Echocardiographic Response From LOT-CRT vs Traditional CRT

Authors, Journal, Affiliations, Type, DOI

• Authors: Gaurav A. Upadhyay, Marek Jastrzębski, Paul Foley, Badrinathan Chandrasekaran, Zachary Whinnett, Robert D. Schaller, Rafał Gardas, Travis Richardson, Pawel Moskal, D'Anne Kudlik, Robert W. Stadler, Patrick Zimmerman, James Burrell, Robert Waxman, Richard N. Cornelussen, Jonathan Lyne, Bengt Herweg, Pugazhendhi Vijayaraman
• Journal: Heart Rhythm 2025;22(10):2616–2624
• Affiliations: University of Chicago; Jagiellonian University; Great Western Hospital (Swindon); Imperial College London; University of Pennsylvania; Medical University of Silesia; Vanderbilt Heart; Medtronic (Mounds View and Bakken Research Center); Beacon Hospital (Dublin); University of South Florida and Tampa General Hospital; Geisinger Heart Institute
• Type: Secondary analysis of the CSPOT study with propensity-matched historical BVP controls (ECG Belt study)
• DOI: 10.1016/j.hrthm.2025.04.026

Overview

This CSPOT secondary analysis assessed 6-month echocardiographic response in 34 LOT-CRT patients and compared them with 34 propensity-matched BVP patients from the ECG Belt study. LOT-CRT produced markedly greater LVEF improvement (+16.1% vs +6.1%) and LVESV reduction (−43.5% vs −20.9%); after adjustment for baseline characteristics the differences remained significant (+7.5% LVEF and −18.4% LVESV). The response was consistent across LBBB and non-specific IVCD, and was greatest in patients with baseline QRS ≥171 ms. Notably, patients with "deep septal optimized therapy" (DOT-CRT, i.e. no terminal r′ in V1) had echocardiographic outcomes similar to those with successful LOT-CRT, suggesting that ECG-based capture classification may underestimate conduction-system engagement in advanced cardiomyopathy. The analysis supports LOT-CRT as a strategy for patients who respond poorly to conventional BVP.

Keywords

CRT; LOT-CRT; Echocardiography; Chronic response; LBBAP; Deep septal pacing; Clinical study

Key Takeaways

Population

• CSPOT: prospective, multicentre study at 5 European and 5 US sites; 51 patients completed CRT implantation, 34 evaluable at 6 months.
• Exclusions from the 34: adverse events (3), death (2), loss to follow-up (2), withdrawal (2), missing echo (6), baseline LVEF >50% (2).
• LOT-CRT group: mean age 64 years; 38% women; NIVCD 47%, LBBB 53%; QRS 175 ms; LVEF 27.6%.
• Matched ECG Belt controls: age 66 years; 41% men? (20 men, 59%); LBBB 53% matched exactly; QRS 165 ms; LVEF 30%.
• Matching: 1:1 propensity score on age, sex, ischaemic cardiomyopathy, QRS duration and LVESV, with exact matching on LBBB vs NIVCD.
• Residual imbalance remained for BMI, diastolic blood pressure, NYHA class, QRS duration and LVEF (standardised mean differences >25%).
• Pacing: paced AV 162 ± 28 ms, sensed AV 121 ± 24 ms; VV 0 ms in 50%, LV CS first in 28%, LBBAP first in 22%.
• Ventricular pacing 97% ± 3% in CSPOT vs 96% ± 7% in controls.

