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Enrolling by Invitation

NCT Number: NCT07664189

LBBP + CSP Versus LBBP Alone for Cardiac Resynchronization Therapy

The purpose of this pilot clinical trial is to evaluate whether a novel cardiac resynchronization strategy, called LOT-CRT, is more effective than standard physiological pacing alone (LBBAP) in patients with heart failure.

This is a randomized, single-center, crossover pilot study involving 10 patients. All participants will receive a specialized pacemaker (CRT-P) with leads implanted in two specific areas: the Left Bundle Branch Area (LBBAP) and the Coronary Sinus (CS).

Because of the crossover design, each patient will serve as their own control, receiving two different pacing configurations in a random order: Active Phase (LOT-CRT): Simultaneous pacing of the left bundle branch and the coronary sinus. Control Phase (LBBAP alone): Pacing only the left bundle branch area. Each treatment phase will last 6 months, for a total follow-up of 12 months per patient.

By testing both strategies in the same patient, this study will help clinicians identify the most effective way to restore heart synchrony and improve clinical outcomes in patients with advanced heart failure and conduction delays.

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Key information

Conditions

Heart Failure Low Output Cardiovascular Diseases Heart Diseases Heart Failure

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Clinica CardioVID

Medellín, Antioquia, 050036, Colombia

About this study

This is a single-center, randomized, crossover pilot clinical trial. Each patient will serve as their own control. Following the successful implantation of a device capable of stimulating the LBBAP and the coronary sinus, participants will be randomly assigned to one of two treatment sequences:

Sequence A: LOT-CRT (LBBAP + CS) for 6 months, followed by LBBAP alone Sequence B: LBBAP alone for 6 months, followed by LOT-CRT Each treatment phase will last 6 months, followed by an end-point evaluation and a crossover. Since the hemodynamic effect of electrical stimulation is immediate, no washout period is required between phases.

This study was designed as an exploratory pilot study; therefore, no formal sample size calculation was performed. The number of patients enrolled is considered adequate to assess the feasibility of the procedure, the safety of the crossover design, and to identify preliminary signals of clinical and electrical efficacy.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age ≥18 years
  • Standard CRT-P indications according to ESC 2021 (EF ≤50%, QRS ≥130 ms, sinus rhythm or controlled AF)
  • NYHA class II-IV
  • Coronary venous anatomy suitable for placement of a coronary sinus electrode.
  • Signed informed consent.
  • Successful implantation of electrodes in the coronary sinus and in the left bundle branch area (LBBAP)

Exclusion criteria

  • Concomitant indication for implantation of an implantable cardioverter-defibrillator (ICD) or CRT-D
  • Significant uncorrected valvular disease or scheduled or anticipated cardiac surgery during the study period.
  • Anatomical or technical contraindication for lead implantation in the coronary sinus or for lead implantation in the coronary sinus (such as sinus stenosis, coronary sinus branches unsuitable for cannulation, inability to advance and/or stabilize the lead, among others)
  • Persistent atrial fibrillation with uncontrolled rate
  • Comorbidities that may limit life expectancy to <1 year
  • Participation in another clinical trial that could confound the evaluation of results within the last 6 months.
  • Pregnancy or inadequate contraception
  • In the researcher's opinion, the participant would not comply with the activities and visits outlined in the study protocol

Treatment and study plan

Left Bundle Branch Optimized CRT

Device

The CS lead will be implanted in a posterolateral or lateral vein using venography and standard IV delivery sheaths. Proper lead placement is confirmed by stable fixation, pacing capture, and absence of diaphragmatic pacing.

The configuration for each phase of the study (LOT-CRT or LBBAP alone) will be assigned during randomization.

Other names: LOT-CRT, Left bundle branch block pacing + coronary sinus pacing, LBBAP + CS, LOT-CRT Strategy, Combined stimulation, Maximized electrical resynchronization

Stimulation of the left bundle branch area (LBBAP)

Device

The LBBAP lead will be implanted via a transvenous approach using the C315His sheath, targeting the left bundle branch area in the right ventricular septum, ideally between the basal septum and the mid-septal region.

Criteria for confirming successful LBBAP capture will include:

  • Evidence of narrowing of the stimulated QRS complex compared to baseline.
  • Right bundle branch block morphology on the ECG-stimulus-to-R-wave time in V6 <80 ms (if available).
  • Low and stable pacing threshold (<1.5 V @ 0.4 ms).
  • Unipolar impedance between 400-1500 ohms. The CS lead will be implanted in a posterolateral or lateral vein using venography and standard IV delivery sheaths. Proper lead placement is confirmed by stable fixation, pacing capture, and absence of diaphragmatic pacing.

Other names: Stimulation of the left branch only

Primary outcomes

  1. Compare the effects of the LOT-CRT strategy versus left bundle branch block pacing (LBBAP) alone in each patient, comparing baseline to the end of the study FEVI, quality of life and functional class by NYHA.

    Time frame: 12 months

    Investigators will evaluate the following parameters in each patient: Left ventricular ejection fraction (LVEF) by echocardiography and electrocardiogram; functional capacity (NYHA class) using the 6-minute walk test and symptoms reported by the patient; quality of life (MLHFQ) using the MLHFQ quality of life scale

Secondary outcomes

  1. Change in end-systolic diameter

    Time frame: 12 months

    Absolute (mm) and relative (%) change in LVESV between baseline and 6 months.

  2. QRS Duration

    Time frame: 12 months

    Absolute (ms) and relative (%) changes in the 12-lead ECG.

  3. Change in end-diastolic diameter

    Time frame: 12 months

    Absolute (mm) and relative (%) change in LVEDV between baseline and 6 months.

  4. NT-proBNP

    Time frame: 12 months

    Absolute (ng/mL) and relative (%) change in NT-proBNP from baseline to 6 months

  5. Echocardiographic responder

    Time frame: 12 months

    LVEF ≥10% elevation or LVESV ≥15% decreased

  6. Echocardiographic super-responder

    Time frame: 12 months

    LVEF ≥50% or LVESV ≥30% decrease

  7. Composite Clinical Outcome

    Time frame: 12 months

    Cardiovascular Death or Hospitalization for Heart Failure

  8. Procedural parameters

    Time frame: 12 months

    Thresholds, P- and R-waves, impedance of each electrode.

  9. Procedure Time/Fluoroscopy

    Time frame: 12 months

    Total procedure time in minutes/ total fluoroscopy time in minutes.

Sponsors and collaborators

Lead sponsor

Clinica Cardio VID

Other

Registry information

Official study title

Left Bundle Branch Pacing + Coronary Sinus Pacing Versus Left Bundle Branch Pacing Alone for Cardiac Resynchronization Therapy in Patients Eligible for CRT-P A Randomized Crossover Pilot Clinical Trial

Acronym: LOTTO-CRT

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
Jun 24, 2026
Registry last updated
Jul 23, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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