An interventional study of Cardiac resynchronization therapy ON and Cardiac resynchronization therapy OFF in Left Ventricular Dyssynchrony, Heart Failure and Cardiomyopathy, Dilated, sponsored by Universitaire Ziekenhuizen KU Leuven. Active, not recruiting at 24 sites in 11 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-04-07.
Sponsored by Universitaire Ziekenhuizen KU Leuven · Not applicable, Interventional, and Treatment
Previous experience with cardiac resynchronization therapy (CRT) candidates suggests that selection of these patients can be improved. Current clinical guideline approaches are mainly too unspecific and lead to a high non-responder rate of 30-40%, which causes a burden on health care systems and puts patients at risk of an unnecessary treatment who might benefit more from a conservative approach. Previous work indicated that using the assessment of mechanical dyssynchrony on echocardiography can lower the non-responder rate at least by 50% without compromising sensitivity for detecting amendable patients. The current prospective, randomized, multi-center trial was therefore designed to prove that the characterization of the mechanical properties of the left ventricle can improve patient selection for CRT. Patients will be randomized into one of two study arms: a control study arm with treatment recommendation based on clinical guidelines criteria, or an experimental study arm with treatment recommendation based on the presence of mechanical dyssynchrony. All patients will receive a CRT implantation. In the control study arm, bi-ventricular pacing will be turned on. In the experimental study arm, bi-ventricular pacing will be turned on or off, depending on the presence or absence of mechanical dyssynchrony, respectively. The primary endpoint will be non-inferiority in outcome of a treatment recommendation based on mechanical dyssynchrony, achieved with a lower number of CRT devices implanted, effectively leading to a lower number needed to treat. Outcome measures are the average relative change in continuously measured LVESV per arm and the percentage 'worsened' according to the Packer Clinical Composite Score per arm after 1 year follow-up.
6,331 studies on the registry are indexed under Heart Failure; 1,396 are open to participants now.
This study's planned enrollment of 500 is above the median of 76 across 4,049 interventional studies indexed under Heart Failure.
Browse Heart Failure studies →Universitaire Ziekenhuizen KU Leuven is the lead sponsor of 963 studies on the registry; 267 are open to participants now.
Of its 5 completed or terminated interventional studies of FDA-regulated products, 0 (0%) have results posted.
Counted across the registry records on this site, refreshed daily.
(- - - - - - - - - Inclusion Criteria - - - - - - - - -)
The proposed inclusion criteria represent the minimum recommendations for CRT implantation in heart failure patients according to the ESC 2021 guidelines. In addition:
(- - - - - - - - - Exclusion Criteria - - - - - - - - -)
Patients with the following conditions will be excluded:
Patients with prior right ventricular pacing between 20% to 80% will be excluded.
Patients with prior right ventricular pacing ≤ 20% or no pacemaker / ICD will be excluded if they have any of the following criteria:
Patients with prior right ventricular pacing ≥ 80% will be excluded if they have any of the following criteria:
Patients with a prior pacemaker / ICD scheduled for LBBaP will be excluded regardless of pacing percentage
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
LVEF (left ventricular ejection fraction)
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Treatment of the patient assigned to this arm will be based on the current guidelines for CRT implantation, as issued by the European Society of Cardiology. All patients will receive CRT implantation, with bi-ventricular pacing ON.
Device: Cardiac resynchronization therapy ON
Treatment of the patients assigned to this arm will be based on the presence of mechanical dyssynchrony. All patients will receive CRT implantation. Bi-ventricular pacing will be either turned ON or OFF, based on respectively the presence or absence of mechanical dyssynchrony.
Device: Cardiac resynchronization therapy ON · Device: Cardiac resynchronization therapy OFF
Implantation of a CRT device. Bi-ventricular pacing will be turned ON.
Implantation of a CRT device. Bi-ventricular pacing will be turned OFF.
Volume response and Packer Clinical Composite Score
Non-inferiority in outcome of a treatment recommendation based on mechanical dyssynchrony, achieved with a lower number of CRT devices implanted, effectively leading to a lower number needed to treat. Outcome measures are the average relative change in left ventricular end-systolic volume and the proportion of patients 'worsened' according to the Packer Clinical Composite Score after 12 months follow-up.
Time frame: 12 months follow-up
Effect on left ventricular function in both arms
* ≥ 10% difference in relative change in left ventricular ejection fraction and/or * ≥1.5% difference in absolute change in global longitudinal strain and/or * improvement in myocardial work from baseline to month 12
Time frame: 12 months follow-up
Difference in quality of life as measured by the Minnesota Living with Heart Failure questionnaire score and EuroQol 5D index score in both arms
* ≥ 5 points difference in change on the Minnesota Living with Heart Failure questionnaire score and/or * ≥0.08 points difference in change on the EuroQol 5D index score from baseline to month 12
Time frame: 12 months follow-up
Difference in 6 minute walk test distance in both arms
≥ 45 meters difference in change from baseline to month 12
Time frame: 12 months follow-up
Difference in predictive value for volume response
≥15% relative reduction in left ventricular end-systolic volume from baseline to month 12 will be considered as a response
Time frame: 12 months follow-up
Difference in predictive value for long-term patient outcome in both arms
Cox's proportional hazards model: * At 1 year for 'worsened' PCCS * At 3 and 5 years for cardiovascular mortality and heart failure hospitalization
Time frame: 1 year, 3 years and 5 years follow-up
Difference in long-term patient outcome in both arms
* Kaplan Meier survival analysis for heart failure hospitalization * Kaplan Meier survival analysis for cardiovascular mortality * Kaplan Meier survival analysis for combined heart failure hospitalization and cardiovascular mortality * Kaplan Meier survival analysis for all-cause mortality
Time frame: 3 years and 5 years follow-up
Plan to share: No — Available upon reasonable request after acceptance of publications.
No publications or documents are linked to this record.
Started Dec 2020 (actual). Primary completion is estimated for Dec 2027, 84 months after the start.
Of 1,118 non-industry interventional studies with no phase under Heart Failure, half reached primary completion within 29 months of starting (the median), counting those still running; a quarter within 16 and three quarters within 50. This study's planned 84 months is above that.
Counting every sponsor, half of 1,354 studies reached it within 31 months; a quarter within 16 and three quarters within 52.
How these figures are worked out, and which studies are left out of them.
This study is active, not recruiting, as verified in Apr 2026. You cannot join it, but the record below documents what was studied.
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