Lumenless and Stylet-Driven Leads for Left Bundle Branch Area Pacing: Materials, Techniques, Benefits, and Trade-Offs of the Two Approaches

Authors, Journal, Affiliations, Type, DOI

• Authors: Simone Taddeucci; Gianluca Mirizzi; Amato Santoro (corresponding)
• Journal: Journal of Clinical Medicine 2024;13(16):4758. Received 3 July 2024; revised 6 August 2024; accepted 7 August 2024; published 13 August 2024. Open access (CC BY)
• Affiliations: Division of Biotechnology, University of Siena; Division of Cardiology, Tuscany Foundation "Gabriele Monasterio", Pisa; Division of Interventional Cardiology, Azienda Ospedaliera Universitaria Senese, Siena, Italy
• Type: Narrative technical review of the pacing leads and delivery systems used for left bundle branch area pacing. No systematic search, no inclusion criteria, no quality appraisal, no own patient data
• DOI: 10.3390/jcm13164758
• Funding: none. Conflicts of interest: declared as none — but the acknowledgements thank named employees of Medtronic, Abbott, Biotronik and Boston Scientific "for their expertise and support during LBBPa", and the review is organised product-by-product across all four manufacturers. That relationship is worth weighing when reading its comparative judgements
• Note on terminology: the paper uses "LBBPa" (left bundle branch pacing area) throughout where the rest of this wiki uses LBBAP

Overview

Almost all early left bundle branch area pacing was done with one lead — the Medtronic SelectSecure 3830, a 4.1 Fr lumenless lead with a fixed isodiametric helix — and the field's technique, learning curve and outcome data are built around it. This review describes the alternative: ordinary stylet-driven leads, which are stiffer, support the septum during screwing, allow continuous ECG monitoring during rotation by clipping the pacemaker analyser to the stylet, but carry an extendable helix that can retract, deform or fracture. It catalogues the materials and delivery systems of the four manufacturers' lead–sheath combinations (Medtronic 3830 with C315/C304; Biotronik Solia S with Selectra 3D; Abbott Tendril STS 2088TC with CPS Locator/CPS Direct; Boston Scientific Ingevity+ with SSPC), explains the specific manoeuvre each system uses to prevent helix retraction (pretensioning the inner coil, integrated locking tools, or a home-made cap), and tabulates the complications common to both routes — septal perforation, macro- and microdislodgment, lead rupture, helix damage, and rare coronary events. Its conclusion is that SDL success is now comparable, but that the two lead types trade support and manoeuvrability against stability and ease of extraction, and that the ideal lead would combine both.

Keywords

left bundle branch area pacing; lumenless leads; stylet-driven leads; pacemaker implantation

Key Takeaways

Abstract

• LBBAP provides better pacing thresholds, fewer macrodislodgments and a reliable CRT strategy compared with HBP
• Lumenless leads (LLL) — small body, fixed helix — guarantee stability, avoid helix retraction and make septal penetration easier; this underlies their favourable learning curve
• Stylet-driven leads (SDL) have shown comparable success rates, with risks of helix retraction and lead fracture, but offer manoeuvrability, support, and continuous ECG-monitored pacing during implantation
• New dedicated tools are being developed to simplify SDL implantation; the review summarises techniques and complications for both

1. Introduction

• LBBAP captures the LBB or its fascicles via conventional or adapted leads through dedicated delivery sheaths, resynchronising the LV
• The HBP comparison: HBP's advantages are counterbalanced by high thresholds, sensing problems, lower resynchronisation capacity in bundle branch block and high displacement rates; backup pacing leads are often required
• LBBAP gives better thresholds and fewer macrodislodgments than HBP
• The evidence imbalance: LBBAP experience is primarily LLL, especially the SelectSecure 3830; SDL use is growing. Short- and mid-term observational studies show higher acute implant success with LLL but comparable LBBAP capture and complication rates; Sritharan et al. reported comparable success after a 50-patient learning curve
• The main SDLs: Solia S (Biotronik), Ingevity (Boston Scientific), Tendril 2088TC (Abbott)
• CSP-specific complications that the traditional lead literature does not cover: early lead fracture, tricuspid regurgitation, macrodislodgment, microdislodgment, and intraprocedural septal perforation

