Cardiac Resynchronization TherapyCONSYST-CRT IINCT06105580
Conduction System Pacing vs Biventricular Pacing in Systolic Dysfunction and Wide QRS: Mortality, Heart Failure Hospitalization or Cardiac Transplant
A study testing Conduction system pacing and Biventricular pacing in people with Cardiac Resynchronization Therapy and Heart Failure, run by Hospital Clinic of Barcelona at 1 site in Spain.
Trial summary
Conduction system pacing vs biventricular resynchronization therapy in systolic dysfunction and wide QRS: mortality, heart failure hospitalization or cardiac transplant (CONSYST-CRT II trial). Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Cardiac Resynchronization Therapy, Heart Failure
- What is being tested?
- Conduction system pacing and Biventricular pacing
- Type of treatment
- Surgery or procedure
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 320 participants
- Where
- 1 siteSpain
- Study dates
- 27 Nov 2023to Jan 2028
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Patient must indicate acceptance to participate in the study by signing an informed consent document.
- Patient must be ≥ 18 years of age.
- Left bundle branch block, QRS ≥130 and LVEF <=35%. No indication of stimulation for AV block.
- Non-left bundle branch block, QRS ≥150 and LVEF <=35%.
- Resynchronization therapy indication for ventricular dysfunction (LVEF <40%) and indication of cardiac pacing for AV block.
- LVEF <=35% in NYHA class III or IV, atrial fibrillation and intrinsic QRS >=130 ms, provided a strategy to ensure biventricular capture is in place.
Who cannot join
- Myocardial infarction, unstable angina or cardiac revascularization during the previous 3 months.
- Pregnancy.
- Participating currently in a clinical investigation that includes an active treatment.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Spain1 site, 1 recruiting
- Recruiting
Hospital Clínic de Barcelona
Barcelona
JM Tolosana, MD, PhD, tolosana@clinic.cat
M Pujol Lopez, MD
About this study
Official title: Conduction System Pacing vs Biventricular Resynchronization Therapy in Systolic Dysfunction and Wide QRS: Mortality, Heart Failure Hospitalization or Cardiac Transplant
Conduction system pacing vs biventricular resynchronization therapy in systolic dysfunction and wide QRS: mortality, heart failure hospitalization or cardiac transplant (CONSYST-CRT II trial).
Superiority trial that aims to study the composite endpoint consisting of all-cause mortality, cardiac transplant or heart failure hospitalization at 12-month follow-up.
Read the detailed description
To date, studies have shown that conduction system pacing could get similar clinical and echocardiographic responses to those obtained with biventricular therapy.
This study will randomize 320 patients to a strategy of biventricular pacing versus conduction system pacing.
CONSYST-CRT II study will analyze a clinical endpoint as primary endpoint and the following parameters in both groups: left ventricular ejection fraction, ventricular volumes, echocardiographic response (>=15% decrease in left ventricular end-systolic volume), NYHA functional class, heart failure hospitalization, all-cause mortality, cardiac transplant, QRS shortening, echocardiographic dyssynchrony (atrioventricular, interventricular, intraventricular) and global longitudinal strain.
As a secondary endpoint, baseline predictors of response to conduction system pacing and biventricular pacing according to cardiac magnetic ressonance and electrocardiographic imaging will be studied.
Clinical, electrocardiographic, echocardiographic follow-up will be performed during 12 months.
- Conditions
- Cardiac Resynchronization Therapy, Heart Failure
- Being tested
- Conduction system pacing, Biventricular pacing
- Keywords
- left bundle branch pacing, biventricular pacing, cardiac resynchronization therapy
- Medical subject headings
- Heart Failure
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Conduction system pacingProcedure or surgery
Conduction system pacing implant as a Resynchronization therapy.
Biventricular pacingProcedure or surgery
Biventricular pacing implant
| Study group | Role | What they receive |
|---|---|---|
| Conduction system pacing | Experimental | Pacing the His-Purkinje system.
Crossover to biventricular pacing allowed in case of failed conduction system pacing: failed His bundle pacing and failed Left bundle branch pacing (high thresholds (>3.5V / 1ms); no left bundle branch pacing criteria; no left bundle branch correction).
Electrocardiographic optimization allowed in order to obtain the narrowest QRS. Receives: Procedure: Conduction system pacing |
| Biventricular pacing | Active comparator | Pacing from the right ventricular and coronary sinus lead. Electrocardiographic optimization with fusion-optimized intervals (FOI).
