Dr. Francis Pagani, a University of Michigan cardiovascular surgeon, and Dr. Leslie Miller, director of cardiology at Washington Hospital Center, led a clinical trial of the HeartMate II left ventricular assist device, which was developed by Thoratec.

The pump is implanted into the patient's body and pumps blood from the weakened left ventricle to the rest of the body at the same rate as a healthy heart. In addition to helping 75 percent of patients stay alive for at least six months, or until a donor heart becomes available, the device assists patients' original hearts regain function, thereby allowing other organs to heal by restoring blood flow.

The experimental device is about the size of a D-cell battery, giving it the potential to help more women, teenagers and smaller men with end-stage heart failure whose bodies aren't big enough for other devices, the researchers said.

The study is detailed in a New England Journal of Medicine article written by Pagani and Miller.