Pursue physiological pacing therapy: A better understanding of left bundle branch pacing and left ventricular septal myocardial pacing

Comparison of acute hemodynamic effect of prioritizing ventricular resynchronization vs left ventricular filling during optimization of cardiac resynchronization therapy

BACKGROUND

Targeting the maximal ventricular resynchronization, with the shortest QRS duration (QRSd), is commonly implemented after cardiac resynchronization therapy (CRT).

OBJECTIVE

The purpose of this study was to compare optimization of ventricular resynchronization with optimization of left ventricular (LV) filling during CRT by measuring their acute hemodynamic effects.

METHODS

Patients with standard CRT indications, recruited from 2 centers, underwent biventricular pacing (BVP) and left bundle branch pacing (LBBP). We performed a within-patient comparison of acute hemodynamic response of systolic blood pressure (SBP) at the atrioventricular delay (AVD) with the shortest QRSd against the AVD with the most efficient LV filling. In a validation substudy, we also performed electrical assessment using QRS area (QRSa) and hemodynamic assessment with the maximum rate of LV pressure rise (dP/dtmax).

RESULTS

Thirty patients (age 65 ± 10 years; 53% male) were recruited. The AVD producing maximal ventricular resynchronization was associated with a significantly shorter QRSd (difference 15 ± 12 ms for BVP and 18 ± 13 ms for LBBP, both P <.01) and a significantly smaller improvement in SBP (difference 3 ± 4 mm Hg for BVP and 2 ± 2 mm Hg for LBBP, both P <.01) compared with the AVD that optimized filling. Similar findings were observed in the substudy, with a significantly smaller improvement in dP/dtmax assessed with QRSd and QRSa (difference 9% ± 7% and 6% ± 4% during BVP, and 5% ± 6% and 3% ± 3% during LBBP, all P <.01).

CONCLUSION

Targeting the maximal ventricular resynchronization results in suboptimal acute hemodynamic performance with both BVP and LBBP as CRT. These findings support prioritizing LV filling when programming AVD for CRT.

Prognostic benefits of His-Purkinje capture in physiological pacemakers for bradycardia

INTRODUCTION

Clinical outcomes of long-term ventricular septal pacing (VSP) without His-Purkinje capture remain unknown. This study evaluated the differences in clinical outcomes between conduction system pacing (CSP), VSP, and right ventricular pacing (RVP).

METHODS

Consecutive patients with bradycardia indicated for pacing from 2016 to 2022 were prospectively followed for the clinical endpoints of heart failure (HF)-hospitalizations and all-cause mortality at 2 years. VSP was defined as septal pacing due to unsuccessful CSP implant or successful CSP followed by loss of His-Purkinje capture within 90 days.

RESULTS

Among 1016 patients (age 73.9 ± 11.2 years, 47% female, 48% atrioventricular block), 612 received RVP, 335 received CSP and 69 received VSP. Paced QRS duration was similar between VSP and RVP, but both significantly longer than CSP (p < .05). HF-hospitalizations occurred in 130 (13%) patients (CSP 7% vs. RVP 16% vs. VSP 13%, p = .001), and all-cause mortality in 143 (14%) patients (CSP 7% vs. RVP 19% vs. VSP 9%, p < .001). The association of pacing modality with clinical events was limited to those with ventricular pacing (Vp) > 20% (pinteraction < .05). Adjusting for clinical risk factors among patients with Vp > 20%, VSP (adjusted hazard ratio [AHR]: 4.74, 95% confidence interval [CI]: 1.57-14.36) and RVP (AHR: 3.08, 95% CI: 1.44-6.60) were associated with increased hazard of HF-hospitalizations, and RVP (2.52, 95% CI: 1.19-5.35) with increased mortality, compared to CSP. Clinical endpoints did not differ between VSP and RVP with Vp > 20%, or amongst groups with Vp < 20%.

CONCLUSION

Conduction system capture is associated with improved clinical outcomes. CSP should be preferred over VSP or RVP during pacing for bradycardia.

Advanced heart failure: a contemporary approach

Advanced heart failure (HF) is defined as the persistence of severe symptoms despite the use of optimized medical, surgical, and device therapies. These patients require timely advanced treatments, such as heart transplantation or long-term mechanical circulatory support (MCS). Inotropic agents are often used to reduce congestion and increase cardiac output, while renal replacement therapy may be beneficial if necessary. Cardiac resynchronization therapy has clear benefits in patients with HF with reduced ejection fraction, particularly with left bundle branch block (QRS duration > 130 ms). The role of implantable cardioverter-defibrillators in advanced HF patients requires further investigation considering the introduction of novel HF medications. In selected patients with significant secondary mitral regurgitation, transcatheter edge-to-edge repair can help delay heart transplantation or long-term MCS. In later stages, the appropriateness of heart transplantation should be evaluated, and the use of short- or long-term MCS may be considered. A multidisciplinary HF management program is crucial for patients with advanced HF. Recent treatment advances, including drugs, devices, and MCS, have broadened the options available to patients with advanced HF and this trend is expected to continue.

