An interventional study of Biventricular pacing and Conduction system pacing in Heart Failure and Reduced Ejection Fraction and Dyssynchrony, sponsored by Imperial College London. Recruiting at 1 site in United Kingdom. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-02-24.
Sponsored by Imperial College London · Not applicable, Interventional, and Treatment
The goal of this clinical trial is to find out which type of specialist pacemaker-known as cardiac resynchronisation therapy (CRT)-works best for people with heart failure and a delay in how the lower chambers of the heart beat together (called electrical dyssynchrony).
The main aims of the study are:
To compare the effects of conventional biventricular pacing (BVP), conduction system pacing (CSP) and left-bundle optimised CRT (LOT-CRT) on heart failure symptoms and heart rhythm problems over six months.
To explore how these pacing methods affect heart muscle strength, electrical activity, and overall heart function.
Participants will:
Attend four hospital visits over a six-month period.
At Visit 1, meet a member of the research team to discuss the study and have screening tests to check eligibility. Participants will also have a smartphone app installed and receive training on how to record their daily heart failure symptoms.
At Visit 2, have a CRT pacemaker implanted. The type of pacemaker will be chosen at random, with a 1 in 3 chance of receiving:
At Visit 3 (around 12 weeks after implantation) and Visit 4 (6 months after implantation), take part in routine follow-up assessments to check the pacemaker and heart function.
At Visits 2 and 4, also undergo non-invasive electrical mapping tests, including wearing a specialised vest and having a low-dose CT scan of the chest. These tests help researchers understand how the heart's electrical system responds to different pacing methods.
227 studies on the registry are indexed under Heart Failure, Systolic; 50 are open to participants now.
This study's planned enrollment of 60 is close to the median of 60 across 162 interventional studies indexed under Heart Failure, Systolic.
Browse Heart Failure, Systolic studies →Imperial College London is the lead sponsor of 824 studies on the registry; 178 are open to participants now.
Of its 9 completed or terminated interventional studies of FDA-regulated products, 6 (67%) have results posted.
Counted across the registry records on this site, refreshed daily.
Patients referred/scheduled for a CRT procedure (new implant or upgrade) who have:
Exclusion Criteria:
Current standard of care cardiac resynchronisation therapy with biventricular pacing (one lead to right ventricular endocardium and one lead to left ventricular epicardium, accessed via the coronary sinus).
Device: Biventricular pacing
Cardiac resynchronisation therapy with single lead targeting direct capture of the conduction system. Primary target should be left bundle area, with backup target of His bundle.
Device: Conduction system pacing
Cardiac resynchronisation therapy delivered by conduction system optimised hybrid configurations. Primary configuration should be conduction system pacing lead targeted at the left bundle area combined with left ventricular epicardial lead accessed via the coronary sinus (LOT-CRT). Backup configuration of conduction system pacing lead targeted at the His bundle combined with left ventricular epicardial lead accessed via the coronary sinus (HOT-CRT).
Device: Left bundle optimised cardiac resynchronisation therapy
Cardiac resynchronisation therapy with one lead to right ventricular endocardium and one lead to left ventricular epicardium, accessed via the coronary sinus.
Also known as: BVP
Cardiac resynchronisation therapy with single lead targeting direct capture of the conduction system. Primary target should be left bundle area, with backup target of His bundle. If direct capture of the conduction system cannot be achieved by conventional clinical criteria, left septal pacing targeted at the left bundle branch area will be accepted.
Also known as: Physiological pacing, CSP, Left bundle branch pacing, Left bundle branch area pacing, Left septal pacing, His bundle pacing, LBBP, LBBAP, LSP, HBP
Cardiac resynchronisation therapy delivered by conduction system optimised hybrid configurations. Primary configuration should be conduction system pacing lead targeted at the left bundle area combined with left ventricular epicardial lead accessed via the coronary sinus (LOT-CRT). Backup configuration of conduction system pacing lead targeted at the His bundle combined with left ventricular epicardial lead accessed via the coronary sinus (HOT-CRT).
