Left Bundle Branch Research Articles

Change in left bundle branch potential-ventricular interval during lead implantation: what is the mechanism?

A 75-year-old male with sick sinus syndrome (SSS) underwent left bundle branch (LBB) pacing (LBBP) implantation. Intraoperative recordings showed that the LBB potential-ventricular (LBB-V) interval gradually decreased from 47 to 19 ms (ms). Two-year follow-up indicated stable pacing parameters and consistent electrocardiogram (ECG) results. Despite potential conduction delays caused by lead implantation, a watchful waiting strategy demonstrated recovery potential without impacting long-term prognosis or pacing parameters.

Relationship Between Electrical Parameters and Cardiac Synchrony in Patients Underwent Left Bundle Branch Area Pacing.

The study aims to assess cardiac synchrony under different left bundle branch area pacing (LBBAP) and evaluate the relationship between different surface or intracardiac electrical parameters and mechanical synchrony. Eighty-two patients with successful LBBAP were recruited. The electrical synchrony, evaluated by paced QRS duration (pQRSD) and Stim-LVAT (stimulus to left ventricular activation time), and mechanical synchrony, evaluated by thestandard deviation of the time-to-peak contraction velocity in 12 left ventricular segments (Tsd-12-LV), were compared between groups in patients underwent LBBAP. To investigate the relationship between different electrical parameters with mechanical synchrony under LBBAP, patients were divided into subgroups according to left ventricular activation time (LVAT, < 60, 60-70, and > 70ms), presence of left bundle branch (LBB) potential (positive, negative), QRS axis (normal, left axis deviation [LAD]), and potential to ventricular interval (PVI, < 20 and > 20ms). Mechanical synchrony was compared among the subgroups respectively 3 days post LBBAP procedure. No statistically significant differences were documented in electrical synchrony, evaluated by pQRSD, and mechanical synchrony, evaluated by Tsd-12-LV among the subgroups divided by the stim-LVAT, LBB potential, PVI duration, or paced QRS axis in the LBBAP group. LBB potential, PVI, or normal paced QRS axis is not the prerequisite for successful LBBAP and optimal cardiac synchrony. Adopting a Stim-LVAT value of less than 75ms to attain ideal electrical and mechanical synchrony during theLBBAP procedure may be applicable. http://www.chictr.org.cn/index.aspx. gov identifier: ChiCTR1800021104.

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

Although left bundle branch area pacing (LBBAP) is an emerging conduction system pacing modality, it is unclear which parameters predict procedural success and how many implant attempts are acceptable. This study aimed to assess predictors of successful LBBAP, left bundle branch (LBB) capture, and factors associated with the number of LBBAP implant attempts. This retrospective observational multicenter study was conducted in Korea. LBBAP was attempted in 119 patients; 89.3% of patients had bradyarrhythmia (atrioventricular block 82.4%), and 10.7% of patients had heart failure (cardiac resynchronization therapy) indication. Procedural success and electrophysiological and echocardiographic parameters were evaluated. The acute success rate of lead implantation in LBBAP was 95.8% (114 of 119 patients) and that of LBB capture was 82.4% (98 of 119 patients). Fewer implant attempts were associated with LBBAP success (three or fewer vs. over three times, p = 0.014) and LBB capture (three or fewer vs. over three times, p = 0.010). In the multivariate linear regression, the patients with intraventricular conduction delay (IVCD) required a greater number of attempts than those without IVCD [estimates = 2.33 (0.35-4.31), p = 0.02], and the larger the right atrial (RA) size, the more the attempts required for LBBAP lead implantation [estimates = 2.08 (1.20-2.97), p < 0.001]. An increase in the number of implant attempts was associated with LBBAP procedural failure and LBB capture failure. The electrocardiographic parameter IVCD and the echocardiographic parameter RA size may predict the procedural complexity and the number of lead implant attempts for LBBAP.

Six transition patterns and seven capture types in different left bundle branch bipolar pacing configurations.

