DENVER — Jim Harbaugh listened to his heart when he began to feel a little bit off in pregame warmups.

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The Los Angeles Chargers coach went into the medical tent and then to the locker room in the first quarter Sunday to get checked out for an irregular heartbeat. An EKG showed his heart was back in normal rhythm and he returned to the sideline with his team already up 3-0.

His team didn’t miss a beat in a 23-16 win over the Denver Broncos. In fact, his quarterback, Justin Herbert, didn’t even know he wasn’t on the sideline. His brother sure did, as Baltimore coach John Harbaugh cut short his postgame news conference after a win over Washington to check in on his brother.

“Everything ended up turning out to be OK,” said Jim Harbaugh, who received IV fluids. “The doctors checked me out, and it got back into normal rhythm. So came back.

“It’s the heart so you take it seriously.”

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Harbaugh’s History with Atrial Flutter

For quite a while, Harbaugh said he’s dealt with atrial flutter, a condition that can cause the heart to beat too quickly. He had an ablation procedure in 1999 to treat the irregular heart rhythms. He also had another one in 2012 when he was coaching the San Francisco 49ers. He vividly remembers that procedure because it was after a Monday night game where Colin Kaepernick led the 49ers to a 32-7 win over the Chicago Bears.

Harbaugh said he hadn’t really experienced another episode until this weekend.

“I started feeling it last night, but wasn’t really sure,” Harbaugh said. “Just like in 2012, it was during the pregame warmups — I kind of started feeling.”

Harbaugh tried to interject some humor — “2-0 in arrhythmias,” he cracked.

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Herbert Unaware of Coach’s Absence

Herbert was caught off guard by the news that his coach had left the sideline — or that anything was amiss. Although, he said Harbaugh mentioned something about his health Saturday night.

“He said he was really excited for the game. He said his blood was flowing and he was excited,” said Herbert, who completed 21 of 34 passes for 237 yards and one touchdown. “I thought everything was good to go. That’s definitely something he should get checked out. He’s a tough guy, though.”

Harbaugh said that when he was in the locker room, the medical staff took his pulse and conducted an EKG.

“Trust the doctors. If you’re not going to trust your doctors, who are you gonna trust?” he said. “Came back in to the locker room, and the paramedics came, got an EKG and said it was back to the sinus (normal) rhythm, and I said, ‘I feel good.’ I went back out there on the field.”

Harbaugh plans to follow up with his cardiologist on Monday.

When he left the sideline as the game started, the Chargers described his absence as an illness. Defensive coordinator Jesse Minter took over until Harbaugh returned midway through the first quarter with the Chargers ahead 3-0 and driving toward another score. The Chargers jumped out to a 23-0 lead in the second half before the Broncos made a late surge.

“It was a great and glorious win for the team,” Harbaugh said. “Really proud of our team, pleased. They’re playing good football, offense, defense and special teams, four quarters of it.

“I felt great about that.”