Permanent His bundle pacing: Recommendations from a Multicenter His Bundle Pacing Collaborative Working Group for standardization of definitions, implant measurements, and follow-up

Effects of adaptive left bundle branch-optimized cardiac resynchronization therapy: a single centre experience

BACKGROUND

Adaptive cardiac resynchronization therapy (aCRT) is associated with improved clinical outcomes. Left bundle branch area pacing (LBBAP) has shown encouraging results as an alternative option for aCRT. A technique that can be accomplished effectively using LBBAP combined with coronary venous pacing (LOT-aCRT). We aimed to assess the feasibility and outcomes of LOT-aCRT.

METHODS

LOT-aCRT, capable of providing two pacing modes, LBBAP alone or LBBAP combined with LV pacing, was attempted in patients with CRT indications. Patients were divided into two groups: those with LBBAP and LV pacing (LOT-aCRT) and those with conventional biventricular pacing (BVP-aCRT).

RESULTS

A total of 21 patients were enrolled in the study (10 in the LOT-aCRT group, 11 in the BVP-aCRT group). In the LOT-aCRT group, the QRS duration (QRSd) via BVP was narrowed from 158.0 ± 13.0 ms at baseline to 132.0 ± 4.5 ms (P = 0.019) during the procedure, and further narrowed to 123.0 ± 5.7 ms (P < 0.01) via LBBAP. After the procedure, when LOT-aCRT implanted and worked, QRSd was further changed to 121.0 ± 3.8 ms, but the change was not significant (P > 0.05). In the BVP-aCRT group, BVP resulted in a significant reduction in the QRSd from 176.7 ± 19.7 ms at baseline to 133.3 ± 8.2 ms (P = 0.011). However, compared with LOT-aCRT, BVP has no advantage in reducing QRSd and the difference was statistically significant (P < 0.01). During 9 months of follow-up, patients in both groups showed improvements in the LVEF and NT-proBNP levels (all P < 0.01). However, compared with BVP-aCRT, LOT-aCRT showed more significant changes in these parameters (P < 0.01).

CONCLUSIONS

The study demonstrates that LOT-aCRT is clinically feasible in patients with systolic heart failure and LBBB. LOT-aCRT was associated with significant narrowing of the QRSd and improvement in LV function.

His-Purkinje conduction system pacing for pacing-induced cardiomyopathy: a systematic literature review and meta-analysis

BACKGROUND

Upgrading to His-Purkinje conduction system pacing (HPCSP) has been proven to reverse ventricular remodeling and improve cardiac function in patients with pacing-induced cardiomyopathy (PICM). This meta-analysis aimed to assess the efficacy and clinical benefit of upgrading to HPCSP in patients with PICM after chronic right ventricular pacing (RVP).

METHODS

We systematically searched PubMed, Cochrane Library, and Embase for relevant articles from databases' establishment to April 22, 2022. Clinical outcomes and pacing parameters included left ventricular ejection fraction (LVEF) pre-RVP, pre-HPCSP, and during follow-up, New York Heart Association (NYHA) functional class at baseline and follow-up, lead-related complications, heart failure hospitalization (HFH), all-cause mortality, pacing thresholds at implant and during follow-up, and QRS duration (QRSd) pre-RVP, pre-HPCSP, and during follow-up.

RESULTS

A total of 6 articles including 144 patients were enrolled in this meta-analysis. QRSd increased from 127 ± 29 ms at baseline to 175 ± 19 ms (P < 0.001) during RVP and then significantly narrowed to 116 ± 18 ms (P < 0.001) after upgrading to HPCSP. During a mean follow-up of 17.9 ± 10.5 months, LVEF improved from 35 ± 8% pre-HPSCP to 48 ± 12% after upgrading to HPCSP (P < 0.001). The capture thresholds were 1.2 ± 0.9 V at baseline and increased slightly during follow-up. NYHA functional class improved significantly from 2.7 ± 0.8 to 1.9 ± 0.8 during follow-up (P < 0.001).

CONCLUSION

Our meta-analysis indicates that upgrading to HPCSP in patients with PICM is feasible and efficient, as it significantly improves electrical synchrony and cardiac function.

Depolarization and repolarization dynamics after His-bundle pacing: Comparison with right ventricular pacing and native ventricular conduction

Background

The current study aimed to evaluate changes in electrical depolarization and repolarization parameters after His‐bundle pacing (HBP) compared with right ventricular pacing (RVP) and its association with ventricular arrhythmia (VA).

Methods

Forty‐one patients (13 with HBP, 14 with RVP, and 14 controls [AAI mode]) were evaluated. After continuous pacing algorithm, QRS duration, QT interval, QTc, JT interval, T‐peak to T‐end (Tpe), and Tpe/QT ratio were measured on electrocardiography at baseline and 1 week, 1 month, and 6 months postoperatively. We investigated VA occurrence and adverse events after implantation.

Results

At 6 months, QRS duration was significantly shorter in the HBP (121.6 ± 15.6 ms) than in the RVP (150.1 ± 14.9 ms) group. The QT intervals were lower in the HBP (424.0 ± 40.9 ms) and control (405.9 ± 23.0 ms) groups than in the RVP (453.0 ± 40.2 ms) group. The Tpe and Tpe/QT ratios at 6 months differed significantly between the HBP and RVP groups (Tpe, 69.8 ± 19.7 ms vs 87.4 ± 11.9 ms and Tpe/QT, 0.16 ± 0.03 vs 0.19 ± 0.02, respectively). The Tpe and Tpe/QT ratios were similarly shortened in the HBP and control groups. VA occurred less frequently in the HBP (15%) and control (7.1%) groups than in the RVP (50%) group (p = 0.020). The non‐RVP group showed significantly lower rates of VA and major adverse events than the RVP group. Patients with VA demonstrated significantly longer QRS duration, QT interval, Tpe, and Tpe/QT at 6 months than those without VA.

Conclusion

HBP showed better depolarization and repolarization stability than RVP.

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.

Physiologic Differentiation Between Selective His Bundle, Nonselective His Bundle and Septal Pacing

His bundle (HB) pacing is an increasingly popular method of physiologic ventricular pacing. The electrocardiographic hallmark of physiologic pacing is the preservation or restoration of physiologic activation times in the left ventricle-a principle of paramount diagnostic importance. The current review focuses on the differentiation between 3 possible capture types when the pacing lead is placed in the HB region: selective HB capture when only HB is activated, nonselective HB capture when there is simultaneous activation of the adjacent right ventricular septal (RVS) myocardium, and selective RVS capture when HB is not activated at all but only septal myocardium.

Generating Evidence to Support the Physiologic Promise of Conduction System Pacing: Status and Update on Conduction System Pacing Trials

Conduction system pacing avoids the potential deleterious effects of right ventricular pacing in patients with bradycardia and provides an alternative approach to cardiac resynchronization therapy. We focus on the available observational and randomized evidence and review studies supporting the safety, feasibility, and physiologic promise of conduction system approaches. We evaluate the randomized data generated from the available clinical trials of conduction system pacing, which have led to the recent inclusion of CSP in international guidelines. The scope for future randomized trials will building on the physiologic promise of conduction system approaches and offering information on clinical end points is explored.

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.

Biventricular versus His bundle pacing after atrioventricular node ablation in heart failure patients with narrow QRS

Background: His bundle pacing (HBP) is a physiological alternative to biventricular (BiV) pacing. We compared short-term results of both pacing approaches in symptomatic atrial fibrillation (AF) patients with moderately reduced left ventricular (LV) ejection fraction (EF ≥35% and <50%) and narrow QRS (≤120 ms) who underwent atrioventricular node ablation (AVNA).Methods: Thirty consecutive AF patients who received BiV pacing or HBP in conjunction with AVNA between May 2015 and January 2020 were retrospectively assessed. Electrocardiographic, echocardiographic, and clinical data at baseline and 6 months after the procedure were assessed.Results: Twenty-four patients (age 68.8 ± 6.5 years, 50% female, EF 39.6 ± 4%, QRS 95 ± 10 ms) met the inclusion criteria, 12 received BiV pacing and 12 HBP. Both groups had similar acute procedure-related success and complication rates. HBP was superior to BiV pacing in terms of post-implant QRS duration, implantation fluoroscopy times, reduction of indexed LV volumes (EDVi 63.8 (49.6-81) mL/m² vs. 79.9 (66-100) mL/m², p = 0.055; ESVi 32.7 (25.6-42.6) mL/m² vs. 46.4 (42.9-68.1) mL/m², p = 0.009) and increase in LVEF (46 (41-55) % vs. 38 (35-42) %, p = 0.005). However, the improvement of the NYHA class was similar in both groups.Conclusions: In symptomatic AF patients with moderately reduced EF and narrow QRS undergoing AVNA, HBP could be a conceivable alternative to BiV pacing. Further prospective studies are warranted to address the outcomes between both 'ablate and pace' strategies.

