 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 Lmin of additional blood flow, giving adequate cardiac support to increase exercise tolerance and improve patients quality of life. The pumps 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. 