Feasibility and safety of left bundle branch area pacing-cardiac resynchronization therapy in elderly patients

BACKGROUND

Left bundle branch area pacing (LBBAP) is an emerging technique to achieve cardiac resynchronization therapy (CRT), but its feasibility and safety in elderly patients with heart failure with reduced ejection fraction and left bundle branch block is hardly investigated.

METHODS

We enrolled consecutive patients with an indication for CRT comparing pacing parameters and complication rates of LBBAP-CRT in elderly patients (≥ 75 years) versus younger patients (< 75 years) over a 6-month follow-up.

RESULTS

LBBAP was successful in 55/60 enrolled patients (92%), among which 25(45%) were elderly. In both groups, LBBAP significantly reduced the QRS duration (elderly group: 168 ± 15 ms to 136 ± 12 ms, p < 0.0001; younger group: 166 ± 14 ms to 134 ± 11 ms, p < 0.0001) and improved LVEF (elderly group: 28 ± 5% to 40 ± 7%, p < 0.0001; younger group: 29 ± 5% to 41 ± 8%, p < 0.0001). The pacing threshold was 0.9 ± 0.8 V in the elderly group vs. 0.7 ± 0.5 V in the younger group (p = 0.350). The R wave was 9.5 ± 3.9 mV in elderly patients vs. 10.7 ± 2.7 mV in younger patients (p = 0.341). The fluoroscopic (elderly: 13 ± 7 min vs. younger: 11 ± 7 min, p = 0.153) and procedural time (elderly: 80 ± 20 min vs. younger: 78 ± 16 min, p = 0.749) were comparable between groups. Lead dislodgement occurred in 2(4%) patients, 1 in each group (p = 1.000). Intraprocedural septal perforation occurred in three patients (5%), 2(8%) in the elderly group (p = 0.585). One patient (2%) in the elderly group had a pocket infection.

CONCLUSIONS

LBBAP is a feasible and safe technique for delivering physiological pacing in elderly patients who are candidates for CRT with suitable pacing parameters and low complication rates.

Additional left ventricular septal lead facilitates R-wave sensing of implantable cardioverter-defibrillator in arrhythmogenic right ventricular cardiomyopathy: a case report

Background

Implantable cardioverter-defibrillator (ICD) implantation is a key therapeutic option in arrhythmogenic right ventricular cardiomyopathy (ARVC) to prevent sudden cardiac death due to ventricular tachycardia (VT) and fibrillation (VF). However, sub-optimized R-wave sensing due to myocardium loss interferes with VT/VF identification and appropriate therapy. We tried to implant a 3830 lead to the left ventricular septum (LVS) to facilitate ICD sensing in an ARVC patient.

Case summary

A 68-year-old woman diagnosed with ARVC was scheduled to undergo ICD implantation. Initially, no sites with suitable R-wave amplitudes were found in the right ventricle (RV) to deploy the defibrillation lead (<3.0 mV). It was likely due to severe RV involvement, but the LVS myocardium was more preserved based on cardiac magnetic resonance imaging. Therefore, we implanted a 3830 lead into the deep area of the septum to facilitate R-wave sensing. During the procedure from the right to left septum, the R-wave amplitude significantly increased (2.6 to 4.3-7.1 mV). Left ventricular septum pacing was finally achieved with favourable R-wave sensing (9.9 mV 24 h post-operation). The 3830 lead was plugged into the IS-1 port, while the defibrillation lead was plugged into the DF-1 port. After a 4-month follow-up, the R-wave amplitude of the 3830 lead was 11.1 mV.

Discussion

When the R-wave sensing is not acceptable for ICD implantation in ARVC patients, it is critical to assess myocardial conditions comprehensively. If the septal myocardium is preserved, implanting a 3830 lead to the deep or LVS is feasible to improve R-wave sensing.

Left bundle branch area pacing: A promising modality for cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is recognized as the first-line management for patients with heart failure (HF) and conduction disorders. As a conventional mode for delivering CRT, biventricular pacing (BVP) improves cardiac function and reduces HF hospitalizations and mortality, but there are still limitations given the high incidence of a lack of response rates. Alternative pacing methods are needed either for primary or rescue therapy. In recent years, conduction system pacing (CSP) has emerged as a more physiological pacing modality for simultaneous stimulation of the ventricles, including His bundle pacing (HBP) and left bundle branch pacing (LBBP). CSP activates the His-Purkinje system, allowing normal ventricular stimulation. However, HBP is technically challenging with a relatively low success rate, high pacing threshold, and failure to correct distal conduction abnormalities. Therefore, LBBP stands out as a novel ideal physiological pacing modality for CRT. Several non-randomized studies compared the feasibility and safety of LBBP with BVP and concluded that LBBP is superior to BVP for delivering CRT with a narrower QRS and greater improvements in left ventricular ejection fraction (LVEF) and New York Heart Association (NYHA) functional class. Concurrently, some studies showed lower and stable pacing thresholds and greater improvement of B-type natriuretic peptide (BNP) levels, as well as better mechanical synchronization and efficiency. LBBP ensures better ventricular electromechanical resynchronization than BVP. In this review, we discuss current knowledge of LBBP, compare LBBP with BVP, and explore the potential of LBBP to serve as an alternative primary therapy to realize cardiac resynchronization.