Echocardiographic outcomes

• Absolute LVEF increase: 16.1% LOT-CRT vs 6.1% BVP (P < .01).
• Relative LVESV reduction: 43.5% vs 20.9% (P < .01).
• After multivariable adjustment: +7.5% absolute LVEF (P < .01) and −18.4% relative LVESV (P < .01) in favour of LOT-CRT.
• Responder rate (LVEF increase ≥5%): 79% (27/34).
• Super-responder rate (LVEF increase ≥14.5%): 56% (19/34).
• No significant difference between LBBB and NIVCD within the LOT-CRT cohort; BVP controls with NIVCD trended toward lower LVEF response (P = .09).
• LOT-CRT patients with QRS ≥171 ms had greater LVEF and LVESV benefit than those with QRS <171 ms (P = .04).
• Successful LOT-CRT (terminal r′/R′ in V1) in 18/33 (55%); the remainder were DOT-CRT.
• No significant difference between successful LOT-CRT and DOT-CRT in LVEF change (13.5% ± 11.0 vs 20.7% ± 15.3; P = .14) or LVESV change (−42.6% ± 19.9 vs −46.2% ± 28.0; P = .68).
• DOT-CRT patients had more dilated hearts (LVEDV 250 ± 69 vs 177 ± 44 mL), longer baseline QRS (183 ± 15 vs 167 ± 19 ms) and longer paced QRS (153 ± 19 vs 135 ± 15 ms), but similar QRS shortening.

Predictors of response

• Longer baseline QRS predicted greater LVEF improvement: each 10 ms increase associated with +1.5% absolute LVEF (P = .01) and −3.1% relative LVESV (P = .03).
• Lower baseline LVEF predicted greater LVEF improvement: each 10% lower baseline EF associated with +4.0% absolute LVEF (P < .01).
• Conduction disease type (LBBB vs NIVCD) was not a significant predictor.

Correlation with acute metrics

• Acute ΔLV dP/dtmax did not correlate with 6-month LVEF change (r = 0.01).
• Acute QRS shortening showed a directional relationship with LVEF change (r = 0.65).

Safety

• Five complications in four patients (12%) related to the LOT-CRT implant or system: excessive CS lead slack, loose set screw, multiple shocks for arrhythmia, heart failure deterioration, and pseudoaneurysm after angiography; all recovered.
• Two deaths, neither adjudicated as related to the procedure or system.

Interpretation

• LOT-CRT may be particularly valuable in patients with complex conduction disease and wider QRS, where conventional BVP underperforms.
• ECG-based classification of LBBAP vs DSP is imperfect in advanced cardiomyopathy; some "DSP" patients may have concealed conduction-system engagement, and the similar outcomes support not abandoning the strategy when typical LBB capture criteria are absent.
• The authors caution that the comparison uses historical controls and that the sample is small.

Limitations of the document

• Historical, propensity-matched controls — unmeasured confounding may persist despite matching; the control group came from a different study with different echocardiographic acquisition (core lab vs local).
• Small sample (n = 34 per group) and short follow-up (6 months).
• Echocardiograms in CSPOT were measured locally, not by a core laboratory, unlike the ECG Belt controls.
• No clinical outcomes (heart failure hospitalisation, mortality) — only echocardiographic surrogates.
• Capture-type classification was ECG-based and may overestimate DSP; no imaging or invasive mapping confirmation.
• High dropout from the original CSPOT cohort (17 of 51 excluded).
• Industry sponsorship: Medtronic funded the study and employs several authors; multiple investigators report device-industry honoraria.

Key Concepts Mentioned

• concepts/LOT-CRT — the intervention
• concepts/Left-Bundle-Branch-Area-Pacing — the DOT-CRT category
• concepts/Cardiac-Resynchronization-Therapy — the clinical context
• concepts/ECG-Conduction-Disturbances — a key subgroup
• concepts/Cardiac-Resynchronization-Therapy — the outcome
• concepts/Left-Bundle-Branch-Area-Pacing — the pacing lead

Key Entities Mentioned

• CSPOT study — the source cohort
• ECG Belt study — the historical control cohort
• Medtronic — sponsor and device supplier
• University of Chicago — lead site

Wiki Pages Updated

• Created: wiki/sources/lot-crt-hrs-2025.md
• Updated: wiki/concepts/LOT-CRT.md
• Updated: wiki/concepts/Electrical-Resynchronization-Metrics.md
• Updated: wiki/sourceindex.md
• Updated: log.md