A Beginner's Guide to Permanent Left Bundle Branch Pacing

Authors, Journal, Affiliations, Type, DOI

• Authors: Weijian Huang, Xueying Chen, Lan Su, Shengjie Wu, Xue Xia, Pugazhendhi Vijayaraman
• Journal: Heart Rhythm 2019;16(12):1791–1796 — "Hands On" section
• Affiliations: Department of Cardiology, The First Affiliated Hospital of Wenzhou Medical University, and Key Lab of Cardiovascular Disease of Wenzhou, Wenzhou, China; Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai; Geisinger Heart Institute, Wilkes Barre, Pennsylvania
• Type: Technique guide / narrative review (single-centre experience; no outcomes cohort)
• DOI: 10.1016/j.hrthm.2019.06.016

Overview

This is the Wenzhou group's foundational "how to do it" description of permanent left bundle branch pacing (LBBP), written for implanters moving from His-bundle pacing. It defines LBBP as capture of the LBB trunk or proximal fascicles — usually together with adjacent septal myocardium — and sets out five electrical signs of LBB capture, a composite rule for confirming it, a step-by-step transseptal implantation sequence, and a set of programming rules for connecting the LBBP lead to CRT and pacing generators. Each procedural step is paired with the electrical or fluoroscopic signal that should accompany it, so the technique is presented as a set of monitored checkpoints rather than a single manoeuvre. It is the source of several rules that later consensus documents and technique papers repeat, including the "w" pattern at the initial site, the fulcrum sign, and the requirement to stop advancing when right bundle branch delay appears.

Keywords

Direct left bundle capture; Left bundle branch pacing; Proximal left conduction system; Retrograde His potential; Stimulus to peak left ventricular activation time

Key Takeaways

Introduction

• Permanent His-bundle pacing (HBP) is feasible and clinically beneficial, but higher pacing thresholds, lower R-wave amplitudes and the potential for distal conduction block have limited its use in some patients.
• LBBP emerged as an alternative that delivers physiological pacing and LV electrical synchrony, particularly in infranodal AV block and LBBB.
• The anatomical rationale: the proximal left bundle branches run through the LV septum and fan out, forming a wider pacing target than the compact His bundle.
• HBP corrected classic LBBB in 97% of patients in the authors' prior work, and Upadhyay et al. showed the block is usually within the His or proximal left bundle — the basis for pacing distal to it.
• LBBP offers low thresholds, large R waves and a lower theoretical risk of distal conduction block because the distal conduction system is targeted.

Definitions and characteristics of LBBP

• Definition: LBBP is capture of the LBB (left bundle trunk or its proximal fascicles), usually with septal myocardial capture at low output (<1.0 V/0.4 ms).
• Three defining features of the technique: transvenous access; transseptal placement of the lead into the LV septal subendocardium in the LBB region; and confirmation of LBB capture.

1. Paced morphology of right bundle branch block pattern

• With the lead placed transseptally from the RV septum to LV septal subendocardium, the paced QRS changes from an LBBB pattern to an RBBB pattern, because the LV activates before the RV.
• The paced morphology is influenced by the pacing site within the LBB, existing bundle disease, and selective versus nonselective capture.

2. Identification of the LBB potential

• In patients with non-LBBB intrinsic rhythm, an LBB potential should always be recorded from the LBBP lead, with a potential-to-ventricle interval of 20–30 ms, to confirm lead position and the level of block.
• In LBBB, LBB potentials can only be recorded during restoration of left bundle conduction by HBP, or under other conditions.

3. Pacing stimulus to LV activation time

• Stim-LVAT is the interval from the pacing stimulus to the peak of the R wave in leads V4–V6, reflecting lateral precordial myocardium depolarisation.
• LBB capture is suggested when Stim-LVAT shortens abruptly with increasing output, or remains shortest and constant at both low and high output.
• Stim-LVAT during LBBP is shorter than during HBP.

