDs. The optimal settings of the A-ATP will be determined in future studies., (© 2024. Springer Nature Japan KK, part of Springer Nature.)

Background: Ventricular tachycardia (VT) reduces cardiac output through high heart rates, loss of atrioventricular synchrony, and loss of ventricular synchrony. We studied the contribution of each mechanism and explored the potential therapeutic utility of His bundle pacing to improve cardiac output during VT., Methods: Study 1 aimed to improve the understanding of mechanisms of harm during VT (using pacing simulated VT). In 23 patients with left ventricular impairment, we recorded continuous ECG and beat-by-beat blood pressure measurements. We assessed the hemodynamic impact of heart rate and restoration of atrial and biventricular synchrony. Study 2 investigated novel pacing interventions during clinical VT by evaluating the hemodynamic effects of His bundle pacing at 5 bpm above the VT rate in 10 patients., Results: In Study 1, at progressively higher rates of simulated VT, systolic blood pressure declined: at rates of 125, 160, and 190 bpm, -22.2%, -42.0%, and -58.7%, respectively (ANOVA p < 0.0001). Restoring atrial synchrony alone had only a modest beneficial effect on systolic blood pressure (+ 3.6% at 160 bpm, p = 0.2117), restoring biventricular synchrony alone had a greater effect (+ 9.1% at 160 bpm, p = 0.242), and simultaneously restoring both significantly increased systolic blood pressure (+ 31.6% at 160 bpm, p = 0.0003). In Study 2, the mean rate of clinical VT was 143 ± 21 bpm. His bundle pacing increased systolic blood pressure by + 14.2% (p = 0.0023). In 6 of 10 patients, VT terminated with His bundle pacing., Conclusions: Restoring atrial and biventricular synchrony improved hemodynamic function in simulated and clinical VT. Conduction system pacing could improve VT tolerability and treatment., (© 2024. The Author(s).)

Rationale: The use of transvenous pacing leads is associated with the risk of tricuspid valve dysfunction, mainly due to the continuous presence of the leads can have an impact on subsequent tricuspid function and possible operation injury of the tricuspid valve during implantation or operation., Patient Concerns: A 69-year-old female with a history of syncope for 9 months was admitted to the hospital. The electrocardiogram showed sinus bradycardia, junctional escape rhythm, and a heart rate of 44 bpm. Echocardiography suggested a downward displacement and severe insufficiency of the tricuspid valve and atrial septal defect., Diagnoses: The cause of syncope was considered to be sick sinus syndrome. The patient was diagnosed with Ebstein anomaly and is considered a candidate for surgical intervention., Interventions: To avoid aggravating tricuspid insufficiency by pacing leads crossing the tricuspid valve and hindering subsequent tricuspid valve surgery, a single-chamber pacing mode with atrial pacing (AAI) lead and Micra AV was chosen for maintaining atrioventricular synchrony after multidisciplinary discussion., Outcomes: The patient had stable parameters and was in good general condition at 1- and 3-month outpatient follow-ups after discharge., Lessons: This is the first case of new implantation of single-chamber atrial pacing + leadless ventricular pacing with Micra AV, an alternative strategy to epicardial or coronary sinus system for tricuspid valve displacement and severe tricuspid regurgitation., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.)

