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This trial will test whether Cardiac Resynchronization Therapy (CRT) devices that use the AdaptivCRT® (aCRT) algorithm have a superior outcome of primary and secondary measures compared to standard CRT devices in CRT-indicated patients with normal atrio-ventricular conduction and left bundle branch block.

Primary Outcome Measures

  • Combined endpoint of all-cause mortality and intervention for heart failure decompensation
  • Intervention for heart failure decompensation is defined as an event requiring invasive intervention or inpatient hospitalization.

Secondary Outcome Measures

  • All-cause mortality
  • Percent of patients with interventions for heart failure decompensation: Intervention for heart failure decompensation is defined as an event requiring invasive intervention or inpatient hospitalization.
  • Clinical Composite Score: The Clinical Composite Score classifies patients according to their clinical status at 6 months post randomization into the following categories: Improved, Unchanged, and Worsened. A patient is classified Worsened in case of death, hospitalization for worsening heart failure, worsened NYHA class (using last observation carried forward), or worsened status on the Global Assessment Score. Also patients that exit the study or cross over because of worsening heart failure are classified Worsened. A patient is classified Improved when not Worsened and there is an improvement in NYHA class or Global Assessment Score. Patients that are not Worsened or Improved are Unchanged.
  • Atrial fibrillation: Incidence of atrial fibrillation lasting >6 hours in one day
  • Change in Quality of Life measured by the Kansas City Cardiomyopathy Questionnaire (KCCQ): The overall summary score of the Kansas City Cardiomyopathy Questionnaire will be analyzed.
  • Change in Quality of Life measured by the EQ-5D. The EQ-5D index score will be analyzed.
  • All-cause re-admissions within 30-days after a heart failure admission
Estimated Enrollment: 3000
Study Start Date: July 2014
Estimated Study Completion Date: March 2020
Estimated Primary Completion Date: December 2019
(Final data collection date for primary outcome measure)


Study Groups

  • Experimental Arm: aCRT ON. The aCRT algorithm has been developed to provide RV-synchronized LV pacing when intrinsic AV conduction is normal or BiV pacing otherwise.
  • Active Comparator Arm: aCRT OFF. Standard CRT algorithm used. CRT device with AdaptivCRT disabled.


Ages Eligible for Study: 18 Years and older
Genders Eligible for Study: Both
Accepts Healthy Volunteers: No


Inclusion Criteria:

  • Subject is willing to sign and date the study Patient Informed Consent Form.
  • Subject is indicated for a CRT device according to local guidelines.
  • Sinus Rhythm at time of enrollment
  • Complete Left Bundle Branch Block (LBBB) as documented on an ECG (within 30 days prior to enrollment). Strauss Criteria used for LBBB.
  • Intrinsic, normal AV conduction as documented on an ECG by a PR interval less than or equal to 200ms (within 30 days prior to enrollment).
  • Left ventricular ejection fraction less than or equal to 35% (documented within 180 days prior to enrollment).
  • NYHA class II, III or IV (documented within 30 days prior to enrollment) despite optimal medical therapy. Optimal medical therapy is defined as maximal tolerated dose of Beta-blockers and a therapeutic dose of ACE-I, ARB or Aldosterone Antagonist.

Exclusion Criteria:

  • Subject is less than 18 years of age (or has not reached minimum age per local law).
  • Subject is not expected to remain available for at least 2 years of follow-up visits.
  • Subject has permanent atrial arrhythmias for which pharmacological therapy and/or cardioversion have been unsuccessful or have not been attempted
  • Subject is, or previously has been, receiving cardiac resynchronization therapy.
  • Subject is currently enrolled or planning to participate in a potentially confounding drug or device trial during the course of this study. Co-enrollment in concurrent trials is only allowed when documented pre-approval is obtained from the Medtronic study manager.
  • Subject has unstable angina, or experienced an acute myocardial infarction (MI) or received coronary artery revascularization (CABG) or coronary angioplasty (PTCA) within 30 days prior to enrollment.
  • Subject has a mechanical tricuspid heart valve or is scheduled to undergo valve repair or valve replacement during the course of the study.
  • Subject is post heart transplant (subjects on the heart transplant list for the first time are not excluded).
  • Subject has a limited life expectancy due to non-cardiac causes that would not allow completion of the study.
  • Subject is pregnant (if required by local law, women of child-bearing potential must undergo a pregnancy test within seven days prior to device implant).
  • Subject meets any exclusion criteria required by local law.

Contact Information
Contact: AdaptResponse Trial Leader:

Sponsors and Collaborators: Medtronic Cardiac Rhythm Disease Management

Study Chair: Bruce Wilkoff, MD, The Cleveland Clinic
Study Director: David Steinhaus, MD, Medtronic Cardiac Rythm Disease Management