Intracardiac Echocardiography–Guided Implantation for Proximal Left Bundle Branch Pacing

Authors, Journal, Affiliations, Type, DOI

• Authors: XiaoHui Kuang, MD; Xi Zhang, MD; YanJu Cui, MD; FeiYu Wei, MD; Peng Wu, MD; XiaoLong Gao, MD; Hong Xiang, MD; HaiYan Wu, MD; Li-Lin Wang, MD; Xiaohong Zhou, MD; Weijian Huang, MD; Jie Fan, MD, et al.
• Journal: Circ Arrhythm Electrophysiol 2023;16:e011408. Received 30 July 2022; accepted 17 February 2023. An editorial by Batul and Vijayaraman accompanies the paper
• Affiliations: Division of Cardiology, Yunnan Arrhythmia Research Center, First People's Hospital of Yunnan Province, Kunming University of Science and Technology, China; CRHF Division, Medtronic PLC, Mounds View, MN (X. Zhou); Department of Cardiology, First Affiliated Hospital (W. Huang — the group behind the first reported LBBP)
• Type: Two-part study — part 2 is a prospective randomized trial: part 1 an anatomical mapping study in 20 patients, part 2 a randomized comparison of ICE-guided versus conventional fluoroscopic implantation in 101 consecutive patients (50 vs 51)
• DOI: 10.1161/CIRCEP.122.011408
• Filename year is correct — the raw file is ICE-Proximal-LBBAP-CircEP-2023.md and the journal of record is 2023

Overview

Every other LBBAP paper in this wiki describes where to place the lead; this one addresses the fact that getting it there takes repeated attempts — "multiple screw-in attempts under fluoroscopy are often needed to place the pacing lead tip near or at the left bundle branch." The proposal is to stop navigating by fluoroscopy alone and visualise the target directly with intracardiac echocardiography (ICE), so the implanter can see the basal left ventricular septum rather than infer it from a two-dimensional projection. The study first maps the proximal LBB (PLBB) using ICE plus 3-D electrical mapping — finding it 10–20 mm from the tricuspid annulus toward the apex, over an area of 4.5 ± 1.1 cm² — and then randomises 101 patients to ICE-guided or conventional implantation. ICE roughly halved procedure and fluoroscopy time, reduced screw-in attempts, and produced more LBB trunk pacing and more PLBB pacing — a rare thing in this literature: randomized, with objective endpoints and large significant effects.

Keywords

Bradycardia ◼ cardiac conduction system ◼ catheters ◼ endocardium ◼ fluoroscopy

Key Takeaways

Background

• His bundle pacing is a physiological modality with clinical benefits in bradycardia or cardiac failure, but has limitations such as difficult implantation
• LBB pacing addresses several of those, but lead placement is the practical bottleneck: multiple screw-in attempts under fluoroscopy are often needed to reach the LBB target
• The study's aim: evaluate the feasibility of implanting an LBB pacing lead in the proximal LBB (PLBB) guided by ICE

Methods

• Part 1 (anatomical, n = 20): the distribution of the LBB was determined by ICE anatomic imaging and 3-dimensional electrical mapping of His and LBB potentials. These patients were candidates for ablation procedures in whom cardiac anatomic markers were mapped with a mapping catheter
• Part 2 (randomized, n = 101): 101 consecutive pacemaker-indicated patients with bradycardia were randomized into ICE-guided (N = 50) and non-ICE (N = 51) groups for LBB pacing implantation; the non-ICE group used conventional fluoroscopy. Procedural details and electrophysiological characteristics were compared
• All procedures were performed by implanters already experienced in LBBP implantation

Results — Part 1: Where the Proximal LBB Actually Is

• PLBB was identified 10 to 20 mm from the tricuspid annulus toward the apex, with an area of 4.5 ± 1.1 cm²
• This is the anatomical definition the randomized part then targets

Results — Part 2: The Randomized Comparison

• LBB pacing in the ICE group generated a shorter QRS duration than in the non-ICE group
• The pattern is coherent: fewer attempts, less time, less radiation, and a better anatomical result (more trunk and more proximal capture) — not merely a faster procedure

