Left bundle branch pacing for symptomatic bradycardia: Implant success rate, safety, and pacing characteristics

Predictors of failed left bundle branch pacing implant in heart failure with reduced ejection fraction: Importance of left ventricular diameter and QRS morphology

BACKGROUND

Left bundle branch pacing (LBBP) is considered an alternative to cardiac resynchronization therapy (CRT). However, LBBP is not suitable for all patients with heart failure.

OBJECTIVE

The aim of our study was to identify predictors of unsuccessful LBBP implantation in CRT candidates.

METHODS

A cohort of consecutive patients with indications for CRT were included. Clinical, echocardiographic, and electrocardiographic variables were prospectively recorded.

RESULTS

A total of 187 patients were included in the analysis. LBBP implantation was successful in 152 of 187 patients (81.2%) and failed in 35 of 187 patients (18.7%). The causes of unsuccessful implantation were unsatisfactory paced QRS morphology (28 of 35 [80%]), inability to screw the helix (4 of 35 [11.4%]), lead instability (2 of 35 [5.7%]), and high pacing thresholds (1 of 35 [2.8%]). The left ventricular end-diastolic diameter (LVEDD), non-LBBB (left bundle branch block) QRS morphology, and QRS width were predictors of failed implantation according to the univariate analysis. According to the multivariate regression analysis, LVEDD (odds ratio 1.31 per 5-mm increase; 95% confidence interval 1.05-1.63 per 5-mm increase; P = .02) and non-LBBB (odds ratio 3.07; 95% confidence interval 1.08-8.72; P = .03) were found to be independent predictors of unsuccessful LBBP implantation. An LVEDD of 60 mm has 60% sensitivity and 71% specificity for predicting LBBP implant failure.

CONCLUSION

When LBBP was used as CRT, LVEDD and non-LBBB QRS morphology predicted unsuccessful implantation. Non-LBBB triples the likelihood of failed implantation independent of LVEDD. Caution should be taken when considering these parameters to plan the best pacing strategy for patients.

Left bundle branch area pacing using a stylet-driven, retractable-helix lead: Short-term results from a prospective multicenter IDE trial (the BIO-CONDUCT study)

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.

Current role of Conduction System Pacing in Patients Requiring Permanent Pacing

His bundle pacing (HBP) and left bundle branch pacing (LBBP) are novel methods of pacing directly pacing the cardiac conduction system. HBP while developed more than two decades ago, only recently moved into the clinical mainstream. In contrast to conventional cardiac pacing, conduction system pacing including HBP and LBBP utilizes the native electrical system of the heart to rapidly disseminate the electrical impulse and generate a more synchronous ventricular contraction. Widespread adoption of conduction system pacing has resulted in a wealth of observational data, registries, and some early randomized controlled clinical trials. While much remains to be learned about conduction system pacing and its role in electrophysiology, data available thus far is very promising. In this review of conduction system pacing, the authors review the emergence of conduction system pacing and its contemporary role in patients requiring permanent cardiac pacing.

Comparison of clinical outcomes between transthoracic echocardiography- and X-ray-guided left bundle branch pacing for bradycardia: A randomized controlled trial

INTRODUCTION

Left bundle branch pacing (LBBP) is a physiological pacing modality. However, the long procedure and fluoroscopy time of LBBP is still a problem. This study aims to compare the clinical outcomes between transthoracic echocardiography (TTE)- and X-ray-guided LBBP.

METHODS

This is a single-center, prospective, randomized controlled study. Consecutive patients who underwent LBBP in our team from June 2022 to November 2022 were enrolled. Procedure and fluoroscopy time, pacing parameters, electrophysiological and echocardiographic characteristics, as well as complications were recorded at implantation and during follow-up.

RESULTS

In this study, 60 patients were enrolled and divided into two groups: 30 patients were allocated to the X-ray group and the remaining 30 to the TTE group. There was no significant difference in the success rate between the two groups (86.7% vs. 76.7%, p = .317). The procedure time of TTE group was comparable to that of the X-ray group (9.0 vs. 12.0 min, p = .063). However, the fluoroscopy time in the TTE group was significantly lower than that of the X-ray group (2.5 vs. 5.0 min, p = .002). There were no statistically significant differences in pacing parameters, electrophysiological and echocardiographic characteristics, or complications between the two groups at implantation and during follow-up.

CONCLUSION

TTE-guided LBBP is a feasible and safe method. Compared with X-ray, TTE showed a comparable success rate and procedure time, but it could significantly reduce the fluoroscopy time of LBBP.

Clinical and Electrophysiological Outcomes of Left Bundle Area Pacing Compared to Biventricular Pacing: An Updated Meta-analysis

Left bundle branch area pacing (LBBAP) is a novel pacing strategy that uses the conduction system distal to the left bundle branch block level for direct activation of the left bundle and right ventricular myocardium. Our meta-analysis compared the structural, electrophysiological, clinical, and procedural outcomes of LBBAP and biventricular pacing (BVP). The meta-analysis included two randomized controlled trials and showed significant reductions in the left ventricular (LV) systolic and diastolic volumes with LBBAP compared to BVP, together with statistically significant reductions in the QRS duration, New York Heart Association (NYHA) functional class, and heart failure (HF) hospitalizations. The fluoroscopic time was also significantly shorter in the LBBAP group. However, no significant change in the LV ejection fraction was noted. Procedural complications were slightly higher in the LBBAP group, albeit not to a statistically significant degree. Our findings suggest that LBBAP may be a superior alternative to standard BVP in improving the structural, electrophysiological, and clinical components of cardiomyopathy, including the NYHA class and HF hospitalizations. LBBAP is a more physiological pacing strategy that results in normal ventricular activation and may be a viable alternative to BVP for cardiac synchronization therapy.

Left bundle branch area pacing versus conventional pacing in patients with advanced atrioventricular conduction abnormalities: a prospective cohort study

BACKGROUND

Left bundle branch area pacing (LBBAP) is an emerging pacing method that may prevent the deleterious effects of right ventricular pacing. The aim of this study is to compare the effects of LBBAP with right ventricular septal pacing (RVSP) in patients with advanced atrioventricular conduction abnormalities and preserved left ventricular ejection fraction.

METHODS

The effect of pacing was evaluated by echocardiographic indices of dyssynchrony, including global myocardial work efficiency (GWE) and peak systolic dispersion (PSD). The primary endpoint was GWE postprocedural, at 3, 6, and 12 months after the procedure.

RESULTS

Twenty patients received LBBAP and 18 RVSP. Complete follow-up was accomplished in 37 patients (97.4%) due to the death of a patient (RVSP arm) from nonrelated cause. GWE was significantly increased in the group of LBBAP compared to RVSP at all time points (90.8% in LBBAP versus 85.8% in RVSP group at 12 months, p = 0.01). PSD was numerically lower in the LBBAP arm at all time points, yet not statistically significant (56.4 msec in LBBP versus 65.1 msec in RVSP arm at 12 months, p = 0.178). The implantation time was increased (median 93 min in LBBAP versus 45 min in RVSP group, p < 0.01), along with fluoroscopy time and dose area product (DAP), in the arm of LBBAP. There were no severe perioperative acute complications in either group.

CONCLUSIONS

LBBAP is an emerging and safe technique for patients with a pacing indication. Despite the longer procedural and fluoroscopy time, as well as higher DAP, LBBAP seems to offer better left ventricular synchrony compared to RVSP, according to GWE measurements.

Is left bundle branch pacing (LBBP) associated with better depolarization and repolarization kinetics than right ventricular mid septal pacing (RVSP)? - Comparison of frontal QRS -T angle in patients with LBBP, RVSP and normal ventricular conduction

AIMS

To assess the frontal QRS- T angle (f QRS- T angle) in patients with left bundle branch pacing (LBBP) as compared to right ventricular mid septal pacing (RVSP) implanted for symptomatic high degree atrioventricular (AV) block and to compare with control subjects with normal ventricular conduction (CSNVC) METHODS: A total of one-fifty subjects were chosen (50 patients with LBBP, 50 patients with RVSP and 50 CSNVC). The indication for pacemaker implantation was symptomatic high degree AV block. Baseline clinical and electrocardiogram (ECG) parameters like QRS duration (QRSD), QRS axis and f QRS-T angle and Ejection Fraction (EF) were assessed. f QRS-T angle was measured as the difference between the computerised mean frontal QRS and T wave axes in the limb leads. If the difference between the QRS axis and T-wave axis exceeds 180°, then the resultant QRS-T angle would be calculated as 360° minus the absolute angle to obtain a value between 0° and 180°. Baseline, immediate post procedural and 6 month follow up (f/u) ECGs and EF were chosen for the analysis.

RESULTS

Patients who underwent LBBP had significantly shorter paced QRSD than patients who had undergone RVSP (112 ± 12 ms vs 146 ± 13 ms; 95 % confidence interval (CI): 43, -31; p<0.001). There was no significant difference in the QRSD before and after LBBP. The QRSD before and after pacing in RVSP was 111 ± 27 ms and 146 ± 13 ms; 95 % CI: 43, -28; p < 0.001. The QRSD in control patients with NVC was 82.94 ± 9.59 ms. RVSP was associated with wider f QRS-T angle when compared with LBBP (103 ± 53° vs 82 ± 43°; 95 % CI: 39, -1.0; p = 0.037). The baseline and immediate post procedure f QRS-T angle in LBBP was 70 ± 48° and 82 ± 43°; 95 % CI: 31, 5.3; p = 0.2. At 6 months f/u, the f QRS-T angle was 61 ± 43°; 95 % CI: 8.5, 35; p=0.002. The baseline and immediate post procedure f QRS-T angle in RVSP was 67 ± 51° and 103 ± 53°; 95 % CI: 54, -17; p < 0.001. At 6 months f/u, the f QRS-T angle in RVSP group was 87 ± 58°; 95 % CI: 2.6, 29; p = 0.020. The f QRS T angle in control patients with NVC was 24 ± 16°. When subgroup analysis was done the difference in the f QRS-T angle was significant between RVSP and LBBP groups only in patients who had wide QRS escape. The mean LVEF at 6-month follow-up in LBBP vs RVSP was 61 ± 3.7 % vs 57.1 ± 7.8 %; 95 % CI:1.48, 6.32, p = 0.002. In the RVSP group, three patients developed pacing induced cardiomyopathy (PIC) whereas no patients in the LBBP group developed PIC at 6-month follow-up; p=0.021. One patient with PIC had deterioration of functional status with new onset HF symptoms. The patient symptoms improved with medical therapy and needed no hospitalisation. The patient declined further interventions including upgradation to CRT or LBB pacing. No deaths or ventricular arrhythmias were observed during the study period.

