Fixation Beats: A Novel Marker for Reaching the Left Bundle Branch Area During Deep Septal Lead Implantation

Authors, Journal, Affiliations, Type, DOI

• Authors: Marek Jastrzębski (corresponding); Grzegorz Kiełbasa; Paweł Moskal; Agnieszka Bednarek; Aleksander Kusiak; Tomasz Sondej; Adam Bednarski; Marek Rajzer; Pugazhendhi Vijayaraman
• Journal: Heart Rhythm 2021;18(4):562–569. © 2020 Heart Rhythm Society
• Affiliations: First Department of Cardiology, Interventional Electrocardiology and Hypertension, Jagiellonian University Medical College, Kraków; Geisinger Heart Institute, Wilkes-Barre
• Type: Retrospective cohort with a prospective confirmation phase — 339 patients, 1,278 lead-rotation events, including the final 21 patients implanted prospectively with fixation-beat guidance
• DOI: 10.1016/j.hrthm.2020.12.019
• Disclosures: Vijayaraman — honoraria, consultant, research and fellowship support from Medtronic; consultant to Abbott, Biotronik, Boston Scientific and Eaglepoint; patent for a His delivery tool. Jastrzębski — consultant and lecture fees from Medtronic

Overview

Deep septal lead implantation has an awkward feedback problem: the operator must advance far enough to reach the left bundle, but not so far as to perforate, and the standard method — stopping every few rotations to reconnect the pacemaker and pace — interrupts momentum and can miss the target. This paper reports a signal that occurs without any pacing at all. As the helix crosses the septum it mechanically irritates tissue, producing ectopic beats, and the ones generated in the left bundle area have a distinctive Qr/qR/rsR′ in V1 and QRS ≤130 ms. In 339 patients and 1,278 rotation events, these "LBB area fixation beats" appeared at 327 of 339 final lead positions but at only 9 of 939 intermediate positions — sensitivity 96.4%, specificity 97.3%, PPV 97.3%, NPV 96.5%. In a prospective phase the operators simply kept rotating (up to 10 turns) until the beats appeared, then stopped; all 21 patients showed them only at the capture depth, 15/21 (71.4%) needed a single rotation episode, and median rotation episodes fell from 3 to 1 (P < .001). The paper also describes the "perforation beats" that look different — a dominant R in V1 with a notch on the descending limb, QRS 190 ms — and argues the marker's main value is knowing when to stop.

Keywords

Conduction system pacing; Deep septal lead implantation; Fixation ventricular premature beats; Left bundle branch pacing; Pacemaker implantation

Key Takeaways

The problem the marker solves

• The target is a corridor: deep enough for LBB capture, not so deep as to perforate, with septal thickness and lead trajectory both variable
• Existing depth guides are coarse: fulcrum sign, sheath angiography, impedance monitoring and ring-electrode pacing are rough estimates, not real-time evidence that the capture area has been reached; ring pacing is the most informative but still indirect
• Notch monitoring in V1 is useful but limited because a substantial proportion of patients have no notch at the initial site
• The interrupted pacemapping method has costs: it prolongs the procedure, loses torque, risks sheath displacement, and can miss the optimal depth — the lead may already be too deep when pacing is checked
• Continuous pacemapping while screwing was the group's earlier solution, but lacked a commercial revolving connector and was limited by the fragile distal-pin connection of the 3830

The definition

• Fixation beats = ectopic ventricular beats occurring during lead rotation for deep intraseptal deployment, captured on the 12-lead ECG and the lead's endocardial electrogram
• Deep septal fixation beats: similar to or narrower than the initial septal paced QRS, without qR/rsR′ in V1, and >130 ms
• LBB area fixation beats: Qr/qR/rsR′ in V1 and/or QRS ≤130 ms — the marker under study
• The mechanistic premise: mechanical irritation produces the same QRS morphology as pacing from the same site, so the fixation-beat morphology reflects the helix position. The paper shows a "shower" of beats with progressive QRS change as the lead descends — RV septal → deep septal → LBB area — often matching the paced QRS obtained at each depth
• A crucial caveat stated by the authors: fixation beats indicate that the area has been reached, not that capture has been achieved; capture still requires the usual criteria and manoeuvres