Also known as: LOT-CRT, His bundle optimised cardiac resynchronisation therapy, HOT-CRT
Primary outcome: Daily ordinal symptom score with clinical over-rides
Daily ordinal scale with mobile application based assessment of quality of life (using visual analogue scale), with clinical over-rides as detailed below: 1. Death 2. Intractable symptoms leading to trial exit/unblinding 3. Heart failure hospitalisation 4. Non-heart failure hospitalisation 5. Appropriate implantable cardioverter defibrillator therapy (anti-tachycardia pacing or shock, deemed appropriate as per clinical care team interrogating device) 6. Symptom score (1-600, with 1 representing minimum limitation from patient ascribed heart failure symptom and 600 representing maximum limitation)
Time frame: From randomisation to 6-months post device implant
Primary arrhythmia outcome
Ordinal arrhythmia scale using clinical endpoints as detailed below: 1. Death 2. Appropriate implantable cardioverter defibrillator therapy (anti-tachycardia pacing or shock, deemed appropriate as per clinical care team interrogating device) 3. Sustained ventricular arrhythmia (VA) (\>30s of rhythm determined to be ventricular in origin by clinical team on device interrogation) 4. Sustained atrial arrhythmia 5. Non-sustained VA 6. \>10% ventricular ectopy on 24h ECG
Time frame: From randomisation to 6-months post device implant
Primary contractility outcome
Ordinal contractility scale using clinical endpoints as detailed below: 1. Death 2. Intractable symptoms leading to trial exclusion/unblinding 3. Heart failure hospitalisation 4. Non-heart failure hospitalisation 5. Left ventricular ejection fraction (measured on transthoracic echocardiogram)
Time frame: From randomisation to 6-months post device implant
Rate of death
Death, any cause
Time frame: From randomisation up to 36 months, or death from any cause, whichever came first.
Number of participants with intractable symptoms leading to trial exit/unblinding
Intractable symptoms leading to exit of trial considered to be a single event. Symptoms will be assessed routinely at a single remote consultation with a blinded research team member 1-4 months after device implant. If at this visit or after a patient directed consultation, symptoms are felt to have deteriorated after the device implant likely due to the device, the case will be discussed with the blinded principal-investigator to adjudicate. If the conclusion is that the deterioration is device mediated, the patient will be unblinded, exit from the trial and the device will be programmed to whatever is felt to be optimal by the clinical team.
Time frame: From randomisation up to 36 months, or intractable symptoms leading to trial exit/unblinding, whichever came first.
Rate of heart failure hospitalisation
Adjudicated unplanned heart failure acute care (hospital admissions or ambulatory diuretic therapy i.e. diuretic lounge visit)
Time frame: From randomisation up to 36 months
Rate of non-heart failure hospitalisation
Adjudicated unplanned non-heart failure acute care (hospital admissions or ambulatory service i.e. ambulatory emergency clinic).
Time frame: From randomisation up to 36 months
Rate of appropriate implantable cardioverter defibrillator device therapy
Anti-tachycardia pacing or shock delivered by device adjudicated to be appropriate for ventricular arrhythmia
Time frame: From randomisation up to 36 months
Daily heart failure symptom score
Bespoke mobile phone application based daily ordinal symptom score. Patients asked to identify their most associated heart failure symptom at the beginning of the study, they then grade that symptom on a 0-600 (non-labelled) continuum rating this symptom's severity for the previous day (0 being not limited at all, 600 being extremely limited).