CONCLUSION

LBBP is associated with narrower f QRS-T angle as compared to RVSP both at post implant period and at 6 month f/u period. These findings might be due to the more physiological depolarization and repolarization kinetics associated with LBBP. RVSP was associated with 6 % incidence of PIC. Hence wide f QRS-T angle might be a predictor of PIC.

An individualized criterion for left bundle branch capture in patients with a narrow QRS complex

BACKGROUND

Left bundle branch (LBB) pacing (LBBP) is a physiological pacing; however, the accuracy of current electrocardiographic criteria for LBBP remains inadequate.

OBJECTIVE

The purpose of this study was to establish a novel individualized criterion to improve the accuracy of LBBP determination in patients with a narrow QRS complex.

METHODS

Patients in whom both LBBP and left ventricular septal pacing (LVSP) were acquired during operation were enrolled. LBB conduction time (LBBCT) was measured from LBB potential (LBBpo) to intrinsic QRS onset. LBBpo-V6RWPT, Native-V6RWPT, and Paced-V6RWPT were respectively measured from LBBpo, intrinsic QRS onset, and stimulus to R-wave peak in V6. ΔV6RWPT was the difference value between Paced-V6RWPT and Native-V6RWPT. The accuracy of ΔV6RWPT criterion for determining LBBP was evaluated.

RESULTS

In all 71 enrolled patients, ΔV6RWPT was <30 ms during LBBP (21.3 ± 4.6 ms; range 9.3-28.3 ms) but was >30 ms during LVSP (38.5 ± 4.6 ms; range 31.1-47.0 ms). The probability distribution of ΔV6RWPT was well separated between LBBP and LVSP. Sensitivity and specificity of the novel criterion of "ΔV6RWPT <30 ms" for determining LBBP both were 100%. However, the optimal cutoff value of Paced-V6RWPT for validation of LBBP was 64.2 ms, and sensitivity and specificity were 84.5% and 97.2%, respectively. Paced-V6RWPT during LBBP was equivalent to LBBpo-V6RWPT in all patients. There was a strong linear correlation between Native-V6RWPT and LBBpo-V6RWPT (r = 0.796; P <.001).

CONCLUSION

ΔV6RWPT could be an accurate individualized criterion for determining LBB capture with high sensitivity and specificity and was superior over the fixed Paced-V6RWPT criterion.

Left bundle branch area pacing improving the left atrial outcomes in pace-dependent patients compared with right ventricular outflow tract septal pacing

BACKGROUND

Recent studies suggested that the left bundle branch area pacing (LBBAP) has a better efficacy to reduce QRS duration and produce a lower pacing threshold than the conventional right ventricular outflow tract septal pacing (RVOP), which resulted in a better cardiac function and ventricular synchronization. However, whether the LBBAP has a better efficacy in improving left atrial structure, function in pace-dependent patients compared with RVOP has not been well studied.

OBJECTIVE

The purpose of this study was to compare the atrial outcomes of pace-dependent patients who received LBBAP or RVOP procedures.

METHODS AND RESULTS

A total of 72 patients (including II° AVB, high AVB, and III° AVB, excluding atrial fibrillation patients with atrioventricular block) consecutively enrolled in this single-center prospective clinical study and randomly assigned to the RVOP group and the LBBP group with 36 patients. All patients were pace-dependent. The changes in echocardiogram, speckle-tracking echocardiography, brain natriuretic peptide (BNP), and 6-min walking distance were documented and compared between two groups at baseline, 7 days, 1, 3, and 6 months after the implantation. There were no significant differences in baseline characteristics between the two groups. The results of the study were as following: (1) left atrial structure index: Our study indicated that there are no significant differences in left atrial anteroposterior dimension (LAAPD), left atrial superoinferior dimension, and left atrial mediolateral dimension between two groups. While the LAAPD in the LBBAP group was significantly reduced at 6 months after implantation ([38.22 ± 2.17] mm vs. [34.13 ± 1.59] mm, p < .05). (2) Left atrial strain index: We observed that the S% was significantly improved in both groups at 3 and 6 months after implantation but more prominent in the LBBAP group at 6 months (36.94 ± 11.67 vs. 25.87 ± 8.93, p = .01). SRs, SRe were improved in the RVOP group at 6 months after implantation but was further significantly increased in the LBBAP group. Similarly, the SRa in the LBBAP group was significantly better than the RVOP group after 6 months (-2.11 ± 0.75 vs. -2.51 ± 0.70, p = .04). (3) Left atrial ejection index: LAEF% in the LBBAP group was significantly improved compared with the RVOP group (60.02 ± 1.88 vs. 53.65 ± 2.45, p = .047) and baseline (60.02 ± 1.88 vs. 49.68 ± 2.75, p < .05) at 6 months after the surgery. (4) Left ventricular ejection index: The LVEF% in the LBBAP group was significantly increased than the RVOP group after 6 months (69.14 ± 4.99 vs. 64.60 ± 4.84, p = .01) and the BNP level was significantly lower in the LBBAP group compared with the RVOP group at 7 days, 1, 3, and 6 months after implantation (p < .05). (5) 6-min walking distance: the 6-min walking distance was significantly increased at 3 and 6 months after implantation compared with that before (p < .05) in both groups, but was more prominent in LBBAP groups ([483.03 ± 11.02] m vs. [431.09 ± 10.69] m,p < .05).

CONCLUSION

Compared with the traditional RVOP, the LBBAP procedure increased left atrial myocardial stress as well as left atrial ejection in pace-dependent patients at follow-up to 6 months.

Evolving Concepts in Cardiac Physiologic Pacing in the Era of Conduction System Pacing

Cardiac physiologic pacing (CPP) has become a well-established therapy for patients with cardiomyopathy (left ventricular ejection fraction <35%) in the presence of a left bundle branch block. In addition, CPP can be highly beneficial in patients with pacing-induced cardiomyopathy and patients with existing cardiomyopathy expected to have a right ventricular pacing burden of >40%. The benefits of CPP with traditional biventricular pacing are only realized if adequate resynchronization can be achieved. However, left ventricular lead implantation can be limited by individual anatomic variation within the coronary venous system and can be adversely affected by underlying abnormal myocardial substrate (i.e., scar tissue), especially if located within the basal lateral wall. In the last 7 years the investigation of conduction system pacing (CSP) and its potential salutary benefits are being realized and have led to a rapid evolution in the field of cardiac resynchronization pacing. However, supportive evidence for CSP for patients eligible for cardiac resynchronization remains limited compared with data available for biventricular cardiac resynchronization, mostly derived from leading CSP investigative centers. In this review, we perform an up-to-date comprehensive review of the available literature on CPP.

Effects of coronary artery disease in patients with permanent left bundle branch area pacing: A retrospective study

Aims

Myocardial ischemia can affect traditional right ventricular (RV) pacing parameters, but it is unclear whether coronary artery disease (CAD) impact the pacing parameters and electrophysiological characteristics of left bundle branch area pacing (LBBaP) as a physiological pacing representative.

Methods

Patients who underwent coronary angiography (CAG) after/before the LBBaP procedure and underwent percutaneous coronary intervention after LBBaP procedure were divided into CAD group and Non-CAD group according to visual CAG. Pacing parameters and electrophysiological characteristics were recorded at LBBaP implantation. Multivariate logistic regression analysis was implemented to evaluate the association between CAD and higher capture threshold. Sensitivity analyses were conducted to verify result stability.

Results

A total of 176 patients met inclusion criteria (115 Non-CAD patients and 61 CAD patients) with a mean age of 71.1 ± 9.0 years. Compared with the Non-CAD patients, CAD patients had the higher capture threshold (0.67 ± 0.22 V vs. 0.82 ± 0.28 V, P < 0.001) and lower R-wave amplitude (12.5 ± 4.8 mV vs. 10.1 ± 2.7 mV, P = 0.001). Moreover, CAD was independently associated with higher capture threshold (adjusted Odds ratio (OR) 3.418, 95% confidence interval (CI): 1.621-7.206, P = 0.001), which was further validated through sensitivity analyses.

Conclusion

Patients without CAD might have safer pacing parameters in the LBBaP procedure. Besides, CAD might be the risk factor of capture threshold increase during permanent LBBaP implantation.

Outcomes of dual-chamber implantable cardioverter defibrillator for left bundle branch area pacing: A systematic review of literature

OBJECTIVE

This systematic review of literature aimed to evaluate the safety and efficacy of dual-chamber ICDs for LBBAP in patients with left bundle branch block (LBBB).

METHODS

Digital databases were searched systematically to identify studies reporting the left bundle branch area pacing (LBBAP) with implantable cardioverter defibrillator (ICD) placement in patients with LBBB. Detailed study and patient-level baseline characteristics including the type of study, sample size, follow-up, number of cases, age, gender, and baseline characteristics were abstracted.

RESULTS

In a total of three studies, 34 patients were included in this review. There was a significant improvement reported in QRS duration in all studies. The mean QRS duration at baseline was 170 ± 17.4 ms, whereas the follow-up QRS duration at follow-up was 121 ± 17.3 ms. Two studies reported a significant improvement of 50% in LVEF from baseline. No lead-related complications or arrhythmic events were recorded in any study. The findings of the systematic review suggest that dual-chamber ICD for LBBAP is a promising intervention for patients with heart conditions.

