The purpose of this study is to evaluate an external device (SonR sensor) that is capable of detecting sounds created by the heart (SonR signal). Based on the sounds created by the heart and recorded by the SonR sensor, optimal timing settings for the cardiac resynchronization therapy defibrillator (CRT-D) device may be determined. The investigators will then compare the timing settings suggested by SonR to the settings suggested from the echocardiogram. The objective of this study is to determine if differences exist between these different methods of timing the contractions of the top and bottom chambers of the heart and if the SonR signal is able to produce results similar to those of an echocardiogram.

Inclusion Criteria:

• Implanted with any current Food and Drug Administration (FDA) approved CRT- D device and leads for 30 days or patients indicated for AV optimization
• ≥18 years of age
• Ability and willingness to provide written informed consent and HIPAA authorization

Exclusion Criteria:

• Chronic Atrial Fibrillation
• Heart Failure decompensation event within two weeks of enrollment
• Hypertrophic Obstructive Cardiomyopathy
• Patient currently enrolled in another ongoing clinical trial
• Pregnancy
• Less than 18 years of age
• Inability or unwillingness to provide written informed consent and HIPAA authorization