Adaptive Cardiac Resynchronization Therapy Optimization at Rest and During Exercise (AdOPT CRT)

Inclusion Criteria:

• Subject is age 18 or greater
• Subject is willing to sign and date the study Informed Consent form
• Subject has been implanted with a clinically indicated CRT-D device (Medtronic Vision 3D or Protecta models) for at least 1 month but less than 7 months from the date of study enrollment

Exclusion Criteria:

• Subject has a history of persistent or permanent AF for which pharmacological therapy and/or cardioversion have been unsuccessful or have not been attempted.
• Subject has atrial or ventricular tachyarrhythmias or frequent atrial or ventricular ectopy at the time of enrollment.
• Subject's resting heart rate at the time of enrollment exceeds 90 bpm.
• Subject had CRT system implanted for more than 7 months from the date of the study enrollment
• Subject has complete AV block.
• Subject had previous mechanical valve surgeries.
• Subject has congenital heart disease.
• Subject has contraindication for an exercise test.
• Subject is unable to perform a sub-maximal exercise test.
• It is not possible to acquire technically acceptable echocardiographic images.
• Subject has medical conditions that would limit study participation.
• Subject is pregnant (all women of child-bearing potential must undergo a pregnancy test within seven days prior to the study visit).
• Subject is enrolled in the Adaptive CRT study
• Subject is enrolled in concurrent studies which could confound the results of this study.
• Subject meets exclusion criteria required by local law