Computed tomography imaging-identified location and electrocardiographic characteristics of left bundle branch area pacing in bradycardia patients

INTRODUCTION

Left bundle branch area pacing (LBBAP) is a novel physiological pacing modality. The relationship between the pacing lead tip location and paced electrocardiographic (ECG) characteristics remains unclear. The objectives are to determine the lead tip location within the interventricular septum (IVS) and assess the location-based ECG QRS duration (QRSd) and left ventricular activation time (LVAT).

METHODS

This multi-center study enrolled 50 consecutive bradycardia patients who met pacemaker therapy guidelines and received LBBAP implantation via the trans-ventricular septal approach. After at least 3 months post implant, 12-lead ECGs and pacing parameters were obtained. Cardiac computed tomography (CT) imaging was performed to assess the LBBAP lead tip distance from the LV blood pool.

RESULTS

Among the 50 patients, analyzable CT images were obtained in 42. In 23 of the 42 patients, the lead tips were within 2 mm to the LV blood pool (the LV subendocardial (LVSE) group), 13 between 2 mm and 4 mm (the Near-LVSE group), and the remaining 6 beyond 4 mm (the mid-LV septal (Mid-LVS) group). No significant differences in paced QRSd were found among the 3 groups (LVSE, 107±15 ms; Near-LVSE, 106±13 ms; Mid-LVS, 104±15 ms; P=0.87). LVAT in the LVSE (64±7 ms) was significantly shorter than in the Mid-LVS (72±8 ms; P<0.05), but not significantly different from that in the Near-LVSE (69±8 ms; P>0.05).

CONCLUSION

In routine LBBAP practice, paced narrow QRSd and fast LVAT, indicative of physiological pacing, was consistently achieved for lead tip location in the LV subendocardial or near LV subendocardial region. This article is protected by copyright. All rights reserved.

Pacing Characteristics of His Bundle Pacing vs. Left Bundle Branch Pacing: A Systematic Review and Meta-Analysis

Background

His bundle pacing (HBP) is a physiological pacing strategy, which aims to capture the His bundle-Purkinje system and synchronously activate the ventricles. Left bundle branch pacing (LBBP) is a newly discovered physiological pacing technique similar to HBP. We conducted this meta-analysis to compare the pacing parameters and clinical results between HBP and LBBP.

Methods

We systematically retrieved studies using the PubMed, Embase database, and Cochrane Library. Mean difference (MD) and relative risk (RR) with their 95% confidence intervals [CIs] were used to measure the outcomes. A random-effect model was used when studies were of high heterogeneity.

Results

A total of seven studies containing 867 individuals were included. Compared with HBP, LBBP was associated with higher implant success rates (RR: 1.12, 95% CI: 1.05–1.18; I² = 60%, P = 0.0003), lower capture threshold at implantation (V/0.5 ms) (MD: 0.63, 95% CI: 0.35–0.90, I² = 89%, P < 0.0001) and capture threshold at follow-up (V/0.5 ms) (MD: 0.76, 95% CI: 0.34–1.18, I² = 93%, P = 0.0004), and larger sensed R wave amplitude (mV) at implantation (MD: 7.23, 95% CI: 5.29–9.16, P < 0.0001) and sensed R wave amplitude (mV) at follow-up (MD: 7.53, 95% CI: 6.85–8.22, P < 0.0001). In LBBP recipients, greater QRS wave complex reduction was found in the paced QRS duration at follow-up compared with HBP recipients at follow-up (MD: 6.12, 95% CI: 1.23–11.01, I² = 0%, P = 0.01). No statistical differences were found in procedure duration, fluoroscopy time, native left ventricular ejection fractions (LVEF), LVEF improvement, native QRS duration, and QRS reduction from the native QRS duration vs. paced QRS duration at implantation.

Conclusion

Current evidence suggests that pacing characteristics are better in LBBP compared with HBP. Further prospective studies are needed to validate the clinical advantages of LBBP.

Complete electrical reverse remodeling of native conduction after resynchronization therapies

BACKGROUND

Electrical reverse remodeling of native conduction is associated with better clinical outcome following cardiac resynchronization therapy (CRT). We aimed to describe characteristics, time course and long-term outcome of patients with complete electrical reverse remodeling (CERR) after resynchronization therapies.

METHODS

CRT candidates were treated with bi-ventricular, His bundle or left bundle branch pacing. CERR was defined if native QRS duration post-implantation was narrowed to ≤120 ms.

RESULTS

A total of 322 patients met the inclusion criteria. Among them, 66 were super-responders and 12 exhibited CERR. All 12 patients were diagnosed of non-ischemic cardiomyopathy with left bundle branch block (LBBB) meeting the Strauss criteria. The mean native QRS duration when CERR was achieved was 110.8 ± 10.0 ms, significantly shorter than the baseline (175.0 ± 18.8 ms). The occurrence of CERR varied from several days post-implantation to 18-month follow-up. The persistence of CERR also showed great variations. Eleven patients (91.7%, 11/12) showed echocardiographic super-response. Patients with CERR showed similar baseline characteristics compared to those with echocardiographic super-response but without CERR. Two patients with CERR showed different responses after bi-ventricular pacing was turned off. One patient remained stable with narrow QRS complex and great response. The other patient had reappearance of LBBB and decreased cardiac function, but recovered by turning on the device again.

CONCLUSIONS

Patients with CERR exhibited great response to different resynchronization therapies. The time course of CERR and echocardiographic super-response varied greatly. The variability of native conduction system and accompanied changes of mechanical remodeling suggest the mechanisms of electrical-disorder related cardiomyopathy.

His bundle pacing guided by automated intrinsic morphology matching is feasible in patients with narrow QRS complexes

Pace mapping and visual comparison of the local pacing response with the intrinsic QRS morphology form the mainstay of His bundle pacing (HBP). We evaluated the performance of a surface lead morphology match algorithm for automated classification of the pacing response in patients with narrow intrinsic QRS undergoing electroanatomic mapping (EAM)-guided HBP. HBP was attempted in 43 patients. In 28 cases with narrow QRS, the EnSite AutoMap Module was used for automated assessment of the QRS morphology resulting from pace mapping in the His cloud area with either a diagnostic catheter or the His lead. An intrinsic morphology match score (IMS) was calculated for 1.546 QRS complexes and assessed regarding its accuracy and performance in classifying the individual pacing response as either selective HBP (S-HBP), nonselective HBP (NS-HBP) or right ventricular stimulation. Automated morphology comparison of 354 intrinsic beats with the individual reference determined a test accuracy of 99% (95% CI 98.96–99.04) and a precision of 97.99–99.5%. For His-lead stimulation, an IMS ≥ 89% identified S-HBP with a sensitivity, specificity and positive predictive value of 1.00 (0.99, 1.00) and a negative predictive value of 0.99 (0.98, 1.00). An IMS between 78 and < 89% indicated NS-HBP with a sensitivity and specificity of 1.00 (0.99, 1.00) and 0.99 (0.98, 1.00), respectively. IMS represents a new automated measure for standardized individual morphology classification in patients with normal QRS undergoing EAM-guided HBP.

Clinical trial registration: NCT04416958.

