The purpose of the study is to demonstrate the safety and functionality of the CircuLite Synergy Pocket Circulatory Assist Device.

The CircuLite Synergy Pocket Circulatory Assist Device is an implantable miniature, mixed-flow blood pump designed o provide partial left ventricular support in patients with advanced heart failure. Treatment for this patient population currently include lifestyle changes, medicines, transcatheter interventions and surgery, including implantation of mechanical ventricular assist devices (VADs); most of the currently available VADs require highly invasive, high-risk surgical procedures to implant due to large device size, and are therefore generally limited to use in patients with terminal heart failure. The Synergy pump is intended for treatment of patients with New York Heart Association (NYHA) Class III and IV heart failure; it is expected that the pump will provide these patients with 2-3 L/min of additional blood flow, giving adequate cardiac support to increase exercise tolerance and improve patients' quality of life. The pump's small size will allow it to be implanted in a less surgically invasive procedure than used with previous VADs, which should result in a reduction of perioperative morbidity. The device wil be implanted in a left atrial to subclavian artery bypass with the pump being located in the infraclavicular fossa like a pacemaker.

Inclusion Criteria:

• Maximum tolerable medical therapy including ACE inhibitors and Beta Blockers
• NYHA Class III or IV despite maximal tolerable medical therapy
• Ambulatory (inpatient or outpatient)
• Patients on the heart transplant list (or, not currently listed but otherwise suitable for heart transplant)
• Life expectancy of at least 6 months without full VAD support

Exclusion Criteria:

• Age >75 years
• Exercise tolerance limited by factors other than heart failure
• Presence of intra-atrial thrombus
• Clinically significant right heart failure
• Serum creatinine >/= 2.5 mg/dl or any dialysis in previous 3 months
• Evidence of intrinsic hepatic disease
• Previous episode of resuscitated sudden death without subsequent treatment with AICD
• Subclavian artery stenosis
• Low platelet count, INR that cannot be corrected prior to implant or contraindication to anticoagulation