Crossover from biventricular pacing to conduction system pacing will be allowed in the following situations: coronary sinus cannot be cannulated; no lateral or posterolateral branches; or phrenic stimulation. Receives: Procedure: Biventricular pacing |
What is being measured
The primary outcome is the main question the study is designed to answer.
Composite end-point: all-cause mortality, cardiac transplant or heart failure hospitalization.
Clinical follow-up at 12 months
Measured: 1 year
Secondary outcomes (14)
Change in left ventricular ejection fraction.
Left ventricular ejection fraction measured with Simpson method with echocardiography.
Measured: 6 months; 1 year
Change in left ventricular end-systolic volume.
Left ventricular volumes measured with echocardiography. Simpson rule from 2- and 4-chamber apical views.
Measured: 6 months; 1 year
Echocardiographic response.
>=15% decrease in left ventricular end-systolic volume
Measured: 6 months; 1 year
Change in NYHA functional class.
NYHA functional class I, II, III, or IV
Measured: 6 months; 1 year
QRS shortening.
QRS duration (milliseconds). QRS onset measured from fast deflection and from spike.
Measured: Immediately after the intervention
Correction of septal flash.
Fast inward-outward movement of the interventricular septum in early systole. Using M-mode in parasternal short and long-axis views, septal flash was quantified (in millimeters) as the highest amplitude of the early inward motion measured from the resting position prior to the onset of septal contraction. The pair of septal flash measures (baseline and final) was obtained at the axis with the highest baseline SF.
Measured: 15 days; 6 months; 1 year
Correction of auriculoventricular dyssynchrony.
Left ventricular filling time. The left ventricular filling time was measured from the onset of the E-wave to the end of the A-wave, and the R-R interval was measured to calculate the percentage of filling time relative to the cardiac cycle (LV filling time/RR, %).
Measured: 15 days; 6 months; 1 year
Correction of interventricular dyssynchrony.
Quantified using pulsed Doppler and calculated as the time difference between QRS onset and the onset of the flow wave in the right and left outflow tracts.
Measured: 15 days; 6 months; 1 year
Change in global longitudinal strain (GLS).
Strain myocardial deformation of the left ventricle was quantified offline from 2-dimensional echocardiography using speckle tracking (2Dstrain, Echo Pac, version 202.41.0, GE Healthcare Milwaukee, WI). The long-axis cine images (2-, 3-, and 4-chamber views), were used to determine GLS.
Measured: 15 days; 6 months; 1 year
Description of baseline predictors of response to conduction system pacing and biventricular pacing. Cardiac fibrosis quantification.
Cardiac fibrosis quantification (grams of fibrosis)
Measured: Baseline (pre intervention).
Description of baseline predictors of response to conduction system pacing and biventricular pacing with Electrocardiographic Imaging. Left ventricular activation time (LVAT), ms.
Left ventricular activation time (LVAT), ms.
Measured: Baseline (pre intervention). And immediately after the intervention
Description of baseline predictors of response to conduction system pacing and biventricular pacing with Electrocardiographic Imaging. Ventricular electrical uncoupling (VEU).
Ventricular electrical uncoupling (VEU) = mean left ventricular activation time - mean right ventricular activation time, ms
Measured: Baseline (pre intervention). And immediately after the intervention
Description of baseline predictors of response to conduction system pacing and biventricular pacing with Electrocardiographic Imaging. Left ventricular dyssynchrony index (LVDI).
Left ventricular dyssynchrony index (LVDI): standard deviation of individual activations recorded from the left ventricle.
Measured: Baseline (pre intervention). And immediately after the intervention
Description of baseline predictors of response to conduction system pacing and biventricular pacing with Electrocardiographic Imaging. Conduction velocity (cm/s).
Conduction velocity (cm/s).
Measured: Baseline (pre intervention). And immediately after the intervention
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted27 Oct 2023
- Study start27 Nov 2023
- Primary completionNov 2027 (estimated)
- Study completionJan 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Cardiac Resynchronization TherapyStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- The first 130 patients have been recruited in the context of the CONSYST I study (ClinicalTrials.gov Identifier: NCT05187611). It is planned to perform an interim analysis (intermediate analysis) for the primary endpoint in all randomized patients who received intervention. The formal limits of stopping the study will be determined by the limits of futility and effectiveness defined by the rules of sequential stopping using the O'Brien-Fleming method. The interim analysis will be performed with a sample recruitment of 50%. Members of the Data Monitoring Committee, but not any trial investigator, will be informed of the results of the interim analysis. A p of 0.0054 (two-sided alpha) will be required for the interim analysis and 0.049 in the final analysis.