Meta-Analysis Comparing Safety and Efficacy of Left Bundle Branch Area Pacing Versus His Bundle Pacing

Although His bundle pacing (HBP) can provide a physiologic ventricular activation pattern, it has disadvantages such as the difficulty of lead implantation, reduced R wave amplitudes, and high and unstable pacing thresholds. Recent studies have demonstrated that left bundle branch area pacing (LBBaP) might overcome these deficiencies. A total of 7 nonrandomized controlled studies including 786 patients (n = 442 receiving LBBaP and n = 344 receiving HBP) with bradyarrhythmia were evaluated. Compared with HBP, LBBaP appeared to result in increased R wave amplitudes (at implant: MD 9.84 mV, 95% confidence interval [CI] 7.61 to 12.06 mV; at follow-up: MD 7.62 mV, 95% CI 6.73 to 8.50 mV), lowered capture thresholds (at implant: MD -0.73 V, 95% CI -0.81 to -0.64 V; at follow-up: MD -0.71 V, 95% CI -0.92 to -0.50 V), shortened procedure times (MD -16.70 minutes, 95% CI -26.51 to -6.90 minutes) and fluoroscopic durations (MD -6.16 min, 95% CI -8.28 to -4.03 minutes), and increased success rates (odds ratio 2.14, 95% CI 1.23 to 3.74); all of these differences were significant. However, paced QRS durations, the lead impedance at implantation and follow-up, and incidence of lead-related complications such as lead dislodgement did not significantly differ between LBBaP and HBP. In conclusion, current evidence suggests that LBBaP is a potential alternative to HBP as a pacing modality with which to maintain an ideal physiologic pattern of ventricular activation through native His-Purkinje system stimulation.

[ESC guidelines 2021 on cardiac pacing and cardiac resynchronization therapy : What's new?]

The new European Society of Cardiology (ESC) guidelines on cardiac pacing and cardiac resynchronization therapy were presented together with the new ESC heart failure guidelines at the ESC congress in September. The new document includes detailed sections on patient evaluation and clinical assessment, implantation, minimizing complications and patient follow-up. The guidelines have been updated and expanded particularly on the approach to reflex syncope, the indications after transcatheter aortic valve implantation (TAVI) and the perioperative management. The indications for cardiac resynchronization therapy (CRT) are now in line with the simultaneously published ESC heart failure guidelines. New physiological forms of stimulation and leadless pacing are now included in the guidelines.

Sincronia Ventricular na Estimulação Cardíaca Parahissiana: Alternativa por Ativação Cardíaca Fisiológica (Estimulação Indireta do Feixe de His)?

Fundamento

A estimulação cardíaca artificial (ECA) por captura direta ou indireta do feixe de His resulta em contração ventricular sincrônica (ECA fisiológica).

Objetivos

Comparar sincronia cardíaca, características técnicas e resultados de parâmetros eletrônicos entre duas técnicas de ECA indireta do feixe de His: a não seletiva e a parahissiana.

Métodos

Intervenção experimental (novembro de 2019 a abril de 2020) com implante de marca-passo definitivo (MPd) DDD em pacientes com fração de ejeção ventricular esquerda > 35%. Foram comparadas a sincronia cardíaca resultante mediante algoritmo de análise eletrocardiográfica da variância espacial do QRS e as características técnicas associadas a cada método entre ECA hissiana não seletiva (DDD-His) e parahissiana (DDD-Var).

Resultados

De 51 pacientes (28 homens), 34 (66,7%) foram alocados no grupo DDD-Var e 17 (33,3%), no grupo DDD-His, com idade média de 74 e 79 anos, respectivamente. No grupo DDD-Var, a análise da variância espacial do QRS (índice de sincronia ventricular) mostrou melhora após o implante de MPd (p < 0,001). Ao ECG pós-implante, 91,2% dos pacientes do grupo DDD-Var mostraram padrão fisiológico de ECA, comprovando ativação similar à do DDD-His (88,2%; p = 0,999). O eixo do QRS estimulado também foi similar (fisiológico) para ambos os grupos. A mediana do tempo de fluoroscopia do implante foi de 7 minutos no grupo DDD-Var e de 21 minutos no DDD-His (p < 0,001), favorecendo a técnica parahissiana. A duração média do QRS aumentou nos pacientes do DDD-Var (114,7 ms pré-MPd e 128,2 ms pós-implante, p = 0,044). A detecção da onda R foi de 11,2 mV no grupo DDD-Var e de 6,0 mV no DDD-His (p = 0,001).

Conclusão

A ECA parahissiana comprova recrutamento indireto do feixe de His, mostrando-se uma estratégia eficaz e comparável à ECA fisiológica ao resultar em contração ventricular sincrônica similar à obtida por captura hissiana não seletiva.

Conduction System Pacing for Post Transcatheter Aortic Valve Replacement Patients: Comparison With Right Ventricular Pacing

Introduction: For patients who develop atrioventricular block (AVB) following transcatheter aortic valve replacement (TAVR), right ventricular pacing (RVP) may be associated with adverse outcomes. We assessed the feasibility of conduction system pacing (CSP) in patients who developed AVB following TAVR and compared the procedural and clinical outcomes with RVP. Methods: Consecutive patients who developed AVB following TAVR were prospectively enrolled, and were implanted with RVP or CSP. Procedural and clinical outcomes were compared among different pacing modalities. Results: A total of 60 patients were enrolled, including 10 who were implanted with His bundle pacing (HBP), 20 with left bundle branch pacing (LBBP), and 30 with RVP. The HBP group had significantly lower implant success rate, higher capture threshold, and lower R-wave amplitude than the LBBP and RVP groups (p < 0.01, respectively). The RVP group had a significantly longer paced QRS duration (153.5 ± 6.8 ms, p < 0.01) than the other two groups (HBP: 121.8 ± 8.6 ms; LBBP: 120.2 ± 10.6 ms). During a mean follow-up of 15.0 ± 9.1 months, the LBBP group had significantly higher left ventricular ejection fraction (LVEF) (54.9 ± 6.7% vs. 48.9 ± 9.1%, p < 0.05) and shorter left ventricular end-diastolic diameter (LVEDD) (49.7 ± 5.6 mm vs. 55.0 ± 7.7 mm, p < 0.05) than the RVP group. While the HBP group showed trends of higher LVEF (p = 0.016) and shorter LVEDD (p = 0.017) than the RVP group. Four patients in the RVP group died-three deaths were due to progressive heart failure and one was due to non-cardiac reasons. One death in the LBBP group was due to the non-cardiac reasons. Conclusions: CSP achieved shorter paced QRS duration and better cardiac structure and function in post-TAVR patients than RVP. LBBP had a higher implant success rate and better pacing parameters than HBP.

A single-center experience with early adoption of physiologic pacing approaches

BACKGROUND

Increasing interest in physiological pacing has been countered with challenges such as accurate lead deployment and increasing pacing thresholds with His-bundle pacing (HBP). More recently, left bundle branch area pacing (LBBAP) has emerged as an alternative approach to physiologic pacing.

OBJECTIVE

To compare procedural outcomes and pacing parameters at follow-up during initial adoption of HBP and LBBAP at a single center.

METHODS

Retrospective review, from September 2016 to January 2020, identified the first 50 patients each who underwent successful HBP or LBBAP. Pacing parameters were then assessed at first follow-up after implantation and after approximately 1 year, evaluating for acceptable pacing parameters defined as sensing R-wave amplitude >5 mV, threshold <2.5 V @ 0.5 ms, and impedance between 400 and 1200 Ω.

RESULTS

The HBP group was younger with lower ejection fraction compared to LBBAP (73.2 ± 15.3 vs. 78.2 ± 9.2 years, p = .047; 51.0 ± 15.9% vs. 57.0 ± 13.1%, p = .044). Post-procedural QRS widths were similarly narrow (119.8 ± 21.2 vs. 116.7 ± 15.2 ms; p = .443) in both groups. Significantly fewer patients with HBP met the outcome for acceptable pacing parameters at initial follow-up (56.0% vs. 96.4%, p = .001) and most recent follow-up (60.7% vs. 94.9%, p ≤ .001; at 399 ± 259 vs. 228 ± 124 days, p ≤ .001). More HBP patients required lead revision due to early battery depletion or concern for pacing failure (0% vs. 13.3%, at a mean of 664 days).

