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Teacher Zach Nelson spent most of his Sunday preparing for the week ahead, working deep into the evening. He put his 5-year-old son to bed, then returned to his laptop to continue with his lesson plans.

Zach felt tired, even dozing off a few times. But it was late, so each time he awoke, it made sense.

Then he awoke in the intensive care unit. Four days later. That made no sense.

On Jan. 22, 2017, Zach's wife, Leah, had gone to bed but was restless waiting for him to join her. Then she heard what sounded like a choking sound. Thinking it was the couple's dog Ike, Leah called for Zach to check on him.

When Zach didn't answer, Leah – who was nearly 6 months pregnant – went out to investigate. She found her husband in his recliner, gasping and shaking. Thinking it may be a seizure, Leah, a nurse, ran for her phone, called 911 and dashed back to Zach, whose face had turned blue.

Realizing he wasn't breathing and that his heart had stopped, she dragged him to the floor and began CPR. She kept 911 dispatchers on the line and shouted for their son to unlock the front door.

Help arrived within minutes, only it wasn't paramedics. It was two neighbors – a nurse and a volunteer firefighter who heard the dispatch call. They relieved Leah until the ambulance arrived.

The EMS crew used a defibrillator to shock Zach's heart into a normal rhythm before transporting him to their local hospital in Hays, Kansas. He was then flown to the University of Kansas Hospital in Kansas City, nearly four hours away.

For the next few days, Zach underwent more tests, but doctors were unable to determine what went wrong with the electrical system of the 31-year-old's heart. Genetic testing also failed to reveal any answers.

Zach received an implantable cardioverter defibrillator, a device that would shock his heart back into rhythm if needed. He's been fine ever since.

Now an elementary school gym teacher in Horton, Kansas, Zach talks to students about heart health. Last school year, he led the school in the ÃÛÑ¿´«Ã½'s Kids Heart Challenge. A couple times a year, he explains his ICD and creates a plan with his students so they know how to get help if he – or anyone else – ever needs it.

After a about him aired on television, several parents told Zach that their kids told them they knew what to do if his ICD went off.

"I was blown away that they remembered," he said.

About 70% of cardiac arrests that occur outside a hospital happen in a home or residential setting. Initiating CPR right away as a bystander, rather than waiting for medical personnel to arrive, can double the chance of survival from cardiac arrest.

Zach and Leah already were trained in CPR for their jobs. But Zach's experience underscores the importance of everyone knowing the lifesaving skill, Leah said.

"No matter what your age, you can't think that it's not going to happen to you," she said. "Everyone should learn CPR, no matter what your job, because if anything happens to one of your loved ones, you might be the first one there, and doing CPR could make the difference in whether they survive."

Stories From the Heart chronicles the inspiring journeys of heart disease and stroke survivors, caregivers and advocates.

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