Electrical Resynchronization and Clinical Outcomes in Intraventricular Conduction Delay Patients Treated With LOT-CRT

Authors, Journal, Affiliations, Type, DOI

• Authors: Xueying Chen, Xiao Li, Yingnan Bai, Jingfeng Wang, Shengmei Qin, Jin Bai, Wei Wang, Yixiu Liang, Haiyan Chen, Yangang Su, Junbo Ge
• Journal: Circulation: Arrhythmia and Electrophysiology 2023;16:e011761
• Affiliation: Department of Cardiology, Zhongshan Hospital, Fudan University; Shanghai Institute of Cardiovascular Diseases; National Clinical Research Center for Interventional Medicine, Shanghai, China
• Type: Prospective, single-centre, non-randomised observational cohort
• DOI: 10.1161/CIRCEP.122.011761

Overview

This single-centre prospective study compared left bundle branch pacing–optimized CRT (LOT-CRT) with conventional biventricular CRT (BiV-CRT) in 85 patients with non-specific intraventricular conduction delay (IVCD), LVEF ≤35%, and a CRT indication. LOT-CRT combined an LBBP lead with a coronary sinus LV lead; BiV-CRT used standard RV and CS leads. LOT-CRT produced substantially greater QRS reduction (42.7 vs 21.9 ms), higher LVEF at every follow-up point through 24 months (37% vs 30.5%), a higher echocardiographic response rate at 6 months (60% vs 31.6%), and a lower composite of cardiovascular mortality or heart failure hospitalisation over 24 months (6.7% vs 25.5%; HR 0.33). The study is one of the few long-term datasets specifically in IVCD — the conduction disease least responsive to conventional CRT — and supports a tailored, multi-site approach in that group.

Keywords

Cardiac resynchronization therapy; Heart failure; Intraventricular conduction delay; Left bundle branch pacing; Long-term follow-up

Key Takeaways

Population and design

• Prospective observational study at Zhongshan Hospital, January 2019–July 2021.
• Inclusion: chronic heart failure NYHA II–IV, LVEF ≤35% on optimal medical therapy, sinus rhythm or AF with IVCD and QRS ≥150 ms, or complete AV block with an IVCD-type escape rhythm.
• Exclusions: intrinsic RBBB, LBBB, or narrow QRS.
• 87 consecutive patients enrolled; LOT-CRT attempted in 31 (30 successful, 96.8%), BiV-CRT in 56 (55 successful, 96.4%).
• Assignment was non-randomised, by physician and patient preference.
• Baseline characteristics comparable: age ~64 years; LVEF 30.0% vs 29.1%; LVEDD 71.8 vs 72.2 mm; permanent AF 36.7% vs 25.5%; ischaemic cardiomyopathy 33.3% vs 21.8%.
• Procedure duration longer with LOT-CRT: 126.5 ± 22.6 vs 105.8 ± 18.1 min (P < .01).
• Ventricular pacing burden ~96% in both groups.

Electrical resynchronisation

• Baseline QRS similar: 183.6 ± 20.3 ms LOT-CRT vs 176 ± 17.9 ms BiV-CRT (P > .05).
• Post-procedure QRS narrower with LOT-CRT: 140.9 ± 17.6 vs 154.1 ± 20.2 ms (P < .005).
• QRS reduction greater with LOT-CRT: 42.7 ± 17.4 vs 21.9 ± 21.5 ms (P < .0001).
• Within the LOT-CRT group, QRS was 140.0 ± 17.6 ms with LOT-CRT vs 168.2 ± 19.6 ms with BVP mode (P < .05) and 155.5 ± 21 ms with LBBAP alone (P < .0001).

Echocardiographic outcomes

• LVEF at 6 months: 36.7% ± 9.8% LOT-CRT vs 30.5% ± 6.4% BiV-CRT (P < .05).
• LVEF at 12, 18 and 24 months remained higher with LOT-CRT (34.8 vs 30.3; 36.3 vs 28.1; 37.0 vs 30.5%; all P < .05 or better).
• LV end-systolic diameter lower with LOT-CRT at 6 months (56.2 ± 11.6 vs 62.5 ± 9.5 mm; P < .05); LVEDD did not differ.
• LVESV and LVEDV were lower with LOT-CRT at 6 months (P = .0425 and P = .0471).
• Echocardiographic response (≥5% LVEF gain) at 6 months: 60.0% vs 31.6% (P < .05).

Clinical outcomes

• NT-proBNP similar at baseline but significantly lower with LOT-CRT at 2 years (P < .005).
• NYHA class improved more with LOT-CRT (2.6 → 2.2; P = .0006).
• Primary composite of cardiovascular mortality or HF hospitalisation over 24 months: 6.7% LOT-CRT vs 25.5% BiV-CRT; HR 0.33 (95% CI 0.14–0.77), P = .035.
• The authors attribute the benefit to greater electrical resynchronisation in a population with diffuse conduction disease, where LBBP alone cannot fully correct the left-sided delay.

Interpretation

• In IVCD, LBBP alone leaves residual LV lateral wall delay; adding a CS lead addresses the distal/myocardial component that proximal conduction-system capture cannot.
• The response rate in both arms was lower than in typical LBBB trials (~70%), consistent with the poor CRT responsiveness of IVCD.
• The benefit was seen despite a wider baseline QRS in the LOT-CRT group, which would usually predict worse outcomes.

Limitations of the document

• Single-centre, non-randomised, small sample (n = 85) with treatment chosen by physician and patient preference — substantial selection bias is possible.
• No core-laboratory or blinded echocardiographic analysis; two echocardiographers were blinded to study design but not to treatment.
• Baseline QRS was numerically wider in the LOT-CRT group, and although not statistically significant, this may confound the comparison.
• Mortality was low and the study was not powered for mortality or subgroup analyses.
• Device programming differed between groups (LBBP lead connected to different ports depending on rhythm and device type), which may affect delivered resynchronisation.
• No cardiac magnetic resonance to characterise scar, a major determinant of CRT response.
• Predominantly male population and single-ethnicity setting limit generalisability.

Key Concepts Mentioned

• concepts/LOT-CRT — left bundle branch pacing–optimized CRT
• concepts/Left-Bundle-Branch-Area-Pacing — the pacing lead
• concepts/ECG-Conduction-Disturbances — the study population
• concepts/Cardiac-Resynchronization-Therapy — the clinical context
• concepts/Cardiac-Resynchronization-Therapy — the comparator
• concepts/Electrical-Resynchronization-Metrics — QRS duration as the endpoint

Key Entities Mentioned

• Zhongshan Hospital, Fudan University — coordinating centre
• Medtronic — 3830 SelectSecure lead and C315HIS sheath
• Shanghai Hospital Development Center, National Natural Science Foundation of China — funding bodies

Wiki Pages Updated

• Created: wiki/sources/lot-crt-circep-2023.md
• Updated: wiki/concepts/LOT-CRT.md
• Updated: wiki/concepts/Cardiac-Resynchronization-Therapy.md
• Updated: wiki/sourceindex.md
• Updated: log.md