CONCLUSION

During initial adoption, HBP is associated with a significantly higher frequency of unacceptable pacing parameters, energy consumption, and lead revisions compared with LBBAP.

His Bundle Pacing: A promising alternative strategy for Antibradycardic-pacing. Report of a single center-experience

His Bundle Pacing (HBP) is proven to be a safe and effective alternative pacing modality that, in addition, avoids Pacemaker-induced Cardiomyopathy (PICM) by achieving a ''physiological'' ventricular stimulation, via the native conduction system. Indications include various causes of bradycardia requiring antibradycardic pacing, inadequately controlled Atrial Fibrillation requiring AV node ablation and established PICM. In addition, HBP may also be used as an alternative therapy for patients with Heart Failure (HF) and an indication for Cardiac Resynchronization Therapy. Available data show a benefit from HBP with regard to preservation or restoration of intra- and inter-ventricular synchronization, improvement in Left Ventricular Ejection Fraction, functional status and Quality of Life, decrease in atrial fibrillation incidence and improvement in HF hospitalization rates, compared to conventional pacing. Nevertheless, superiority in terms of mortality rates has not been consistently demonstrated and long-term efficacy and safety remains to be proven. In the present manuscript, we review the status of HBP and we present our current experience with this novel pacing modality.

Adopting permanent His bundle pacing: learning curves and medium-term outcomes

AIMS

This study aims to determine procedural characteristics, acute success rates, and medium-term outcomes of consecutive patients undergoing His bundle pacing (HBP); and learning curves of experienced electrophysiologists adopting HBP.

METHODS AND RESULTS

Consecutive HBP patients at three hospitals were recruited. Clinical characteristics, acute procedural details, and medium-term outcomes were extracted from electronic medical records. Two hundred and thirty-three patients [mean age 74.6 ± 10.1 years, 48% female, 68% narrow QRS, 71% normal left ventricular ejection fraction (LVEF), 55.8% atrioventricular block] underwent HBP. Acute procedural success was 81.1% (mean procedural and fluoroscopic times of 105.5 ± 36.5 and 13.8 ± 9.3 min). Broad QRS was associated with lower HBP success (odds ratio 0.39, P = 0.02). Fluoroscopic and procedural times decreased and plateaued after 30-40 cases per operator. Implant HBP threshold was 1.3 ± 0.7 V at 1.0 ± 0.2 ms and R wave was 5.0 ± 3.9 mV. During follow-up, loss of HBP occurred in a further 12.4% and 11.3% of patients experienced a ≥1 V increase in HBP threshold. Five (2.6%) patients required HBP revision for pacing difficulties. About 8.6% of patients had a >50% decrease in R wave but lead revision for sensing issues was not necessary. On an intention to treat basis, 56.7% of patients in whom HBP was attempted had persisting HBP capture and thresholds of <2 V.

CONCLUSION

Physicians adopting HBP should be cognizant of the learning curve and preferentially select non-dependent patients with normal QRS and LVEF, to minimize risk of lead revision. Further rises in HBP threshold may increase battery drain and need for reoperations, important considerations when choosing HBP for cardiac resynchronization therapy.

Estimulação do Ramo Esquerdo do Sistema His-Purkinje: Experiência Inicial

Fundamento

A estimulação ventricular direita convencional aumenta o risco de fibrilação atrial e insuficiência cardíaca em portadores de marca-passo. A estimulação do ramo esquerdo (RE) do sistema His-Purkinje pode evitar os desfechos indesejados da estimulação ventricular direita.

Objetivo

Analisar retrospectivamente os desfechos intraoperatórios, eletrocardiográficos e os dados clínicos do seguimento inicial de pacientes submetidos à estimulação do RE.

Métodos

Foram avaliados os parâmetros eletrônicos do implante e eventuais complicações precoces de 52 pacientes consecutivos submetidos à estimulação do sistema de condução. O nível de significância alfa adotado foi igual a 0,05.

Resultados

52 pacientes foram submetidos a estimulação do RE do sistema His-Purkinje, obtendo sucesso em 50 procedimentos. 69,2% dos pacientes eram do sexo masculino e a mediana e intervalo interquatil da idade no momento do implante foi de 73,5 (65,0-80,0) anos. A duração do QRS pré-implante foi de 146 (104-175) ms e de 120 (112-130) ms após o procedimento. O tempo de ativação do ventrículo esquerdo foi de 78 (70-84) ms. A amplitude da onda R foi de 12,00 (7,95-15,30) mV, com limiar de estimulação de 0,5 (0,4-0,7) V × 0,4 ms e impedância de 676 (534-780) ohms. O tempo de procedimento foi de 116 (90-130) min e o tempo de fluoroscopia foi de 14,2 (10,0-21,6) min.

Conclusão

A estimulação cardíaca do sistema de condução His-Purkinje por meio da estimulação do ramo esquerdo é uma técnica segura e factível. Nesta casuística, apresentou alta taxa de sucesso, foi realizada com tempo de procedimento e fluoroscopia baixos e obteve medidas eletrônicas adequadas.

Fortuitous Left Bundle Branch Area Pacing in a Small Child

Deep septal pacing is an emerging technique for physiologic pacing in adults. We report a case where left bundle capture was inadvertently achieved in a small child with routine lead deployment into a thin septum and discuss the potential feasibility of this technique for future study. (Level of Difficulty: Advanced.)

ECG and Pacing Criteria for Differentiating Conduction System Pacing from Myocardial Pacing

During His-Purkinje conduction system (HPS) pacing, it is crucial to confirm capture of the His bundle or left bundle branch versus myocardialonly capture. For this, several methods and criteria for differentiation between non-selective (ns) capture - capture of the HPS and the adjacent myocardium - and myocardial-only capture were developed. HPS capture results in faster and more homogenous depolarisation of the left ventricle than right ventricular septal (RVS) myocardial-only capture. Specifically, the depolarisation of the left ventricle (LV) does not require slow cell-to-cell spread of activation from the right side to the left side of the interventricular septum but begins simultaneously with QRS onset as in native depolarisation. These phenomena greatly influence QRS complex morphology and form the basis of electrocardiographic differentiation between HPS and myocardial paced QRS. Moreover, the HPS and the working myocardium are different tissues within the heart muscle that vary not only in conduction velocities but also in refractoriness and capture thresholds. These last two differences can be exploited for the diagnosis of HPS capture using dynamic pacing manoeuvres, namely differential output pacing, programmed stimulation and burst pacing. This review summarises current knowledge of this subject.

[His bundle and left bundle branch pacing]

Cardiac pacemakers are an extremely effective treatment for bradycardia but can, however, cause desynchronization of ventricular contraction leading to cardiomyopathy. Pacing of the conduction system can prevent and even reverse desynchronization, which is impressively visible in echocardiography with speckle tracing. His' bundle and left bundle branch pacing requires a specific implantation technique, sheaths and leads which can achieve successful stimulation of the conduction system in up to 98% of cases. Data on conduction system pacing have been acquired in numerous studies but only a few randomized outcome studies. Therefore, in the current European guidelines His' bundle and left bundle branch pacing only have a low level recommendation. The guidelines recommend His' bundle pacing in patients in whom a coronary sinus lead cannot be implanted and in patients with permanent atrial fibrillation and planned atrioventricular (AV) node ablation for heart rate control. Additionally, conduction system pacing appears to be meaningful in patients with an AV block who require pacing of the ventricle for ≥20% of the time or who already show a slightly or moderately reduced left ventricular ejection fraction (36-50%). Even in patients scheduled for generator replacement who have developed a cardiac pacemaker-induced cardiomyopathy, the opportunity should not be missed to upgrade the system by implantation of a His' bundle electrode.

