Atrial Fibrillation (AF)SYNC-AFNCT07560891
LBBAP vs. CS Pacing for CRT in Permanent Atrial Fibrillation and Heart Failure (SYNC-AF)
A study testing Left Bundle Branch Area Pacing (LBBAP) for CRT and Coronary Sinus (CS) Lead-Based Biventricular CRT in people with Atrial Fibrillation (AF) and Heart Failure, run by Yonsei University.
Trial summary
This is a prospective, multicenter, randomized controlled trial comparing Left Bundle Branch Area Pacing (LBBAP)-based cardiac resynchronization therapy (CRT) with conventional coronary sinus (CS) lead-based CRT in patients with permanent atrial fibrillation (AF) and heart failure (HF) who meet indications for CRT… Read more about this study
- Who is it for?
- Ages 19 years and older
- Conditions the study is for
- Atrial Fibrillation (AF), Heart Failure, Cardiomyopathies
- What is being tested?
- Left Bundle Branch Area Pacing (LBBAP) for CRT and Coronary Sinus (CS) Lead-Based Biventricular CRT
- Type of treatment
- Medical device
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 44 participants
- Where
- No sites listed yet
- Study dates
- 30 Jun 2026to 31 Dec 2029
- 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 19 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Age ≥19 years
- Indication for CRT (CRT-P or CRT-D) device implantation per current guidelines
- Permanent atrial fibrillation (with or without planned AVJ ablation)
- Ability to understand the purpose of the study and provide written informed consent
Who cannot join
- Prosthetic tricuspid valve
- Prior myocardial infarction involving the interventricular septal area
- Life expectancy less than 12 months
- Unable to comply with planned 12-month follow-up for any reason
- Pregnancy
- History of heart transplantation
- Persistent left superior vena cava (PLSVC)
Trial locations and contacts
No sites are listed yet. Contact the study team or a site near you to ask about taking part.
About this study
Official title: Left Bundle Branch Area Pacing Versus Coronary Sinus Pacing for Cardiac Resynchronization Therapy for Patients With Permanent Atrial Fibrillation and Heart Failure: The SYNC-AF Trial
This is a prospective, multicenter, randomized controlled trial comparing Left Bundle Branch Area Pacing (LBBAP)-based cardiac resynchronization therapy (CRT) with conventional coronary sinus (CS) lead-based CRT in patients with permanent atrial fibrillation (AF) and heart failure (HF) who meet indications for CRT device implantation.
Atrial fibrillation and heart failure frequently coexist, and both rapid heart rate and its irregularity contribute to worsening cardiac function. Atrioventricular junction (AVJ) ablation combined with CRT (biventricular pacing) has been established as an effective strategy for rate control and cardiac resynchronization in this population, supported by Class I recommendation in the 2021 ESC guidelines. However, conventional biventricular CRT via the CS lead can induce artificial electrical dyssynchrony, particularly in patients with a narrow QRS complex, potentially limiting its benefit.
Read more
Conduction system pacing (CSP), including LBBAP, has emerged as a physiologic alternative that directly stimulates the native conduction system, preserving synchronous ventricular activation. Recent evidence (ALTERNATIVE-AF trial) suggests CSP may be superior to biventricular CRT in permanent AF patients undergoing AVJ ablation. However, no randomized controlled trial has directly compared LBBAP-based CRT with CS lead-based CRT in this specific population.
The SYNC-AF trial will randomize 44 patients (22 per arm) to either LBBAP or CS pacing for CRT. The primary endpoint is change in left ventricular ejection fraction (LVEF) at 12 months as assessed by echocardiography in a blinded core laboratory. Secondary endpoints include changes in QRS duration, major adverse clinical events, device/procedure-related complications, and ventricular arrhythmia burden.
Read the detailed description
ECHOCARDIOGRAPHIC CORE LAB:
All echocardiographic assessments (LVEF, LVESV, LVEDV, etc.) are performed and interpreted by a blinded independent core laboratory at Severance Hospital to ensure objective and consistent measurement.
FOLLOW-UP SCHEDULE:
Screening (implant day) → Visit 1 (2 weeks-1 month) → Visit 2 (3 months ±3 months) → Visit 3 (6 months ±3 months) → Visit 4 (12 months ±3 months).
