Left Bundle Branch Area Pacing Guided by Continuous Uninterrupted Monitoring of Unipolar Pacing Characteristics

Authors, Journal, Affiliations, Type, DOI

• Authors: Kris Gillis, MD, PhD; Louisa O'Neill, MD, PhD; Jean-Yves Wielandts, MD, MSc, PhD; Gabriela Hilfiker, MD; Alina Vlase, MD; Sébastien Knecht, MD, PhD; Mattias Duytschaever, MD, PhD; et al.
• Journal: J Cardiovasc Electrophysiol 2022;33:299–307. © 2021 Wiley Periodicals LLC. Received 10 July 2021; revised 9 October 2021; accepted 27 October 2021
• Affiliations: Department of Cardiology, Sint-Jan Hospital, Brugge, Belgium; Department of Cardiology, Centre Hospitalier de Wallonie picarde, Tournai, Belgium; Department of Internal Medicine, Ghent University, Ghent, Belgium
• Type: Single-centre, non-randomised comparison plus feasibility study — 30 patients, of whom 10 had conventional interrupted implantation and 20 the novel uninterrupted technique. No randomisation, no outcome endpoint
• DOI: 10.1111/jce.15302
• ⚠ Filename is misdated by one year. The raw file is Impedance-LBBAP-JCE-2021.md, reflecting the 2021 submission dates, but the article of record is 2022;33:299–307 — the citation line inside the PDF reads "J Cardiovasc Electrophysiol. 2022;33:299–307". This slug deliberately uses 2022; raw_path still points at the 2021-named file

Overview

The problem this addresses is procedural: confirming left bundle branch capture normally requires interrupting the implant — stop rotating, test at different outputs, read the pacing characteristics, then resume. That leaves the operator blind during the part of the manoeuvre where a lead can perforate the septum. This study's innovation is to pace from the inserted lead stylet (LS) rather than the connector pin (CP), which makes unipolar pacing characteristics available continuously while the lead is being screwed in — impedance, sensed electrogram and paced QRS morphology all monitored beat-to-beat, with no interruption. The validation is that LS pacing is a faithful surrogate for CP pacing (impedance R² = 0.9481), and the feasibility result is that it may make first-attempt success more common (90% vs 70%) while showing a recognisable impedance trajectory across the septum. The study is small and explicitly not powered to show superiority; its contribution is technical.

Keywords

His bundle pacing; left bundle branch area pacing; physiologic pacing

Key Takeaways

Background and Rationale

• During LBBAP lead implantation, intermittent monitoring of unipolar pacing characteristics confirms LBB capture and can detect septal perforation
• The aim: demonstrate that continuous uninterrupted unipolar pacing from an inserted lead stylet (LS) is feasible and facilitates implantation

Methods

• 30 patients (mean age 76 ± 14 years) implanted with a stylet-driven pacing lead (Biotronik Solia S60)
• 10 patients (comparison group): conventional implantation with interrupted unipolar pacing, comparing unipolar pacing characteristics between LS (lead stylet) and CP (connector-pin) pacing
• 20 patients (uninterrupted group): novel uninterrupted pace-mapping technique — pacing cables connected to the LS (cathode) and to the patient's body (anode)

Criteria of Successful LBB Capture (as applied here)

• LBB capture was accepted with a narrow paced QRS (<120 ms) or a left bundle branch potential on the sensed electrogram
• When both were absent, a short and stable pLVAT at differential high and low pacing outputs confirmed capture, defined as pLVAT <85 ms for a narrow native QRS or <100 ms for a wide native QRS or complete AV block at baseline
• Selective vs nonselective was determined during decremental pacing from high to low output, looking for a transition in QRS morphology; selective LBBP was characterised by a distinct isoelectric interval between the pacing spike and the onset of the paced QRS complex

Results

Validation of LS Against CP Pacing (the study's core claim)

• In the comparison group, LBBAP was obtained in all 10 patients: nonselective in 4/10 (40%), selective in 6/10 (60%)
• Unipolar pacing impedance from the LS and from the CP correlated excellently at each step of implantation: R² = 0.9481, p < .0001, with an insignificant bias of 12 ± 37 Ω — and comparable sensed electrograms and paced QRS morphologies
• This is what licenses the technique: pacing from the stylet measures the same thing as pacing from the connector pin, so the operator can monitor continuously without changing what is being observed

Performance of Continuous LS Pacing

• In the uninterrupted group, all 20 patients showed selective (14/20, 70%) or nonselective (6/20, 30%) LBB capture at the end of the continuous rotation manoeuvre
• Associated with a stable median pLVAT of 73 ms [IQR 68–80.5] and a median paced QRS duration of 120 ms [IQR 112–152]
• The impedance trajectory across the septum — a recognisable signature the operator can watch:
  • a small initial increase, then a progressive decrease as the lead passes from the RV septum to the LV sub-endocardial region (mean difference 143 ± 87 Ω)
  • followed by a discrete increase immediately before reaching the final position

