no subjects enrolled

Single center investigator initiated sponsored by Guidant Boston Scientific Corp. to evaluate the benefit of ventricular rate regularization (VRR) in patients with congestive heart failure (CHF) and significant atrial fibrillation (AF) burden.

Inclusion Criteria:

• Be between 18-85 years old
• Be willing and able to give informed consent
• Patient currently has a CRT-D or ICD with > 20% atrial fibrillation burden as recorded by defibrillator follow up report or a history of atrial fibrillation prior to implant.
• Patient has the ability to complete a Six minute walk test with the only limiting factors to be fatigue or shortness of breath.

Exclusion Criteria:

• Expected mortality less than 6 months due to non-cardiac causes.
• Pregnant women.
• Creatinine greater than or equal to 2.5 mg/dl.
• Anemia (HCT less than 30)
• COPD causing significant dyspnea
• Orthopedic problems affecting 6 minute walk.

Patients implanted with a new Guidant ICD/ CRT-D: Indication for CRT-D and ICD with history of atrial fibrillation. Patients with new implants will not be enrolled until their three month follow up visit in the pacemaker clinic.

Patients currenlty implanted with a Guidant ICD/ CRT-D: More than 20% atrial fibrillation burden as recorded by defibrillator follow up report or with history of atrial fibrillation.