4. Determination of selective and nonselective LBBP

• Selective LBBP: a discrete local component separate from the stimulus artifact on the unipolar electrogram from the LBBP lead — the direct sign of LBB-only capture.
• Nonselective LBBP: capture of both the LBB and adjacent septal myocardium, with no discrete local EGM and a paced ECG slightly different from selective LBBP.

5. Evidence for direct LBB capture

• The interval between the pacing stimulus and a retrograde His potential or an anterograde distal LBB potential recorded with an additional lead/catheter confirms capture.
• This is definitive but need not be used routinely in clinical practice.

The composite clinical rule

• Patients meeting criteria 1 and 2 plus at least one of the latter three criteria can be confirmed to have LBB capture.

Procedure description

Preprocedure evaluation and implantation tools

• Assess basal interventricular septal thickness and septal scar before the procedure.
• Ventricular backup pacing is recommended before LBBP implantation in LBBB, because RBB injury during the procedure can cause complete AV block.
• Tools: Medtronic 3830 lead and C315His sheath.
• Threshold and impedance are measured unipolar; final R-wave amplitude is measured bipolar.

How to determine the initial site

• Perform HBP first and save the fluoroscopic image of the distal HBP position as a marker.
• The initial LBBP site is ~1–1.5 cm distal to the HBP lead in the RV septum, along the line between the HBP site and the RV apex, in RAO 30°.
• At this site, the paced QRS before fixation usually shows a "w" pattern with a notch at the nadir of the QRS in V1.
• A "dual lead technique" can improve success in challenging implants or provide direct evidence of capture.

Deep fixation into the septum

• Rotate the sheath counterclockwise to keep the lead tip perpendicular to the septal surface and to support screwing.
• Rapid rotations, 3–4 turns at a time, then release and repeat, to drive the lead body behind the screw into the septum.
• A myocardial current of injury (COI) is often recorded on the EGM.
• Expected signs of advancement:
  1. The notch in paced V1 moves from the nadir to the end of the QRS → RBBB pattern.
  2. Unipolar pacing impedance rises.
  3. The fulcrum sign appears on fluoroscopy — the hinge point where the lead body meets the RV septum.
• If perforation into the LV occurs, simply withdrawing the lead is not adequate — reposition at a different location.

Monitoring, stopping rules and depth

• At a depth of ~6–8 mm (fulcrum sign, contrast injection, RBBB-paced morphology and/or RBBB-pattern PVCs), perform low- and high-output pacing: high output that shortens paced QRS and LVAT indicates the left conduction system is nearby.
• As the lead advances, the V1 notch moves up and becomes R′; RBBB-pattern PVCs are often seen during fixation.
• Avoid perforation by rotating half to one turn at a time, monitoring paced QRS and impedance, which should remain >500 Ω on unipolar pacing.
• Stop rotating once LBB capture is confirmed at a low threshold, usually <1.5 V/0.5 ms.
• Depth can be estimated from the hinge point to the helix and confirmed by contrast injection through the sheath in LAO 35°, or by intraprocedural echo / post-procedural CT.
• Difficult fixation is commonly caused by tissue in the helix, a deformed sheath or helix, scar/fibrosis at the site, or inadequate sheath support; remedies are to remove the tissue, replace the sheath/lead, and reposition distally and inferiorly.

Removing the sheath and confirming fixation

• Unlike HBP, there is no significant rebound or torque back after fixation.
• Pull the sheath back to the atrium while gently advancing the lead to create slack; recheck pacing parameters.
• Adequate slack is needed to avoid perforation or dislodgement after slitting the sheath.

Potential complications

• RBB injury: keeping the lead inside the sheath, pulling the sheath back from the ventricle with slight counterclockwise rotation and fixing the lead at the inferior septum may reduce it. Avoid fixing into the septum when a potential that is probably the RBB is seen.
• Lead dislodgement and septal perforation: pre-implant echo or MRI is useful in noncompaction, thin septum or septal scar. Monitor paced QRS and impedance at each step. Adequate slack avoids both dislodgement (too little) and perforation (too much).
• Coronary artery injury: place the lead inferiorly and posteriorly, because the large septal perforator branches are in the anterior septum.