Interrupted vs Continuous Implantation

• Comparison group (interrupted): successful LBBAP at first attempt in 7/10 (70%). Failure at first attempt was due to difficulty progressing the lead after the initial penetration
• Uninterrupted group: first attempt 18/20 (90%), second attempt 1 (5%), third attempt 1 (5%). Failure at first attempt was exclusively due to suboptimal sheath orientation
• At final position, nonselective capture in 6/20 (30%) — p = .77 versus comparison — and selective in 70% (p = .584)
• No significant difference in paced QRS duration between groups (median 116 ms [IQR 109–…])

Complications

• No perforation into the LV cavity occurred in any patient
• One patient in the uninterrupted group developed Dressler syndrome after implant, which responded well to conservative medical management; echocardiography confirmed correct LBBAP lead position without perforation, and no lead repositioning was needed
• All patients had stable pacing characteristics and LBB capture at discharge

Discussion

• 4.1 Continuous unipolar pacing characteristic monitoring to guide LBBAP — the technique's rationale
• 4.2 / 4.3 Pace-mapping options with lumenless versus stylet-driven pacing leads — notably, the absence of a revolving connector is identified as the practical obstacle that LS pacing overcomes for stylet-driven leads
• 4.4 The ideal pacing lead for LBBAP
• Comparison of stylet-driven and lumenless leads has shown similar performance

Conclusion

• Unipolar pacing from the inserted LS allows accurate determination of pacing impedance and generates similar paced QRS morphologies and sensed electrograms to CP pacing
• Continuous unipolar LS pacing allows real-time monitoring of impedance and paced QRS morphology, which facilitates safe and effective LBBAP lead implantation

Limitations of the document

Authors' own stated limitations

• Only one lead was studied — the Biotronik Solia S60 with its regular stylet — so the results cannot be extrapolated to other stylet-driven leads or stylet–lead combinations
• Small sample size may have led to an underestimation of septal perforation incidence; further studies are needed to confirm that early detection of QRS morphology transition and impedance monitoring can actually prevent perforation
• The comparison was not a clean one, for ethical reasons: in the comparison group, LS pacing was used between pace-mapping steps to inform the implanter of lead progression, so the traditional approach was not observed in isolation
• Patients were not randomised between groups, and the study is underpowered to demonstrate superiority of either technique in complications. The authors state the aim was accuracy, feasibility and safety rather than superiority

Additional limitations evident in the study

• No outcome endpoint, and the 90% vs 70% first-attempt difference is not statistically tested. With 10 and 20 patients, a 7/10 versus 18/20 difference is well within chance; the paper reports it descriptively. The headline impression of improved success is therefore unsupported by any inferential test
• The core correlational claim is validated in the same 10 patients used to generate it, and R² quantifies agreement of impedance — the claim that LS pacing gives comparable sensed electrograms and QRS morphologies is stated more qualitatively
• Interobserver and learning-curve effects are unaddressed. The uninterrupted technique requires the operator to interpret a continuous trace in real time, which is a skill the study does not characterise
• The impedance trajectory is descriptive, not thresholded. A "discrete increase immediately before final position" is offered as a landmark, but no cut-off or sensitivity/specificity is given, so its reliability as a stopping cue is unquantified
• Dressler syndrome in one patient is reported without discussion of whether it is plausibly related to the technique — a single event in 20, unresolvable either way
• The population is elderly and narrow (mean age 76) and no comparison group received a genuinely unmodified interrupted procedure, so the technique's incremental value over standard practice remains unmeasured
• Rating rationale: single-centre, non-randomised, small, technical feasibility with no outcome endpoint and no inferential testing of its central practical claim — hence medium

Key Concepts Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — the technique this monitoring method is designed to guide
• concepts/Conduction-System-Pacing — the umbrella category
• Lead stylet (LS) vs connector-pin (CP) pacing — the distinction that makes continuous monitoring possible; validated here as equivalent for impedance
• Unipolar pacing impedance — the continuously observable signal; trajectory across the septum described as initial rise → progressive fall (mean difference 143 ± 87 Ω) → discrete pre-final increase
• pLVAT (peak left ventricular activation time) — the capture criterion when QRS and LBB potential are unhelpful; <85 ms for narrow native QRS, <100 ms for wide QRS or complete AV block
• Selective vs nonselective LBBP — determined by decremental pacing; selective marked by an isoelectric interval between spike and paced QRS onset
• Septal perforation — the complication the technique is intended to help prevent; none occurred here

Key Entities Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — primary concept page
• Biotronik Solia S60 — the only pacing lead studied; a stylet-driven lead, and the basis of the limitation on generalisability
• Sint-Jan Hospital, Brugge — the investigating centre; Ghent University; Centre Hospitalier de Wallonie picarde
• Wiley Periodicals — publisher (J Cardiovasc Electrophysiol)

Wiki Pages Updated

• Created: wiki/sources/impedance-lbbap-jce-2022.md
• Updated: wiki/concepts/Left-Bundle-Branch-Area-Pacing.md
• Updated: wiki/sourceindex.md
• Updated: wiki/wikiindex.md