This study aims to explore the different transition patterns and capture types during two bipolar pacing tests based on the selective left bundle branch (LBB) capture determined by the continuous pacing and recording technique. In total, 67 patients completed two unipolar and two bipolar pacing tests based on selective LBB capture during screwing-in for left bundle branch pacing (LBBP) using the continuous pacing and recording technique. The electrophysiological characteristics and potential mechanisms of different pacing configurations were further evaluated in this study. We found six transition patterns and derived seven capture types in two bipolar pacing tests according to the analysis of continuous electrocardiogram and electrogram changes. Compared with the conventional configuration of "Tip-Ring+" bipolar pacing, "Ring-Tip+" testing had a lower threshold for simultaneous capture of the LBB and the left and right ventricular septum myocardium (1.57 vs. 2.84 V at 0.5 ms) and was the only configuration to yield the peculiar "LBBP + right ventricular septum pacing (RVSP)" capture type. In this study, we observed for the first time that "Ring-Tip+" bipolar pacing allows for a lower clinically applicable pacing threshold for simultaneous capture of the LBB and left and right ventricular septum myocardium, and the peculiar "LBBP + RVSP" capture type. This may be a more advantageous physiological pacing configuration, warranting further investigation and application in the future. Based on the specific selective LBB capture, we first found six transition patterns and derived seven capture types in two bipolar pacing tests due to the different thresholds of the LBB, left ventricular septal myocardial, and right ventricular septal myocardial. Compared with the conventional configuration of "Tip-Ring+" bipolar pacing, "Ring-Tip+" testing had a lower threshold for simultaneous capture of the LBB and the left and right ventricular septum myocardium (1.57 vs. 2.84 V at 0.5 ms) and was the only configuration to yield the peculiar "LBBP + RVSP" capture type. More pacing strategies should be released and investigated to achieve the best physiological pacing according to the individualized electrophysiological characteristics of patients.

Electrocardiographic Criteria for the Diagnosis of Acute Myocardial Infarction in Patients with Left Bundle Branch Block

During normal conduction system, the first segment depolarized is interventricular septum, normal ventricular depolarization begins with the septal fascicle of the left bundle branch followed by a simultaneous depolarization of the remaining ventricular walls from endocardium to pericardium via the right and left bundle branches. In left bundle branch block (LBBB) condition, the left ventricular activation is delayed, and the initial septal activation is from right to left, secondary ST segment and T wave abnormalities occur, and septal Q waves indicative of an MI are absent. About 0.5 percent of patients with acute myocardial infarction had left bundle-branch block Patients with left bundle branch block (LBBB) and suspected of acute myocardial infarction (MI) is challenge to the clinician. A diagnosis of MI with electrocardiogram (ECG) is especially difficult in the setting of LBBB because of the characteristic ECG changes caused by altered septal and left free wall ventricular depolarization. Here we review the pathophysiology of LBBB in MI, highlight evolving paradigms for the diagnosis of suspected MI in patients with LBBB.

Accelerated idioventricular rhythm after left bundle branch pacing lead implantation

Premature ventricular contractions with right bundle branch block morphology induced during left bundle branch (LBB) pacing (LBBP) lead implantation serve as a marker indicating that the lead is close to or has reached the LBB region. However, no reports to date have described accelerated idioventricular rhythm (AIVR) induced by LBBP lead deployment.We herein describe a patient who underwent LBBP for complete atrioventricular block. The patient's intrinsic escape rhythm was overtaken by AIVR induced immediately after LBBP lead deployment.AIVR is another marker indicating that the lead has reached the LBB region.

Extraction of lumenless pacing leads from the His bundle and left bundle branch area: outcomes of the high-volume centre.

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. 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. The CSP lead extraction is safe and feasible with a low complication rate and high rate of CSP lead reimplantation.