CONCLUSION

The procedure offers significant improvements in QRS duration and LVEF, and there were no lead-related complications or arrhythmic events recorded in any of the studies.

Autothreshold algorithm feasibility and safety in left bundle branch pacing

AIMS

Autothreshold algorithms enable remote monitoring of patients with conventional pacing, but there is limited information on their performance in left bundle branch pacing (LBBP). Our objective was to analyse the behaviour of the autothreshold algorithm in LBBP and compare it with conventional pacing and manual thresholds during initial device programming (acute phase), after 1-7 days (subacute), and 1-3 months later (chronic).

METHODS AND RESULTS

A prospective, non-randomized, single-centre comparative study was conducted. Consecutive patients with indication for cardiac pacing were enrolled. Implants were performed in the left bundle branch area or the right ventricle endocardium at the discretion of the operator. Left bundle branch pacing was determined according to published criteria. Autothreshold algorithm was activated in both groups whenever allowed by the device. Seventy-five patients were included, with 50 undergoing LBBP and 25 receiving conventional pacing. Activation of the autothreshold algorithm was more feasible in later phases, showing a favourable trend towards bipolar pacing. Failures in algorithm activation were primarily due to insufficient safety margins (82.8% in LBBP and 90% in conventional pacing). The remainder was attributed to atrial tachyarrhythmias (10.3% and 10%, respectively) and electrical noise (the remaining 6.9% in the LBBP group). In the LBBP group, there were not statistically significant differences between manual and automatic thresholds, and both remained stable during follow-up (mean increase of 0.50 V).

CONCLUSION

The autothreshold algorithm is feasible in LBBP, with a favourable trend towards bipolar pacing. Automatic thresholds are similar to manual in patients with LBBP, and they remain stable during follow-up.

The Zwolle experience with left bundle branch area pacing using stylet-driven active fixation leads

AIMS

Left bundle branch area pacing (LBBAP) is a novel physiological pacing modality and is regarded as a viable alternative to His bundle pacing. LBBAP has mostly been performed with the lumen-less permanent pacing lead (SelectSecure™ Model 3830, Medtronic, Inc.) with a fixed helix. The aim of this study was to compare the non-stylet driven lumen-less lead (LLL) (Medtronic 3830) with a standard stylet-driven active fixation lead (SDL) (Tendril™ STS Model 2088TC-38, Abbott Laboratories) in terms of lead parameters, procedural success and complication rates.

METHODS

Patients receiving a LBBA pacemaker in the Isala Hospital, The Netherlands, were prospectively enrolled. The majority received a standard right ventricular (RV) lead as backup, the implanter chose between LLL and SDL for the LBBAP lead.

RESULTS

The study included 94 patients with a mean follow-up of 30 weeks. 30/31 LLL procedures were successful, compared with 62/63 in the SDL group. Including the participants that lost LBBAP during follow-up resulted in success rates of 90.3% for LLL versus 96.8% for SDL, P = 0.199. Mean number of deployments was significantly lower in the SDL group compared with the LLL group (2 ± 2.3 versus 4 ± 3.4, P = 0.005), implantation and procedural times were comparable. Pacing thresholds were low and remained low in both groups (at last follow-up 0.8 ± 0.30 V for LLL versus 0.6 ± 0.20 V for SDL). Complication rates did not differ significantly between both groups, P = 0.805.

CONCLUSION

LBBAP using SDL is feasible and has comparable success rates with lower number of deployments of the active fixation screw.

Left Bundle Branch Pacing: A Paradigm Shift in Physiological Pacing for Patients With Atrioventricular Block and Preserved Left Ventricular Systolic Function, A Systematic Review and Meta-analysis

His-Purkinje conduction system pacing (HPCSP) via His bundle pacing (HBP) and Left Bundle Branch Pacing (LBBP) offer a physiological approach to pacing by restoring normal ventricular activation. This meta-analysis compares the feasibility, outcomes, and success rates of HBP and LBBP in patients with atrioventricular block (AVB) and preserved left ventricular function. A systematic search identified studies comparing LBBP with HBP in AVB patients with preserved systolic function. Primary outcomes included QRS duration, success rates, pacing threshold, and improvement in R-wave amplitudes. Secondary outcomes were procedure time and fluoroscopy time. Random-effects models calculated odds ratios (OR) and mean differences (MD) with 95% confidence intervals (CI). Methodological quality was assessed using the Newcastle-Ottawa scale. Among 382 screened articles, seven observational studies involving 1035 patients were analyzed. The mean age was 69.9 years, the mean LVEF was 59.3%, and the average follow-up duration was 8.7 months. LBBP showed higher R-wave amplitudes (MD 7.88, 95% CI 7.26 to 8.50, P < 0.0001) and lower pacing thresholds (MD -0.64, 95% CI -0.81 to -0.47, P < 0.0001) compared to HBP. LBBP had shorter procedure time (MD -17.81, 95% CI -30.44 to -5.18, P = 0.006) and reduced fluoroscopy time (MD -5.39, 95% CI -8.81 to -1.97, P = 0.002). No significant differences were observed in QRS duration or success rates. LBBP offers advantages over HBP, including improved electrical activation, lower pacing thresholds, and shorter procedure and fluoroscopy times. Success rates and QRS duration reductions were comparable between LBBP and HBP. These findings support LBBP as a feasible and effective alternative to HBP in AVB patients with preserved systolic function.

Feasibility and safety of left bundle branch area pacing for patients with stable coronary artery disease

Aims

Stable coronary artery disease (CAD) is a prevalent comorbidity among patients requiring pacemaker implantation. This comorbidity may have an impact on the safety and prognosis of traditional right ventricular pacing (RVP). Left bundle branch area pacing (LBBaP) is a new physiological pacing modality. Our aim was to investigate the feasibility and safety of LBBaP in patients with the stable CAD.

Methods

This study included 309 patients with symptomatic bradycardia who underwent LBBaP from September 2017 to October 2021. We included 104 patients with stable CAD (CAD group) and 205 patients without CAD (non-CAD group). Additionally, 153 stable CAD patients underwent RVP, and 64 stable CAD patients underwent His-bundle pacing (HBP) were also enrolled in this study. The safety and prognosis of LBBaP was assessed by comparing pacing parameters, procedure-related complications, and clinical events.

Results

During a follow-up period of 17.4 ± 5.3 months, the safety assessment revealed that the overall rates of procedure-related complications were similar between the stable CAD group and the non-CAD group (7.7% vs. 3.9%). Likewise, similar rates of heart failure hospitalization (HFH) (4.8% vs. 3.4%, stable CAD vs. non-CAD) and the primary composite outcome including death due to cardiovascular disease, HFH, or the necessity for upgrading to biventricular pacing (6.7% vs. 3.9%, stable CAD vs. non-CAD), were observed. In stable CAD patients, LBBaP demonstrated lower pacing thresholds and higher R wave amplitudes when compared to HBP. Additionally, LBBaP also had significantly lower occurrences of the primary composite outcome (6.7% vs. 19.6%, P = 0.003) and HFH (4.8% vs. 13.1%, P = 0.031) than RVP in stable CAD patients, particularly among patients with the higher ventricular pacing (VP) burden (>20% and >40%).

Conclusion

Compared with non-CAD patients, LBBaP was found to be attainable in stable CAD patients and exhibited comparable mid-term safety and prognosis. Furthermore, in the stable CAD population, LBBaP has demonstrated more stable pacing parameters than HBP, and better prognostic outcomes compared to RVP.

A Comparative Assessment of Myocardial Work Performance during Spontaneous Rhythm, His Bundle Pacing, and Left Bundle Branch Area Pacing: Insights from the EMPATHY Study

BACKGROUND

Physiological pacing has gained significant interest due to its potential to achieve optimal hemodynamic response. This study aimed to assess left ventricular performance in terms of electrical parameters, specifically QRS duration and mechanical performance, evaluated as myocardial work. We compared His Bundle Pacing (HBP) and Left Bundle Branch Area Pacing (LBBAP) to evaluate their effects.

METHODS

Twenty-four patients with class I or IIa indications for pacing were enrolled in this study, with twelve patients undergoing HBP implantation and another twelve undergoing LBBAP implantation. A comprehensive analysis of myocardial work was conducted.

RESULTS

Our findings indicate that there were no major differences in terms of spontaneous and HBP activation in myocardial work, except for global wasted work (217 mmHg% vs. 283 mmHg%; p 0.016) and global work efficiency (87 mmHg% vs. 82 mmHg%; p 0.049). No significant differences were observed in myocardial work between spontaneous activation and LBBAP. Similarly, no significant differences in myocardial work were found between HBP and LBBAP.

CONCLUSIONS

Both pacing modalities provide physiological ventricular activation without significant differences when compared to each other. Moreover, there were no significant differences in QRS duration between HBP and LBBAP. However, LBBAP demonstrated advantages in terms of feasibility, as it achieved better lead electrical parameters compared to HBP (threshold@0.4 ms 0.6 V vs. 1 V; p = 0.045-sensing 9.4 mV vs. 2.4 mV; p < 0.001). Additionally, LBBAP required less fluoroscopy time (6 min vs. 13 min; p = 0.010) and procedural time (81 min vs. 125 min; p = 0.004) compared to HBP.

Comparison of ventricular synchrony in children with left bundle branch area pacing and right ventricular septal pacing

OBJECTIVE

This study aimed to determine the ideal pacing site in children by comparing the postoperative ventricular synchrony in children with left bundle branch area pacing and those with right ventricular septal pacing.

METHODS

This retrospective study included children with complete atrioventricular block who underwent permanent pacemaker implantation from March 2019 to August 2021. Patients were grouped according to their ventricular pacing site, the left bundle branch area pacing group and the right ventricular septal pacing group. Two-dimensional speckle tracking echocardiography was used to evaluate the ventricular synchrony.

