Chargers coach Jim Harbaugh has had heart problems before, but what are the next steps?

Chargers coach Jim Harbaugh (center) returned to the bench after being treated in the Denver locker room for heart problems. (Dawid Zalubowski / Associated Press)

The setting was different, but for Jim Harbaugh the feeling was incredibly familiar.

It started the night before the Chargers' Sunday game against the Denver Broncos, when an irregular heartbeat – a problem he struggled with in 1999 and 2012 – left him uncomfortable. He informed at least some of his players about it, saying he was just excited to play.

But the arrhythmia – diagnosed as atrial flutter – returned in a more dramatic fashion during pregame warm-ups, prompting him to briefly dip into a blue medical tent on the sidelines and then head to the locker room with the team's medical staff.

There's so much going on on the NFL sideline that many players had no idea that defensive coordinator Jesse Minter had taken over as head coach in Harbaugh's absence.

Meanwhile, in the visiting locker room, paramedics measured the electrical activity of Harbaugh's heart by performing an electrocardiogram. Marco Zucconi, the Chargers' director of health, wellness and player performance, administered an IV drip and magnesium to the coach to treat his condition.

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“It's heart,” Harbaugh said after the 23-16 victory, “so take it seriously.”

Within minutes, his heart returned to a normal rhythm and he was back in the game, coming down the sideline and receiving a red flag challenge from Minter, who was Harbaugh's defensive coordinator at the University of Michigan.

After two previous episodes of atrial flutter, Harbaugh underwent ablation, a minimally invasive procedure designed to treat irregular heartbeats by destroying heart tissue that causes abnormal electrical signals.

Thirteen years passed between the first and second ablation, and the second one took place 12 years ago.

“I thought I was getting close to the 13-year mark and would need another one,” he said.

Chargers coach Jim Harbaugh (left) receives congratulations from Broncos coach Sean Payton after Los Angeles' road victory.Chargers coach Jim Harbaugh (left) receives congratulations from Broncos coach Sean Payton after Los Angeles' road victory.

Chargers coach Jim Harbaugh (left) receives congratulations from Broncos coach Sean Payton after Los Angeles' road victory. (Dustin Bradford / Getty Images)

Harbaugh looked tired after the win, but was otherwise normal. He is fit and trains with his players, looking younger than his 60 years, but he leaned forward and placed his hands on his knees before walking to the team bus, ostensibly to catch his breath.

He said he didn't know if the altitude in the Mile High City aggravated his symptoms.

CBS showed video of Harbaugh leaving and returning to the field, but the reason was not publicly known until the coach revealed it at his postgame news conference. His family did know, however, because his older brother John, coach of the Baltimore Ravens, interrupted the press conference after four questions to get information about his brother.

Chargers general manager Joe Hortiz, a Ravens native, called Eric DeCosta, his Baltimore counterpart, and informed him of the situation. Chad Steele, who handles media relations for the Ravens, then cut John Harbaugh off from the podium.

John in turn called his parents, Jack and Jackie Harbaugh, in Ann Arbor, Michigan. During this time, he received news that his younger brother had been cleared to return to the field.

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“From a troubling standpoint, whenever people have this type of rhythm, their heart rate increases dramatically,” said Dr. Nikhil Warrier, medical director of electrophysiology at MemorialCare Heart & Vascular Institute at Orange Coast Medical Center in Fountain Valley.

“They can be sitting and doing nothing and all of a sudden their heart rate goes up to 130, 140, 150 beats per minute, which is unusual for anyone.”

Warrier said there are a number of factors that can lead to the disease, including excessive stress and caffeine consumption, as well as structural heart problems.

“We often see that patients have no other risk factors other than the fact that they came in and have an arrhythmia,” he said. “In this case, ablation is curable. So this is the most common strategy we use.”

Harbaugh was playing quarterback for the Chargers when he first experienced atrial flutter. The second episode occurred while he was coaching the San Francisco 49ers during their Monday night game against the Chicago Bears.

The first time, he missed a day or two of training. The second time, in addition to ablation, he underwent electrical cardioversion, during which paddles that deliver electric current are used to restore the heart's normal rhythm.

After Sunday's game, he said he planned to see a cardiologist on Monday.

“Trust the doctors,” he said. “If you don't trust your doctors, who will you trust?”

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This story originally appeared in the Los Angeles Times.