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 320 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Hospital Clinic of Barcelona
- Sponsor type
- University, hospital or other
- Collaborators
- Institut d'Investigacions Biomèdiques August Pi i Sunyer
- Responsible party
- Principal investigator, Josep Lluis Mont Girbau, Hospital Clinic of Barcelona
- Investigators
- José Mª Tolosana, MD, PhD, Principal investigator, Hospital Clínic de Barcelona. Institut d'Investigacions Biomèdiques August Pi i SunyerMargarida Pujol López, MD, Principal investigator, Hospital Clínic de Barcelona. Institut d'Investigacions Biomèdiques August Pi i SunyerLluís Mont, MD, PhD, Study chair, Hospital Clínic de Barcelona. Institut d'Investigacions Biomèdiques August Pi i Sunyer
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06105580
- Sponsor's protocol ID
- CONSYST-CRT II
- Acronym
- CONSYST-CRT II
- Status last verified
- Mar 2026
- First submitted
- 4 Oct 2023
- Last updated
- 3 Apr 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 3 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Conduction System Pacing vs Biventricular Resynchronization Therapy in Systolic Dysfunction and Wide QRS: Mortality, Heart Failure Hospitalization or Cardiac Transplant
- ClinicalTrials.gov ID
- NCT06105580
- Acronym / sponsor ID
- CONSYST-CRT II / CONSYST-CRT II
- Conditions
- Cardiac Resynchronization Therapy, Heart Failure
- Keywords
- left bundle branch pacing, biventricular pacing, cardiac resynchronization therapy
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 320 participants (estimated)
- Lead sponsor
- Hospital Clinic of BarcelonaUniversity, hospital or other
- Collaborators
- Institut d'Investigacions Biomèdiques August Pi i Sunyer
- Study start
- 27 Nov 2023 (actual)
- Primary completion
- Nov 2027 (estimated)
- Study completion
- Jan 2028 (estimated)
- First posted
- 27 Oct 2023 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Conduction system pacing vs biventricular resynchronization therapy in systolic dysfunction and wide QRS: mortality, heart failure hospitalization or cardiac transplant (CONSYST-CRT II trial).
Superiority trial that aims to study the composite endpoint consisting of all-cause mortality, cardiac transplant or heart failure hospitalization at 12-month follow-up.
Detailed description
To date, studies have shown that conduction system pacing could get similar clinical and echocardiographic responses to those obtained with biventricular therapy.
This study will randomize 320 patients to a strategy of biventricular pacing versus conduction system pacing.
CONSYST-CRT II study will analyze a clinical endpoint as primary endpoint and the following parameters in both groups: left ventricular ejection fraction, ventricular volumes, echocardiographic response (>=15% decrease in left ventricular end-systolic volume), NYHA functional class, heart failure hospitalization, all-cause mortality, cardiac transplant, QRS shortening, echocardiographic dyssynchrony (atrioventricular, interventricular, intraventricular) and global longitudinal strain.
As a secondary endpoint, baseline predictors of response to conduction system pacing and biventricular pacing according to cardiac magnetic ressonance and electrocardiographic imaging will be studied.
Clinical, electrocardiographic, echocardiographic follow-up will be performed during 12 months.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (participant)
- Number of arms
- 2
- Model description
- The first 130 patients have been recruited in the context of the CONSYST I study (ClinicalTrials.gov Identifier: NCT05187611). It is planned to perform an interim analysis (intermediate analysis) for the primary endpoint in all randomized patients who received intervention. The formal limits of stopping the study will be determined by the limits of futility and effectiveness defined by the rules of sequential stopping using the O'Brien-Fleming method. The interim analysis will be performed with a sample recruitment of 50%. Members of the Data Monitoring Committee, but not any trial investigator, will be informed of the results of the interim analysis. A p of 0.0054 (two-sided alpha) will be required for the interim analysis and 0.049 in the final analysis.