RESULTS

Forty-eight children (median age, 2.7 years; interquartile range, 1.7-4.6 years) were included. The paced QRS duration in the left bundle branch area pacing group was significantly narrower than that in the right ventricular septal pacing group (100.2 ± 9.3 versus 115.4 ± 15.1 ms, p = 0.001). The median follow-up duration was 1.5 years (interquartile range, 1-2 years). At the last follow-up, the average capture threshold of the ventricular electrode in the left bundle branch area pacing group was lower than that in the right ventricular septal pacing group (0.79 ± 0.18 versus 1.20 ± 0.56 V, p = 0.008). The left ventricular intraventricular synchrony parameters in the left bundle branch area pacing group were better than those in the right ventricular septal pacing group (e.g. standard deviation of the time to peak longitudinal strain, 37.4 ± 4.3 versus 46.6 ± 8.2 ms, p = 0.000). The average interventricular mechanical delay time in the left bundle branch area pacing group was significantly shorter than that in the right ventricular septal pacing group (36.4 ± 14.2 versus 52.5 ± 22.7 ms, p = 0.016).

CONCLUSION

Compared with right ventricular septal pacing, left bundle branch area pacing in children produces a narrower QRS duration and better pacing and ventricular synchrony parameters postoperatively.

Predictors of implantation failure in left bundle branch area pacing using a lumenless lead in patients with bradycardia

Background

Left bundle branch area pacing (LBBAP) is a novel conduction system pacing technique. In this multicenter study, we aimed to evaluate the procedural success, safety, and preoperative predictors of procedural failure of LBBAP.

Methods

LBBAP was attempted in 285 patients with pacemaker indications for bradyarrhythmia, which were mainly atrioventricular block (AVB) (68.1%) and sick sinus syndrome (26.7%). Procedural success and electrophysiological and echocardiographic parameters were evaluated.

Results

LBBAP was successful in 247 (86.7%) patients. Left bundle branch (LBB) capture was confirmed in 54.7% of the population. The primary reasons for procedural failure were the inability of the pacemaker lead to penetrate deep into the septum (76.3%) and failure to achieve shortening of stimulus to left ventricular (LV) activation time in lead V6 (18.4%). Thickened interventricular septum (odds ratio [OR], 2.48; 95% confidence interval [CI], 1.15-5.35), severe tricuspid regurgitation (OR, 8.84; 95% CI, 1.22-64.06), and intraventricular conduction delay (OR, 8.16; 95% CI, 2.32-28.75) were preoperative predictors of procedural failure. The capture threshold and ventricular amplitude remained stable, and no major complications occurred throughout the 2-year follow-up. In patients with ventricular pacing burden >40%, the LV ejection fraction remained high regardless of LBB capture.

Conclusions

Successful LBBAP was affected by abnormal cardiac anatomy and intraventricular conduction. LBBAP is feasible and safe as a primary strategy for patients with AVB, depending on ventricular pacing.

Electrical Synchrony Optimization for Left Bundle Branch Area Pacing in Patients With Bradycardia and Heart Failure

Left bundle branch area pacing (LBBAP) has emerged as a promising physiological pacing modality. This study was designed to investigate the acute impact of the atrioventricular delay (AVD) on cardiac electrical characteristics and identify an optimal range of AVDs for LBBAP to achieve electrical atrioventricular and interventricular synchrony. Patients indicated for ventricular or biventricular pacing were studied during routine follow-ups at least 3 months after LBBAP implantation. Patients were excluded if they had a complete AV block or persistent atrial fibrillation. AVD was programed from 40 to 240 ms or until intrinsic conduction occurred. Optimal AVD was determined by the electrocardiography criteria, including QRS duration, reduced R-wave in lead V1, reduced notching or slurring in lateral leads, and more desirable precordial QRS transition. A total of 38 patients (age 68.7 ± 10.3 years; 16 male (42%); 18 dual-chamber pacemakers and 20 cardiac resynchronization therapy devices; average follow-up period 15.1 ± 10.2 months) were included. The fusion of LBBAP and intrinsic right ventricular conduction occurred in 21 patients with corresponding optimal AVD determined. A great proportion (∼85%) of the optimal AVDs ranged from 50% to 80% of the observed atrium-to-left bundle branch-sensing (A-LBBS) intervals. The linear correlation between the optimal AVD and corresponding A-LBBS interval (optimal AVD = 0.84 × [A-LBSs interval] - 36 ms) produced R = 0.86 and p <0.0001. In conclusion, AVD selection during LBBAP greatly impacted the ventricular electrical characteristics and the optimal AVD was linearly correlated with the corresponding A-LBBS interval.

Septal scar as a barrier to left bundle branch area pacing

BACKGROUND

The use of left bundle branch area pacing (LBBAP) for bradycardia pacing and cardiac resynchronization is increasing, but implants are not always successful. We prospectively studied consecutive patients to determine whether septal scar contributes to implant failure.

METHODS

Patients scheduled for bradycardia pacing or cardiac resynchronization therapy were prospectively enrolled. Recruited patients underwent preprocedural scar assessment by cardiac MRI with late gadolinium enhancement imaging. LBBAP was attempted using a lumenless lead (Medtronic 3830) via a transeptal approach.

RESULTS

Thirty-five patients were recruited: 29 male, mean age 68 years, 10 ischemic, and 16 non-ischemic cardiomyopathy. Pacing indication was bradycardia in 26% and cardiac resynchronization in 74%. The lead was successfully deployed to the left ventricular septum in 30/35 (86%) and unsuccessful in the remaining 5/35 (14%). Septal late gadolinium enhancement was significantly less extensive in patients where left septal lead deployment was successful, compared those where it was unsuccessful (median 8%, IQR 2%-18% vs. median 54%, IQR 53%-57%, p < .001).

CONCLUSIONS

The presence of septal scar appears to make it more challenging to deploy a lead to the left ventricular septum via the transeptal route. Additional implant tools or alternative approaches may be required in patients with extensive septal scar.

Conduction system pacing on track to replace CRT? Review of current evidence and prospects of conduction system pacing

Conduction system pacing (CSP) has been emerging over the last decade as a pacing option instead of conventional right ventricular (RV) pacing and biventricular (BiV) pacing. Numerous case reports, some observational studies and a few randomized control trials have looked at optimum pacing strategies for heart failure (HF) with left bundle branch block (LBBB) or cases where left ventricular (LV) dysfunction is anticipated due to chronic RV pacing (RVP). Evolution of pacing strategies from standard RVP to septal RVP, BiV pacing and now CSP have shown improving hemodynamic responses and possible ease of implantation of CSP systems. In this review article, we review the literature on the evolution of CSP and common scenarios where it might be beneficial.

Pacing of Specialized Conduction System

Right ventricular pacing for bradycardia remains the mainstay of pacing therapy. Chronic right ventricular pacing may lead to pacing-induced cardiomyopathy. We focus on the anatomy of the conduction system and the clinical feasibility of pacing the His bundle and/or left bundle conduction system. We review the hemodynamics of conduction system pacing, the techniques to capture the conduction system and the electrocardiogram and pacing definitions of conduction system capture. Clinical studies of conduction system pacing in the setting of atrioventricular block and after AV junction ablation are reviewed and the evolving role of conduction system pacing is compared with biventricular pacing.

Comparison of Pacing Performance and Clinical Outcomes Between Left Bundle Branch and His Bundle Pacing

BACKGROUND

Left bundle branch (LBBP) and His-bundle pacing (HBP) provide physiological ventricular activation.

OBJECTIVES

This study investigated differences in feasibility, device performance, and clinical outcomes between LBBP and HBP.

METHODS

Consecutive patients with LBBP and HBP from 2018 to 2021 in 2 centers were prospectively studied. The primary endpoint was optimal device performance during follow-up, defined as the presence of pacing thresholds <2.5 V, R-wave amplitude ≥5 V, and absence of conduction system pacing (CSP)-related complications. The secondary endpoint was the composite of heart failure hospitalizations or all-cause mortality.

RESULTS

Among 338 patients, 282 underwent successful CSP (119 HBP, 163 LBBP). Success rates, CSP-related complications, and need for reoperations did not differ between LBBP and HBP (P > 0.05). Pacing thresholds were lower, whereas R-wave amplitudes and lead impedance were higher in LBBP (P < 0.05). The primary endpoint was more frequent in LBBP than HBP (79% vs 34%; P < 0.001), with LBBP independently associated with 9-fold increased odds of optimal device performance (adjusted OR: 9.31; 95% CI: 5.14-16.86). LBBP was less likely to have increased pacing thresholds by >1 V (1% vs 19% HBP, P < 0.001). The secondary outcome was less frequent in LBBP than HBP (9% vs 24%, P = 0.001), with LBBP trending towards higher event-free survival (HR: 0.62; 95% CI: 0.31-1.23). The secondary outcome was independent of pacing burden or pacing indication.

CONCLUSIONS

Despite similar feasibility and safety profiles, LBBP confers additional benefits in pacing performance and reliability, shows trends towards improved survival compared to HBP, and should be the preferred first-line CSP modality of choice.

Optimization of the atrioventricular delay in conduction system pacing

INTRODUCTION

In patients receiving conduction system pacing (CSP), it is not well established how to program the sensed atrioventricular delay (sAVD), with respect to the type of capture obtained (selective, nonselective His-bundle [HB] capture or left bundle branch [LBB] capture). The aim of this study was to acutely assess the effectiveness of an electrophysiology (EP)-guided method for sAVD optimization by comparing it with the echocardiogram-guided optimization.

METHODS AND RESULTS

Consecutive patients undergoing HB or LBB pacing were enrolled. The EP-guided sAVD was defined as the sAVD leading to a PR interval of 150 ms on surface electrocardiogram (ECG). In HB pacing patients, EP-guided sAVD was obtained subtracting the time from the onset of the P wave on ECG to the local atrial electrogram (EGM) recorded by the atrial lead (right atrial sensing latency, RASL) and the His-ventricular interval from 150 ms; in LBB pacing patients, subtracting RASL from 150 ms. Transmitral flow assessment by pulsed wave Doppler was used to find the echo-optimized sAVD by a modified iterative method. The discordance between the EP-guided and the echo-optimized sAVD was recorded.

