SANTA CLARA – Coach Jim Harbaugh had what the 49ers termed a "minor procedure" Thursday after being diagnosed with an irregular heartbeat the night before.

Harbaugh, 48, sought help Wednesday evening at Stanford University Hospital, which is near his home and where 49ers players have physicals and medical procedures.

It's not known what the procedure entailed, but a 49ers spokesman said Harbaugh is expected at the team facility today. Special teams coach and assistant head coach Brad Seely, who is on the field next to Harbaugh on game days and whom Harbaugh often uses as a sounding board, conducted Thursday's practice.

Linebacker Patrick Willis said Harbaugh sat behind him during a defensive meeting Wednesday and that he didn't detect anything amiss. Willis said players were informed of Harbaugh's condition at their morning walk-through. A team spokesman notified the media shortly thereafter.

"Coach Harbaugh, like he always tells us, he's tougher than a two-dollar steak," Willis said. "We know he's going to be all right. We've got a bunch of great coaches here that are going to keep everything on track, and we're going to practice today as if he was here."

Dr. William Bommer, a UC Davis professor and the President of the California chapter of the American College of Cardiology, said it sounded as if Harbaugh might have had atrial fibrillation, the most common cardiac arrhythmia and one that wouldn't have been picked up during the annual physical examinations Harbaugh has had since joining the 49ers.

One of the contributing factors for atrial fibrillation is stress, Bommer said.

"I can imagine if you're under pressure to win all the time, that could be a little stressful," Bommer said.

A common procedure to treat atrial fibrillation, Bommer said, is elective cardioversion, during which the patient is sedated and an electric impulse is used to put the heart back into a regular rhythm.

"It works in well over 90 percent of the cases," Bommer said. "Literally within four hours, the patient can go home."

Bommer said that, in general, doctors tell patients who have had cardioversion to get plenty of sleep, to cut down on caffeine and alcohol and to work on reducing stress in their lives. How Harbaugh, who is among the most animated coaches on game days, handles that last recommendation should be interesting.

Harbaugh's players said Thursday they were initially concerned and mystified by their coach's absence but relieved when told by Seely that Harbaugh would be back on the job today.

"He's a real tough guy and a competitor," safety Dashon Goldson said. "We have no doubt that he'll be back. Our prayers are with him and his family.

"We'll be glad to see him here tomorrow coming in the building."

© Copyright The Sacramento Bee. All rights reserved.

• Read more articles by Matthew Barrows

Order Reprint