Backgrounds: Permanent pacemaker implantation (PPMI) is one of the greatest disadvantages of transcatheter aortic valve implantation (TAVI). To seek the predictors and clinical impacts of PPMI and investigate the recovery rate from conduction disorders., Methods: We retrospectively analysed data from 745 consecutive patients who underwent TAVI for severe aortic stenosis from November 2013 to July 2022. The ventricular pacing (VP) rate was recorded at 1 and 6 months after PPMI and the recovery from conduction disorders was defined as the VP rate <1%., Results: Postoperative PPMI was performed in 7.1% (53/745) of patients. Balloon predilatation was significantly frequent in the PPMI (-) group (52.8% (28/53) vs 80.6% (558/692); p<0.001) and the oversizing ratio was significantly greater in the PPMI (+) group (11.8%±10.1% vs 9.1%±9.7%; p=0.035). Freedom from rehospitalisation due to heart failure rate was significantly higher in the PPMI (-) group (p=0.032). In patients with postoperative PPMI, recovery from conduction disorders was observed in 17.0% and 27.9% of patients at 1 and 6 months, respectively., Conclusions: Recovery from conduction disorders occurred frequently. Avoidance of oversizing and extension of observation time may reduce the need for PPMI after TAVI., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: To evaluate the effect of body position on transesophageal atrial pacing (TEAP) in dogs., Study Design: Prospective, experimental trial., Animals: A total of eight mixed-breed dogs, median body mass 25 kg (range 11-31 kg)., Methods: TEAP was performed using a 6 Fr (2 mm) pacing catheter introduced transorally and positioned in the lower esophagus in left lateral recumbency. The catheter was withdrawn in 5 mm increments until successful TEAP. The minimum pacing threshold (MPT) was determined at each 5 mm increment until atrial capture could not be achieved at a maximal pulse amplitude of 40 mA. The zone of capture (ZOC) was the total distance over which TEAP was achieved. The same process was repeated in right lateral, ventral and dorsal recumbency. A linear mixed model was used to assess the impact of body position on TEAP and ZOC., Results: TEAP was achieved in all body positions. There was significant random effect of individual dogs on ZOC (p = 0.048) but not on MPT (p = 0.109). MPT was 11.56 ± 8.65 mA (mean ± SD), 8.43 ± 2.29 mA, 10.63 ± 6.91 mA and 10 ± 7.44 mA for dorsal, left and right lateral, and ventral recumbency, respectively. ZOC was 5.12 ± 2.08 cm, 6.35 ± 2.41 cm, 5.94 ± 3.23 cm and 5.31 ± 2.2 cm for dorsal, left lateral and right lateral, and ventral recumbency, respectively. Neither ZOC (p = 0.363) nor MPT (p = 0.716) varied significantly between body positions., Conclusions and Clinical Relevance: TEAP can be performed successfully in all body positions in dogs. Body position did not significantly influence MPT or ZOC values for TEAP. Further studies are needed to compare the efficacy of TEAP with the efficacy of standard pharmacological therapy for management of bradycardia during general anesthesia in dogs., (Copyright © 2024 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Competing Interests: Funding Support and Author Disclosures Drs Lustgarten, Habel, and Meyer have received research funding from Medtronic, Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Background: Currently, the interrupted recording technique is commonly used to perform left bundle branch (LBB) pacing (LBBP). However, this method requires repeated testing to confirm that the LBB is captured and perforations are avoided. An automated solution may make this repetitive work easier., Case Summary: LBBP was performed using an uninterrupted recording technique in an 86-year-old woman. Lead position and LBB capture was confirmed by the characteristics of the intrinsic filtered and unfiltered intracardiac electrograms., Conclusion: Continuous mapping and recording technique may help achieve more accurate positioning of LBBP lead in the ventricular septum., Competing Interests: Declaration of competing interest The corresponding author owns the patent for John Jiang's connecting cable. The other author declares no conflict of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Competing Interests: Disclosures The authors have no conflicts of interest to disclose.

The adenovirus-mediated somatic transfer of the embryonic T-box transcription factor 18 (TBX18) gene can convert chamber cardiomyocytes into induced pacemaker cells. However, the translation of therapeutic TBX18-induced cardiac pacing faces safety challenges. Here we show that the myocardial expression of synthetic TBX18 mRNA in animals generates de novo pacing and limits innate and inflammatory immune responses. In rats, intramyocardially injected mRNA remained localized, whereas direct myocardial injection of an adenovirus carrying a reporter gene resulted in diffuse expression and in substantial spillover to the liver, spleen and lungs. Transient expression of TBX18 mRNA in rats led to de novo automaticity and pacemaker properties and, compared with the injection of adenovirus, to substantial reductions in the expression of inflammatory genes and in activated macrophage populations. In rodent and clinically relevant porcine models of complete heart block, intramyocardially injected TBX18 mRNA provided rate-adaptive cardiac pacing for one month that strongly correlated with the animal's sinus rhythm and physical activity. TBX18 mRNA may aid the development of biological pacemakers., (© 2024. The Author(s).)