2. LBBP lead placement technique

• Signal setup: display the unipolar signal from the lead tip, filtered 30–500 Hz to identify conduction-system signals; optimal sheaths should allow easy His-potential identification. If no His signal is found, tricuspid valve potentials (separated atrial and ventricular EGMs with an isoelectric interval) can substitute, and contrast injection confirms the delivery position
• Navigation: after a His electrogram in unipolar configuration, advance the whole system 2–3 cm in RAO along the LBB area. RAO shows antero-posterior anatomy; a pure fluoroscopic method divides the RV silhouette in RAO into nine segments from base to apex and aims at the central segment of the basal/medial parts
• Check for coronary sinus cannulation in LAO — it occurs frequently with both fixed double-curve and deflectable devices
• Anatomy that helps and hinders: the LBB fans out into the septal myocardium with less stringent demarcation than the His bundle or RBB. This facilitates engagement of the conduction system but is also why selective LBBAP is often not achieved — interindividual variability is wide
• Positioning: in LAO the septal curve of the sheath should point to the septum at 2–3 o'clock; contrast confirms septal position and perpendicular lead orientation
• LLL is "floppy" and needs perpendicular delivery with tight adherence to the septum — otherwise it bends and fails to penetrate, which is necessary for conduction-tissue capture. SDL is more supportive, so strict adherence is not required for septal penetration, but selective LBBAP is rarely achieved without it
• The initial paced morphology: unipolar pacing should give a "W" pattern in V1 with discordant or negative concordant QRS in II and III. Negative concordance suggests the lead points inferiorly toward the posterior fascicle; positive concordance suggests the anterior fascicle as the landing site
• Screwing: up to 10 initial clockwise turns, with 8–12 turns reported for LLL and wide variation by sheath position, septal thickness and myocardial pathology. The delivery must stay firmly against the myocardium and perpendicular; if too much lead lies outside the sheath, torque spreads over the lead body and produces supercoiling without deep penetration
• Final morphology target: early–mid precordial transition with a positive QRS in V6, fundamental for LBBB capture; typically Rs or RS in more apical positions
• The EHRA stepwise criteria, as restated here:
  1. QRS transition morphology during pacing-threshold testing
  2. V6RWPT <75 ms for native narrow QRS or RBBB; <80 ms for LBBB, asystole, or IVCD with RBBB and fascicular block; <90 ms accepted in severely dilated LV or conduction system disease
  3. V6–V1 interpeak interval >44 ms
  4. QRS transition to selective LBBAP during programmed stimulation
• Continuous surveillance during screwing: frequent checks of impedance, unipolar unfiltered current of injury and paced QRS both confirm capture and reduce perforation risk

Selective versus non-selective capture — the intracardiac criteria

• S-LBB capture: absence of local ventricular EGM within the stimulus artefact with discrete isoelectric components on the paced bipole and immediately adjacent bipoles (2 mm spacing); and an isoelectric interval between pacing spike and QRS, with the spike–QRS interval approximating the left Purkinje–QRS interval
• NS-LBB capture: direct capture of the local ventricular EGM into the pacing stimulus artefact with recruitment of ventricular components on adjacent bipoles; no isoelectric interval
• The QRS paradox, stated as a rule: S-LBBP predominantly yields a wide QRS because of delayed RBB synchronisation, whereas NS-LBBP produces a shorter QRS. In most patients the narrowest QRS during LBBAP is produced by fusion of intrinsic right bundle activation with NS-LBBP — consistent with the direct-evidence finding that selective capture widens the QRS

