Babec, the older of the Birmingham Zoo gorillas, had a second heart pacemaker inserted Saturday to replace another apparently damaged in a fight.
The 400-pound silverback gorilla made history last September with his first pacemaker.
Assistant zoo director Jeff Cook said he had been doing well, but got into a tussle a week ago.
It appeared initially that his fight with fellow gorilla Jamie had resulted in only a few cuts. But coughing, a loss of appetite and lethargic behavior later suggested that the pacemaker may have been damaged.
Babec was the first gorilla to ever have a cardiac resynchronization therapy device implanted. That device was replaced in a procedure that took a little over five hours at the zoo's Animal Health Center.
Doctors and zoo director Bill Foster said Saturday's surgery went well. Babec's recovery will be at the primate house rather than the health center.