| Arm | Type | Receives |
|---|---|---|
| Conduction system pacing | Experimental | Procedure: Conduction system pacingPacing the His-Purkinje system. Crossover to biventricular pacing allowed in case of failed conduction system pacing: failed His bundle pacing and failed Left bundle branch pacing (high thresholds (>3.5V / 1ms); no left bundle branch pacing criteria; no left bundle branch correction). Electrocardiographic optimization allowed in order to obtain the narrowest QRS. |
| Biventricular pacing | Active comparator | Procedure: Biventricular pacingPacing from the right ventricular and coronary sinus lead. Electrocardiographic optimization with fusion-optimized intervals (FOI). Crossover from biventricular pacing to conduction system pacing will be allowed in the following situations: coronary sinus cannot be cannulated; no lateral or posterolateral branches; or phrenic stimulation. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (6 listed)
- Patient must indicate acceptance to participate in the study by signing an informed consent document.
- Patient must be ≥ 18 years of age.
- Left bundle branch block, QRS ≥130 and LVEF <=35%. No indication of stimulation for AV block.
- Non-left bundle branch block, QRS ≥150 and LVEF <=35%.
- Resynchronization therapy indication for ventricular dysfunction (LVEF <40%) and indication of cardiac pacing for AV block.
Key exclusion criteria (3 listed)
- Myocardial infarction, unstable angina or cardiac revascularization during the previous 3 months.
- Pregnancy.
- Participating currently in a clinical investigation that includes an active treatment.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Conduction system pacingConduction system pacing implant as a Resynchronization therapy. | Procedure or surgery | Conduction system pacing |
| Biventricular pacingBiventricular pacing implant | Procedure or surgery | Biventricular pacing |
Primary outcome
Composite end-point: all-cause mortality, cardiac transplant or heart failure hospitalization.
Time frame: 1 year
Clinical follow-up at 12 months
14 secondary outcomes
Change in left ventricular ejection fraction.
Time frame: 6 months; 1 year
Change in left ventricular end-systolic volume.
Time frame: 6 months; 1 year
Echocardiographic response.
Time frame: 6 months; 1 year
Change in NYHA functional class.
Time frame: 6 months; 1 year
QRS shortening.
Time frame: Immediately after the intervention
Correction of septal flash.
Time frame: 15 days; 6 months; 1 year
Correction of auriculoventricular dyssynchrony.
Time frame: 15 days; 6 months; 1 year
Correction of interventricular dyssynchrony.
Time frame: 15 days; 6 months; 1 year
Change in global longitudinal strain (GLS).
Time frame: 15 days; 6 months; 1 year
Description of baseline predictors of response to conduction system pacing and biventricular pacing. Cardiac fibrosis quantification.
Time frame: Baseline (pre intervention).
Description of baseline predictors of response to conduction system pacing and biventricular pacing with Electrocardiographic Imaging. Left ventricular activation time (LVAT), ms.
Time frame: Baseline (pre intervention). And immediately after the intervention
Description of baseline predictors of response to conduction system pacing and biventricular pacing with Electrocardiographic Imaging. Ventricular electrical uncoupling (VEU).
Time frame: Baseline (pre intervention). And immediately after the intervention
Description of baseline predictors of response to conduction system pacing and biventricular pacing with Electrocardiographic Imaging. Left ventricular dyssynchrony index (LVDI).
Time frame: Baseline (pre intervention). And immediately after the intervention
Description of baseline predictors of response to conduction system pacing and biventricular pacing with Electrocardiographic Imaging. Conduction velocity (cm/s).
Time frame: Baseline (pre intervention). And immediately after the intervention
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 3 Apr 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
José Mª Tolosana, MD, PhD principal investigator
Hospital Clínic de Barcelona. Institut d'Investigacions Biomèdiques August Pi i Sunyer
Margarida Pujol López, MD principal investigator
Hospital Clínic de Barcelona. Institut d'Investigacions Biomèdiques August Pi i Sunyer
Lluís Mont, MD, PhD study chair
Hospital Clínic de Barcelona. Institut d'Investigacions Biomèdiques August Pi i Sunyer
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Conduction system pacing and Biventricular pacing in people with Cardiac Resynchronization Therapy and Heart Failure, run by Hospital Clinic of Barcelona at 1 site in Spain.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 3 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Spain. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Jose Mª Tolosana, MD, PhD (93 2271778 (2094), tolosana@clinic.cat), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Composite end-point: all-cause mortality, cardiac transplant or heart failure hospitalization. (time frame: 1 year). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 3 Apr 2026.