Methods

• Setting: every patient at the institution receives a conduction-system pacing device; LBB pacing was chosen as primary or after a failed HBP attempt
• Screening: 784 consecutive patients from 12 June 2018; 358 received LBB pacing devices, 313 HBP, 36 biventricular CRT, 59 RV pacing; 339 included after excluding 5.3% (artefacts, file loss, alternative technique)
• Implant technique: 3830 lead and SelectSite sheaths only. Site chosen by RV septal pacemapping and tricuspid summit position, without an extensive His-potential search. Optimal paced QRS = R in II, RS/rS/QS in III, QS with notched nadir in V1
• Target: approximately 2 cm apical from the tricuspid summit, extending conically 2 cm superiorly and inferiorly to the mid-septum
• Standard (retrospective) approach: initial 5 rapid rotations, then interrupted pacemapping; more rotations added until satisfactory QRS or capture
  • Entanglement response (torque not transmitted) → change site
  • Drill effect (no progressive QRS change) → more forward pressure, modify sheath angle, or change site
• Prospective (fixation-beat-guided) approach: continue initial rotations (up to 10) with the lead disconnected until LBB area fixation beats appear; stop immediately and pacemap to confirm the final position
  • Satisfactory deep septal QRS = initial QS in V1 becomes Qr/QR or rsR′/rSr′ (terminal R/r appears) or QRS narrows to ≤120 ms measured from true QRS onset
• Recording: continuous 12-lead ECG plus the 3830 endocardial electrogram on a LabSystem Pro EP system; rotation episodes are identifiable by the noise signal from the disconnected alligator clip

Results

The diagnostic performance

• Deep septal fixation beats (the intermediate morphology) occurred in 136/339 (40.1%) — and their morphology closely matched the paced QRS at that intermediate depth
• The prospective phase: fixation beats in all 21 patients, and only at the LBB capture depth; 15/21 (71.4%) required a single rotation episode; median rotation episodes fell to 1 (1) versus 3 (4) (P < .001)
• Pacing parameters were unchanged: paced QRS 145.7 ± 21.7 vs 151.7 ± 20.5 ms (P = .19), sensing 9.3 ± 3.9 vs 8.5 ± 3.0 mV (P = .36), capture threshold 0.9 ± 0.4 vs 0.8 ± 0.5 V (P = .65); fluoroscopy 7.6 ± 5.3 vs 11.4 ± 11.0 min (P = .12)

Perforation and the "perforation beats"

• Six acute LV perforations occurred, all in the retrospective phase. In the last, the operator continued rotating after LBB area fixation beats had appeared, and a shower of ectopics from free movement inside the LV followed
• Perforation beats differ from LBB area fixation beats:
  • Perforation: dominant R in V1 with a notch on the descending limb (Marriott's sign), wide QRS (190 ms)
  • LBB area fixation beat: Qr in V1, QRS ≤125 ms
• Prospective phase: no obvious perforations, but one suspected microperforation occurred when the rule was broken and 1–2 "bonus" rotations were added after the marker, looking for a larger LBB potential. It was suspected from a threshold rise on the tip electrode and a low threshold with an exceptionally narrow QRS on the ring electrode; the lead was repositioned, and this time rotations stopped at the first fixation beat
• The safety argument is therefore procedural, not statistical: the marker tells the operator when to stop, and every observed perforation sequence involved passing that point

Why the method is practical

• It requires no pacing connection, so it does not interrupt the rotation
• The target is often reached in a single uninterrupted rotation episode, preserving momentum and reducing the opportunity for drill-effect dislodgement
• The marker appears at 96% even when nobody is looking for it (retrospective phase), and at 100% when the operator rotates until it appears — which the authors interpret as sensitivity of the underlying signal, though the prospective figure is partly a product of the stopping rule