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.

Short QRS Duration After His-Purkinje Conduction System Pacing Predicts Left Ventricular Complete Reverse Remodeling in Patients With True Left Bundle Branch Block and Heart Failure

Objective

This study aimed to explore the outcomes of His-Purkinje conduction system pacing (HPCSP) and to screen the predictors of left ventricular (LV) complete reverse remodeling in patients with true left bundle branch block (LBBB) and heart failure with reduced ejection fraction (HFrEF).

Methods

Patients who underwent HPCSP for true LBBB and HFrEF from April 2018 to August 2020 were consecutively enrolled. All participants were followed up for at least 1 year. Thrombosis, infection, lead dislodgement, perforation, and other complications were observed after HPCSP. Clinical data, including echocardiographic parameters, electrocardiogram measurements, and cardiac function, were assessed before and after the procedure.

Results

A total of 46 patients were enrolled. HPCSP was successfully deployed in 42 cases (91.30%), which included 37 cases with His bundle pacing (HBP) and 5 cases with left bundle branch pacing (LBBP). The QRS duration decreased significantly (169.88 ± 19.17 ms vs. 113.67 ± 20.68 ms, P < 0.001). Left ventricular end-systolic volume (LVESV) (167.67 ± 73.20 ml vs. 85.97 ± 62.24 ml, P < 0.001), left ventricular end-diastolic diameter (LVEDD) (63.57 ± 8.19 mm vs. 55.46 ± 9.63 mm, P = 0.003) and left ventricular ejection fraction (LVEF) (26.52 ± 5.60% vs. 41.86 ± 11.56%, P < 0.001) improved dramatically. Complete reverse remodeling of the LV with normalized LVEF and LVEDD was found in nearly half of the patients (45.24%). A short QRS duration after HPCSP was a strong predictor of normalized LVEF and LVEDD (P < 0.001). The thresholds increased markedly in two patients approximately 6 months after HBP. No patients died during the total follow-up period of 20.07 ± 6.45 months.

Conclusion

Complete reverse remodeling of the LV could be found in nearly half of the patients with HFrEF and true LBBB after HPCSP, and the short QRS duration after HPCSP was a strong predictor.

Left Bundle Branch Area Pacing in a Giant Atrium With Atrial Standstill: A Case Report and Literature Review

Atrial standstill (AS) is a rare condition defined by the lack of atrial electrical and mechanical activities. It is usually clinically manifested as symptomatic bradycardia, which requires permanent pacemaker (PPM) implantation. Traditional right ventricular apical pacing causes electrical and mechanical dyssynchrony resulting in left ventricular dysfunction, heart failure, and arrhythmias. As a novel physiological pacing strategy, left bundle branch area pacing (LBBaP) has demonstrated effectiveness and safety in recent years, but its application in exceptional conditions is rarely reported. We report the case of a 47-year-old female, who was diagnosed with AS complicated with a giant atrium, and successfully received a single-chamber PPM with LBBaP.

Anatomical and histological assessment of left bundle branch area pacing in human heart with refractory heart failure

As an emerging pacing technique, left bundle branch area pacing (LBBAP) has served as a physiological pacing modality that overcomes the limitations of His bundle pacing (HBP) or right ventricular pacing. Three patients with terminal heart failure who were waiting for heart transplantation and met the indications of pacemaker implantations received LBBAP. Symptoms were relieved and stabilized and eventually received heart transplantation. Diseased hearts from the recipients were dissected post‐transplantation, and the direct visual of pacing lead locations in the interventricular septum were evaluated, and the histopathological examination around the lead was conducted for the first time in human. As a result, we found that the locations of LBBAP leads were matched with fluoroscopic views during the procedure and Masson's staining showed extensive fibrosis occur around the lead but did not result in high thresholds.

Left bundle branch pacing in heart failure patients with left bundle branch block: a systematic review and meta-analysis

BACKGROUND

The clinical benefit of cardiac resynchronization therapy (CRT) in heart failure patients with left bundle branch block (LBBB) has been demonstrated. However, a non-response rate of CRT nearly 1/3. Recent studies have reported left bundle branch pacing (LBBP) has achieved remarkable effect in CRT. This study aim to explore the efficacy and safety of LBBP in heart failure patients with LBBB.