RESULTS

Seventy-one patients were enrolled: 12 with selective, 32 nonselective HB capture, and 27 LBB capture. Overall, the rate of concordance between the EP-guided and the echo-optimized sAVD was 71.8%, with no significant differences between the three groups.

CONCLUSION

In CSP patients, an optimal sAVD can be programmed, in more than 70% of cases, considering only simple EGM intervals to obtain a physiological PR interval on surface ECG.

Left bundle branch area pacing prevents pacing induced cardiomyopathy in long-term observation

BACKGROUND

Left bundle branch area pacing (LBBAP) is one of the methods to deliver conduction system pacing which potentially avoids the negative impact of conventional right ventricular pacing.

OBJECTIVE

To assess echocardiographic outcomes in a long-term observation in patients with LBBAP implemented for bradyarrhythmia indications.

METHODS AND RESULTS

A total of 151 patients with symptomatic bradycardia and LBBAP pacemaker implanted, were prospectively included in the study. Subjects with left bundle branch block and CRT indications (n = 29), ventricular pacing burden <40% (n = 11), and loss of LBBAP (n = 10) were excluded from further analysis. At baseline and the last follow-up visit, echocardiography with global longitudinal strain (GLS) assessment, 12-lead ECG, pacemaker interrogation, and blood level of NT-proBNP were performed. The median follow-up period was 23 months (15.5-28). None of the analyzed patients fulfilled the criteria for pacing induced cardiomyopathy (PICM). Improvement in left ventricular ejection fraction (LVEF) and GLS was observed in patients with LVEF <50% at baseline (n = 39): 41.4 ± 9.2% versus 45.6 ± 9.9%, and 12.9 ± 3.6% versus 15.5 ± 3.7%, respectively. In the subgroup with preserved EF (n = 62), LVEF and GLS remained stable at follow-up: 59.3 ± 5.5% versus 60 ± 5.5%, and 19 ± 3.9% versus 19.4 ± 3.8%, respectively.

CONCLUSION

LBBAP prevents PICM in patients with preserved LVEF and improves left ventricle function in subjects with depressed LVEF. LBBAP might be the preferred pacing modality for bradyarrhythmia indications.

Left bundle branch pacing as an alternative to biventricular pacing for cardiac resynchronisation therapy

BACKGROUND

Left bundle branch pacing (LBBP) is a novel physiological pacing technique which may serve as an alternative to biventricular pacing (BVP) for the delivery of cardiac resynchronisation therapy (CRT). This study assessed the feasibility and outcomes of LBBP in comparison to BVP.

METHODS

LBBP was attempted in 40 consecutive patients as the first-line method for delivering CRT. To evaluate LBBP versus BVP, 40 patients with identical inclusion criteria who received BVP were compared with the LBBP group. Acute success rate, complications, functional and echocardiographic outcomes as well as hospitalisation for heart failure and all-cause mortality 6 months after implantation were evaluated.

RESULTS

LBBP was successfully performed in 31 (78%) patients and resulted in significant QRS narrowing (from 166 ± 16 to 123 ± 18 ms, p < 0.001), improvement in left ventricular ejection fraction (LVEF; from 28 ± 8 to 43 ± 12%, p < 0.001) and New York Heart Association functional class (from 2.8 ± 0.5 to 1.6 ± 0.6, p < 0.001) at 6 months. No LBBP-related complications occurred. Compared to BVP, LBBP resulted in a greater reduction in QRS duration (44 ± 17 vs 15 ± 26 ms, p < 0.001) with comparable absolute improvement in LVEF (15.2 ± 11.7 vs 9.6 ± 12.1%, p = 0.088). Hospitalisation for heart failure and all-cause mortality were similar in the two groups.

CONCLUSIONS

LBBP is feasible and was safe in 78% of patients with favourable electrical resynchronisation and functional improvement and may serve as an alternative to BVP.

Approach to Left Bundle Branch Pacing

Cardiac pacing refers to the implantation tool serving as a treatment modality for various indications, the most common of which is symptomatic bradyarrhythmia. Left bundle branch pacing has been noted in the literature to be safer than biventricular pacing or His-bundle pacing in patients with left bundle branch block (LBBB) and heart failure, thereby becoming the focus of further research on cardiac pacing. A review of the literature was conducted using a combination of keywords, including "Left Bundle Branch Block," "Procedural techniques," "Left Bundle Capture," and "Complications." The following factors have been investigated as key criteria for direct capture: paced QRS morphology, peak left ventricular activation time, left bundle potential, nonselective and selective left bundle capture, and programmed deep septal stimulation protocol. In addition, complications of LBBP, inclusive of septal perforation, thromboembolism, right bundle branch injury, septal artery injury, lead dislodgement, lead fracture, and lead extraction, have also been elaborated on. Despite clinical implications based on clinical research comparing the use of LBBP with other forms such as right ventricular apex pacing, His-bundle pacing, biventricular pacing, and left ventricular septal pacing, a paucity in the literature on long-term effects and efficacy has been noted. LBBP can thus be considered to have a promising future in patients requiring cardiac pacing, assuming that additional research on clinical outcomes and the limitation of significant complications such as thromboembolism can be established.

Clinical use conditions of lead deployment and simulated lead fracture rate in left bundle branch area pacing

INTRODUCTION

Left bundle branch area pacing (LBBAP) is achieved by advancing the lead tip deep in the septum. Most LBBAP implants are performed using the Medtronic SelectSecure™ MRI SecureScan™ Model 3830 featuring a unique 4 Fr fixed helix lumenless design. Details of lead use conditions and long-term reliability have not been reported. This study was designed to quantify the mechanical use conditions for the 3830 lead during and after LBBAP implant, and to evaluate reliability using bench testing and simulation.

METHODS

Fifty bradycardia patients with implantation of the 3830 lead for LBBAP were enrolled. Use conditions of lead deployment at implantation were collected and computed tomography (CT) scans were performed at 3-month follow-up. Curvature amplitude along the pacing lead was determined with CT images. Fatigue bending was performed using accelerated testing in a more severe environment than routine clinical use conditions. Conductor fracture rate in a simulated patient population was estimated based on clinical use conditions and fatigue test results.

RESULTS

The number of attempts to place the 3830 lead for LBBAP was 2.1 ± 1.3 (range: 1-7) with 13 ± 6 lead rotations at the final attempt. Extreme implant conditions were simulated in bench testing with 5 applications of 20 turns followed by up to 400 million bending cycles. Reliability modeling predicted a 10-year fracture rate of 0.02%.

CONCLUSIONS

LBBAP implants require more lead rotations than standard pacing implants and result in unique lead bending. Application of simulated LBBAP use conditions to the 3830 lead in an accelerated in-vitro model does not produce excess conductor fractures. IMAGE-LBBP Study ID of ClinicalTrial.GOV: NCT04119323.

The effectiveness and feasibility of using multi-lead ECG monitoring combined with a programmed intracavitary ECG to complete left bundle branch area pacing

BACKGROUND

Left bundle branch area pacing (LBBaP) as an alternative method for delivering physiological pacing, is difficult for many primary hospitals that lack the electrophysiological multichannel recorder to carry out. We hope to find a simple and feasible method that combines the multi-lead surface electrocardiogram (ECG) monitoring and the intracavity ECG of the pacing programmer to achieve LBBaP.

METHODS

A total of 50 patients with bradycardia indications who attempted permanent pacemaker implantation were included in this study. We referred to multi-lead surface ECG monitoring and pacing system analyzer (PSA), combined with the nine-zone pacing method of the LBBaP, to complete LBBaP. We assessed multiple parameters to verify whether the LBBaP was successfully achieved and used univariable analysis of variance for repeated measures to judge the feasibility and effectiveness of LBBaP without the electrophysiological multichannel recorder.

RESULTS

LBBaP was successfully archived without the electrophysiological multichannel recorder in 44 of 50 patients (88%). In the study, paced QRS duration and the stimulus to peak left ventricular activation time (Sti-LVAT) were 117.04 ± 10.34 ms and 71.10 ± 7.91 ms and had no significant changes in the 3-month follow-up. The unipolar pacing threshold and R-wave amplitudes were 0.85 ± 0.32 V and 10.36 ± 5.24 mV at baseline respectively, which also showed stability during the 1-month and 3-month follow-up. During the 3-month follow-up, no lead-related complication was recorded.

CONCLUSION

It is effective and feasible to achieve LBBaP combining the multi-lead ECG monitoring and the intracavitary ECG of PSA without the electrophysiological multichannel recorder, which could be an alternative to perform LBBaP.

Left Bundle Branch Pacing for Bradycardia in Non-obstructive Hypertrophic Cardiomyopathy Patients: Feasibility, Safety, and Effect

PURPOSE

Left bundle branch pacing (LBBP) is as an innovative physiological pacing approach. The research on LBBP in non-obstructive hypertrophic cardiomyopathy (NOHCM) patients is scarce. This study aimed to assess the feasibility, safety, and effect of LBBP in bradycardia NOHCM patients with permanent pacemaker (PPM) implantation indication.

METHODS

Thirteen consecutive patients with NOHCM who received LBBP were retrospectively enrolled as a hypertrophic cardiomyopathy (HCM) group. Following 1:3 matching, 39 patients without HCM were randomly matched as a control group. Echocardiographic index and pacing parameters were collected.

RESULTS

The successful LBBP was achieved in 96.2% of all cases (50/52), and the success rate of the HCM group was 92.3% (12/13). In the HCM group, the paced QRS duration (from the pacing stimulus to QRS end) was 145.6±20.8 ms. The stimulus to left ventricular activation time (s-LVAT) was 87.4±15.2 ms. In the control group, the paced QRS duration was 139.4±17.2 ms, and the s-LVAT was 79.9±14.1 ms. During the implantation, R-wave sensing and the pacing threshold of the HCM group were significantly higher than the control group (20.2±10.5 vs 12.5±5.9 mV, P < 0.05; 0.8±0.3 vs 0.6±0.2V/0.4 ms, P < 0.05). In addition, the fluoroscopic duration and procedural duration were longer in the HCM group (14.8±8.3 vs 10.3±6.6min, P = 0.07; 131.8±50.5 vs 101.4±41.6 min, P < 0.05). The lead insertion depth was 15±2 mm in the HCM group, and no procedure-related complications occurred. During the 12-month follow-up, pacing parameters remained stable and were of no significance in the two groups. The cardiac function did not deteriorate, and the left ventricular outflow tract gradient (LVOTG) did not increase in the follow-up.

