The MOMENTUM III Clinical Trial is designed to evaluate the safety and effectiveness of the HeartMate III Left Ventricular Assist System (LVAS) by demonstrating non-inferiority to the HeartMate II Left Ventricular Assist System when used for the treatment of advanced, refractory left ventricular heart failure. The trial is the largest of its kind, with 1028 patients at up to 60 trial sites. The HMIII LVAS incorporates Full MagLev flow technology, which allows the device's rotor to be magnetically levitated, or suspended, by magnetic forces. This contact-free environment is designed for hemocompatibility, with large blood flow pathways designed to reduce blood trauma and minimize complications. The HeartMate III LVAD is surgically connected to the patient's native circulatory system via an inflow cannula placed into the left ventricular apex, and an outflow graft anastomosed to the ascending aorta. The pump operates in parallel with the heart, such that either can supply blood to the aorta. The patient wears an external controller and a battery system that powers the pump. Intended for a broad spectrum of advanced heart failure patients, the HMIII LVAS has a wide range of operation, pumping up to 10 liters of blood per minute--the full output of a healthy heart. Appropriate for an active lifestyle, HeartMate III is designed to restore blood flow while improving survival, functional status, and quality of life. If a patient meets the criteria below, he or she may be a candidate for the trial: ?NYHA Functional Class III with dyspnea upon mild physical activity, or NYHA Functional Class IV ?Adults with body surface area greater than or equal to 1.2 square meters. ?Left ventricular ejection fraction less than or equal to 25% ?Inotrope dependent OR cardiac index <2.2 while not on inotropes For more information on MOMENTUM III Clinical Trial study enrollment, please contact the HeartMate III investigative team.