3. Lumenless leads — Medtronic SelectSecure 3830

Construction

• 4.1 Fr bipolar, fixed helix, isodiametric tip, high tensile strength; the smallest commercialised LBBAP lead
• Lengths: 59, 69, 74 cm, plus a 49 cm non-MRI length
• Materials: polyurethane outer insulator; silicone and ETFE inner insulators; MP35N conductor; titanium-nitride-coated helix and ring electrodes on a platinum alloy base; beclomethasone dipropionate steroid elution to limit inflammation
• Delivery sheaths:
  • C315 His — 3D double-curve fixed sheath; 7 F outer / 5.4 F inner; the secondary "His-shaped" curve is always preshaped and, in the authors' experience, more angulated and easier for His access
  • C304 — deflectable; 8.4 F outer / 5.7 F inner; hydrophilic-coated; an additional option for difficult anatomy

Advantages

• Minimal myocardial injury, improved long-term outcomes, reduced helix damage and fewer procedural complications
• The isodiametric helix — the same diameter as the lead body — smooths septal penetration; the exposed helix cannot retract
• The 1.8 mm helix is tightly connected to the coil, adding strength and possibly reducing helix rupture
• Durability: in vitro and in vivo bending tests predicted a 10-year fracture rate of 0.02%; LBBAP implants need more rotations and bend the lead uniquely, but accelerated testing showed no excess conductor fractures
• Historical route: first developed for unconventional pacing sites, particularly congenital heart disease; now CE-approved for CSP and the most commonly used lead for this purpose

Limitations

• Extraction is the main concern: a lumenless design does not allow a locking stylet, and the high torquability and tensile force can make extraction technically difficult — possibly requiring lead extenders and compression ties
• The same fixed, isodiametric helix that helps at implantation can perforate or avulse myocardium adhered to the tip during extraction, potentially causing permanent conduction system damage
• Initial extraction experience in a small cohort reported no major complications, but further investigation is required
• Compared with SDL, LLL may lack support, stability and steerability during transseptal screwing

4. Stylet-driven leads

The evidence base and the first cases

• SDL have been the traditional choice for RV apical pacing; they are stiffened by a stylet during implantation
• The first two LBBAP cases with SDL were reported by Zanon et al. using a Selectra 3D sheath and a Solia S 60 lead
• After four years of worldwide experience, SDL LBBAP success has been reported at 96.1% (Sritharan)

Advantages

• Sheaths are slightly more rigid and transfer torque without kinking; stylets of different stiffness add manoeuvrability and support for septal penetration
• ⭐ The defining advantage: continuous ECG monitoring during rotation. Connecting the crocodile clamp to the stylet allows pacing and morphology monitoring while the lead is being screwed, so penetration can be gauged without interrupting the manoeuvre — the same principle the wiki records from the stylet-pacing and rotatable-connector studies
• Low lead revision and dislodgment rates, similar to or lower than traditional leads
• The counterweights: risk of entanglement and fragility of the extendable helix

Limitations

• Helix retraction: clockwise rotation of the outer lead body can retract the helix. Prevented by pretensioning the inner coil, ensuring lead progression in the septum, and continuous impedance checks; dedicated locking tools (Biotronik, Abbott) reduce it
• Entanglement and helix fragility can cause helix deformation or fracture
• Perpendicularity matters for selectivity: SDL allows non-perpendicular screwing without strict sheath adherence, but selective LBBAP is then rarely achieved
• Repeated screwing and retraction damages the helix; several attempts with wrong angulation are a particular risk
• Lead fracture is a major concern because of the fulcrum point (between sheath tip and myocardium) and high friction. Observational studies show higher early fracture rates with SDL than LLL, though numbers are very low and long-term inference is not possible; careful handling and alignment appear protective
• Practical constraints: the assembled lead–sheath length can restrict the space available for the slitter (solvable by cutting the sleeve before slittering and repositioning it); and the stylet must remain fully inserted during rotation — even a small retraction prevents septal advancement. No manufacturer offers a universal locking system

