The purpose of this study is to determine whether combined mortality and hospitalization in heart failure patients receiving optimal pharmacologic therapy can be reduced by combining optimal pharmacologic therapy and 1) biventricular pacing therapy alone or 2) biventricular pacing with defibrillation.

Evaluation of new therapies for the treatment of heart failure should address mortality, morbidity, hospitalization, and cardiac symptoms and function when compared to standard pharmacologic therapy. The COMPANION trial is designed to address all of these objectives. This clinical investigation is an open-label, prospective, multi-center, randomized clinical trial. Every patient enrolled in the study is to be prescribed to optimal pharmacologic heart failure therapy, as tolerated, regardless of randomization.

Inclusion Criteria:

• Moderate or severe heart failure, defined as symptomatic heart failure for at least six months with NYHA Class III or IV symptoms at the time of enrollment, AND at least one of the following events in the previous 12 months:
• Hospitalization for heart failure management
• Outpatient visit in which intravenous (IV) inotropes or vasoactive infusion were administered continuously for at least 4 hours
• Emergency room visit of at least twelve hours duration in which IV heart failure medications were administered (including diuretics)
• QRS > or = 120 ms and PR interval > 150 ms from any two leads of a 12-lead ECG
• Left ventricular ejection fraction < or = 35%
• Left ventricular end diastolic dimension > or = 60 mm (required only if LVEF measured by echo) or > 3.0 cm/m2 [The cm/m2 is calculated by LVEDD (in cm) divided by BSA (body surface area)].
• Age > or = 18 years
• Optimal pharmacologic therapy for heart failure

Exclusion Criteria:

• Unable or unwilling to undergo device implant and follow-up testing
• Meet the general indications for an implantable cardioverter defibrillator
• Meet the general indications for antibradycardia pacing
• Expected to receive a heart transplant in the next six months
• Chronic, medically refractory atrial tachyarrhythmias
• Unexplained syncope
• Myocardial infarction within 60 days of randomization
• History of non-compliance with oral heart failure therapy
• Progressive or unstable angina
• Uncontrolled blood pressure: Systolic BP > 160 mm Hg or < 85 mm Hg or diastolic BP > 90 mm Hg
• Patients with a hypersensitivity to a 0.7 mg nominal dose of dexamethasone acetate
• Surgically uncorrected primary valvular heart disease
• Coronary artery disease (CAD) in which surgical or percutaneous correction is recent (within 60 days of randomization)
• Women who are pregnant or not using medically acceptable birth control
• Hypertrophic obstructive cardiomyopathy
• Amyloid disease
• Hospitalization for heart failure or IV inotropic or vasoactive therapy in excess of 4 hours in the 30 days prior to enrollment
• Have a tricuspid prosthesis
• Involved in any other investigational studies
• Life expectancy < 6 months due to any other medical conditions