METHODS

We searched PubMed, Cochrane Library, Web of science and CNKI databases for studies about LBBP in heart failure patients with LBBB. QRS duration (QRSd), New York Heart Association (NYHA) classification, B-type natriuretic peptide (BNP) concentration, left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD), pacing threshold and other related data were extracted and summarized.

RESULTS

A total of 6 studies were included, and the success rate of LBBP was 93.2%. Compared with baseline, LBBP could shorten QRSd (MD = 61.23, 95%CI: 58.21 ∼ 64.25, P < 0.01). Echocardiographic parameters including LVEF and LVEDD significantly improved (both with P < 0.01). Clinical outcomes including NYHA classification and BNP dramatically reduced (both with P < 0.01). Compared with biventricular pacing (BVP), LBBP could further improve QRSd, LVEF, LVEDD, and NYHA classification (all with P < 0.01). However, the pacing threshold at follow-up was 0.06V higher than that at baseline (P < 0.01), and the incidence of complications was 2.4%.

CONCLUSIONS

LBBP is effective and safe in heart failure patients with LBBB, whether it is better than BVP needs to be verified by randomized controlled trials. This article is protected by copyright. All rights reserved.

Feasibility and Safety of Left Bundle Branch Pacing for Advance Aged Patients: A Multicenter Comparative Study

Background: Left bundle branch pacing (LBBP) has been shown to be a safe and effective means to achieve physiological pacing. However, elderly patients have increased risks from invasive procedures and the risk of LBBP in elderly patients is not known. We aimed to investigate the safety and efficacy of LBBP in elderly patients >80 years of age.

Methods: From December 2017 to June 2019, 346 consecutive patients with symptomatic bradycardia, 184 patients under 80 years of age and 162 over 80 years, were included and underwent LBBP. The safety and prognosis of LBBP were comparatively evaluated by measured pacing parameters, periprocedural complications, and follow-up clinical events.

Results: Compared with the younger, the elderly group had worse baseline cardiac and renal function. LBBP was achieved successfully in both groups with comparable fluoroscopic time and paced QRS duration (110.0 [102.0, 118.0] ms for the young vs. 110.0 [100.0, 120.0] ms for the elderly, P = 0.874). Through a follow-up of 20.0 ± 6.1 months, pacing parameters were stable while higher threshold and impedance were observed in the elderly group. In the evaluation of safety, overall procedure-related complication rates were comparable (4.4 vs. 3.8%, young vs. elderly). For prognosis, similar rates of major adverse cardiocerebrovascular events (7.1 vs. 11.9%, young vs. elderly) were observed.

Conclusions: Compared to younger patients, LBBP could achieve physiological pacing in patients over 80 with comparable midterm safety and prognosis. Long-term safety and benefits of LBBP, however, necessitate further evaluation.

Feasibility and Outcomes of Upgrading to Left Bundle Branch Pacing in Patients With Pacing-Induced Cardiomyopathy and Infranodal Atrioventricular Block

His bundle pacing (HBP) can reverse left ventricular (LV) remodeling in patients with right ventricular (RV) pacing-induced cardimyopathy (PICM) but may be unable to correct infranodal atrioventricular block (AVB). Left bundle branch pacing (LBBP) results in rapid LV activation and may be able to reliably pace beyond the site of AVB. Our study was conducted to assess the feasibility, safety, and outcomes of permanent LBBP in infranodal AVB and PICM patients. Patients with infranodal AVB and PICM who underwent LBBP for cardiac resynchronization therapy (CRT) were included. Clinical evaluation and echocardiographic and electrocardiographic assessments were recorded at baseline and follow-up. Permanent LBBP upgrade was successful in 19 of 20 patients with a median follow-up duration of 12 months. QRS duration (QRSd) increased from 139.3 ± 28.0 ms at baseline to 176.2 ± 21.4 ms (P < 0.001) with right ventricular pacing (RVP) and was shortened to 120.9 ± 15.2 ms after LBBP (P < 0.001). The mean LBBP threshold was 0.7 ± 0.3 V at 0.4 ms at implant and remained stable during follow-up. The left ventricular ejection fraction (LVEF) increased from 36.3% ± 6.5% to 51.9% ± 13.0% (P < 0.001) with left ventricular end-systolic volume (LVESV) reduced from 180.1 ± 43.5 to 136.8 ± 36.7 ml (P < 0.001) during last follow-up. LBBP paced beyond the site of block, which results in a low pacing threshold with a high success rate in infranodal AVB patients. LBBP improved LV function with stable parameters over the 12 months, making it a reasonable alternative to cardiac resynchronization pacing via a coronary sinus lead in infranodal AVB and PICM patients.