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

BackgroundAlthough output-dependent QRS transition is a specific indicator that confirms left bundle branch (LBB) capture during left bundle branch area pacing (LBBAP), its durability remains unclear. ObjectiveThe purpose of this study was to evaluate the presence of output-dependent QRS transition and capture thresholds of the LBB and left ventricular septal myocardium immediately and up to 1 year after the LBBAP procedure. MethodsWe enrolled 129 patients with successful LBBAP who were available for 1-year follow-up postoperatively. Threshold testing was performed immediately after LBBAP on postoperative day 0 (POD-0) and after 3 days (POD-3), 6 months (POD-180), and 1 year (POD-360). ResultsOutput-dependent QRS transition persisted in 64 patients (88%) on POD-360, from among the 73 patients with output-dependent QRS transition on POD-0. In contrast, 55 of 56 patients without QRS transition on POD-0 (98%) did not exhibit QRS transition thereafter. LBB thresholds were slightly elevated on POD-360, albeit without statistical significance, compared with those on POD-0 (1.22 ± 1.00 V vs 1.43 ± 1.29 V at 0.4 ms; P = .26). The LBB thresholds increased by ≥1.5 V in 7 patients (11%). However, in 93% of patients with an LBB threshold of ≤2.5 V on POD-0, LBB capture was maintained at 2.5 V on POD-360. Left ventricular septal thresholds were similar on POD-0 and POD-360 (0.81 ± 0.36 V vs 0.83 ± 0.24 V; P > .99) and did not increase by ≥1.5 V in any patient. ConclusionOutput-dependent QRS transitions were highly reproducible after implantation. Furthermore, LBB thresholds remained stable in most cases during the first postoperative year.

Detecting elevated left ventricular end diastolic pressure from simultaneously measured femoral pressure waveform and electrocardiogram

Objective. Instantaneous, non-invasive evaluation of left ventricular end-diastolic pressure (LVEDP) would have significant value in the diagnosis and treatment of heart failure. A new approach called cardiac triangle mapping (CTM) has been recently proposed, which can provide a non-invasive estimate of LVEDP. We hypothesized that a hybrid machine-learning (ML) method based on CTM can instantaneously identify an elevated LVEDP using simultaneously measured femoral pressure waveform and electrocardiogram (ECG). Approach. We studied 46 patients (Age: 39–90 (66.4 ± 9.9), BMI: 20.2–36.8 (27.6 ± 4.1), 12 females) scheduled for clinical left heart catheterizations or coronary angiograms at University of Southern California Keck Medical Center. Exclusion criteria included severe mitral/aortic valve disease; severe carotid stenosis; aortic abnormalities; ventricular paced rhythm; left bundle branch and anterior fascicular blocks; interventricular conduction delay; and atrial fibrillation. Invasive LVEDP and pressure waveforms at the iliac bifurcation were measured using transducer-tipped Millar catheters with simultaneous ECG. LVEDP range was 9.3–40.5 mmHg. LVEDP = 18 mmHg was used as cutoff. Random forest (RF) classifiers were trained using data from 36 patients and blindly tested on 10 patients. Main results. Our proposed ML classifier models accurately predict true LVEDP classes using appropriate physics-based features, where the most accurate demonstrates 100.0% (elevated) and 80.0% (normal) success in predicting true LVEDP classes on blind data. Significance. We demonstrated that physics-based ML models can instantaneously classify LVEDP using information from femoral waveforms and ECGs. Although an invasive validation, the required ML inputs can be potentially obtained non-invasively.

Left bundle branch pacing guide by uninterrupted recording of intrinsic filtered and unfiltered intracardiac electrograms

BackgroundCurrently, 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 summaryLBBP 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. ConclusionContinuous mapping and recording technique may help achieve more accurate positioning of LBBP lead in the ventricular septum.

Left bundle fascicular versus left bundle trunk pacing: A comparison of their electrical synchrony parameters

BackgroundVariation in human left bundle branch (LBB) anatomy has a significant effect on the sequence of left ventricular depolarization. However, little is known regarding the electrophysiological characteristics of pacing different LBB fascicles. ObjectiveWe aimed to analyse the different electrocardiographic characteristics of LBB pacing (LBBP) attending to the site of pacing at the LBB system. MethodsIn 200 consecutive patients with confirmed LBBP, we distinguished left bundle trunk capture (LBTP) from any LB fascicular pacing (LBFP) based on the presence of LB potentials and paced QRS morphologies. We compared them regarding procedure, LBBP criteria and electrical synchrony parameters. ResultsOne hundred and seventy-three patients with LBFP were compared to 25 patients with LBTP. Left septal and posterior fascicles were significantly more prevalent than left anterior in LBFP (46.8 %, 41.0 % and 12.2 % respectively). QRS transition criteria (80.0 % vs 61.8 %; p = 0.077), selective LBBP (40.0 vs 21.5 %; p = 0.101), paced QRS width (110.3 ± 16.8 ms vs 115.4 ± 14.9 ms; p = 0.117), V6-RWPT (79.2 ± 10.7 ms vs 75.3 ± 9.7 ms; p = 0.068) and interpeak interval (42.5 ± 19.1 ms vs 45.7 ± 12.9 ms; p = 0.282) were not significantly different between LBTP and LBFP. All short-term complications occurred in LBFP, mainly driven by septal perforations (n = 23), without any difference in the pacing parameters. Among the LBFP subgroups, only aVL-RWPT was longer when the posterior fascicle was paced. ConclusionsLBFP is much more prevalent than LBTP in unselected consecutive patients with LBBP. LBFP seems more feasible, and as good as LBTP in terms of electrical synchrony and pacing safety.

