A Novel 9-Partition Method Using Fluoroscopic Images for Guiding Left Bundle Branch Pacing

Authors, Journal, Affiliations, Type, DOI

• Authors: Hai Jiang, MD; Xiaofeng Hou, MD; Zhiyong Qian, MD, PhD; Yao Wang, MD, PhD; Lijun Tang, MD; Yuanhao Qiu, MD; Zeyu Jiang, MD; Xing Chen, MD; et al.
• Journal: Heart Rhythm 2020;17(10):1759–67 (October 2020). © 2020 Heart Rhythm Society. All rights reserved
• Affiliations: Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, Nanjing; Department of Cardiology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing
• Type: Single-centre observational study of an imaging method — 70 patients enrolled, 45 with successful HB or LBB pacing lead implantation analysed. No comparator arm, no randomised allocation, no clinical outcome endpoint
• DOI: 10.1016/j.hrthm.2020.05.018
• ⚠ Filename is misdated. The raw file is named 9-LBBAP-HRS-2024.md, but the article's own citation line reads "(Heart Rhythm 2020;17:1759–1767)" and the running header "Vol 17, No 10, October 2020". The DOI likewise carries 2020. This is a 2020 paper. The filename should not be read as a publication year

Overview

Left bundle branch pacing had no agreed fluoroscopic method — operators had no standard target to aim at, which is a problem for a procedure whose success depends on where the lead tip lands within the interventricular septum. This study derives one from anatomy. In the RAO 30° projection, the ventricular contraction ring is identified; CT confirms that ring is composed of cardiac valves, making it an anatomical landmark rather than an arbitrary line. The septum between that ring and the apex is then divided equally into high, medium and low segments and crossed with three further divisions, producing 9 partitions. The method's validation is the observed distribution of leads: all 11 His bundle leads fell in a single partition (the second), while 94.3% of the 35 LBB leads fell in the junctional area of the second and fifth partitions — a clean separation of two anatomically adjacent but functionally distinct targets. The paper is short, single-centre and descriptive, but it supplies something the technique had lacked: a reproducible fluoroscopic coordinate system.

Keywords

Computed tomography; Fluoroscopy; His bundle pacing; Left bundle branch pacing; 9-partition method

Key Takeaways

Background

• LBB pacing is a novel pacing modality, but there is no standard fluoroscopic methodology for guiding it

Methods

• Study population: 70 patients who underwent HB or LBB pacing were enrolled; 45 patients (29 men; mean age 67 ± 12 years) underwent successful implantation of HB or LBB pacing, and 35 LBB pacing leads and 11 HB pacing leads were analysed
• Implantation: HB and LBB pacing lead implantation performed per the centre's procedure; postprocedural definitions of successful HB and LBB pacing applied
• Fluoroscopic acquisition: images of the pacing lead in RAO 30°, left anterior oblique 45°, and anterior-posterior projections were acquired in fluoroscopic acquisition mode after the procedure
• Cardiac CT acquisition and processing was used to validate the anatomy

The 9-Partition Method

1. Identify the ventricular contraction ring in the RAO 30° projection during the procedure
2. From the contraction ring to the apex, divide the IVS equally into high, medium, and low segments
3. Three further divisions across the septum produce 9 partitions
4. Assess the distribution of all HB and LBB pacing lead positions in the 9 partitions

Results

Patient Characteristics and Implantation

• 45 patients underwent successful implantation (29 men; mean age 67 ± 12 years)
• 35 LBB pacing leads and 11 HB pacing leads were included for analysis
• An internal inconsistency in the source: the abstract states "HB and LBB pacing leads were successfully implanted in 11 and 35 patients respectively" — totalling 46 — while the results text reports 45 patients. The discrepancy is in the paper, not the extraction, and is recorded rather than reconciled
• Screening/enrolment flow is presented in Figure 1 (as an image, not machine-readable text)

Constitution of the Ventricular Contraction Ring

• CT confirmed that the ventricular contraction ring is composed of cardiac valves — establishing it as a genuine anatomical structure rather than an imaging artefact, which is what allows it to serve as a fixed fluoroscopic landmark