CONCLUSION

LBBP might be feasible and safe for NOHCM patients with conventional bradycardia pacing indication, and there is no deterioration in cardiac function and LVOTG of patients with NOHCM.

A novel approach for developing left bundle branch pacing and left bundle branch block in a canine model

BACKGROUND AND OBJECTIVE

Left bundle branch pacing (LBBP) has shown the benefits in the treatment of dyssynchronous heart failure (HF). The purpose of this study was to develop a novel approach for LBBP and left bundle branch block (LBBB) in a canine model.

METHODS

A "triangle-center" method by tricuspid valve annulus angiography for LBBP implantation was performed in 6 canines. A catheter was then applied for retrograde His potential recording and left bundle branch (LBB) ablation simultaneously. The conduction system was stained to verify the "triangle-center" method for LBBP and assess the locations of the LBB ablation site in relation to the left septal fascicle (LSF).

RESULTS

The mean LBB potential to ventricular interval and stimulus-peak left ventricular activation time were 11.8 ± 1.2 and 35.7 ± 3.1 ms, respectively. The average intrinsic QRS duration was 44.7 ± 4.7 ms. LBB ablation significantly prolonged the QRS duration (106.3 ± 8.3 ms, p < .001) while LBBP significantly shortened the LBBB-QRS duration to 62.5 ± 5.3 ms (p < .001). After 6 weeks of follow-up, both paced QRS duration (63.0 ± 5.4 ms; p = .203) and LBBB-QRS duration (107.3 ± 7.4 ms; p = .144) were unchanged when comparing to the acute phase, respectively. Anatomical analysis of 6 canine hearts showed that the LBBP lead-tip was all placed in LSF area.

CONCLUSION

The new approach for LBBP and LBBB canine model was stable and feasible to simulate the clinical dyssynchrony and resynchronization. It provided a useful tool to investigate the basic mechanisms of underlying physiological pacing benefits.

Adverse effects of right ventricular pacing on cardiac function: prevalence, prevention and treatment with physiologic pacing

Right ventricular (RV) pacing is the main treatment modality for patients with advanced atrioventricular (AV) block. Chronic RV pacing can cause cardiac systolic dysfunction and heart failure (HF). In this review, we discuss studies that have shown deleterious effects of chronic RV pacing on systolic cardiac function causing pacing-induced cardiomyopathy (PiCM), heart failure (HF), HF hospitalization, atrial fibrillation (AF) and cardiac mortality. RV apical pacing is the most widely used and studied. Adverse effects of RV pacing appear to be directly related to pacing burden and are worse in patients with pre-existing left ventricular (LV) dysfunction. Chronic RV pacing is also associated with heart failure with preserved ejection fraction (HFpEF). Mechanisms, risk factors, clinical and echocardiographic features, and strategies to minimize RV pacing-induced cardiac dysfunction are discussed in light of the latest data. Studies on biventricular (Bi-V) pacing upgrade in patients who develop RV PiCM, use of alternate RV pacing sites, de novo Bi-V pacing, and physiologic pacing using HIS bundle pacing (HBP) and left bundle area (LBBA) pacing in patients with an anticipated high RV pacing burden are discussed.

Distance between the lead-implanted site and tricuspid valve annulus in patients with left bundle branch pacing: Effects on postoperative tricuspid regurgitation deterioration

BACKGROUND

Left bundle branch pacing (LBBP) is an alternative strategy for His-bundle pacing (HBP); however, little is known about tricuspid regurgitation (TR) deterioration after LBBP implantation.

OBJECTIVES

The purpose of this study was to characterize the incidence of post-LBBP TR deterioration and identify predicting factors, especially lead position parameters.

METHODS

Patients who received LBBP were continuously enrolled from January 2018 to August 2020. The progression of TR and the anatomic position of LBBP were characterized by echocardiography.

RESULTS

A total of 89 patients were enrolled and assigned to 2 subgroups based on the degree of TR before LBBP implantation: 58 (65.2%) with relatively normal tricuspid valve (TV) function (grade 0/1 subgroup: with none/trivial or mild TR) and 31 (34.8%) with more severe TR (grade 2/3 subgroup: with moderate or severe TR). At 19.0 ± 6.5 months of follow-up, 29 patients (32.6%) had TR deterioration, and 23 of them were in the grade 0/1 subgroup. In the grade 0/1 subgroup, patients with TR deterioration had a shorter distance between the lead-implanted site and TV (Lead-TA-dist) than those without TR (19.0 ± 7.6 vs 23.9 ± 5.4; P = .006). The receiver operating characteristic (ROC) curve (area under the curve 0.721; 95% confidence interval [CI] 0.575-0.867; P = .005) indicated the favorable efficacy of Lead-TA-dist for predicting TR deterioration after LBBP. Lead-TA-dist ≤16.1 mm was independently associated with TR deterioration after LBBP (hazard ratio 0.20; 95% CI 0.06-0.76; P = .017).

CONCLUSION

TR was a common complication of LBBP implantation. In patients with none/trivial or mild TR, Lead-TA-dist ≤16.1 mm was an independent predictor of TR deterioration after LBBP implantation.

High-pass filter settings and the role and mechanism of discrete ventricular electrograms in left bundle branch pacing

Objective

The characteristics of discrete intracardiac electrogram (EGM) in selective left bundle branch (SLBB) pacing (SLBBP) have not been described in detail previously. This study aimed to examine the effect of different high-pass filter (HPF) settings on discrete local ventricular components in an intracardiac EGM and to analyze its possible mechanisms.

Methods

This study included 144 patients with indications of permanent cardiac pacing. EGMs were collected at four different HPF settings (30, 60, 100, and 200 Hz) with a low-pass filter at 500 Hz, and their possible mechanisms were analyzed.

Results

LBBP was successfully achieved in 91.0% (131/144) of patients. SLBBP was achieved in 123 patients. The occurrence rates of discrete local ventricular EGM were 16.7, 33.3, 72.9, and 85.4% for HPF settings of 30, 60, 100, and 200 Hz, respectively. The analysis of discrete EGM detection showed significant differences between the different HPF settings. By using the discrete local ventricular component and isoelectric interval as the SLBB capture golden standard, the results of EGMs revealed that the 30 Hz HPF has a sensitivity of 19% and specificity of 100%. The 60 Hz HPF had a sensitivity of 39% and a specificity of 100%. The 100 Hz HPF had a sensitivity of 85% and a specificity of 100%. The 200 Hz HPF had a sensitivity of 100% and specificity of 100%.

Conclusion

An optimal HPF setting of 200 Hz is recommended for discrete local ventricular EGM detection. A discrete local ventricular EGM should exhibit an isoelectric interval. A steep deflection and high-frequency ventricular EGM morphology nearly identify an intrinsic EGM morphology.

Bipolar anodal septal pacing with direct LBB capture preserves physiological ventricular activation better than unipolar left bundle branch pacing

Background

Left bundle branch pacing (LBBP) produces delayed, unphysiological activation of the right ventricle. Using ultra-high-frequency electrocardiography (UHF-ECG), we explored how bipolar anodal septal pacing with direct LBB capture (aLBBP) affects the resultant ventricular depolarization pattern.

Methods

In patients with bradycardia, His bundle pacing (HBP), unipolar nonselective LBBP (nsLBBP), aLBBP, and right ventricular septal pacing (RVSP) were performed. Timing of local ventricular activation, in leads V1-V8, was displayed using UHF-ECG, and electrical dyssynchrony (e-DYS) was calculated as the difference between the first and last activation. Durations of local depolarizations were determined as the width of the UHF-QRS complex at 50% of its amplitude.

Results

aLBBP was feasible in 63 of 75 consecutive patients with successful nsLBBP. aLBBP significantly improved ventricular dyssynchrony (mean -9 ms; 95% CI (-12;-6) vs. -24 ms (-27;-21), ), p < 0.001) and shortened local depolarization durations in V1-V4 (mean differences -7 ms to -5 ms (-11;-1), p < 0.05) compared to nsLBBP. aLBBP resulted in e-DYS -9 ms (-12; -6) vs. e-DYS 10 ms (7;14), p < 0.001 during HBP. Local depolarization durations in V1-V2 during aLBBP were longer than HBP (differences 5-9 ms (1;14), p < 0.05, with local depolarization duration in V1 during aLBBP being the same as during RVSP (difference 2 ms (-2;6), p = 0.52).

Conclusion

Although aLBBP improved ventricular synchrony and depolarization duration of the septum and RV compared to unipolar nsLBBP, the resultant ventricular depolarization was still less physiological than during HBP.

Initial Experience with Left Bundle Branch Area Pacing in Patients with Atrioventricular Block and Impaired LV Function

Chronic right ventricular (RV) pacing can exacerbate heart failure in patients with a low left ventricular ejection fraction (LVEF). Left bundle branch area pacing (LBBAP) has emerged as a novel physiological pacing technique; however, information remains limited on its use among patients with a low EF. This study investigated the safety and short-term clinical outcomes of LBBAP among patients with impaired left ventricular (LV) function. This retrospective analysis of pacemakers at Chosun University Hospital, South Korea, included all patients with impaired LV function (EF<50%) who underwent pacemaker implantation for atrioventricular blockage from 2019-2022. Clinical characteristics, 12-lead electrocardiography findings, echocardiography findings, and laboratory parameters were evaluated. Composite outcomes were defined as all-cause mortality, cardiac death, and hospitalization due to heart failure during the 6-month follow-up. Altogether 57 patients (25 men; mean age, 77.4±10.8 y; LVEF, 41.5±3.8%) were divided into LBBAP (n=16), biventricular pacing (BVP; n=16), and conventional RV pacing (RVP; n=25) groups. In the LBBAP group, the mean paced QRS duration (pQRSd) was narrower (119.5±14.7 vs. 140.2±14.3 vs. 163.2±13.9; p<0.001) and cardiac troponin I level was elevated post-pacing (1.14±1.29 vs. 0.20±0.29 vs. 0.24±0.51, p=0.001). Lead parameters were stable. One patient was hospitalized, and four died (one patient each from heart failure admission, myocardial infarction, unexplained death, and pneumonia in RVP vs. one from intracerebral hemorrhage in BVP) during the follow-up period. In conclusion, LBBAP is feasible in patients with impaired LV function without acute or significant complications and provides a remarkably narrower pQRSd with a stable pacing threshold.