Electrocardiographic Criteria for Diagnosis of Acute Myocardial Infarction in Patients with Left Bundle Branch Block

In patients with normal heart and normal conduction system, the initial depolarized segment in ventricle is interventricular septum which begins with septal fascicle of the left bundle branch from left side and direction to right side followed by a simultaneous depolarization of the remaining ventricular free walls from endocardium to pericardium via the right and left bundle branches. But among patients with left bundle branch block (LBBB), the initial septal activation is changing direction and become from right to left then the left ventricular activation is delayed, ST segment and T wave abnormalities occur, and septal Q waves indicative of an MI are absent in this condition. About 0.5 percent of patients with acute myocardial infarction had left bundle-branch block. Because this changes the patients with left bundle branch block (LBBB) and acute myocardial infarction (MI) is challenge to the clinician. The diagnosis of MI with electrocardiogram (ECG) is so difficult in the setting of LBBB because of the characteristic ECG changes caused by altered interventricular septal and left ventricle free wall depolarization. Here we review the ECG diagnostic criteria included all criteria until now and short summary of patient with acute MI and LBBB condition.

A porcine large animal model of radiofrequency ablation-induced left bundle branch block

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Medtronic Background and Objective ECG features of left bundle branch (LBB) block (LBBB) can be observed in up to 20–30 % of patients that suffer from heart failure with reduced ejection fraction. The resulting mechanical intraventricular asynchrony contributes to the worsening of left ventricular hemodynamics and has a relevant impact on the prognosis of the affected patients. The fact that we still cannot accurately predict which LBBB patients will benefit from cardiac resynchronization therapy (CRT) underscores that our understanding of the pathophysiology of LBBB remains incomplete. Here, a translational animal model of LBBB could be a major contributor to improving our knowledge of the molecular and translational pathomechanisms underlying LBBB. Methods A total of 15 male pigs underwent RF catheter ablation of the LBB, guided by fluoroscopy and intracardiac ECG signals. Before LBBB induction and after a follow-up period of one week or three weeks, a thorough clinical characterization was performed including 12-lead ECG, echocardiography, and electroanatomical mapping. To further test the feasibility of cardiac resynchronization in our model, 3 pigs were implanted with a CRT pacemaker on day seven after LBB ablation. Results Upon LBB ablation, 12-lead ECGs displayed typical characteristics of LBBB like a QRS broadening, a QRS slurring in left lateral leads, and a change of the QRS axis. The QRS width was prolonged from 64.2±4.2 ms to 93,4±7.4 ms and the R wave peak time in V6 was extended from 19.3±3.9 ms to 42.7±4.2 ms. Cardiac electromechanical asynchrony was further confirmed by echocardiography, where the appearance of a septal flash, the prolongation of the septal to posterior wall movement delay and extended left ventricular as well as interventricular electromechanical delays were documented. Electroanatomical mapping demonstrated a shift of the left ventricular breakthrough site. After LBBB-induction, left ventricular activation times, defined as the average of the maximum 10 % of activation times minus the average of the minimum 10 % of activation times were significantly prolonged from 36.3±7.1 ms to 60.8±10.2 ms while right ventricular activation times remained unchanged. Finally, RF-induced LBBB persisted over an observation period of three weeks. The pigs that underwent CRT showed a reduction in QRS duration from 99.1±8.2 ms on day seven after LBBB induction to 75.5±8.2 ms and echocardiography provided additional evidence of successful resynchronization. Conclusions In summary, our porcine large animal model accurately recapitulates the electrical and electromechanical phenotype, observed in LBBB patients. This closed-chest model of LBBB therefore provides an experimental platform to study both, molecular and translational characteristics of cardiac electromechanical asynchrony in a reproducible and clinically relevant setting.