Hemodynamic Effects of Permanent His Bundle Pacing Compared to Right Ventricular Pacing Assessed by Two-Dimensional Speckle-Tracking Echocardiography

We compared the effects of right ventricular (RVP; n = 26) and His bundle (HBP; n = 24) pacing in patients with atrioventricular conduction disorders and preserved LVEF. Postoperatively (1D), and after six months (6M), the patients underwent global longitudinal strain (GLS) and peak systolic dispersion (PSD) evaluation with 2D speckle-tracking echocardiography, assessment of left atrial volume index (LAVI) and QRS duration (QRSd), and sensing/pacing parameter testing. The RVP threshold was lower than the HBP threshold at 1D (0.65 ± 0.13 vs. 1.05 ± 0.20 V, p < 0.001), and then it remained stable, while the HBP threshold increased at 6M (1.05 ± 0.20 vs. 1.31 ± 0.30 V, p < 0.001). The RVP R-wave was higher than the HBP R-wave at 1D (11.52 ± 2.99 vs. 4.82 ± 1.41 mV, p < 0.001). The RVP R-wave also remained stable, while the HBP R-wave decreased at 6M (4.82 ± 1.41 vs. 4.50 ± 1.09 mV, p < 0.02). RVP QRSd was longer than HBP QRSd at 6M (145.0 ± 11.1 vs. 112.3 ± 9.3 ms, p < 0.001). The absolute value of RVP GLS decreased at 6M (16.32 ± 2.57 vs. 14.03 ± 3.78%, p < 0.001), and HBP GLS remained stable. Simultaneously, RVP PSD increased (72.53 ± 24.15 vs. 88.33 ± 30.51 ms, p < 0.001) and HBP PSD decreased (96.28 ± 33.99 vs. 84.95 ± 28.98 ms, p < 0.001) after 6 months. RVP LAVI increased (26.73 ± 5.7 vs. 28.40 ± 6.4 mL/m², p < 0.05), while HBP LAVI decreased at 6M (30.03 ± 7.8 vs. 28.73 ± 8.7 mL/m², p < 0.01). These results confirm that HBP does not disrupt ventricular synchrony and provides advantages over RVP.

His-Purkinje conduction system pacing: A systematic review and network meta-analysis in bradycardia and conduction disorders

BACKGROUND

His-Purkinje conduction system pacing (HPCSP) has emerged as an effective alternative to overcome the limitations of right ventricular pacing (RVP) via physiological left ventricular activation, but there remains a paucity of comparative information for His bundle pacing (HBP) and left bundle branch pacing (LBBP).

METHODS

A Bayesian random-effects network analysis was conducted to compare the relative effects of HBP, LBBP, and RVP in patients with bradycardia and conduction disorders. PubMed, Embase, Cochrane Library, and Web of Science were systematically searched from database inception until September 21, 2021.

RESULTS

Twenty-eight studies involving 4160 patients were included in this meta-analysis. LBBP significantly improved success rate, pacing threshold, pacing impedance, and R-wave amplitude compared with HBP. LBBP also demonstrated a nonsignificant trend towards superior outcomes of lead complications, heart failure hospitalization, atrial fibrillation, and all-cause death. However, HBP was associated with significantly shorter paced QRS duration relative to LBBP. Despite higher success rates, shorter procedure/fluoroscopy duration, and fewer lead complications, patients receiving RVP were more likely to experience reduced left ventricular ejection fraction, longer paced QRS duration, and higher rates of heart failure hospitalization than those receiving HPCSP. No statistical differences were observed in the remaining outcome measures.

CONCLUSIONS

This network meta-analysis demonstrates the efficacy and safety of HPCSP for the treatment of bradycardia and conduction disorders, with differences in pacing parameters, electrophysiology characteristics, and clinical outcomes between HBP and LBBP. Larger-scale, long-term comparative studies are warranted for further verification.

Physiologic lead placement with electroanatomic mapping: A case series

INTRODUCTION

His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) have emerged as attractive alternatives to traditional biventricular pacing to achieve cardiac resynchronization therapy. Early reported results have been inconsistent, particularly amongst patients in whom initial placement with traditional approaches has been unsuccessful or those with complex anatomy or congenital abnormalities. In this report, we describe the use of three-dimensional electroanatomic mapping (EAM) in five selected cases.

METHODS

Five patients from multiple clinical sites underwent EAM-guided HBP or LBBAP by highly trained electrophysiologists with significant experience with conduction system pacing. Each patient in this series underwent EAM-guided conduction system pacing due to complex anatomy and/or prior failed lead implantation.

RESULTS

EAM-guided lead implantation was successful in all five cases. Capture thresholds were relatively low and patients continued to have evidence of successful lead implantation with minimum 1-month follow-up. The fluoroscopy time varied, likely owing to the variable complexity of the cases.

CONCLUSIONS

The use of EAM, in combination with traditional intracardiac electrograms with or without fluoroscopy, allows more targeted and precise placement of leads for HBP and LBBAP pacing. Further investigation is needed to determine this strategy's long-term performance and to optimize patient selection.

His-optimized cardiac resynchronization therapy in a patient with heart failure and right bundle branch block: a case report

Background 

Cardiac resynchronization therapy (CRT) is an option for treatment for chronic heart failure (HF) associated with left bundle branch block (LBBB). Patients with HF and right bundle branch block (RBBB) have potentially worse outcomes in comparison to LBBB. Traditional CRT in RBBB can increase mortality and HF deterioration rates over native disease progression. His bundle pacing may improve the results of CRT in those patients. Furthermore, atrioventricular node ablation (AVNA) for rate control in atrial fibrillation (AF) can be challenging in patients with previously implanted leads in His region.

Case summary 

We report the case of 74-year-old gentleman with a 5-year history of HF, permanent AF with a rapid ventricular response, and RBBB. He was admitted to the hospital with complaints of severe weakness and shortness of breath. Left ventricular ejection fraction (LVEF) was decreased (41%), right ventricle (RV) was dilated (41 mm), and QRS was prolonged (200 ms) with RBBB morphology. The patient underwent His-optimized CRT with further left-sided AVNA. As a result, LVEF increased to 51%, RV dimensions decreased to 35 mm with an improvement of the clinical status during a 6-month follow-up.

Discussion 

Patients with AF, RBBB, and HF represent the least evaluated clinical subgroup of individuals with less beneficial clinical outcomes according to CRT studies. Achieving the most effective resynchronization could require pacing fusion from sites beyond traditional with the intention to recruit intrinsic conduction pathways. This approach can be favourable for reducing RV dilatation, improving LVEF, and maximizing electrical resynchronization.

Impact of physiological pacing on functional mitral regurgitation in systolic dysfunction: Initial echocardiographic remodeling findings after His bundle pacing

BACKGROUND

Although His bundle pacing (HBP) has been shown to improve left ventricular ejection fraction (LVEF), its impact on mitral regurgitation (MR) remains uncertain.

OBJECTIVES

The aim of this study was to evaluate change in functional MR after HBP in patients with left ventricular (LV) systolic dysfunction.

METHODS

Paired echocardiograms were retrospectively assessed in patients with reduced LVEF (<50%) undergoing HBP for pacing or resynchronization. The primary outcomes assessed were change in MR, LVEF, LV volumes, and valve geometry pre- and post-HBP. MR reduction was characterized as a decline in ≥1 MR grade post-HBP in patients with ≥grade 3 MR at baseline.

RESULTS

Thirty patients were analyzed: age 68 ± 15 years, 73% male, LVEF 32% ± 10%, 38% coronary artery disease, 33% history of atrial fibrillation. Baseline QRS was 162 ± 31 ms: 33% left bundle branch block, 37% right bundle branch block, 17% paced, and 13% narrow QRS. Significant reductions in LV end-systolic volume (122 mL [73-152 mL] to 89 mL [71-122 mL], P = .006) and increase in LV ejection fraction (31% [25%-37%] to 39% [30%-49%], P < .001) were observed after HBP. Ten patients had grade 3 or 4 MR at baseline, with reduction in MR observed in 7. In patients with at least grade 3 MR at baseline, reduction in LV volumes, improved mitral valve geometry, and greater LV contractility were associated with MR reduction. Greater reduction in paced QRS width was present in MR responders compared to non-MR responders (-40% vs -25%, P = .04).

CONCLUSIONS

In this initial detailed echocardiographic analysis in patients with LV systolic dysfunction, HBP reduced functional MR through favorable ventricular remodeling.