STATISTICAL ANALYSIS:
Primary analysis follows the Intention-To-Treat (ITT) principle. Per-Protocol (PP) analysis will be performed as sensitivity analysis. The primary endpoint (LVEF change at 12 months) will be compared using Student's t-test or Wilcoxon rank-sum test. Time-to-event analyses will use Kaplan-Meier survival curves with log-rank test and Cox proportional hazards model.
SAMPLE SIZE:
44 patients total (22 per arm). Based on the assumption of an absolute 10% greater improvement in LVEF with LBBAP-CRT vs. BiV-CRT, with 80% power and 5% two-sided alpha, with 10% dropout allowance.
PARTICIPATING CENTERS:
Multiple centers in the Republic of Korea (at least 4 centers), led by Severance Hospital, Yonsei University College of Medicine.
- Conditions
- Atrial Fibrillation (AF), Heart Failure, Cardiomyopathies
- Being tested
- Left Bundle Branch Area Pacing (LBBAP) for CRT, Coronary Sinus (CS) Lead-Based Biventricular CRT
- Keywords
- LBBAP, Left Bundle Branch Area Pacing, CRT, Cardiac Resynchronization Therapy, Permanent Atrial Fibrillation, Conduction System Pacing, AVJ Ablation, Heart Failure
- Medical subject headings
- Atrial Fibrillation, Heart Failure, Cardiomyopathies
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Left Bundle Branch Area Pacing (LBBAP) for CRTDevice
CRT device (CRT-P or CRT-D) implantation using LBBAP as the left ventricular pacing lead. A pacing lead is advanced through the interventricular septum to achieve left bundle branch area capture, confirmed by pacing parameters and electrocardiographic criteria (RBBB-like pattern with short R-peak latency in V5/V6). RV lead is implanted in standard fashion. AVJ ablation may be performed per clinical indication.
Coronary Sinus (CS) Lead-Based Biventricular CRTDevice
CRT device (CRT-P or CRT-D) implantation using a conventional coronary sinus (CS) lead as the left ventricular pacing lead. The CS lead is advanced via the coronary sinus into a lateral or posterolateral cardiac vein to achieve biventricular pacing. RV lead is implanted in standard fashion. AVJ ablation may be performed per clinical indication.
| Study group | Role | What they receive |
|---|---|---|
| LBBAP Group | Experimental | Participants undergo CRT device implantation (CRT-P or CRT-D) with Left Bundle Branch Area Pacing (LBBAP) as the left ventricular lead strategy. LBBAP is attempted first; if not feasible, crossover to CS lead is permitted. AVJ ablation is performed per clinical indication. Receives: Device: Left Bundle Branch Area Pacing (LBBAP) for CRT |
| CS Pacing Group | Active comparator | Participants undergo CRT device implantation (CRT-P or CRT-D) with conventional Coronary Sinus (CS) lead-based pacing as the left ventricular lead strategy. AVJ ablation is performed per clinical indication. Receives: Device: Coronary Sinus (CS) Lead-Based Biventricular CRT |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change from Baseline Left Ventricular Ejection Fraction (LVEF) at 12 Months
Change in left ventricular ejection fraction (LVEF) from baseline to 12 months post-implantation, as measured by transthoracic echocardiography performed and interpreted by a blinded independent central core laboratory. LVEF is assessed using the biplane Simpson method.
Measured: Baseline (at the time of device implantation) and 12 months post-implantation
Secondary outcomes (13)
Proportion of patients with absolute LVEF increase ≥5% at 12 months
Echocardiographic CRT response defined as absolute improvement in LVEF of ≥5% or ≥10% from baseline at 12 months, assessed by blinded core lab.
Measured: 12 months post-implantation
Proportion of patients with absolute LVEF increase ≥10% at 12 months
Echocardiographic CRT response defined as absolute improvement in LVEF of ≥5% or ≥10% from baseline at 12 months, assessed by blinded core lab.
Measured: 12 months post-implantation
Change in QRS Duration From Baseline
QRS duration measured from surface ECG in milliseconds.