Left bundle fascicular versus left bundle trunk pacing: a comparison of their electrical synchrony parameters

Abstract Background Variation in human left bundle branch (LBB) anatomy has a significant effect on the sequence of left ventricular depolarization. However, little is known regarding the electrophysiological characteristics of pacing different LBB fascicles. Objective We aimed to analyse the different electrocardiographic characteristics of LBB pacing (LBBP) attending to the site of pacing at the LBB system. Methods In consecutive patients with confirmed LBBP, we distinguished left bundle trunk capture (LBTP) from any LB fascicular pacing (LBFP) based on the presence of LB potentials and paced QRS morphologies in the frontal axis. We compared them regarding procedure, LBBP criteria and electrical synchrony parameters. Results 309 patients with LBBAP attempt were analysed, with 290 successful cases. Among them, 223 were considered LBBP. 25 cases without a proper ECG tracing in the frontal leads were excluded from the final analysis. 173 patients with LBFP were compared to 25 patients with LBTP. There were not significant differences in the baseline characteristics, but the native QRS width was higher in the LBFP group (119.2±31.4 ms vs 103.2±20.5 ms; p=0.014). Regarding the procedural duration, there was not any significant difference. QRS transition criteria (80.0% vs 61.8%; p=0.077), selective LBBP (40.0 vs 21.5%; p=0.101), paced QRS width (110.3±16.8 ms vs 115.4±14.9 ms; p=0.117), V6-RWPT (79.2±10.7 ms vs 75.3±9.7 ms; p=0.068) and interpeak interval (42.5±19.1 ms vs 45.7±12.9 ms; p=0.282) were not significantly different between LBTP and LBFP. All short-term complications occurred in LBFP, mainly driven by septal perforations (n=23), without any difference in the pacing parameters. Among the LBFP subgroups, left septal (LSFP) and posterior (LPFP) fascicles were significantly more prevalent than left anterior (LAFP) in LBFP (46.8%, 41.0% and 12.2% respectively). Regarding the baseline characteristics, the procedural performance and the electrical synchrony parameters, there were not significant differences among the LBFP subgroups. Only aVL-RWPT was longer when the posterior fascicle was paced, and shorter in LAFP (84.7±13.3 ms vs 64.9±15.1 ms; p&amp;lt;0.001). The consecution of LSFP was more frequent with lumenless leads (97.5% vs 83.1% vs 81.0%, p=0.006). Attending to the LBBP criteria, transition criteria were more frequent in LSFP (71.6% vs 53.2%; p=0.039), along with selective capture (29.6% vs 16.3%%; p=0.042), and transition during pacing manoeuvres (82.8% vs 69.2% vs 40.0%; p=0.013). Conclusions LBFP is much more prevalent than LBTP in unselected consecutive patients with LBBP. LBFP seems more feasible, and as good as LBTP in terms of electrical synchrony and pacing safety, without significant differences among the LBFP subgroups. The recognition of the different paced QRS morphologies in the frontal axis, along with the analysis of the Purkinje potentials, arise as important tools to fully understand the whole map of LBBAP.Left bundle branch area sites of pacingProcedural and LBBP characteristics

Tailored electrocardiographic-based criteria for different pacing locations within the left bundle branch