Left Bundle Branch Area Pacing: Implant Technique, Definitions, Outcomes, and Complications

PURPOSE OF REVIEW

Conduction system pacing (CSP) has emerged during the last few years as the cornerstone of physiological pacing. Two different CSP modalities have been described so far: His bundle pacing (HBP) and left bundle branch area pacing (LBBAP). This review will be focused on the description of LBBAP technique, definitions, outcomes, and complications.

RECENT FINDINGS

Large observational studies have demonstrated the safety and feasibility of LBBAP in different scenarios. LBBAP has been associated with excellent pacing electrical parameters (pacing threshold and R wave sensing) and low complication rates including lead revision < 1%. In patients with cardiac resynchronization therapy (CRT) indication, LBBAP has shown significant improvement of functional class and left ventricular ejection fraction during short-term follow-up. LBBAP is a relatively new CSP modality showing excellent results for patients with conventional bradycardia pacing indications and promising expectations about its potential role for CRT.

Novel Wide-Band Dielectric Imaging System Guided Lead Deployment for His Bundle Pacing: A Feasibility Study

Introduction: His bundle pacing (HBP) is the most widely used physiological pacing modality, but difficulties in locating the His bundle lead to high fluoroscopic exposure. An electroanatomical mapping (EAM) system can be an efficient tool to achieve HBP implantation with near-zero fluoroscopic visualization.

Methods: In the study, 20 patients who had indications for pacemaker implantation were prospectively enrolled and underwent HBP implantation either with the conventional fluoroscopy approach (the standard group) or guided by a novel KODEX-EPD mapping system (the EAM-guided group). The success rate, procedural details, pacing parameters, and procedure-related complications were compared between the two groups.

Results: In the study, 20 consecutive patients were randomized with 10 patients in each group. HBP was successfully achieved in nine patients in the standard group and nine patients in the EAM-guided group. The procedural time was similar between the EAM-guided group vs. the standard group (85.40 ± 22.34 vs. 86.50 ± 15.05 min, p = 0.90). In comparison with the standard group, the EAM-guided group had a significant shorter total fluoroscopic time (FT) (1.45 ± 0.58 vs. 12.36 ± 5.46 min, p < 0.01) and His lead fluoroscopic time (HL-FT) (0.84 ± 0.56 vs. 9.27 ± 5.44 min, p < 0.01), while lower total fluoroscopic dose (3.13 ± 1.24 vs. 25.38 ± 11.15 mGy, p < 0.01) and His lead fluoroscopic dose (1.85 ± 1.17 vs. 19.06 ± 11.03 mGy, p < 0.01). No significant differences were observed in paced QRS duration and pacing parameters between the two groups. During a 3-month follow-up, one patient had a capture threshold increased >1 V/1.0 ms in the standard group, while no other complications were recorded in either group.

Conclusion: The KODEX-EPD system could facilitate HBP implantation with significantly reduced FT and dose without compromising the procedural time.

Permanent His-bundle pacing using distal His-bundle electrogram-guided approach in patients with atrioventricular block

BACKGROUND

Permanent His-bundle pacing (HBP) is effective and safe; however, the success rate of HBP is low, especially in patients with infranodal block. This study aimed to assess the efficacy and feasibility of HBP implantation using an electrophysiological guided approach targeting a distal His-bundle electrogram (HBE) in patients with atrioventricular block (AVB).

METHODS

Thirty-four consecutive patients with AVB (infranodal block in 28 patients) who underwent HBP were enrolled. During implantation, we attempted to target the distal part of the HBE (distal HBE) beyond the block site based on unipolar mapping. The His-capture threshold was evaluated for 1 year after implantation.

RESULTS

HBP was achieved in 26 patients and in 21 patients (75%) with infranodal block. Detection of distal HBE was significantly higher in the successful HBP group than in the HBP failure group (65.4% vs. 0%, p = .001). Among 15 patients with intra-Hisian block, 14 patients (93%) successfully achieved HBP with distal HBE detection. During the 1-year follow-up period, an increase in His-capture threshold by ≥1.0 V at 1.0 ms occurred in five (19.2%) of 26 patients. The increased His-capture threshold group exhibited significantly less detection of distal HBE (20% vs. 76.2%; odds ratio 0.078, 95% confidence interval 0.07-0.87, p = .038) and a higher His-capture threshold at implantation (2.0 ± 1.1 V vs. 1.1 ± 0.9 V; odds ratio 1.702, 95% confidence interval 1.025-2.825, p = 0.04) than the non-increased His-capture threshold group.

CONCLUSION

HBP implantation guided by distal HBE approach may be feasible with subsequent stable pacing in patients with intra-Hisian and atrioventricular nodal block.

How to Implant His Bundle and Left Bundle Pacing Leads: Tips and Pearls

Cardiac pacing is the treatment of choice for the management of patients with bradycardia. Although right ventricular apical pacing is the standard therapy, it is associated with an increased risk of pacing-induced cardiomyopathy and heart failure. Physiological pacing using His bundle pacing and left bundle branch pacing has recently evolved as the preferred alternative pacing option. Both His bundle pacing and left bundle branch pacing have also demonstrated significant efficacy in correcting left bundle branch block and achieving cardiac resynchronisation therapy. In this article, the authors review the implantation tools and techniques to perform conduction system pacing.

Novel approach to diagnosis of His bundle capture using individualized left ventricular lateral wall activation time as reference

BACKGROUND

During nonselective His bundle (HB) pacing, it is clinically important to confirm His bundle capture versus right ventricular septal (RVS) capture. The present study aimed to validate the hypothesis that during HB capture, left ventricular lateral wall activation time, approximated by the V₆ R-wave peak time (V₆ RWPT), will not be longer than the corresponding activation time during native conduction.

METHODS

Consecutive patients with permanent HB pacing were recruited; cases with abnormal His-ventricle interval or left bundle branch block were excluded. Two corresponding intervals were compared: stimulus-V₆ RWPT and native HB potential-V₆ RWPT. The difference between these two intervals (delta V₆ RWPT), which was diagnostic of lack of HB capture, was identified using receiver operating characteristic (ROC) curve analysis.

RESULTS

A total of 723 electrocardiograms (ECGs) (219 with native rhythm, 172 with selective HB, 215 with nonselective HB, and 117 with RVS capture) were obtained from 219 patients. The native HB-V₆ RWPT, nonselective-, and selective-HB paced V₆ RWPT were nearly equal, while RVS V₆ RWPT was 32.0 (±9.5) ms longer. The ROC curve analysis indicated delta V₆ RWPT > 12 ms as diagnostic of lack of HB capture (specificity of 99.1% and sensitivity of 100%). A blinded observer correctly diagnosed 96.7% (321/332) of ECGs using this criterion.

CONCLUSIONS

We validated a novel criterion for HB capture that is based on the physiological left ventricular activation time as an individualized reference. HB capture can be diagnosed when paced V₆ RWPT does not exceed the value obtained during native conduction by more than 12 ms, while longer paced V₆ RWPT indicates RVS capture.

Safety and feasibility of conduction system pacing in patients with congenital heart disease

INTRODUCTION

Conduction system pacing (CSP) has emerged as an ideal physiologic pacing strategy for patients with permanent pacing indications. We sought to evaluate the safety and feasibility of CSP in a consecutive series of unselected patients with congenital heart disease (CHD).

METHODS

Consecutive patients with CHD in which CSP was attempted were included. Safety and feasibility, implant tools and electrical parameters at implant and at follow-up were evaluated.

RESULTS

A total of 20 patients were included (10 with a previous device). A total of 10 patients had complex forms of CHD, 9 moderate defects and 1 a simple defect. CSP was achieved in 75% of cases (10 His bundle pacing, 5 left bundle branch pacing) with left ventricular septal pacing in the remaining 5 patients. Procedure times and fluoroscopy times were prolongued (126 ± 82 min and 27 ± 30 min, respectively). Ventricular lead implant times widely varied ranging from 4 to 115 min, (mean 31 ± 28 min) and the use of multiple delivery sheaths was frequent (50%). The QRS width was reduced from 145 ± 36 ms at baseline to 116 ± 18 ms with CSP. Implant electrical parameters included: CSP pacing threshold 0.95 ± 0.65 V; R wave amplitude 9.2 ± 8.8 mV and pacing impedance 632 ± 183 Ohms, and remained stable at a median follow-up of 478 days (interquartile range: 225-567). Systemic ventricle systolic function and NYHA class (1.50 ± 0.51 vs. 1.10 ± 0.31; p = .008) significantly improved at follow-up. Lead revision was required in one patient at Day 4.