Time frame: From randomisation up to 36 months
Rate of sustained ventricular arrhythmia
Adjudicated sustained arrhythmia suspected to be ventricular in origin of \>30s on device interrogation
Time frame: From randomisation up to 36 months
Rate of sustained atrial arrhythmia
Adjudicated sustained arrhythmia suspected to be atrial in origin of \>30s on device interrogation
Time frame: From randomisation up to 36 months
Rate of non-sustained ventricular arrhythmia
Adjudicated non-sustained arrhythmia suspected to be ventricular in origin of \<30s on device interrogation
Time frame: From randomisation up to 36 months
Number of participants with >10% ventricular ectopy on 24h ECG
Time frame: At 12-weeks post implant
Left ventricular ejection fraction (LVEF)
LVEF within group differences
Time frame: From baseline echocardiogram (pre device implant) to follow-up echocardiogram (at 6 months)
Left ventricular repolarisation heterogeneity
Non-invasive epicardial electrical mapping (ECGi) derived left ventricular repolarisation time and left ventricular repolarisation gradient
Time frame: From implant to 6-months
Left ventricular activation
Non-invasive epicardial electrical mapping (ECGi) derived left ventricular activation time and left ventricular activation recovery interval
Time frame: From implant to 6-months
QT dispersion
Measured from 24h ECG monitors patients are fitted with 12 weeks after device implant
Time frame: From randomisation to 6 months post device implant
Left ventricular end diastolic volume (LVEDV)
LVEDV within group differences
Time frame: From baseline echocardiogram (pre device implant) to follow-up echocardiogram (at 6 months)
Left ventricular end systolic volume (LVESV)
LVESV within group differences
Time frame: From baseline echocardiogram (pre device implant) to follow-up echocardiogram (at 6 months)
Six minute walk test
Within group comparison
Time frame: From baseline to 6 months post device implantation
Serum B-type natriuretic peptide (BNP)
Within group comparison
Time frame: From baseline to 6 months post device implant
Quality of life assessed via HeartQoL questionnaire
14 point questionnaire consisting of Likert scale answers to determine quality of life affected by heart disease. Score between 0-42 with a lower score indicating worse quality of life.
Time frame: From baseline to 6 months post device implant
Kansas City Cardiomyopathy Questionnaire 12 (KCCQ-12)
12 point questionnaire consisting of Likert scale answers to determine quality of life affected by heart failure. Scores between 12-70 with the lower score suggesting a greater reduction in quality of life and worse symptoms.
Time frame: From baseline to 6 months post device implant
Minnesota Living With Hearth Failure Questionnaire (MLWHFQ)
21 point questionnaire consisting of Likert scale answers to determine quality of life affected by heart disease. Scores between 0-125 with a lower score representing a better quality of life.
Time frame: From baseline to 6 months post device implant
Heart failure status assessed by New York Heart Association classification
Time frame: From baseline to 6 months post device implantation
Device derived patient activity level
Activity levels as measured by the implanted pacemaker generator.
Time frame: At 6 months post device implant
Device determined atrial fibrillation burden
Proportion of time rhythm is atrial fibrillation as determined by implanted pacemaker detetection.
Time frame: At 6 months post pacemaker implant
Percentage of days outside of the normal range device measured intrathoracic impedance or triggering device warning for fluid status
Taken from device checks at 3 and 6 months. Manufacturer specific defined alerts and intrathoracic normal ranges used, to allow to inter-manufacturer comparisons.
Time frame: From implant to 6 months post pacemaker implant
Blinding index
Assessed using Bang Blinding Index (BBI), with patients asked regarding allocated treatment arm at the point of discharge following device implant and again before unblinding at 6 months. Scores will be allocated -1 for stating the incorrect treatment arm, 0 for the patient stating they do not know he treatment arm and +1 for a correctly stating the treatment arm.
Time frame: From device implant, to 6 months post device implant
Number of patients with treatment related adverse events
Treatment related adverse events include; device infections (requiring device extraction or hospital admission), need for lead revision or reimplantation, premature generator change within study period, haematoma, pericardial effusion requiring intervention and pneumothorax. Other treatment related adverse events non included in this list, but adjudicated by trial steering committee may also be included.
Time frame: From device implant to 36 months post device implant
Plan to share: Undecided
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Imperial College London