Programming considerations

• Connection depends on rhythm and device type:
  • Chronic AF: connect the LBBP lead to the atrial port of a CRT generator.
  • Sinus rhythm: connect to the LV port if it completely corrects the LBBB, and adjust the AV delay to allow native conduction via the right bundle branch.
  • IVCD: the LBBP lead can sometimes be used together with the LV lead for better LV synchrony.
• Unlike HBP, routine changes to sensitivity and pacing output may not be needed initially, because LBBP parameters are typically low and stable.
• Different outputs and configurations produce different paced QRS morphologies. At higher output, anodal capture of the RV septum by bipolar pacing can compensate RV delay, so the paced QRS may not resemble a typical RBBB.
• Document the anodal capture threshold and the nonselective-to-selective LBBP thresholds during follow-up testing.
• Bipolar pacing at ~3.5 V/0.4 ms is suggested to achieve anodal capture for partial RV delay compensation, but programming above anodal capture is not mandatory; the final output balances anodal capture against battery drain.

Conclusion

• LBBP is described as safe and feasible in routine clinical practice.
• Two long-term concerns are named: lead performance under excessive myocardial contractile strain on the deeply seated lead, and the ability to safely extract these leads in future.
• New deflectable sheaths and leads with a longer helix and/or stylet may make the technique easier.
• Large prospective randomised studies are needed to confirm long-term safety and effectiveness.

Limitations of the document

• Single-centre technique experience presented as a beginner's guide, not a cohort study: there is no patient series, no success rate, no complication rate and no follow-up in this paper. Its claims about safety and feasibility are assertions from the authors' practice, not measured outcomes.
• The composite capture rule is expert consensus, not validated against direct electrophysiological evidence in this paper. It combines five signs of unequal strength, and the paper gives no sensitivity, specificity or interobserver data for the combination.
• The "RBBB pattern" criterion is treated as necessary, but later studies show it is also produced by LV septal pacing without LBB capture, so the guide's central morphological sign is not specific on its own.
• Depth and stopping rules are given as single values (6–8 mm; impedance >500 Ω; threshold <1.5 V/0.5 ms) derived from one practice, with no adjustment for septal thickness, scar or lead type.
• The programming advice predates dedicated conduction-system pacing generators and is written for off-label connections to standard CRT ports; it does not address pacing-polarity interactions with anodal capture in a systematic way.
• No long-term lead data: the conclusion explicitly leaves lead performance under contractile strain and future extraction unresolved.
• Conflict of interest: one author reports speaker, consultant, research and fellowship support from Medtronic, and consultancy for Boston Scientific, Abbott, Biotronik and Merrit Medical — the manufacturer of the lead and sheath described.

Key Concepts Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — the technique this guide defines and operationalises
• concepts/Conduction-System-Pacing — the broader family of physiological pacing
• concepts/His-Bundle-Pacing — the preceding technique and the anatomical reference point for the LBBP entry site
• concepts/Cardiac-Resynchronization-Therapy — the indication for most LBBP in this guide, and the device programming context
• concepts/Atrioventricular-Block — infranodal block is a principal indication
• concepts/LBBB-Criteria — the conduction disease LBBP is intended to correct

Key Entities Mentioned

• Medtronic 3830 lead and C315His sheath — the implantation tools named
• Wenzhou Medical University / First Affiliated Hospital — authors' centre where the technique was developed
• Geisinger Heart Institute — co-author affiliation
• His bundle — anatomical landmark for the initial site
• Left bundle branch — the capture target

Wiki Pages Updated

• Created: wiki/sources/lbbap-beginners-guide-hrs-2019.md
• Updated: wiki/concepts/Left-Bundle-Branch-Area-Pacing.md
• Updated: wiki/concepts/Conduction-System-Pacing.md
• Updated: wiki/sourceindex.md
• Updated: log.md