Biotronik Solia S — the most popular SDL for LBBAP

• Bipolar, coaxial, silicone-insulated, commercialised 2009
• Preparation: extend the helix before implantation to pretension the inner coil and prevent retraction; the fixation tool is rotated clockwise to extend and then lock the helix
• Selectra 3D delivery sheaths: three fixed curves, three lengths, supplied with a dilator, valved contrast lumen, tungsten radiopaque tip, internal hydrophilic coating. In conventional anatomy the sheath can be advanced with the lead without a dilator; in complex anatomy, over a wire with a dilator
• Navigation: unipolar signal from the tip identifies the His signal; advance in LAO; the W sign suggests the target. The helix can be advanced within the sheath before deployment, which may give a more appropriate starting impedance
• Screwing: crocodile clips on the stylet, clockwise rotation during unipolar (tip–skin) pacing; display both filtered (30–500 Hz) and unfiltered (0.5–500 Hz) EGMs. The unfiltered current of injury rises progressively during septal penetration and falls on perforation
• Keep the delivery firm to avoid stressing the fulcrum, the usual site of fracture. Amvia DR/SR/HF generators and dedicated left-branch leads have CE approval for physiological stimulation

Abbott Tendril STS 2088TC

• 5.8 Fr, 2 mm extended helix; Optim insulation (silicone and silicone-rubber copolymer) for abrasion resistance — relevant because lead abrasion and friction are fracture risks in LBBAP
• Delivery:
  • CPS Locator 3D — fixed-curve family in five dimensions (small, medium, large, extra-long medium, extra-long large); 9 F outer / 7 F inner
  • CPS Direct Universal 3D (2023) — 8 F inner / 10 F outer, valved, radiopaque distal tip, PEBAX with decreasing durometry (softer at the tip)
• Technique: advance the helix after navigating to the septum; 20–30 standard clockwise turns of the connector pin; the helix mechanism is protected from overturning; the helix advances with the lead body as it grips; contrast through an external valve confirms deep septal penetration
• ⭐ The helix locking tool blocks the inner coil over the outer coil in IS-1 connectors, allowing manual rotation and helix extension while co-rotating both coils — so the outer body can be rotated safely without helix retraction. No counter-torque should be perceived while rotating the body; counter-torque signals failed penetration (e.g. entanglement). Pinch tools can be applied through dedicated spaces. Compatible with St. Jude Medical cables 4051A, 4051L, 401748
• Rotation count cannot be standardised — individualise by surface ECG and electrical parameters. Prefer the 69 cm Tendril; with the 58 cm lead the sleeve can be removed to improve the slitter, and longitudinal cuts allow easy repositioning

Boston Scientific Ingevity+

• 6 F, high-impedance design; co-radial trifilar MP35N inner coil and single-filar MP35N outer coil with a silver core; the inner-coil change improves torque transmission versus earlier Ingevity leads
• Delivery: the Site Selective Pacing Catheter (SSPC) family; SSPC 2 ("multipurpose") and SSPC 3 Extended Hook are the most used, with three fixed curves numbered 1 (smallest) to 3
• Two implantation techniques:
  1. Conventional: initial helix deployment, then clockwise rotation with the pinch tool — 10–15 rotations fully extend the helix (confirmed in LAO), then torque the lead body to advance. Wider sheaths (especially curve 3) follow the torque and lose angulation with the septum; a 20–30° counter-clockwise rotation of the guide catheter restores it. Reassess in LAO 20–30° with contrast throughout
  2. The De Pooter custom locking tool: a silicone-cut lead cap bridges the stylet guide tool and the outer lead body, locking the inner coil during manual outer-body rotation — preventing helix retraction without a manufactured tool. SSPC 2 is the usual first choice for common anatomy because its angle gives good perpendicular contact