Aims: In complete atrioventricular block (AVB) with underlying sinus rhythm, it is recommended to implant a dual-chamber pacemaker rather than a single-chamber pacemaker. However, no large-scale study has been able to demonstrate the superiority of this choice on hard clinical criteria such as morbimortality., Methods and Results: This retrospective observational study included all patients who received a primary pacemaker implantation in the indication of complete AVB with underlying sinus rhythm in France, based on the national administrative database between January 2013 and December 2022. After propensity score matching, we obtained two groups containing 19 219 patients each. The incidence of all-cause mortality was 9.22%/year for the dual-chamber pacemaker group, compared with 11.48%/year for the single-chamber pacemaker group (hazard ratio (HR) 0.807, P < 0.0001]. Similarly, there was a lower incidence of cardiovascular mortality (HR 0.766, P < 0.0001), heart failure (HR 0.908, P < 0.0001), atrial fibrillation (HR 0.778, P < 0.0001), and ischaemic stroke (HR 0.873, P = 0.008) in the dual-chamber pacemaker group than in the single-chamber pacemaker group. Regarding re-interventions and complications, there were fewer upgrades (addition of atrial lead or left ventricular lead) in the dual-chamber group (HR 0.210, P < 0.0001), but more haematomas (HR 1.179, P = 0.006) and lead repositioning (HR 1.123, P = 0.04)., Conclusion: In the indication of complete AVB with underlying sinus rhythm, our results are consistent with current recommendations to prefer implantation of a dual-chamber pacemaker rather than a single-chamber pacemaker for these patients. Implantation of a dual-chamber pacemaker is associated with a lower risk of mortality, heart failure, atrial fibrillation, and stroke during follow-up., Competing Interests: Conflict of interest: B.P.: consultant or speaker for Abbott, Biotronik, Boston Scientific, and Microport; L.F.: consultant or speaker for AstraZeneca, Bayer, BMS/Pfizer, Boehringer Ingelheim, Boston Scientific, Medtronic, Novartis, Novo, and Zoll. All remaining authors have declared no conflicts of interest., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Aims: The application of conduction system pacing (CSP) in clinical practice is growing, and the need for lead extraction will also increase. The data on outcomes and safety of CSP lead extraction are limited. The aim of this study was to assess procedural outcomes and safety of CSP lead removal., Methods and Results: Forty-seven patients from the EXTRACT Registry with the indication for CSP lead removal were enrolled in the study conducted at the Department of Electrocardiology in Katowice, Poland. Extraction technique, outcomes, safety, and complication were evaluated. Forty-three (91.5%) leads were successfully removed, and 41 (87.2%) were removed with traction only. The dwelling time of 28 extracted leads was longer than 1 year, and the oldest extracted lead was implanted for 89 months. Seven (14.9%) leads were removed from the left bundle branch (LBB) area and 36 from the His bundle (HB). Transient complete atrioventricular block occurred during the procedure in two patients. In 27 out of 31 attempts (87.1%), new CSP leads were implanted: nine (33.3%) HB pacing leads and 18 (66.7%) LBB area pacing leads., Conclusion: The CSP lead extraction is safe and feasible with a low complication rate and high rate of CSP lead reimplantation., Competing Interests: Conflict of interest: none declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.)

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., (© 2024. The Author(s).)

