"They had to do a little procedure, cardiovert," Harbaugh told the Chicago media as his team prepares for Monday night's game against the Bears. "Get it back normal. It's amazing they can do a procedure like that."
Cardioversion involves an electric shock that gets the heart back into a normal rhythm. Harbaugh was in and out of the hospital in a day for the procedure. He even stopped at the 49ers' facility Thursday before being escorted out and told to rest, according to receiver Kyle Williams.
It wasn't the first heart procedure for Harbaugh, who said he'll be on the sideline Monday night.
"About 13 years ago, I had a cardio ablation for the same thing," he said. "An atrial flutter is what I have."
The coach had visited with doctors Wednesday night after feeling ill, and they advised him to have the procedure done at Stanford Hospital. Players were informed of Harbaugh's hospitalization by assistant head coach and special teams coordinator Brad Seely during Thursday morning's walk-through. Seely also oversaw team meetings and the afternoon practice.
Players haven't noticed a difference in Harbaugh.
"He's fine, and if he's not, he's not showing it at all," Williams said Friday on "The Carmen, Jurko & Harry Show" on ESPN 1000. "He's in here; he's here early. He's studying tape. He feels good.
"He did show up yesterday for a brief moment, I think they had to run him out of here and make him get some rest. But he wanted to be here. There's no way they were going to keep him away from this facility for two days straight. He's in here ready to work and ready to get out there Monday night."
Harbaugh said he is "full-go" and is excited about facing the Bears, whom he quarterbacked for seven of his 14 years in the NFL.
"If you're a football player, it's a game you live for. If you're not, it's another day at the office," he said. "I hope it's everything they live for."