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 ofstudy enrollment

Exclusion Criteria:

• Subject has a history of persistent or permanent AF for which pharmacological therapyand/or cardioversion have been unsuccessful or have not been attempted.

• Subject has atrial or ventricular tachyarrhythmias or frequent atrial or ventricularectopy 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 studyenrollment

• 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 pregnancytest 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 thisstudy.

• Subject meets exclusion criteria required by local law