Background: A dual-chamber leadless pacemaker system has been designed for atrioventricular synchronous pacing using wireless, beat-to-beat, implant-to-implant (i2i) communication between distinct atrial and ventricular leadless pacemakers. The atrioventricular synchrony achieved across various ambulatory scenarios has yet to be systematically evaluated., Methods: A prospective, single-arm, unblinded, multicenter, international clinical trial of the leadless pacemaker system was conducted in patients with a conventional dual-chamber pacing indication enrolled from February 2022 to March 2023. Leadless pacemaker systems were implanted, and 12-lead Holter electrocardiographic recordings were collected 3 months after implantation over various postures/activities: sitting, supine, left lateral recumbent, right lateral recumbent, standing, normal walk, and fast walk. An independent Holter core laboratory performed a manual adjudication of the percent of atrioventricular synchronous beats using the standard 300-millisecond PR interval limit. Atrium-to-ventricle and ventricle-to-atrium i2i communication success rates were also assessed. Post hoc summary statistics describing the relationships between atrioventricular synchrony and i2i success, posture/activity, implantation indication, atrioventricular event, and heart rate were calculated., Results: In the evaluable population (n=384 of 464 enrolled [83%]; 61% male; age, 70 years; weight, 82 kg; 60% ejection fraction; 95% of beats evaluable), the mean atrioventricular synchrony of 98% of beats observed across all postures using the standard 300-millisecond limit was greater than both atrial-to-ventricular i2i (94%) and ventricular-to-atrial i2i (94%; P <0.001), exceeding both i2i values in 95% of patients. Atrioventricular synchrony was achieved in >95% of evaluable beats across all postures/activities, implantation indications, atrioventricular paced/sensed event combinations, and heart rate ranges (including >100 bpm)., Conclusions: This dual-chamber leadless pacemaker system demonstrated atrioventricular synchrony in 98% of evaluable beats at 3 months after implantation. Atrioventricular synchrony was maintained across postures/activities and remained robust for heart rates >100 bpm., Competing Interests: Dr Ip reports consulting fees from Abbott and Medtronic and serves as a Steering Committee member for Abbott and a Data Safety Monitoring Committee member for Boston Scientific. Dr Rashtian reports research grants and consulting fees from Abbott. Dr Exner reports consulting fees and research grants from Abbott and Medtronic and, unrelated to this article, reports consulting fees and research grants from Boston Scientific and GE Healthcare, as well equity in CorVista, Clarius, eMurmur, HelpWear, and ProtonIntel. Dr Reddy is a consultant to Abbott. Unrelated to this article, he serves as a consultant for and has equity in Ablacon, Acutus Medical, Affera-Medtronic, Apama Medical-Boston Scientific, Anumana, APN Health, Aquaheart, Atacor, Autonomix, Axon Therapies, Backbeat, BioSig, CardiaCare, CardioNXT/ AFTx, Circa Scientific, CoRISMA, Corvia Medical, Dinova-Hangzhou DiNovA EP Technology, East End Medical, EPD-Philips, EP Frontiers, Epix Therapeutics-Medtronic, EpiEP, Eximo, Farapulse-Boston Scientific, Field Medical, Focused Therapeutics, HRT, Intershunt, Javelin, Kardium, Keystone Heart, Laminar, LuxMed, Medlumics, Middlepeak, Neutrace, Nuvera-Biosense Webster, Oracle Health, Restore Medical, Sirona Medical, SoundCath, and Valcare; unrelated to this work, has served as a consultant for AtriAN, Biosense Webster, BioTel Heart, Biotronik, Boston Scientific, Cairdac, Cardiofocus, Cardionomic, CoreMap, Fire1, Gore & Associates, Impulse Dynamics, Medtronic, Novartis, Philips, Pulse Biosciences; and he has equity in DRS Vascular, Manual Surgical Sciences, Newpace, Nyra Medical, Surecor, and Vizaramed. Dr Doshi reports consulting fees from Abbott and serves as a steering committee member for Abbott. Dr Badie, J.R. Nevo, and A. Goil are employees of Abbott. Dr Defaye reports research grants from Abbott, Boston Scientific, and Medtronic. Dr Canby reports consulting fees from Medtronic. Dr Grazia Bongiorni serves as a steering committee member for Abbott. Dr Shoda serves as a Steering Committee member for Abbott. Dr Hindricks serves as a Steering Committee member for Abbott. Dr Knops reports research grants, consulting fees, and serving as a Steering Committee member for Abbott and Boston Scientific and speaking fees from Medtronic.