Measured: Immediately post-implant and at 12 months
Time to First Treated Ventricular Arrhythmia
Time from randomization to first detection of treated ventricular arrhythmia (VT/VF) recorded by the implanted device within 12 months.
Measured: Up to 12 months
Composite of All-Cause Death and Heart Failure Hospitalization
Clinical events adjudicated by an independent committee. Heart failure hospitalization defined as unplanned outpatient/ED visit or inpatient admission with HF signs/symptoms requiring intravenous therapy.
Measured: Up to 12 months (first occurrence)
All-cause mortality
Clinical events adjudicated by an independent committee. Heart failure hospitalization defined as unplanned outpatient/ED visit or inpatient admission with HF signs/symptoms requiring intravenous therapy.
Measured: Up to 12 months (first occurrence)
Heart failure hospitalization
Clinical events adjudicated by an independent committee. Heart failure hospitalization defined as unplanned outpatient/ED visit or inpatient admission with HF signs/symptoms requiring intravenous therapy.
Measured: Up to 12 months (first occurrence)
Cardiovascular death
Clinical events adjudicated by an independent committee. Heart failure hospitalization defined as unplanned outpatient/ED visit or inpatient admission with HF signs/symptoms requiring intravenous therapy.
Measured: Up to 12 months (first occurrence)
Immediate procedural success rate of LBBAP lead implantation
Successful LBBAP lead placement defined by achievement of left bundle branch capture with acceptable pacing threshold (≤1.5V/0.5ms), impedance (300-1200Ω), and electrocardiographic criteria (RBBB pattern, short R-peak latency in V5/V6).
Measured: Immediately after the implantation procedure
Lead capture loss rate at 12 months
Loss of left bundle branch capture or inability to maintain pacing threshold <2.5V/0.5ms at 12 months.
Measured: 12 months post-implantation
Composite Rate of Worsening Heart Failure by Echocardiographic Criteria
Composite endpoint defined as ≥5% absolute decrease in LVEF from baseline or ≥15% increase in LVESV from baseline during follow-up.
Measured: Up to 12 months
Device and Procedure-Related Complications
All device/procedure-related complications and reinterventions occurring up to 12 months, adjudicated by an independent events committee.
Measured: Up to 12 months (device/procedure-related complications within 7 days for acute; up to 12 months for chronic)
Reintervention Rate
All device/procedure-related complications and reinterventions occurring up to 12 months, adjudicated by an independent events committee.
Measured: Up to 12 months
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted1 May 2026
- Study start30 Jun 2026 (estimated)
- Primary completion30 Jun 2029 (estimated)
- Study completion31 Dec 2029 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Atrial Fibrillation (AF)Studies of the same condition, open and under way.
- More trials run by Yonsei UniversityThe sponsor's other registered studies.
- 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
- Two parallel arms: LBBAP group (experimental) vs. CS pacing group (active comparator). 1:1 randomization. Open-label design with blinded echocardiographic core lab assessment.
- Masking
- Single blind
- Who is masked
- Outcomes assessor
- Enrolment
- 44 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Yonsei University
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07560891
- Sponsor's protocol ID
- 4-2025-1786
- Acronym
- SYNC-AF
- Status last verified
- Apr 2026
- First submitted
- 23 Apr 2026
- Last updated
- 1 May 2026
- Results posted
- No
- Data monitoring committee
- Yes
- 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 1 May 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Left Bundle Branch Area Pacing Versus Coronary Sinus Pacing for Cardiac Resynchronization Therapy for Patients With Permanent Atrial Fibrillation and Heart Failure: The SYNC-AF Trial
- ClinicalTrials.gov ID
- NCT07560891
- Acronym / sponsor ID
- SYNC-AF / 4-2025-1786
- Conditions
- Atrial Fibrillation (AF), Heart Failure, Cardiomyopathies
- Keywords
- LBBAP, Left Bundle Branch Area Pacing, CRT, Cardiac Resynchronization Therapy, Permanent Atrial Fibrillation, Conduction System Pacing, AVJ Ablation, Heart Failure
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 44 participants (estimated)
- Lead sponsor
- Yonsei UniversityUniversity, hospital or other
- Study start
- 30 Jun 2026 (estimated)
- Primary completion
- 30 Jun 2029 (estimated)
- Study completion
- 31 Dec 2029 (estimated)
- First posted
- 1 May 2026 (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.
