Former San Francisco 49ers lineman Robert Karren was recovering Saturday from heart transplant surgery performed earlier in the week at University Hospital in Salt Lake City, his doctors said.

Karren, 47, Las Vegas, Nev., who received the new heart June 15, was listed in critical but stable condition, a routine post-operative condition for heart transplant recipients, a hospital spokeswoman said Saturday. "He's doing very, very well."

Cardiologists determined in 1984 that Karren, who played on the 49ers specialty teams and offensive squad in 1961-62, had two previous "silent" heart attacks that permanently damaged his heart muscle.

"Bob was given six month to live," 41/2 years ago, said Karren's wife, Helen. "But his will to live was tremendous, and he never gave up."

The couple moved to Salt Lake City in April with hopes the UTAH Cardiac Transplant Program would have a better chance than physicians at Stanford University Medical Center in locating a heart large enough for his 6-foot-3, 210-pound frame, she said.