CONTAK RENEWAL 3 AVT

Inclusion Criteria: Patients who meet the following criteria should be given consideration for inclusion in the clinical investigation: Meet all device indications and contraindications Willing and capable of providing informed consent, undergoing a device implant, participating in all testing associated with this clinical investigation at an approved clinical investigational center and at the intervals defined by this protocol Prescribed to stable optimal pharmacologic therapy for heart failure Creatinine < 2.5 mg/dL obtained no more than two weeks prior to enrollment Age 18 or above, or of legal age to give informed consent specific to state and national law Geographically stable residents who are available for follow-up Able to provide documented evidence of one or more episodes of AF/AT within 12 months of implantation NOTE: Guidant recommends anticoagulation therapy per physician discretion. Exclusion Criteria: Patients who will be excluded from the investigation are those who meet any one of the following criteria: Have a preexisting non-Guidant left ventricular lead Have a preexisting unipolar pacemaker that will not be explanted/abandoned Documented life expectancy of less than six months or expected to undergo heart transplant within the next six months Have an atrial tachyarrhythmia that is permanent (i.e., does not terminate spontaneously and cannot be terminated with medical intervention) within 180 days prior to enrollment Have a known hypersensitivity to a 0.7 mg dose of dexamethasone acetate Have surgically uncorrected primary valvular heart disease Currently requiring hemo-dialysis Have had a myocardial infarct, unstable angina, percutaneous coronary intervention, or coronary artery bypass graft during the preceding 30 days prior to enrollment Have hypertrophic obstructive cardiomyopathy or infiltrative cardiomyopathy (e.g., amyloidosis, sarcoidosis) Have a mechanical tricuspid heart valve Enrolled in any concurrent study, without Guidant written approval, that may confound the results of this study A Cerebral Vascular Event/ Transient Ischemic Attack within 12 months of implantation During the four weeks prior to implantation, a patient experiences an episode of AF ³ 48 hours in duration and was not anticoagulated at an adequate therapeutic level for the 4 weeks prior to enrollment with an INR = 2.0-3.0 at enrollment Women who are pregnant or plan to become pregnant Note: Women of childbearing potential must have a negative pregnancy test within 7 days of enrollment