Abstract Background QRS morphology transition criteria are the current gold-standard for the confirmation of LBB capture during LBBAP, but they are seen in less than 40% of procedures. Thus, physiologic ECG-based criteria are widely used to confirm LBBP. Current CSP guidelines recommend 100% specific cut-off points (V6-RWPT&amp;lt; 75 ms or V6-V1 interpeak interval &amp;gt; 44 ms) to confirm LBB capture but these values were never validated for different pacing locations. Purpose To describe diagnostic performance of paced V6-RWPT, V6-V1 interpeak interval and paced aVL-RWPT for different pacing sites within the LBB and to determine 100% specific values at each pacing location. Methods Consecutive patients with an attempt of LBBAP procedure were screened at our institution. Only patients with unequivocal LBB capture according to QRS transition criteria were selected. The study population was divided into subgroups according to the site of pacing (left bundle trunk pacing (LBTP), left septal fascicular pacing (LSFP), left posterior fascicular pacing (LPFP) and left anterior fascicular pacing (LAFP)). Results 147 patients with unequivocal LBB capture were analyzed (mean age 77.5±10.4 years, 50.3% male, 95.2% preserved LVEF, and 94.6% with bradycardia pacing indication. Non-diseased LBB (narrow QRS complex or isolated RBBB) was present in 70.7% of patients (n=104). Left fascicular pacing was the most common type of LBB capture achieved (82.8%) while LBTP accounted for 17.2% of cases. LFSP was the most frequent fascicular capture (54.1%), followed by LPFP (36%) and LAFP (9.9%). The ROC curves of paced V6-RWPT for the differential diagnosis of LBBP and LVSP showed good diagnostic performance among different pacing locations (figure 1). The highest AUC were found in patients with LSFP and LAFP (94.9% and 93.2%, respectively). The 100% V6-RWPT specific cut-off value was 68 ms (SN) 25%) in LPFP, 75 ms (SN 56.5%) in LBTP, 79.5 ms (SN 75%) in LSFP and 81 ms (SN 90.9%) in LAFP (figure 1). The diagnostic performance of V6-V1 interpeak interval was also good among study subgroups (figure 2). The highest AUC were found in patients with LBTP and LSFP (89% and 89.4%, respectively). The 100% V6-V1 interpeak interval specific cut-off value was 35.5 ms (SN 65.2%) in LBTP, 53.5 ms (SN 32.5%) in LPFP, 46 ms (SN 44.1%) in LSFP and 41 ms (SN 63.6%) in LAFP (figure 2). Diagnostic performance of paced aVL-RWPT was good among study subgroups (AUC of 93% in LAFP, 80.1% in LBTP, 84% in LSFP and 77.5% in LPFP). The 100% specific cut-off values for LBBP confirmation were 74 ms, 74.5 ms and 73.5 ms for LBTP, LSFP and LPFP patients, respectively, but it was 68 ms in patients with LAFP (SN 66.7%). Conclusions Diagnostic performance of the physiologic ECG-based criteria for the discrimination of LBBP, was good among different pacing locations within the LBB. Tailored cut-off values depending on the site of pacing might be useful additional tools for better LBB capture confirmation.Figure 1Figure 2

An incremental energy stimulation test to predict success in left bundle branch capture

Abstract Introduction Left bundle branch (LBB) stimulation is guided by fluoroscopic projections and electrocardiographic criteria limited by positional variations. Purpose To evaluate an incremental energy stimulation test (IEST) to optimize success. Methods Prospective, non-randomized experimental study for proof-of-concept analysis (N=23), consisting on: (i) stimulation at three locations at the high, middle and low right mid-ventricular septum (right oblique 30o); and (ii) continuous unipolar stimulation (lumenless fixed helix electrode) at each location with increasing outputs (2 volt x 0.5 ms up to 10 vol x 1.5 ms). The final position for lead penetration was made by the operator blinded to the results of the IEST. Results IEST shortened the S-LVAT (δ-S-LVAT) up to 6.4±5 ms (range 0 to 18 ms), 8±8 ms (range 0 to 36 ms) and 5.5±5 ms (range 0 to 20 ms) respectively for high, mid, and low sites (Figure, panel A and B). There was not observed any paired correlation between the magnitude of the δ-S-LVAT at the three different positions (Pearson 0.36, 0.12 and 0.22; p= 0.1, 0.6 and 0.4 respectively), suggesting that the δ-S-LVAT is site specific. The final position for lead penetration was medium in 17 cases vs low in 6 cases. The low-output S-LVAT interval at the final position before lead penetration was positively correlated with the final S-LVAT achieved after lead penetration (Pearson 0.44; p=0.04), but the magnitude of the correlation increased with the high-output S-LVAT interval (Pearson 0.57; p=0.006) suggesting a better prediction performance (Figure, panel C). A complex relationship was observed where higher δ-S-LVAT values were associated with shorter S-LVAT after penetration and final position of the lead. In fact, for cases with low-output S-LVAT interval &amp;gt; 100 ms, the δ-S-LVAT significantly correlated with S-LVAT after penetration and final position of the lead (Pearson -0.61; p=0.026). Conclusions IEST lead to a site-specific shortening of the S-LVAT, pointing to optimized positions for LBB pacing. The technique provides with additional diagnostic criteria to determine the better site for lead penetration.