This is a prospective, multicenter, randomized controlled trial comparing Left Bundle Branch Area Pacing (LBBAP)-based cardiac resynchronization therapy (CRT) with conventional coronary sinus (CS) lead-based CRT in patients with permanent atrial fibrillation (AF) and heart failure (HF) who meet indications for CRT device implantation.
Atrial fibrillation and heart failure frequently coexist, and both rapid heart rate and its irregularity contribute to worsening cardiac function. Atrioventricular junction (AVJ) ablation combined with CRT (biventricular pacing) has been established as an effective strategy for rate control and cardiac resynchronization in this population, supported by Class I recommendation in the 2021 ESC guidelines. However, conventional biventricular CRT via the CS lead can induce artificial electrical dyssynchrony, particularly in patients with a narrow QRS complex, potentially limiting its benefit.
Conduction system pacing (CSP), including LBBAP, has emerged as a physiologic alternative that directly stimulates the native conduction system, preserving synchronous ventricular activation. Recent evidence (ALTERNATIVE-AF trial) suggests CSP may be superior to biventricular CRT in permanent AF patients undergoing AVJ ablation. However, no randomized controlled trial has directly compared LBBAP-based CRT with CS lead-based CRT in this specific population.
The SYNC-AF trial will randomize 44 patients (22 per arm) to either LBBAP or CS pacing for CRT. The primary endpoint is change in left ventricular ejection fraction (LVEF) at 12 months as assessed by echocardiography in a blinded core laboratory. Secondary endpoints include changes in QRS duration, major adverse clinical events, device/procedure-related complications, and ventricular arrhythmia burden.
Detailed description
ECHOCARDIOGRAPHIC CORE LAB:
All echocardiographic assessments (LVEF, LVESV, LVEDV, etc.) are performed and interpreted by a blinded independent core laboratory at Severance Hospital to ensure objective and consistent measurement.
FOLLOW-UP SCHEDULE:
Screening (implant day) → Visit 1 (2 weeks-1 month) → Visit 2 (3 months ±3 months) → Visit 3 (6 months ±3 months) → Visit 4 (12 months ±3 months).
STATISTICAL ANALYSIS:
Primary analysis follows the Intention-To-Treat (ITT) principle. Per-Protocol (PP) analysis will be performed as sensitivity analysis. The primary endpoint (LVEF change at 12 months) will be compared using Student's t-test or Wilcoxon rank-sum test. Time-to-event analyses will use Kaplan-Meier survival curves with log-rank test and Cox proportional hazards model.
SAMPLE SIZE:
44 patients total (22 per arm). Based on the assumption of an absolute 10% greater improvement in LVEF with LBBAP-CRT vs. BiV-CRT, with 80% power and 5% two-sided alpha, with 10% dropout allowance.
PARTICIPATING CENTERS:
Multiple centers in the Republic of Korea (at least 4 centers), led by Severance Hospital, Yonsei University College of Medicine.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (outcomes assessor)
- Number of arms
- 2
- Model description
- Two parallel arms: LBBAP group (experimental) vs. CS pacing group (active comparator). 1:1 randomization. Open-label design with blinded echocardiographic core lab assessment.
