A mechanical device inserted surgically into the chest that enhances or takes over the pumping action of the HEART, thus maintaining the necessary level of circulation of blood through the brain and other body structures. An artificial heart was first used in humans in 1985, and existing devices are intended to tide over a patient who is extremely ill until a live heart can be transplanted from a donor. The results from artificial hearts have been disappointing because of complications and also because the patients are already dangerously ill.