Comprehensive approach and real-life patient registry: exploring management and patient outcomes in dealing with septal complications during left bundle branch area pacing

Abstract Background Left bundle branch area pacing (LBBAP) aims to capture the left bundle branch (LBB) through a transventricular septal approach. Pacing this left-sided conduction system requires deep septal lead positioning due to the subendocardial course of the LBB at the left-sided septum. Such deep septal lead deployment might cause iatrogenic septal complications and collateral damage to septal vasculature. Purpose This study aims to explore both the immediate and medium-term clinical results of septal complications during LBBAP in a large single-center patient cohort, while also entailing the management strategies employed to address these issues. Methods The LBBAP implant procedure was conducted using a lumen-less (LLL) or a stylet-driven pacing lead (SDL) and a dedicated delivery sheath. Septal complications encompassed septal perforations into the left ventricular cavity, septal coronary artery or venous fistulas (SCAF/SCVF) and septal hematomas, which were identified using fluoroscopy, echocardiography and electrocardiographic criteria. Enrollment included adult patients who required permanent pacing for bradycardia or heart failure indications in whom LBBAP was attempted between November 2019 and October 2023. Results The study enrolled 508 patients, with a mean age of 71±16 years and 60% male. Successful LBBAP was achieved in 471 (93%) patients. Septal complications during implant occurred in 24/508 patients (5%), including 19 cases of septal perforation (4%), 4 cases of SCAF (0.8%) and 1 case of SCVF (0.2%). All cases of septal perforation were identified during the implantation procedure and were effectively managed by lead retraction and septal repositioning, eventually resulting in successful LBBAP. With regard to SCAF and SCVF, all but one were detected via septography during implantation and were addressed by lead repositioning. One case of SCAF was detected the day after implant on post-procedural echocardiography and was conservatively managed without lead repositioning. No ventricular septal defects were observed on echocardiography, either immediately or during follow-up (mean follow-up period of 25±12 months). Septal kinetics remained unaffected on follow-up echocardiography (mean follow-up 23±9 months), and all SCAF cases healed spontaneously. Additionally, no septal hematomas were observed. Importantly, no late septal perforations occurred during the follow-up period. Furthermore, no cardiac ischemia or thoracic discomfort were reported among any of these patients. Conclusions The findings of this study underscore the safety of deep septal lead deployment in LBBAP, and highlight that LBBAP provides near physiologic pacing with a high success rate and a low incidence of septal complications. The majority of these complications are promptly detected during the implant procedure and often remain asymptomatic. Furthermore, they exhibit spontaneous healing without enduring persistent septal harm throughout the follow-up period.

Left bundle branch area pacing in the setting of cardiac amyloidosis: a case series

