Heart patients who have reached end-stage heart failure may have a pump surgically inserted to help blood flow to the rest of the body. This mechanical implant is called a ventricular assist device (VAD), and it can prolong and improve patients' lives. Though physicians have been performing this surgery for years, the patient outcomes are not as predictable as might be expected. While some patients do very well post-surgery, others do not live long after receiving a VAD. In additional cases, patients who seem to be viable candidates for the surgery never receive the device.