5. Potential complications in LBBAP

• Septal perforation — the most common complication: reported in up to 10.2% of LLL and 11.6% of SDL implants. Diagnosed by a marked fall in current-of-injury amplitude with a "QS" morphology and impedance <450 Ω. The lead can pass into the LV and evoke LV ectopy; pacing thresholds can rise
• Macrodislodgment: a technical problem during implantation (drill effect during screwing) that may cause loss of capture; displacement can be into the RV, or into the LV if the septum is perforated
• Microdislodgment: diagnosed per-operatively by loss of the terminal R′/r′ in V1 and/or QRS widening
• Lead rupture: subtricuspidal friction, most commonly between the lead body and the ring. LLL can also fracture, and fractures at atypical locations suggest multiple implantation attempts as a risk factor
• Helix damage: endocardial entanglement or deep septal penetration into thick myocardium impedes advancement, and counter-clockwise retraction can be ineffective. Repositioning is often necessary and is itself a source of complications; in rare cases helix elongation precedes rupture into the interventricular septum
• Chest pain and ST elevation: acute coronary events are rare (<1%), usually with intraprocedural chest pain and possible ST elevation; helix/lead retraction resolves the symptoms, and coronary angiography is negative. Persistent ST elevation should raise coronary vasospasm

6. Conclusions and the authors' development agenda

• LLL, particularly the 3830, has favourable stable parameters and low complication rates; SDL now offers comparable success. The comparative figure presents the trade as support and manoeuvrability (SDL) versus stability and extraction simplicity (LLL)
• Four technical priorities for the field:
  1. More supportive delivery systems with radiopaque tips for navigation and precision
  2. More devices designed specifically for physiological stimulation
  3. Simplified screw-fixation systems that permit pacing during insertion — the SDL advantage generalised
  4. Better integration of the two lead philosophies into one design

Limitations of the document

Authors' own stated limitations

• None are stated. The article has no limitations section, no search strategy and no discussion of the strength of its comparative claims

Additional limitations evident in the review

• It is a narrative review, not a systematic one. There is no search strategy, no inclusion or exclusion criteria, no PRISMA flow, no quality appraisal and no quantitative synthesis. The evidence cited is selected to illustrate technique, not to answer a comparison question
• It is a product-by-product technical guide written with manufacturer input. The acknowledgements thank named staff from all four manufacturers for "expertise and support", and each section describes the manufacturer's own recommended workflow. No conflicts are declared, which is difficult to reconcile with that level of involvement. The comparative statements ("the most popular SDL", "the preferred choice globally") are not sourced to a survey or registry, and the review should be read as an operator's manual with a clinical introduction, not as an evidence synthesis
• No own data and no head-to-head comparison. The review reports no success, capture, complication or follow-up rates from the authors' centre. Its central claim — "comparable success rates" for SDL — is inherited from observational series that use different success definitions (LBBP or LVSP), the same definitional problem that makes LBBAP registry success rates non-commensurable
• ⚠ The perforation figures are unreconciled and far above the registry experience. The review states up to 10.2% with LLL and 11.6% with SDL, sourced to a single-centre complications series. The multicentre SDL registry in this wiki reports 2% (8/353), and other LBBAP series report 0–14.1%. The review does not define perforation (echocardiographic micro-perforation vs clinical perforation with LV passage), does not distinguish asymptomatic from clinically significant events, and does not attempt to explain the spread — so the two numbers most likely to be quoted from this paper are the two least contextualised
• The EHRA criteria are reproduced uncritically. The review lists V6RWPT <75/<80/<90 ms and V6–V1 >44 ms as the confirmation standard and moves on. It does not mention that QRS transition is obtainable in only ~26–41% of cases, nor that the criteria have been found highly specific but poorly sensitive when re-tested in a cohort with proven capture (JACC:EP 2025: V6–V1 >33 ms SN 0.23, >44 ms SN 0.21). A technical guide that teaches the criteria as a checklist without that caveat will systematically over-diagnose capture
• The selective/non-selective QRS rule is stated without its qualifications. "S-LBBP predominantly yields a wide QRS … NS-LBBP results in shorter QRS" is consistent with the direct-evidence study, but the review does not note that selective capture is transient, inflated by repeated testing, and absent in most patients at follow-up — so the rule describes a state many operators will never observe
• The extraction evidence is thin and directional. LLL extraction is described as "a main concern", supported by one small cohort with no major complications; no extraction success rate, complication rate, follow-up or comparison with SDL extraction is given. The review also does not resolve whether the extendable helix is easier to extract — the obvious counter-advantage to its greater retraction risk
• Lead fracture rates are asserted rather than quantified. "Higher early lead fracture rates in SDL compared with LLL" is supported only by the statement that "numbers are still very low and long-term consideration cannot be made". No absolute rates, denominators or follow-up durations are given, so the trade-off between the 3830's predicted 0.02% ten-year fracture rate and the SDL figure cannot be assessed
• The tricuspid-regurgitation risk named in the introduction is never analysed. It is listed among CSP-specific complications and then absent from the complications section
• Rapidly dating content. The review is tied to specific products and versions (CPS Direct released 2023, specific generator models, specific cable part numbers), so parts of its practical advice will become obsolete faster than a physiological review would
• No cost, learning-curve, procedure-time, fluoroscopy-time or operator-volume data, despite these being the practical variables that determine which lead a centre adopts
• Rating rationale: rated medium. The technical content is detailed, accurate and genuinely useful — this is the best description in the wiki of how each lead–sheath system is actually prepared and screwed, and of the helix-retraction problem and its three solutions. But it is a narrative, manufacturer-assisted product review with no methodology, no own data, no head-to-head evidence, unreconciled complication figures, uncritical repetition of the ECG criteria, and no clinical outcomes — so it should inform technique, not evidence judgements