Distribution of Pacing Sites — the method's validation

• All HB pacing leads were distributed in the second partition (Figure 4A)
• 94.3% (33 of 35) of LBB pacing leads were in the fifth and second partitions — specifically the junctional area of the two; 2.9% (1 of 35) in the third partition and 2.9% (1 of 35) in the sixth partition (Figure 4B)
• The distributions of LBB and HB pacing leads differed significantly
• Anatomical distance: the distance from the lead tip to the junction of the noncoronary cusp and right coronary cusp was 3.8 ± 0.6 cm for LBB leads versus 1.9 ± 0.2 cm for HB leads — a roughly two-fold separation, and the quantitative basis for distinguishing the two targets

ECG Characteristics

• HB potential and LBB potential during intrinsic rhythm, and lead position on CT, are shown in Figure 5 — including a "QR"-shaped pacing morphology in lead V1 for LBB lead tip pacing and a "W"-shaped morphology for LBB ring pacing
• A flowchart for LBB pacing guided by the 9-partition method is given in Figure 6

Complications

• Acute lead dislodgement occurred in 1 patient during withdrawal of the sheath; this patient underwent successful repositioning
• No loss of capture, lead removal, late lead dislodgement, or perforation into the LV cavity was observed in any patient

Discussion

• Anatomical relationship between HB and LBB pacing leads: the two targets are fluoroscopically distinguishable, and the 9-partition method formalises where each sits
• Distribution of LBB potential and application of the method in LBB pacing: the partition distribution is used to explain where an LBB potential is obtainable and therefore where the lead should be steered

Conclusion

• The distributions of HB and LBB pacing leads exhibited unique imaging characteristics
• A new 9-partition method is useful to guide successful LBB pacing

Limitations of the document

Authors' own stated limitations

• Single-centre observational study with a relatively small sample size
• Although the results suggest the method could be helpful prospectively, it needs to be verified in a large population
• No consensus existed on the definition of LBB pacing, so the authors chose LBB potential as a necessary condition for defining it — an arbitrary criterion that the field had not agreed

Additional limitations evident in the study

• No comparator and no outcome endpoint. The study demonstrates that leads landed in particular partitions; it does not test whether using the method prospectively improves implant success, reduces procedure time, or changes capture thresholds or clinical outcomes. "Useful to guide successful LBB pacing" is an inference from the observed distribution, not a tested intervention
• The method is validated on the same cohort used to derive it. The partitions were developed and then shown to separate HB from LBB leads in the same 45 patients, with no independent validation cohort — the principal reason the rating is medium despite a clean separation
• Only 11 HB leads. The claim that "all HB pacing leads were distributed in the second partition" rests on 11 patients; the specificity of partition 2 as a His target is correspondingly uncertain
• The partition number is anatomically over-specified relative to its justification. A 3×3 grid of a two-dimensional RAO projection is being used to describe a three-dimensional septal position; the projection cannot resolve depth (anterior-posterior position within the septum), which is precisely the dimension that distinguishes LVSP from LBBP in other work
• Requires RAO 30° and a visible contraction ring. Both are operator- and image-quality-dependent, and the paper does not report how often the ring could not be identified
• Reproducibility across operators is untested — there is no interobserver analysis of partition assignment
• The source contains an unexplained numerical inconsistency (45 patients stated, 46 leads counted), which is minor but means the analysed denominator should be quoted with care
• Rating rationale: single-centre, small, observational, no comparator, no outcome endpoint, and validated on its own derivation cohort — hence medium

Key Concepts Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — the technique this method is designed to guide
• concepts/His-Bundle-Pacing — the comparator target; all its leads fell in partition 2
• concepts/Conduction-System-Pacing — the umbrella category
• Ventricular contraction ring — the CT-validated fluoroscopic landmark; composed of cardiac valves
• 9-partition method — division of the septum between contraction ring and apex into high/medium/low segments crossed with three further divisions
• Noncoronary cusp / right coronary cusp junction — the anatomical reference for measuring lead-tip distance (LBB 3.8 ± 0.6 cm vs HB 1.9 ± 0.2 cm)
• LBB potential — adopted as a necessary condition for defining LBB pacing in the absence of consensus

Key Entities Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — primary concept page
• The First and Second Affiliated Hospitals of Nanjing Medical University — the investigating centre
• Heart Rhythm Society — publishing society
• Jiang H, Hou X, Qian Z — co-first authors

Wiki Pages Updated

• Created: wiki/sources/lbbap-9-partition-hrs-2020.md
• Updated: wiki/concepts/Left-Bundle-Branch-Area-Pacing.md
• Updated: wiki/concepts/His-Bundle-Pacing.md
• Updated: wiki/sourceindex.md
• Updated: wiki/wikiindex.md