Conclusions

• The basal left ventricular septum can be better visualized using ICE
• ICE-guided PLBB pacing is feasible and safe, requires shorter procedure and fluoroscopy durations, and generates greater LBB trunk pacing and PLBB pacing

Limitations of the document

Authors' own stated limitations

• Single-centre prospective randomized study with a relatively small sample size (n = 50 vs 51)
• ICE can be considered expensive at various clinical centres — an explicit cost caveat, and unusual for authors to state so plainly
• The authors propose selective rather than routine use: ICE "can be selectively used in challenging LBBP implantation or in patients requiring cardiac resynchronization therapy for whom PLBB pacing may be more beneficial"

Additional limitations evident in the study

• The endpoints are procedural surrogates, not clinical outcomes. Attempts, procedure time, fluoroscopy time, QRS duration and capture location are all measured; no mortality, heart-failure event, hospitalisation or lead-durability outcome is reported. The trial therefore shows that ICE makes the procedure easier and better-targeted, not that it makes patients better off — which is the question a pacing technique ultimately has to answer
• All operators were already experienced in LBBP. Given that MELOS found the learning curve plateaus only after 250 cases, this benefit is demonstrated in expert hands and says nothing about whether ICE helps an operator still on the curve — plausibly the population that would gain most from direct visualisation
• Procedural trials cannot be blinded, so the operative endpoints (attempts, and to a lesser degree time) are susceptible to expectation effects from operators who knew the assignment. The anatomical endpoints (capture location) are more robust to this than the counting endpoints
• Capture-type classification is itself contested. The same difficulty that produced the term "LBBAP" applies here: without a gold standard, the difference between "LBB trunk pacing" (46.8% vs 25%) and "PLBB pacing" (91.5% vs 72.7%) rests on criteria the field has not standardised — and MELOS showed that 21.5% of supposedly LBB-capturing implants were in fact septal-only
• Part 1 was performed in ablation candidates, not the pacemaker population randomised in part 2, so the anatomical mapping and the randomised cohort are different populations
• n = 101 is small for the capture-location endpoints, where the comparison is between proportions (91.5% vs 72.7%) on roughly 50 patients per arm
• Disclosed industry relationship: a co-author (X. Zhou) is employed by Medtronic; the study is otherwise from a Chinese academic centre
• Rating rationale: rated high — the only randomized evidence among the eight LBBAP sources in this wiki, with large and consistent significant effects on objective procedural measures, published in Circ Arrhythm Electrophysiol with an accompanying editorial. Not very high: single-centre, small, procedural surrogate endpoints only, expert operators, and a disclosed device-industry author

Key Concepts Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — the technique whose implantation this improves
• concepts/Conduction-System-Pacing — umbrella category
• Intracardiac echocardiography (ICE) guidance — direct visualisation of the basal LV septum instead of fluoroscopic inference
• Proximal left bundle branch (PLBB) — the target, 10–20 mm from the tricuspid annulus toward the apex, area 4.5 ± 1.1 cm²
• LBB trunk pacing vs PLBB pacing — the two capture locations the ICE approach increases (46.8% vs 25%, and 91.5% vs 72.7%)
• Screw-in attempts — the practical burden of fluoroscopic-only implantation (1.43 vs 1.98)
• Fluoroscopy time and radiation — 7.4 vs 10.7 minutes for the implantation itself

Key Entities Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — primary concept page
• Weijian Huang — co-author; the group behind the first reported LBBP (Huang et al., cited as the origin in sources/lbbap-jacc-2019)
• Medtronic PLC — employer of a co-author
• Yunnan Arrhythmia Research Center / First People's Hospital of Yunnan Province, Kunming — the investigating centre
• Batul and Vijayaraman — authored the accompanying editorial
• Wolters Kluwer / American Heart Association — publisher

Wiki Pages Updated

• Created: wiki/sources/ice-guided-plbb-circep-2023.md
• Updated: wiki/concepts/Left-Bundle-Branch-Area-Pacing.md
• Updated: wiki/sourceindex.md
• Updated: wiki/wikiindex.md