Key Concepts Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — the technique this review equips
• concepts/Conduction-System-Pacing — the umbrella category
• Lumenless lead (LLL) — fixed-helix, cable-conductor lead (Medtronic 3830); isodiametric, no locking stylet, cannot retract its helix
• Stylet-driven lead (SDL) — hollow lead stiffened by a stylet; extendable helix; supports the septum and permits pacing from the stylet during insertion
• Helix retraction — the SDL-specific failure mode in which outer-body rotation turns the lead without advancing the helix
• Inner-coil pretensioning / locking tools — the three countermeasures: pretension by rotation, the Abbott integrated locking tool, the De Pooter cut-cap tool
• Selective vs non-selective LBB capture — intracardiac criteria (local EGM inside or outside the stimulus artefact; presence or absence of an isoelectric interval) and the QRS paradox (S-LBBP wider than NS-LBBP)
• Stim-LVAT / V6RWPT and the V6–V1 interpeak interval — the EHRA capture criteria as restated here
• Current of injury (COI) — unfiltered unipolar signal that rises during septal penetration and falls with perforation
• Septal perforation — COI drop + QS morphology + impedance <450 Ω
• Fulcrum point — the lead segment between sheath tip and myocardium, the usual site of SDL fracture
• Lead extraction — the principal LLL limitation, because a lumenless lead accepts no locking stylet

Key Entities Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — primary concept page
• Medtronic — SelectSecure 3830 lead; C315 His and C304 delivery sheaths
• Biotronik — Solia S lead; Selectra 3D sheath; Amvia DR/SR/HF generators
• Abbott — Tendril STS 2088TC lead; CPS Locator 3D and CPS Direct Universal 3D sheaths; helix locking tool
• Boston Scientific — Ingevity+ lead; Site Selective Pacing Catheter (SSPC) family
• Zanon et al. — first two SDL LBBAP cases
• De Pooter et al. — the customised locking-tool technique, and the multicentre SDL registry already in this wiki
• Sritharan et al. — SDL-versus-LLL comparison and the 50-patient learning curve
• Burri / EHRA — the clinical consensus statement whose stepwise criteria the review reproduces
• University of Siena; Tuscany Foundation "Gabriele Monasterio"; Azienda Ospedaliera Universitaria Senese — the authors' institutions
• MDPI / Journal of Clinical Medicine — publisher

Wiki Pages Updated

• Created: wiki/sources/lumenless-vs-stylet-leads-jcm-2024.md
• Updated: wiki/concepts/Left-Bundle-Branch-Area-Pacing.md
• Updated: wiki/concepts/Conduction-System-Pacing.md
• Updated: wiki/sourceindex.md
• Updated: wiki/wikiindex.md