Aims: Right phrenic nerve (RPN) injury is a disabling but uncommon complication of atrial fibrillation (AF) radiofrequency ablation. Pace-mapping is widely used to infer RPN's course, for limiting the risk of palsy by avoiding ablation at capture sites. However, information is lacking regarding the distance between the endocardial sites of capture and the actual anatomic RPN location. We aimed at determining the distance between endocardial sites of capture and anatomic CT location of the RPN, depending on the capture threshold., Methods and Results: In consecutive patients undergoing AF radiofrequency ablation, we defined the course of the RPN on the electroanatomical map with high-output pacing at up to 50 mA/2 ms, and assessed RPN capture threshold (RPN-t). The true anatomic course of the RPN was delineated and segmented using CT scan, then merged with the electroanatomical map. The distance between pacing sites and the RPN was assessed. In 45 patients, 1033 pacing sites were analysed. Distances from pacing sites to RPN ranged from 7.5 ± 3.0 mm (min 1) when RPN-t was ≤10 mA to 19.2 ± 6.5 mm (min 9.4) in cases of non-capture at 50 mA. A distance to the phrenic nerve > 10 mm was predicted by RPN-t with a ROC curve area of 0.846 [0.821-0.870] (P < 0.001), with Se = 80.8% and Sp = 77.5% if RPN-t > 20 mA, Se = 68.0% and Sp = 91.6% if RPN-t > 30 mA, and Se = 42.4% and Sp = 97.6% if non-capture at 50 mA., Conclusion: These data emphasize the utility of high-output pace-mapping of the RPN. Non-capture at 50 mA/2 ms demonstrated very high specificity for predicting a distance to the RPN > 10 mm, ensuring safe radiofrequency delivery., Competing Interests: Conflict of interest: F.M.: consultant for Biosense-Webster and Abbott., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Aims: Leadless pacemaker therapy was introduced to overcome lead- and pocket-related complications in conventional transvenous pacemaker systems. Implantation via the femoral vein, however, may not always be feasible. The aim of this study was to evaluate leadless pacemaker implantation using a jugular vein approach and compare it to the standard implantation via the femoral vein., Methods and Results: The records of the first consecutive 100 patients undergoing Micra™ leadless pacemaker implantation via the right internal jugular vein from two centres were included in this study. Peri-procedural safety and efficacy of the jugular approach were compared to the first 100 patients using a femoral implantation approach at the University Hospital Zurich. One hundred patients underwent successful implantation of a leadless pacemaker via the internal jugular vein (mean age, 81.18 ± 8.29, 60% males). Mean procedure time was 35.63 ± 10.29 min with a mean fluoroscopy time of 4.66 ± 5.16 min. The device was positioned at the inferior septum in 25 patients, at the high septum in 24 patients, and mid-septum in 51 patients. The mean pacing threshold was 0.56 ± 0.35 V at 0.24 ms pulse width with a sensed amplitude of 10.0 ± 4.4 mV. At follow-up, electrical parameters remained stable in all patients. Compared with femoral implantation, patients undergoing the jugular approach were of similar age and had similar comorbidities. Mean procedure (48.9 ± 21.0 min) and fluoroscopy times (7.7 ± 7.8 min, both P < 0.01) were shorter compared to the femoral approach. Electrical parameters were similar between the two approaches. There were only two complications during jugular veinous implantations (1 pericardial effusion and 1 dislocation), compared to 16 complications using the femoral approach (1 pericardial effusion, 2 femoral artery injuries, and 13 major groin haematomas)., Conclusion: The jugular approach may represent a safe and efficient alternative to femoral implantation of the Micra leadless pacemaker., Competing Interests: Conflict of interest: N.M. has nothing to declare to the content of this article. S.S.-T. has received consultant and/or speaker fees from Medtronic HR; has received consultant and/or speaker fees from Medtronic DH; and reports educational grants, consultant or speaker fees, and fellowship support from Abbott, Medtronic, Biotronik, Boston Scientific, Biosense Webster, Novartis, Bayer, Pfizer, and Spectranetics. A.B. has received consultant and/or speaker fees from Abbott, Bayer Healthcare, Biosense Webster, Biotronik, Boston Scientific, Bristol-Myers Squibb, Cook Medical, Daiichi Sankyo, Medtronic, Pfizer, and Spectranetics/Philips. J.S. has received consultant and/or speaker fees from Abbott, Bayer, Berlin Chemie, Biosense Webster, Biotronik, Boehringer Ingelheim, Boston Scientific, BMS, Daiichi Sankyo, Medscape, Medtronic, Menarini, Pfizer, Saja, Servier, and WebMD and reports ownership of Swiss EP and CorXL., (© Crown copyright 2024.)