Criteria for differentiating left bundle branch pacing and left ventricular septal pacing: A systematic review

Background

As a novel physiological pacing technique, left bundle branch pacing (LBBP) can preserve the left ventricular (LV) electrical and mechanical synchronization by directly capturing left bundle branch (LBB). Approximately 60-90% of LBBP were confirmed to have captured LBB during implantation, implying that up to one-third of LBBP is actually left ventricular septal pacing (LVSP). LBB capture is critical for distinguishing LBBP from LVSP.

Methods and results

A total of 15 articles were included in the analysis by searching PubMed, EMBASE, Web of Science, and the Cochrane Library database till August 2022. Comparisons of paced QRS duration between LVSP and LBBP have not been uniformly concluded, but the stimulus artifact to LV activation time in lead V5 or V6 (Stim-LVAT) was shorter in LBBP than LVSP in all studies. Stim-LVAT was used to determine LBB capture with a sensitivity of 76-95.2% and specificity of 78.8-100%, which varied across patient populations.

Conclusion

The output-dependent QRS transition from non-selective LBBP to selective LBBP or LVSP is direct evidence of LBB capture. LBB potential combined with short Stim-LVAT can predict LBB capture better. Personalized criteria rather than a fixed value of Stim-LVAT are necessary to confirm LBB capture in different populations, especially in patients with LBB block or heart failure.

Randomized Trial of Left Bundle Branch vs Biventricular Pacing for Cardiac Resynchronization Therapy

BACKGROUND

Left bundle branch pacing (LBBP) is the most rapidly growing conduction system pacing technique that is capable of correcting intrinsic left bundle branch block (LBBB). As such, it is potentially an optimal alternative to cardiac resynchronization therapy (CRT) with biventricular pacing (BiVP).

OBJECTIVES

The authors sought to compare the efficacy of LBBP-CRT with BiVP-CRT in patients with heart failure and reduced left ventricular ejection fraction (LVEF).

METHODS

This is a prospective, randomized trial of patients with nonischemic cardiomyopathy and LBBB with 6-month preplanned follow-up. Crossovers were allowed if LBBP or BiVP were unsuccessful. The primary endpoint was the difference in LVEF improvement between 2 groups. The secondary endpoints included changes in echocardiographic measurements, N-terminal pro-B-type natriuretic peptide (NT-proBNP), New York Heart Association functional class, 6-minute walk distance, QRS duration, and CRT response.

RESULTS

The study included 40 consecutive patients (20 males, mean age 63.7 years, LVEF 29.7% ± 5.6%). Crossovers occurred in 10% of LBBP-CRT and 20% of BiVP-CRT. All patients completed follow-up. Intention-to-treat analysis showed significantly higher LVEF improvement at 6 months after LBBP-CRT than BiVP-CRT (mean difference: 5.6%; 95% CI: 0.3-10.9; P = 0.039). LBBP-CRT also appeared to have greater reductions in left ventricular end-systolic volume (-24.97 mL; 95% CI: -49.58 to -0.36 mL) and NT-proBNP (-1,071.80 pg/mL; 95% CI: -2,099.40 to -44.20 pg/mL), and comparable changes in New York Heart Association functional class, 6-minute walk distance, QRS duration, and rates of CRT response compared with BiVP-CRT.

CONCLUSIONS

LBBP-CRT demonstrated greater LVEF improvement than BiVP-CRT in heart failure patients with nonischemic cardiomyopathy and LBBB. (Left Bundle Branch Pacing Versus Biventricular Pacing for Cardiac Resynchronization Therapy [LBBP-RESYNC]; NCT04110431).

Long-term follow-up results of patients with left bundle branch pacing and exploration for potential factors affecting cardiac function

Background: Left bundle branch pacing (LBBP) is an alternative strategy for His bundle pacing (HBP). This study aimed to analyze the long-term performance of LBBP and the potential factors affecting long-term cardiac function.

Methods: Patients with LBBP were continuously enrolled from January 2018 to August 2020. Pacing parameters, electrocardiogram (ECG), and echocardiography were collected. The anatomic position of LBBP leads was described by echocardiographic and fluoroscopic parameters.

Results: A total of 91 patients with a median follow-up of 18 months were enrolled. Most patients maintained stable pacing parameters during follow-up. The intra-septal position of the 3830 lead also remained stable as the distance from the lead tip to the left surface of the ventricular septum was 0.4 (0, 1.4) mm. The overall level of left ventricular ejection fraction (LVEF) slightly increased. 59 patients had improved LVEF (∆LVEF &gt; 0), while 28 patients had unchanged or reduced LVEF (∆LVEF ≤ 0). The declines of baseline LVEF, ∆ Paced QRSd, and corrected longitudinal distance (longit-dist) of lead-implanted site correlated with LVEF improvement, and these three factors had negative linear correlations with ∆LVEF. Patients with tricuspid valve regurgitation (TVR) deterioration had longer follow-up duration (20.5 vs. 15.0 months, p = 0.01) and shorter Lead-TVA-dist (18.6 vs. 21.6 mm, p = 0.04) than those without TVR deterioration.

Conclusion: Patients with LBBP generally remained stable in pacing performance, anatomic lead positions, and cardiac function in long-term follow-up. Baseline LVEF, ∆ Paced QRSd, and corrected longit-dist might be associated with potential LVEF decrease, which required further confirmation.

Case report: Three-dimensional printing as an educational tool for optimal lead positioning to left bundle branch pacing

Left bundle branch pacing (LBBP) has been widely adopted as a physiological pacing approach. However, LBBP fails to achieve in some cases because it is difficult to maintain the orientation of the lead tip perpendicular to the interventricular septum (IVS). Three-dimensional (3D) printing technology has emerged as a promising tool for modeling and teaching cardiovascular interventions. Seeking confirmation of optimal lead placement relative to the IVS, we used 3D printing technology to generate a 3D printed heart from a selected patient with successful and proven LBBP. Our model successfully illustrated that the lead tip was perpendicular to the IVS. Application of the 3D technology has potential to help the early-operator understand the optimal lead placement relative to IVS and diminish the learning-curve.

Changes of repolarization parameters after left bundle branch area pacing and the association with echocardiographic response in heart failure patients

Background: Left bundle branch area pacing (LBBAP) has become a safe and effective option for heart failure (HF) patients indicated for cardiac resynchronization therapy (CRT) and/or ventricular pacing, yet the response rate was only 70%. Repolarization parameters were demonstrated to be associated with cardiac mechanics and systolic function. This study aimed to investigate the effects of LBBAP on repolarization parameters and the potential association between those parameters and echocardiographic response.

Methods and results: A total of 59 HF patients undergoing successful LBBAP were consecutively included. QTc, Tpeak-Tend (TpTe), and TpTe/QTc were measured before and after the implantation. The results turned out that the dispersion of ventricular repolarization (DVR) improved after LBBAP among the total population. Although trends of repolarization parameters varied according to different QRS configurations at baseline, the post-implant parameters showed no significant difference between groups. The association between repolarization parameters and LBBAP response was then evaluated among patients with wide QRS. Multivariate analysis demonstrated that post-implant TpTe was the independent predictor of LBBAP response (p < 0.05). Receiver operating characteristic analysis indicated an area under the curve of 0.77 (95% CI, 0.60–0.93) with a cutoff value of 81.2 ms (p < 0.01). Patients with post-implant TpTe<81.2 ms had a significantly higher rate of echocardiographic response (93.3 vs. 44.4%, p < 0.01). Further subgroup analysis indicated that the predictive value of post-implant TpTe for LBBAP response was more significant in non-left bundle branch block (LBBB) patients than in LBBB patients.

Conclusion: LBBAP improved DVR significantly in HF patients. Post-implant TpTe was associated with the echocardiographic response after LBBAP among patients with wide QRS, especially for non-LBBB patients.

Right subclavian vein approach for selective left bundle branch pacing: A case report

We reported a 65-year-old man with symptomatic bradycardia caused by chronic atrial fibrillation who underwent pacemaker implantation by left bundle branch pacing (LBBP) via right subclavian vein (RSV) approach. A tricuspid valve annulus (TVA) angiography was performed, and a different connecting cable that can monitor electrocardiograms (ECG) and intracardiac electrograms (EGM) in real time was used during the process. By TVA angiography, we could easily find the ideal location of LBBP; a new connecting cable helped us avoid perforation and guide effective endpoint without the need to stop pacing. The case showed that it was feasible and safe to use the new method for LBBP through RSV route.

Physiologic Pacing Targeting the His Bundle and Left Bundle Branch: a Review of the Literature

PURPOSE OF REVIEW

Conduction system pacing (CSP) has emerged as a means to preserve or restore physiological ventricular activation via pacing at the His bundle or at more distal targets in the conduction system, including the left bundle branch area. This review examines strengths, weaknesses, and clinical applications of CSP performed via these approaches.

RECENT FINDINGS

His bundle pacing (HBP) has been successfully utilized for standard bradyarrhythmia indications and for QRS correction among patients receiving devices for cardiac resynchronization therapy (CRT). Limitations of HBP pacing have included implant complexity and rising pacing thresholds over time. Left bundle branch area pacing (LBBAP) appears to deliver similar physiological benefits with shorter implant times and more stable thresholds. More recently, hybrid systems utilizing HBP or LBBAP in combination with left ventricular leads have been used to treat heart failure (HF) patients, and may be useful in multilevel or mixed conduction blocks. There is growing interest in CSP for bradycardia and HF indications, although high quality data with randomized controlled trials are needed to help guide future treatment paradigms.