CONCLUSIONS

Permanent CSP is safe and feasible in patients with CHD although implant technique is complex.

The relationship between anatomy and electrical parameters in His bundle pacing: A transthoracic echocardiography evaluation

PURPOSE

The implantation site of the His bundle (HB) lead may influence pacing parameters. Our aim was to characterize the anatomical location of the HB lead tip and its relationship with acute electrical parameters.

METHODS

Consecutive patients who underwent HB lead implantation, guided by standard fluoroscopy and electrophysiology, were prospectively enrolled. The relationship between HB lead tip and tricuspid valve plane (TVP) was assessed with post-procedure transthoracic echocardiography.

RESULTS

Twenty-five patients were studied. In 11 patients (44%), the HB lead tip did not cross the TVP (A group): in 7 cases it was screwed in the right atrium at a mean distance of -6.1 mm from the TVP and, in 4 cases, at the level of the tricuspid annulus. In the remaining 14 patients (56%), the lead tip crossed the TVP (V group): it was screwed in the right ventricle at a mean distance of 9.3 mm from the TVP. A and V groups had comparable HB capture thresholds (1.6 ± 1 V vs 1.7 ± 0.7 V, 1 ms pulse-width; p = 0.66); selective HB capture was significantly more represented in the A group (91% vs 21%; p = 0.001). Significantly higher R-wave amplitudes were seen in the V group (6.7 ± 3 vs 2.5 ± 1.7 mV; p = 0.0004), and they positively correlated with the distance from the TVP (p = 0.0038). Atrial oversensing was never observed.

CONCLUSION

In a consecutive cohort of HB pacing recipients, the rate of patients who had an effective HB capture in the atrium was substantial and was characterized by different electrophysiological properties than in the ventricle.

Is His-optimized superior to conventional cardiac resynchronization therapy in improving heart failure? Results from a propensity-matched study

BACKGROUND

His bundle pacing (HBP), alone or optimized in association with coronary sinus pacing (HBP+LV) has recently been proposed as an alternative to conventional cardiac resynchronization therapy (CRT). However, there is lack of controlled studies that assessed clinical outcome.

METHODS

We did a single-center, propensity-score matched, case-control study of comparison of HBP and HBP+LV versus conventional CRT in patients with heart failure (HF) and standard indications for CRT. The study group patients were consecutively enrolled in the year 2019. The control group patients were selected, by propensity score matching, among those CRT implantations performed in the years 2015-2018.

RESULTS

There were 27 patients in each group. In the active group, 12 (44%) patients received HBP alone and 12 (44%) patients HBP+LV pacing. HBP failed in three (11%) patients. In the control group, conventional CRT was achieved in 26 (96%) patients and failed in one. Paced QRS width was shorter in the active than in the control group (128 ± 18 vs. 148 ± 27 ms, p = .004). During a mean of 9.6 months of follow-up, a composite clinical outcome of death, hospitalization for HF or worsening HF occurred in three (11%) in the active group and in four (15%) in the control group, p = .58. No difference was also observed with softer endpoints: NYHA class (1.9 ± 0.7 vs. 2.1 ± 0.7), subjective improvement (74% vs. 74%) and LV ejection fraction (40.7% vs. 40.7%).

CONCLUSION

Compared with conventional CRT, a shorter QRS width can be obtained with HBP alone or in association with coronary sinus pacing but we were unable to show a better clinical outcome. There is urgent need for large, randomized trials.

His bundle pacing capture threshold stability during long-term follow-up and correlation with lead slack

AIMS

His bundle pacing (HBP) is the most physiologic form of pacing. Long-term HBP capture threshold stability and its relation to lead characteristics at the time of implantation have not been adequately described. The aim of this study was to characterize HB capture threshold in follow-up and to identify potential lead characteristics predictive of lead capture instability.

METHODS AND RESULTS

Consecutive patients with successful HBP for bradycardia indications were identified from the Geisinger HBP registry. His bundle capture thresholds, baseline comorbidities, and radiographic lead slack characteristics were analysed. An increase in HB capture threshold ≥1 V above implant values at any time during follow-up was tracked. Forty-four of the 294 studied (15%) experienced HB capture threshold increase by ≥ 1 V. Threshold increase was seen early (41% by 8 weeks, 66% by 1 year). Eighteen (6%) patients required lead revision in follow-up. Abnormal slack shape was associated with a trend toward capture threshold increase [hazard ratio (HR) 2.07; 95% confidence interval (CI) 0.9-4.6; P = 0.08]. Non-perpendicular angle of lead insertion on radiography was associated with the capture threshold increase (HR 2.81, 95% CI 1.4-5.8; P < 0.01).

CONCLUSION

His bundle capture threshold remains stable in the majority (85%) of patients. Implant characteristics may predict the threshold rise. Further evaluation of the aetiology of threshold increase and design changes in lead and delivery systems may lead to chronically stable capture thresholds.

Comparison of synchronization between left bundle branch and his bundle pacing in atrial fibrillation patients: An intra-patient-controlled study

Background

His bundle pacing (HBP) is a physiological pacing strategy to preserve the electrical synchrony of ventricular conduction and left ventricular (LV) function. Left bundle branch pacing (LBBP) has emerged as an alternative physiological pacing technique.

Objective

To evaluate cardiac electrical and mechanical synchrony comparing LBBP and HBP in patients with permanent atrial fibrillation (AF).

Methods

Consecutive patients with symptomatic bradycardia and AF were enrolled from January to June of 2019. The cardiac electrical and mechanical synchrony in different pacing mode were evaluated at baseline and after implantation.

Results

Both HBP and LBBP were performed in 20 patients. LBBP significantly widened the QRS duration compared with the intrinsic conduction (113.2 ± 14.5  vs. 96.5 ± 16.2 ms; p = .01), while HBP did not (104.5 ± 22.3  vs. 96.5 ± 16.2 ms; p = .12). Both LBBP and HBP patients had similar LV myocardial strain measurements for the mechanical synchrony evaluation without significant change compared with baseline. There was no significant difference in right ventricular synchrony measurement between LBBP and HBP. Compared to HBP, LBBP had less interventricular synchrony (IMVD, 14.7 ± 9.2  vs. 3.1 ± 12.7 ms, p < .01; Ts‐LV‐RV, 37.9 ± 10.7  vs. 18.5 ± 10.8 ms, p < .001).

Conclusions

Although LBBP's a physiological pacing mode can achieve a similar cardiac electrical and mechanical synchronization when compared to HBP, LBBP results in modest delay in RV activation, and the clinical implication remains to be studied.

Effect of Nonselective His Bundle Pacing on Delayed Myocardial Activation in Left-axis Deviation and Left Bundle Branch Block

It has been suggested that nonselective His bundle pacing (NS-HBP) corrects terminal conduction delay in right bundle branch block by early excitation of the right ventricular free wall. A similar analysis of NS-HBP, in patients with left bundle branch block (LBBB) and left-axis deviation (LAD) has not been done. Therefore, we compared the baseline QRS parameters in LAD and LBBB during NS-HBP and selective HBP (S-HBP). In LAD patients (n = 16), NS-HBP normalized the QRS axis from −35° ± 10° to 30° ± 34° (p < 0.01) and increased the lead 1 voltage (L1V) from 0.55 ± 0.3 mV to 0.88 ± 0.2 mV (p < 0.001) without increasing the peak lateral wall activation time (PLWAT) (p = not significant). In 23 of 41 LBBB patients, NS-HBP decreased the prolonged PLWAT by 73 ms (p < 0.0001), resolved the mid-QRS notch, normalized the QRS axis, and increased the L1V from 0.5 ± 0.3 mV to 1.15 ± 0.3 mV (p < 0.0001). In the remaining 18 LBBB patients, NS-HBP did not resolve the mid-QRS notch; however, the peak septal activation time decreased by 45 ms (p < 0.0001), PLWAT decreased by 53 ms (p < 0.0001), L1V increased from 0.5 ± 0.3 mV to 0.87 ± 0.4 mV (p < 0.0001), and the QRS axis normalized. All patients who developed S-HBP at lower pacing showed uncorrected LBBB (n = 6) or LAD (n = 7). In conclusion, NS-HBP, which causes myocardial activation in advance of simultaneously initiated S-HBP, results in a paced QRS complex with a normal axis and shorter activation times and restores the L1V in patients with LAD and LBBB. In some patients, a mid-QRS notch was seen with NS-HBP, which suggests fusion with S-HBP, which conducts without LBBB correction. A higher L1V in association with a shorter PLWAT and a normal QRS axis suggests that a more organized degree of left ventricular activation occurs with NS-HBP as compared to LBBB.