Limitations of the document

Authors' own stated limitations

• The prospective phase was small (21 patients), though consistent with the retrospective findings
• Single university centre with experience of nearly 1,000 conduction-system implants — results may not transfer to lower-volume operators
• During rapid advancement in a non-LBB area, LV septal perforation could occur despite the absence of fixation beats
• In patients with underlying RBBB, monitoring for LBB area fixation beats can be challenging
• Fixation beats are not diagnostic of LBB capture — they only show the area was reached

Additional limitations evident in the study

• The retrospective phase dominates the evidence and is vulnerable to ascertainment and classification bias. The operators knew the hypothesis, the beats were classified by the implanting team, and there was no blinded adjudication or core laboratory. The prospective phase is a confirmation, not an independent validation
• Specificity is calculated per patient, not per beat or per position. Nine intermediate positions with fixation beats in 339 patients yield the reported 97.3% specificity by a definition that counts a patient with any early fixation beat as one false positive. The per-event false-positive rate (9/939 intermediate positions) is a different, and arguably more relevant, number
• The prospective and retrospective phases are not contemporary. The prospective cases are the final 21 in a chronological series at a single centre, so the improvement in rotation count and fluoroscopy time is confounded by the learning curve and by operator enthusiasm for the new method
• The 100% prospective detection rate is partly circular. The protocol was to keep rotating until the beats appeared; a beat-free patient would either have required more rotations or been classified differently. The study cannot distinguish a true 100% biological rate from a rule that guarantees the observation
• No information on sedation/anaesthesia, septal scar, or fatty infiltration, all of which plausibly suppress mechanically induced ectopy. Patients in whom fixation beats never appear are the ones in whom the method fails, and their characteristics are not reported
• The technique needs an EP recording system with continuous 12-lead and intracardiac display, and depends on recognising the rotation noise signal; this is not available in every implanting laboratory, and the paper does not report a simpler ECG-only implementation
• The perforation-prevention claim is uncontrolled. Six perforations occurred before the method was adopted and none obvious after, but the comparison is historical, the prospective cohort is 21 patients, and one suspected microperforation still occurred. No sample size could support a safety claim at this event rate
• The RBBB caveat is important and unresolved: in RBBB the LBB fixation beat and the native/irritable RV beat can share morphology, so the marker may be unreadable in exactly the conduction-disease population that receives LBBAP
• No long-term follow-up — lead stability, late perforation, and capture loss are not reported
• Rating rationale: rated high. It is a large, carefully characterised cohort with a simple, mechanistically grounded marker, a prospective confirmation, and a clinically decisive application (when to stop rotating). It is not very high because the evidence is predominantly retrospective and unblinded, single-centre, the specificity is defined per patient, the prospective improvement is confounded by chronology, and the safety benefit is inferred from a handful of historical perforations

Key Concepts Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — the technique; this paper supplies an implantation-time marker
• concepts/Conduction-System-Pacing — the umbrella category
• Fixation beats — mechanically induced ectopic beats during lead rotation; their morphology reflects helix position
• LBB area fixation beats — Qr/qR/rsR′ in V1 and/or QRS ≤130 ms; the marker of having reached the target
• Deep septal fixation beats — intermediate morphology without qR/rsR′, >130 ms; present in 40.1%
• Perforation beats — dominant R in V1 with a descending-limb notch (Marriott's sign), wide QRS; distinguish from LBB area beats
• Interrupted pacemapping vs continuous rotation — the trade-off the method is designed to resolve
• Entanglement response and drill effect — the two failure modes of rotation, and the responses to each
• Tricuspid summit target — ~2 cm apical, with a conical 2 cm superior/inferior extent
• Marriott's sign — the notched descending R in V1 that suggests LV perforation

Key Entities Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — primary concept page
• Jagiellonian University Medical College, Kraków — the single investigating centre
• Geisinger Heart Institute — co-authoring centre
• Medtronic SelectSecure 3830 lead and SelectSite sheaths — the only system used
• Boston Scientific LabSystem Pro — the EP recording system
• Marek Jastrzębski; Pugazhendhi Vijayaraman — the investigators
• Huang; Vijayaraman — the implantation technique the protocol modifies
• Heart Rhythm Society / Elsevier — publisher

Wiki Pages Updated

• Created: wiki/sources/fixation-beats-hrs-2020.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