Use of extendable helix leads for conduction system pacing: differences in lead handling and performance: Conclusion

INTRODUCTION

Pacing leads with extendable-retractable helix (EHL) are alternatives to fixed-helix leads (FHL) for conduction system pacing (CSP), but data on handling characteristics are limited. This study evaluated a dual-center experience of lead handling and performance during CSP.

METHODS AND RESULTS

Consecutive patients with His-bundle pacing (HBP) or left bundle branch pacing (LBBP) were evaluated for the primary outcome of lead failure, defined as structural damage to the lead necessitating lead replacement. Differences in pacing characteristics were compared. Among 280 patients (mean age 74±11 years, 44% male, 50% LBBP), 246 (88%) received FHL and 34 (12%) received EHL. Of 299 leads used, lead failure occurred more frequently among patients with EHL than FHL (29% vs 2%, p<0.001), regardless of CSP modality. Majority of damaged leads (89%) in the form of helix deformation were successfully removed, with failure occurring in only 2 patients, both EHL, leading to helix fracture and retention within the septal myocardium. EHL, compared to FHL, was associated with 25-fold increased odds of lead failure (odds ratio 25.21, 95% confidence interval 7.35-86.51), and persisted after adjustment in turn for age, pacing modality and indication. CSP implant success rates did not differ by lead design (FHL 80% vs EHL 71%, p=0.18), with similar pacing thresholds at implant and follow-up. This article is protected by copyright. All rights reserved.

Feasibility, safety and outcomes of upgrading to left bundle branch pacing in patients with right ventricular pacing induced cardiomyopathy

BACKGROUND

Right ventricular pacing (RVP) induces abnormal electrical activation and asynchronous ventricular contraction and leads to pacing induced cardiomyopathy (PICM) in 10-20% of patients. Cardiac resynchronization therapy (CRT) utilizing biventricular pacing (BVP) is the recommended treatment. Left bundle branch pacing (LBBP) is a novel physiological pacing technique which may serve as an alternative to CRT. This study assessed feasibility and outcomes of LBBP delivered CRT in patients with PICM.

METHODS

Twenty consecutive patients with PICM who received an upgrade of their pacemaker to LBBP were prospectively studied. Acute success rate, complications, functional and echocardiographic response and hospitalization for heart failure within six months from implantation were evaluated.

RESULTS

LBBP was successfully delivered in all patients. Median duration of RVP before upgrade to LBBP was 3.8 years and the RVP percentage was 99. LBBP resulted in significant QRS narrowing (from 193 ± 18 to 130 ± 17 ms (p<0.001)), improvement in LVEF (from 32 ± 6 percent to 47 ± 8 percent (p<0.001)) and NYHA class (from 2.8 ± 0.4 to 1.4 ± 0.5 (p<0.001)) at 6 months. No LBBP-related complications occurred. No patients were hospitalized for heart failure or died.

CONCLUSION

LBBP is feasible and safe in delivering CRT in PICM. Preliminary analyses demonstrated significant electrical resynchronization and favourable improvement in LV function and NYHA functional class at short term follow-up. Data need to be validated in large randomized controlled trials. This article is protected by copyright. All rights reserved.

Influence of Capture Selectivity and Left Intrahisian Block on QRS Characteristics During Left Bundle Branch Pacing

OBJECTIVES

This study sought to examine QRS and intracardiac characteristics during selective (S) and nonselective (NS) left bundle branch pacing (LBBP) from direct left septal recordings.

BACKGROUND

Criteria for S-LBBP and NS-LBBP have not been validated with intracardiac mapping.

METHODS

Pacing was performed from multielectrode Purkinje recordings below the left-sided His. S-LBBP and NS-LBBP were performed in patients with narrow QRS (n = 9), right bundle branch block (n = 3), intraventricular conduction delay (n = 5), and left bundle branch block (n = 10). QRS duration was measured from stimulus onset (QRS_st) and from the intrinsicoid deflection of the R-wave in V₁-V₂ (QRS_id) to QRS end. Retrograde left bundle branch conduction was assessed by stimulus-to-retrograde His intervals.

RESULTS

Among 27 patients analyzed, 20 demonstrated both NS- and S-LBBP and were studied in paired comparisons. NS-LBBP resulted in narrower QRS compared to S-LBBP (QRS_st: 163 ms [interquartile range (IQR): 144-179 ms] vs 181 ms [IQR: 173-203 ms]; P < 0.001; QRS_id: 125 ms [IQR: 117-142 ms] vs 150 ms [IQR: 135-157 ms]; P < 0.001). Left ventricular activation time was also significantly shorter for NS-LBBP compared to S-LBBP (88 ms [IQR: 75-111 ms] vs 97 ms [IQR: 82-123 ms]; P = 0.019). Left intrahisian block was bidirectional in 10 patients with long retrograde stimulus-to-His intervals. QRS_st duration was significantly longer in patients with complete conduction block compared to those with intact Purkinje activation during NS-LBBP (181 ms [IQR: 162-195 ms] vs 157 ms [IQR: 139-168 ms]; P = 0.022).

CONCLUSIONS

In contrast to His-bundle pacing, S-LBBP predominantly yields a wide QRS as a result of delayed RBB synchronization, whereas NS-LBBP results in shorter QRS duration because of recruitment of the basal right ventricular septum. A wider-paced morphology of LBBP was noted in patients with complete conduction block caused by bidirectional left intrahisian block. Achievement of narrow QRS during LBBP is predicated upon capture nonselectivity or programmed atrioventricular fusion, rather than intrinsic physiologic synchrony from left bundle branch stimulation.

Evaluation of the Shortening of the Stimulus to Peak Left Ventricular Activation Time at Continuous Low Output to Confirm Selective Left Bundle Branch Pacing

Background

Left bundle branch area pacing (LBBAP) is a physiological pacing method for treatment of atrioventricular block. However, there is a need for a new convenient and safe method for performing left bundle branch pacing (LBBP) and to confirm left conduction system capture.

Objective

This study aimed to explore a new convenient and safe method for performing selective LBBP.

Methods

A total of 28 patients who had indications for pacing therapy and received LBBAP were recruited retrospectively. Demographic and baseline patient characteristics, electrocardiograms, pacing parameters, and intracardiac electrogram pattern were evaluated. Continuous unipolar pacing at low output (2 V / 0.5 ms) was performed during the whole period of LBBP lead implantation. Successful left bundle branch (LBB) capture was defined as the abrupt change of the pacing stimulus to the peak of R wave in lead V₅ during continuous pacing at low output (2 V / 0.5 ms).

Results

The parameters of the 2 shortenings (stimulus-to-peak left ventricular activation time [S-peak LVAT] before shortening, S-peak LVAT after shortening, and the duration of shortening) all showed a significant positive correlation (Pearson product-moment correlation coefficient [PCC] = 0.915, P < .001; PCC = 0.897, P < 0.001; PCCs = 0.765, P < 0.001). Shortening of the S-peak LVAT with continuous low output had a 100% sensitivity and 33.3% specificity for predicting stimulus-ventricular potential interval (S-V interval).

Conclusion

Abrupt shortening of the S-peak LVAT at continuous low output was associated with abrupt shortening of the S-peak LVAT at low and high output. High rate of selective LBB capture can be achieved with the method of continuous low output, shortening the S-peak LVAT.

Preliminary experience of permanent left bundle branch area pacing using stylet-directed pacing lead without delivery sheath

BACKGROUND

Left bundle branch area pacing (LBBAP) aims to capture the cardiac conduction system in area of the left bundle branch. Currently, LBBAP is mainly performed using lumen-less pacing leads (LLLs) with pre-shaped sheath. However, the data on LBBAP with stylet-driven leads (SDLs) without sheath is limited.

OBJECTIVE

This study presents the feasibility, safety, and pacing characteristics of LBBAP using stylet-driven leads (SDLs) without the support of sheath.

METHODS

A total of 25 patients with bradycardia indications who received LBBAP implantation with an attempt of SDL (FINELINE II 4471 lead, Boston Scientific, MA, US) between August 2020 and April 2021 at Sir Run Run Shaw Hospital were included in this retrospective cohort study. Twenty of them finally were paced with SDL in priority (SDL-LBBAP group). Twenty propensity score matching patients who underwent LBBAP with LLL (Select Secure 3830 lead, Medtronic, MN, US) and 20 right ventricular septal pacing (RVSP) with regular active fixation lead respectively in the same period (the LLL-LBBAP group and RVSP group) were compared using ECG characteristics, pacing parameters and complications during 6-month follow-up.

RESULTS

LBBAP was successful with SDL in 23 of 25 patients (92%) and 20 of them were paced with SDL first. In the SDL-LBBAP group, the average age was 70.4 ± 8.2 years, and 55% of patients were male. Paced QRS duration and the stimulus to peak left ventricular activation time (Sti-LVAT) in SDL-LBBAP group were similar with those in LLL-LBBAP group and significantly shorter than those in RVSP group (126.1±14.1ms vs 124.8±10.9ms, P = 1.00; 77.7±11.2ms vs 73.5±9.3ms, P = 0.75; 126.1±14.1ms vs 147.7±22.5ms, P<0.001; 77.7±11.2ms vs 97.0±13.2ms, P<0.001). The pacing threshold and R-wave amplitude of SDL-LBBAP group were 0.53±0.18V and 11.53±3.63mV at baseline respectively, which were comparable with the other two groups. During the 6-month follow-up, the pacing parameters remained stable and no lead-related complication was recorded.

CONCLUSION

It is feasible and safe to use stylet-directed pacing lead for permanent LBBAP without a delivery sheath. Similar to LLL, LBBAP using SDL showed stable parameters and narrower paced QRS duration compared with RVSP, which could be an alternative to LLL in LBBAP. This article is protected by copyright. All rights reserved.