Doctors at St. Joseph's Hospital transplanted an artificial heart into a dying man, hoping to keep the patient alive with the mechanical device until a human donor heart can be found.

The surgery took six hours and the recipient, John Eldridge, 50, of Knoxville, Tenn., was moved into the hospital's intensive care unit in critical condition Saturday, said a hospital spokeswoman.

The patient was transported to St. Joseph's via helicopter Wednesday and his condition quickly worsened, prompting doctors to decide to use the metal and plastic Jarvik 7.