| Arm | Type | Receives |
|---|---|---|
| LBBAP Group | Experimental | Device: Left Bundle Branch Area Pacing (LBBAP) for CRTParticipants undergo CRT device implantation (CRT-P or CRT-D) with Left Bundle Branch Area Pacing (LBBAP) as the left ventricular lead strategy. LBBAP is attempted first; if not feasible, crossover to CS lead is permitted. AVJ ablation is performed per clinical indication. |
| CS Pacing Group | Active comparator | Device: Coronary Sinus (CS) Lead-Based Biventricular CRTParticipants undergo CRT device implantation (CRT-P or CRT-D) with conventional Coronary Sinus (CS) lead-based pacing as the left ventricular lead strategy. AVJ ablation is performed per clinical indication. |
Who may qualify
- Ages
- 19 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (4 listed)
- Age ≥19 years
- Indication for CRT (CRT-P or CRT-D) device implantation per current guidelines
- Permanent atrial fibrillation (with or without planned AVJ ablation)
- Ability to understand the purpose of the study and provide written informed consent
Key exclusion criteria (7 listed)
- Prosthetic tricuspid valve
- Prior myocardial infarction involving the interventricular septal area
- Life expectancy less than 12 months
- Unable to comply with planned 12-month follow-up for any reason
- Pregnancy
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 |
|---|---|---|
| Left Bundle Branch Area Pacing (LBBAP) for CRTCRT device (CRT-P or CRT-D) implantation using LBBAP as the left ventricular pacing lead. A pacing lead is advanced through the interventricular septum to achieve left bundle branch area capture, confirmed by pacing parameters and electrocardiographic criteria (RBBB-like pattern with short R-peak latency in V5/V6). RV lead is implanted in standard fashion. AVJ ablation may be performed per clinical indication. | Device | LBBAP Group |
| Coronary Sinus (CS) Lead-Based Biventricular CRTCRT device (CRT-P or CRT-D) implantation using a conventional coronary sinus (CS) lead as the left ventricular pacing lead. The CS lead is advanced via the coronary sinus into a lateral or posterolateral cardiac vein to achieve biventricular pacing. RV lead is implanted in standard fashion. AVJ ablation may be performed per clinical indication. | Device | CS Pacing Group |
Primary outcome
Change from Baseline Left Ventricular Ejection Fraction (LVEF) at 12 Months
Time frame: Baseline (at the time of device implantation) and 12 months post-implantation
Change in left ventricular ejection fraction (LVEF) from baseline to 12 months post-implantation, as measured by transthoracic echocardiography performed and interpreted by a blinded independent central core laboratory. LVEF is assessed using the biplane Simpson method.
13 secondary outcomes
Proportion of patients with absolute LVEF increase ≥5% at 12 months
Time frame: 12 months post-implantation
Proportion of patients with absolute LVEF increase ≥10% at 12 months
Time frame: 12 months post-implantation
Change in QRS Duration From Baseline
Time frame: Immediately post-implant and at 12 months
Time to First Treated Ventricular Arrhythmia
Time frame: Up to 12 months
Composite of All-Cause Death and Heart Failure Hospitalization
Time frame: Up to 12 months (first occurrence)
All-cause mortality
Time frame: Up to 12 months (first occurrence)
Heart failure hospitalization
Time frame: Up to 12 months (first occurrence)
Cardiovascular death
Time frame: Up to 12 months (first occurrence)
Immediate procedural success rate of LBBAP lead implantation
Time frame: Immediately after the implantation procedure
Lead capture loss rate at 12 months
Time frame: 12 months post-implantation
Composite Rate of Worsening Heart Failure by Echocardiographic Criteria
Time frame: Up to 12 months
Device and Procedure-Related Complications
Time frame: Up to 12 months (device/procedure-related complications within 7 days for acute; up to 12 months for chronic)
Reintervention Rate
Time frame: Up to 12 months
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 1 May 2026.
- Individual participant dataSharing planned: No
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ATRIAL APPENDAGE CLOSURE for ATRIAL FIBRILLATION, Atrial Fibrillation (AF)
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.
Questions about this trial
What is this clinical trial studying?
A study testing Left Bundle Branch Area Pacing (LBBAP) for CRT and Coronary Sinus (CS) Lead-Based Biventricular CRT in people with Atrial Fibrillation (AF) and Heart Failure, run by Yonsei University.
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 4 inclusion and 7 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: opening soon, as of the sponsor's last update on 1 May 2026. Status can change between updates, so confirm with the study contact before making plans.
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 Tae-Hoon Kim, Professor (+82-2-2228-8467, thkimcardio@yuhs.ac), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change from Baseline Left Ventricular Ejection Fraction (LVEF) at 12 Months (time frame: Baseline (at the time of device implantation) and 12 months post-implantation). 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 1 May 2026.