The initial diagnosis is that Harbaugh will be back with the team shortly.
"Coach Harbaugh is not at the facility today under doctor's orders," the 49ers' statement read. "He is having a minor procedure done at Stanford Hospital today for an irregular heartbeat. We anticipate that he will be back at the facility tomorrow, but do not have any further information to share at this time.
"Assistant head coach and special teams coordinator Brad Seely will be overseeing today's practice and meetings. When more information regarding Coach Harbaugh is available, we will pass that along."
Team spokesman Bob Lange said no incident had occurred at the facility. Instead, Harbaugh visited with doctors Wednesday night after feeling ill, and they advised him to have the procedure done at Stanford Hospital.
"It's one of those things that, like Coach Harbaugh always tells us, he's tougher than a $2 steak," Willis said, via The Associated Press. "We know he's going to be all right. We know we have a bunch of great coaches here that keep everything on track, and we're going to practice today as if he was here."
The 49ers face the Chicago Bears on Monday night, so in theory, that gives Harbaugh an extra day to get fully healthy if he chooses to be on the sideline for the game. We wish him all the best in his recovery.
Follow Gregg Rosenthal on Twitter @greggrosenthal.