Abstract Background Cardiac amyloidosis (CA) is a highly prevalent cause of congestive heart failure. It often requires cardiac pacing due atrioventricular conduction (AV) system disorders, often with cardiac resynchronization (CRT) to prevent development/deterioration of left ventricular (LV) dysfunction. Left bundle branch area pacing (LBBAP) is an emerging alternative to CRT, offering a strict physiological LV activation and very limited use of iodinated contrast. The feasibility of LBBAP in CA is considered limited due to the presence of septal pseudohypertrophy which theoretically limits left-sided conduction system engagement. Purpose To evaluate the feasibility and effectiveness of LBBAP in cardiac amyloidosis. Methods Consecutive patients with CA (both light-chain -AL- or wild-type transtiretin -wtATTr) with a pacing indication for AV conduction disorders were enrolled. Patients underwent baseline echocardiographic examination. LBBAP was achieved by means of stylet-driven leads advanced transeptally (right ventricle (RV) to LV) via dedicated delivery systems, with continuous monitoring of 12-lead electrocardiographic morphology and impedance until a typical QRS morphology in V1 was obtained (usually rSr’ or Sr’). Standard measures for left bundle (LB) capture were used (stimulus to peak R in V6 – S-RV6, V6-V1 interpeak interval, presence of transition in these measures during threshold testing, presence of fascicular signal during spontaneous QRS). Results Between January 2022 and June 2023, among 63 patients undergoing LBBAP, 7 patients (11%) had CA, 2 AL (28%) and 5 (72%) wtATTR. Patients were prevalently old (78±7 y) males (6, 85%); LV mean septal thickness was 17±2 mm (min 16, max 20 mm) and mean LV ejection fraction (LVEF) was 45±6%. Indications were PR prolongation in 3, bradycardic atrial fibrillation and LB branch block (LBBB) in 2, primary LBBB in 1 and chronic RV pacing in 1. Baseline QRS duration was 145±47 ms (QRS&amp;lt;120 ms: 97±15 ms, QRS&amp;gt;120 ms: 182±13 ms). LBBAP success was 100%. Fascicular electrograms were observed in ¾ of patients without LBBB; S-RV6 interval was 74 ±11 ms (³70 ms in 3), RV6-RV1 interpeak interval was 47±9 ms (³ 30 ms in 6 patients). DQRS in baseline broad QRS was -52 ms and +32 ms in narrow. No complications were observed. Over a short follow up of 6 months, an increase in average LVEF was observed (LVEF at 6 months: 51±3%, p&amp;lt;0.05). Conclusions In patients with CA, LBBAP is easily achievable with stylet-driven systems with frequent selective engagement of conduction system. QRS narrowing in baseline broad QRS is significant while QRS broadening in baseline narrow QRS is limited. Early results regarding follow-up of surrogate endpoint such as LVEF are promising.

Left bundle branch pacing and cardiac remodeling in HF patients with type 2 diabetes mellitus: epigenetic pathways and clinical outcomes.

Left bundle branch (LBB) pacing could achieve cardiac resynchronization therapy (CRT) in patients who cannot be resynchronized via the placement of the left ventricle (LV) lead into the coronary sinus. LBB pacing could improve cardiovascular outcomes in heart failure (HF) patients with LBB block who are affected by type 2 diabetes mellitus (T2DM). LBB pacing could increase the number of CRT responders and lead to the best clinical outcomes in HF patients with T2DM, inducing cardiac remodeling and improving left ventricle ejection fraction (LVEF) via microRNA (miR) modulation. In a multicenter observational study, we enrolled 334 HF patients with LBB block and an indication to receive LBB pacing for CRT. In these patients, we evaluated the CRT responder rate, clinical outcomes, and miR expression at 1 year of follow-up. At 1 year of follow-up, we had 223 responders (66.8%), 132 hospitalizations for HF (39.5%), 24 cardiac deaths (7.2%), and 37 all-cause deaths (11.1%), with a higher rate of HF hospitalizations (77 (69.4%) vs 55 (24.7%), p < 0.05), and cardiac deaths (13 (11.7% vs 11 (4.9%), p < 0.05) in non-responders vs responders. At the end of follow-up, we found the lowest expression of miR-26, miR-29, miR-30, miR-92, and miR-145 in LBB-pacing non-responders vs responders (p < 0.05), and a direct correlation between miR-30 (0.340, [0.833-1.915]; p 0.001), the 6-minute-walking test (6MWT; 0.168, [0.008-0.060]; p 0.011), angiotensin-receptor-neprilysin inhibitors (ARNI; 0.157, [0.183-4.877]; p 0.035), sodium-glucose-transporter-2 inhibitors (0.245, [2.242-7.283]; p 0.001), and LVEF improvements. C reactive protein (CRP) inversely correlated with LVEF improvement (-0.220, [-(0.066-0.263)]; p 0.001). ARNI (1.373, CI 95% [1.007-1.872], p 0.045), miR-30 (2.713, CI 95% [1.543-4.769], p 0.001), and 6MWT (1.288, CI 95% [1.084-1.998], p 0.001) were predictors of LBB pacing responders at 1 year of follow-up. LBB-pacing responders evidenced miR modulation, which was linked to significant improvement of the cardiac pump. Specifically, miR-30 was linked to cardiac pump improvement and predicted responders at 1 year of follow-up in patients with T2DM.

Safety of One-Stage Atrioventricular Junction Ablation after Pacemaker Implantation for Left Bundle Branch Pacing

Safety of One-Stage Atrioventricular Junction Ablation after Pacemaker Implantation for Left Bundle Branch Pacing