Tricuspid regurgitation associated with implantable electrical device insertion: A systematic review and meta-analysis

BACKGROUND

Implantable cardioverter defibrillator (ICD) and permanent pacemaker (PPM) lead placement may worsen or result in tricuspid regurgitation (TR). While the association between lead placement and the incidence of TR has been established, current understanding of this problem remains incomplete. This systematic review and meta-analysis sought to pool the existing evidence to better understand the occurrence and severity of TR associated with cardiac implantable electrical device (CIED) insertion.

METHODS

An electronic search was performed to identify all relevant studies published from 2000 to 2018. Overall, 15 studies were selected for the analysis comprising 4019 patients with data reported on TR development following ICD or PPM lead placement. Demographic information, perioperative clinical variables, and clinical outcome measures, including pre and postoperative echocardiographic TR grade changes, were extracted and pooled for systematic review.

RESULTS

Mean patient age was 69 years [95% CI: 64.62-73.59], and 63% [95% CI: 57-68] were male. Devices implanted included ICD in 57% [95%CI: 43-70] and PPM in 41% [95%CI: 31-52]. The most common indications for pacemaker implantation were sick sinus syndrome in 22% [95% CI: 22-37] and AV block in 21% [95%CI:12-34. The commonest indications for ICD implantation were primary and secondary prevention of sudden cardiac death. Atrial fibrillation was present in 37% [95%CI: 28-46] and congestive heart failure in 15% [95%CI: 2-57]. Baseline distribution of TR grades were as follows: grade 0/1 TR in 89% [95%CI: 82-93], grade 2 TR in 8% [95%CI: 5-13], grade 3 TR in 2% [95%CI: 0-7] and grade 4 TR in 2% [95%CI: 1-4]. Post-procedure, grade 0/ 1 TR decreased to 68% [95% CI: 51-81] (p < 0.01), grade 2 TR increased to 21% [15-28] (p < 0.01), grade 3 TR increased to 13% [95%CI: 5-32] (p = 0.02), and grade 4 TR increased to 7% [95%CI: 5-9] (p < 0.01).

CONCLUSION

ICD and PPM lead placement is associated with increased TR post-procedure. Further studies are warranted to evaluate changes in TR grade in the long term.

The feasibility and safety of left bundle branch pacing vs. right ventricular pacing after mid-long-term follow-up: a single-centre experience

AIMS

The aim of this study is to prospectively assess the feasibility and safety of left bundle branch pacing (LBBP) when compared with right ventricular pacing (RVP) during mid-long-term follow-up in a large cohort.

METHODS AND RESULTS

Patients (n = 554) indicated for pacemaker implantation were prospectively and consecutively enrolled and were non-randomized divided into LBBP group and RVP group. The levels of cTnT and N-terminal pro-B type natriuretic peptide were measured and compared within 2 days post-procedure between two groups. Implant characteristics, procedure-related complications, and clinical outcomes were also compared. Pacing thresholds, sensing, and impedance were assessed during procedure and follow-up. Left bundle branch pacing was feasible with a success rate of 94.8% with high incidence of LBB potential (89.9%), selective LBBP (57.8%), and left deviation of paced QRS axis (79.7%) with mean Sti-LVAT of 65.07 ± 8.58 ms. Paced QRS duration was significantly narrower in LBBP when compared with RVP (132.02 ± 7.93 vs. 177.68 ± 15.58 ms, P < 0.0001) and the pacing parameters remained stable in two groups during 18 months follow-up. cTnT elevation was more significant in LBBP when compared with RVP within 2 days post-procedure (baseline: 0.03 ± 0.03 vs. 0.02 ± 0.03 ng/mL, P = 0.002; 1 day post-procedure: 0.13 ± 0.09 vs. 0.04 ± 0.03 ng/mL, P < 0.001; 2 days post-procedure: 0.10 ± 0.08 vs. 0.03 ± 0.08 ng/mL, P < 0.001). The complications and cardiac outcomes were not significantly different between two groups.

CONCLUSION

Left bundle branch pacing was feasible in bradycardia patients associated with stable pacing parameters during 18 months follow-up. Paced QRS duration was significantly narrower than that of RVP. Though cTnT elevation was more significant in LBBP within 2 days post-procedure, the complications, and cardiac outcomes were not significantly different between two groups.

A simple and practical criterion for determining a failed His-bundle pacing

AIMS

To establish a simple criterion for determining a failed His-bundle pacing (HBP). This criterion states that if stimulus to QRS end interval is longer than His-bundle potential to QRS end interval ('S-QRSend > H-QRSend') then a failed HBP can be determined.

METHODS AND RESULTS

We performed retrospective analysis on 737 pacing tests around His-bundle in 241 patients and prospective analysis on 400 tests in 123 patients. A successful HBP is defined as that whole His-bundle is captured with or without capture of adjacent ventricular myocardium, otherwise, a failed HBP was considered. The output criteria and effective refractory period criteria were used as the gold standards for determining a successful HBP. The gold standards are that if decreasing the pacing output or pacing cycle length to a certain level results in duration or morphology changes of QRS, then a successful HBP is ascertained. In retrospective analysis of patients with normal His-Purkinje conduction, a failed HBP was determined in 31% (154/492) of pacing tests according to 'S-QRSend > H-QRSend'; all of them were validated by the gold standards (specificity = 100%). In prospective study, a failed HBP was confirmed according to the simple criterion with 100% accuracy in 33% (79/241) pacing tests. This simple criterion was also suitable for patients with His-Purkinje conduction disease although cases with 'S-QRSend > H-QRSend' rarely occurred.

CONCLUSION

A failed HBP can be easily and reliably determined solely by 'S-QRSend > H-QRSend' in more than 30% pacing tests.

Early improvement of left ventricular ejection fraction by cardiac resynchronization through His bundle pacing in patients with heart failure

AIMS

Permanent His bundle pacing (p-HBP) can correct intraventricular conduction disorders and could be an alternative to traditional cardiac resynchronization therapy (CRT) via the coronary sinus. We describe the short-term impact of HBP on left ventricular ejection fraction (LVEF) and improvement of left intraventricular synchrony.

METHODS AND RESULTS

This prospective descriptive study, performed from January 2018 to February 2019, included patients with left bundle branch block (LBBB) and an CRT indication who were resynchronized by p-HBP. We used the Medtronic C315 His catheter or a combination of the CPS-Direct-Universal introducer, CPS-AIM™-Universal subselector (Abbot), and SelectSecure™ MRI-SureScan™ 3830 lead. Correction of the LBBB by HBP had been previously checked. At 1 month of follow-up, we analysed the quantification of LVEF and measurement of the delay of the septal wall with the posterior wall as a parameter of intraventricular synchrony. We included 48 patients with LBBB and an indication for CRT. With HBP, we corrected the LBBB in 81% of patients (n = 39), and we achieved cardiac resynchronization through permanent HBP in 92% of these patients (n = 36). Left ventricular ejection fraction and intraventricular mechanical resynchronization improved in all patients, which was demonstrated by echocardiography through the improvement of the delay of the septal wall with the posterior wall from 138 ms (range 131-151) to 41 ms (19-63).

CONCLUSION

There is early improvement after p-HBP in LVEF and left ventricular electromechanical synchronization in patients with LBBB, heart failure, and an indication for CRT.