There are five million cases of heart failure in the United States each year. When a heart fails, its ventricles - or pumping chambers - become too weak to pump blood. In such cases, doctors will often implant a Ventricular Assist Device (VAD) to aid the heart. When both of the heart's ventricles fail, however, a VAD may not be effective. Instead, doctors turn to the CardioWest Temporary Total Artificial Heart, or TAH-t, which is used to sustain a patient until a transplant heart is available. Patients who undergo this "bridge to transplant" increase their odds of living another year by almost 40 percent. On March 26, 2006, Danuel Allen, 57, underwent this procedure at the University Medical Center in Tucson, Arizona. Two months later, on May 14, he received a new heart.