Aims: Physiological activation of the heart using algorithms to minimize right ventricular pacing (RVPm) may be an effective strategy to reduce adverse events in patients requiring anti-bradycardia therapies. This systematic review and meta-analysis aimed to evaluate current evidence on clinical outcomes for patients treated with RVPm algorithms compared to dual-chamber pacing (DDD)., Methods and Results: We conducted a systematic search of the PubMed database. The predefined endpoints were the occurrence of persistent/permanent atrial fibrillation (PerAF), cardiovascular (CV) hospitalization, all-cause death, and adverse symptoms. We also aimed to explore the differential effects of algorithms in studies enrolling a high percentage of atrioventricular block (AVB) patients. Eight studies (7229 patients) were included in the analysis. Compared to DDD pacing, patients using RVPm algorithms showed a lower risk of PerAF [odds ratio (OR) 0.74, 95% confidence interval (CI) 0.57-0.97] and CV hospitalization (OR 0.77, 95% CI 0.61-0.97). No significant difference was found for all-cause death (OR 1.01, 95% CI 0.78-1.30) or adverse symptoms (OR 1.03, 95% CI 0.81-1.29). No significant interaction was found between the use of the RVPm strategy and studies enrolling a high percentage of AVB patients. The pooled mean RVP percentage for RVPm algorithms was 7.96% (95% CI 3.13-20.25), as compared with 45.11% (95% CI 26.64-76.38) of DDD pacing., Conclusion: Algorithms for RVPm may be effective in reducing the risk of PerAF and CV hospitalization in patients requiring anti-bradycardia therapies, without an increased risk of adverse symptoms. These results are also consistent for studies enrolling a high percentage of AVB patients., Competing Interests: Conflict of interest: G.B. reports small speaker fees from Bayer, Boehringer Ingelheim, Boston, BMS, Daiichi, Sanofi, and Janssen, outside the submitted work. The other authors do not have conflict of interests to report., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Background: Biventricular pacing is a well-established therapy for patients with heart failure (HF), left bundle branch block (LBBB) and left ventricular (LV) dysfunction. Left bundle branch pacing (LBBP) has emerged as an alternative to biventricular pacing., Objectives: The aim of this study was to assess the retrograde conduction properties of the left bundle branch in patients with nonischemic cardiomyopathy and LBBB during LBBP and its clinical implications., Methods: Patients undergoing successful LBBP for nonischemic cardiomyopathy with LV ejection fraction (LVEF) ≤35% and LBBB were included. Continuous recording of His potential was performed using a quadripolar catheter. Unidirectional block was defined as retrograde His bundle activation during LBBP with stimulus to His potential (SH) duration less than or equal to antegrade HV interval and bidirectional block as VH dissociation or SH duration greater than HV interval. HF hospitalization, ventricular arrhythmias, and mortality were documented., Results: A total of 165 patients were included. The mean follow-up duration was 21.8 ± 13.1 months. Bidirectional block (group I) was observed in 82% (n = 136), and these patients were noted to have advanced HF stage and prolonged baseline QRS duration. Unidirectional block (group II) with intact retrograde conduction was observed in 18% (n = 29) and was associated with narrow paced QRS duration and higher LVEF during follow-up. Super-response (LVEF ≥50%) was observed in 54.4% (n = 74) in group I compared with 73.3% (n = 22) in group II (P = 0.03). The OR for LVEF normalization was 4.1 (95% CI: 1.26-13.97; P = 0.02), with unidirectional block compared with bidirectional block in patients with LBBB and LV dysfunction. Adverse clinical outcomes as measured by a composite of HF hospitalization, ventricular arrhythmias, and mortality were significantly higher in group I compared with group II (12.5% vs 0%; P = 0.04)., Conclusions: Bidirectional block in LBBB was characterized by advanced HF symptoms, while unidirectional block was associated with better clinical outcomes after cardiac resynchronization therapy by LBBP., Competing Interests: Funding Support and Author Disclosures Dr Ponnusamy is a consultant for Medtronic. Dr Vijayaraman is a speaker and consultant for and has received research and fellowship support from Medtronic; is a consultant for Abbott, Biotronik, and Boston Scientific; and holds a patent on an HBP delivery tool. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Purpose of the Review: Cardiac pacing has evolved in recent years currently culminating in the specific stimulation of the cardiac conduction system (conduction system pacing, CSP). This review aims to provide a comprehensive overview of the available literature on CSP, focusing on a critical classification of studies comparing CSP with standard treatment in the two fields of pacing for bradycardia and cardiac resynchronization therapy in patients with heart failure. The article will also elaborate specific benefits and limitations associated with CSP modalities of His bundle pacing (HBP) and left bundle branch area pacing (LBBAP)., Recent Findings: Based on a growing number of observational studies for different indications of pacing therapy, both CSP modalities investigated are advantageous over standard treatment in terms of narrowing the paced QRS complex and preserving or improving left ventricular systolic function. Less consistent evidence exists with regard to the improvement of heart failure-related rehospitalization rates or mortality, and effect sizes vary between HBP and LBBAP. LBBAP is superior over HBP in terms of lead measurements and procedural duration. With regard to all reported outcomes, evidence from large scale randomized controlled clinical trials (RCT) is still scarce. CSP has the potential to sustainably improve patient care in cardiac pacing therapy if patients are appropriately selected and limitations are considered. With this review, we offer not only a summary of existing data, but also an outlook on probable future developments in the field, as well as a detailed summary of upcoming RCTs that provide insights into how the journey of CSP continues., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: The excitable gap (EG), defined as the excitable tissue between two subsequent wavefronts of depolarization, is critical for maintaining reentry that underlies deadly ventricular arrhythmias. EG in the His-Purkinje Network (HPN) plays an important role in the maintenance of electrical wave reentry that underlies these arrhythmias., Objective: To determine if rapid His bundle pacing (HBP) during reentry reduces the amount of EG in the HPN and ventricular myocardium to suppress reentry maintenance and/or improve defibrillation efficacy., Methods: In a virtual human biventricular model, reentry was initiated with rapid line pacing followed by HBP delivered for 3, 6, or 9 s at pacing cycle lengths (PCLs) ranging from 10 to 300 ms (n=30). EG was calculated independently for the HPN and myocardium over each PCL. Defibrillation efficacy was assessed for each PCL by stimulating myocardial surface EG with delays ranging from 0.25 to 9 s (increments of 0.25 s, n=36) after the start of HBP. Defibrillation was successful if reentry terminated within 1 s after EG stimulation. This defibrillation protocol was repeated without HBP. To test the approach under different pathological conditions, all protocols were repeated in the model with right (RBBB) or left (LBBB) bundle branch block., Results: Compared to without pacing, HBP for >3 seconds reduced average EG in the HPN and myocardium across a broad range of PCLs for the default, RBBB, and LBBB models. HBP >6 seconds terminated reentrant arrhythmia by converting HPN activation to a sinus rhythm behavior in the default (6/30 PCLs) and RBBB (7/30 PCLs) models. Myocardial EG stimulation during HBP increased the number of successful defibrillation attempts by 3%-19% for 30/30 PCLs in the default model, 3%-6% for 14/30 PCLs in the RBBB model, and 3%-11% for 27/30 PCLs in the LBBB model., Conclusion: HBP can reduce the amount of excitable gap and suppress reentry maintenance in the HPN and myocardium. HBP can also improve the efficacy of low-energy defibrillation approaches targeting excitable myocardium. HBP during reentrant arrhythmias is a promising anti-arrhythmic and defibrillation strategy., Competing Interests: Declaration of competing interest All authors have participated in (a) conception and design, or analysis and interpretation of the data; (b) drafting the article or revising it critically for important intellectual content; and (c) approval of the final version. This manuscript has not been submitted to, nor is under review at, another journal or other publishing venue. The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)