A teen survived cardiac arrest. Then his mom. Then his sister.

Joe Krejci of Dallas was almost to the finish line of a 100-yard dash during his middle-school gym class when he collapsed onto the track.

His gym teacher thought Joe had tripped. Then he saw the 13-year-old on his back with his eyes open. The teacher called out to the two fastest runners in class: "Go get the nurse and AED!" He called 911 as the students headed toward the school building.

Minutes later, the boys raced back with the school nurse; she brought an automated external defibrillator, a device that analyzes heart rhythm and delivers an electric shock to stabilize a person's heart rate.

Paramedics arrived shortly after the AED advised a shock and while CPR was still underway.

In the emergency room, doctors put Joe in an induced coma to help him recover. He remained unconscious with a breathing tube for 48 hours. As his family waited, they feared he could have lasting cognitive challenges from having gone without oxygen to his brain.

When Joe woke up, his speech was gibberish and he couldn't remember what happened. His mother, Virginia, wet his lips with a sponge. "Stop it," Joe said, moving and trying to brush her off. Virginia knew her Joe was back.

Joe had experienced a sudden cardiac arrest. It's an electrical problem that happens when the heart malfunctions and abruptly stops beating. Doctors didn't know why Joe's heart glitched. So they took steps to make sure it didn't happen again.

Three days later, Joe received an implantable cardioverter defibrillator, or ICD. It's a battery-powered device that monitors heart rate and, if it detects a problem, delivers a shock to restore a normal heartbeat. Joe was back at school the following week.

The week after that, Joe was on the track again during gym class when he collapsed a second time. His ICD kicked in and shocked him. It was clear then: Joe couldn't do track anymore.

Doctors explained the problem with Joe's heart rhythm was likely linked to adrenaline, a hormone that tends to increase in response to exciting or stressful events. When Joe's adrenaline rose, it interrupted his normal heart rhythm.

Over the next three years, Joe collapsed twice more – both while running around playing games with friends. "He had to learn what his capabilities were," Virginia said.

Luckily, Joe preferred fishing and hunting. Now, eight years later, he's a healthy 21-year-old sophomore at Texas A&M studying wildlife fisheries while competing on the school's bass fishing team.

Four years after Joe fell, Virginia and her husband, Mike, were enjoying a date night. As they left the restaurant, Mike walked to a nearby convenience store. Virginia went to get the car. Before she got there, she collapsed in the middle of the road.

Bystanders called 911. When Mike wandered back toward the car, he saw a commotion. Once he saw that it centered on Virginia, he rushed over and started CPR. It was a skill he and the rest of the family learned in the hospital after Joe's heart problems.

Virginia, too, had experienced a sudden cardiac arrest. In the hospital, neither an MRI nor blood work offered any clues as to why. She was petrified it could happen again, leaving her kids without a mom.

Three days later, she got an ICD.

Like Joe, she was also healthy and active. Only a few years before, at age 43, she completed an Ironman race. She also played in soccer and softball leagues in her 30s. Her childhood was athletic too, filled with volleyball and other sports.

Now that this happened to two members of the immediate family, they all went for genetic testing: Virginia, Mike, Joe and his older sister, Sara. The results were unsatisfying. Without finding an underlying cause, Sara couldn't help but wonder whether she, too, would collapse. And if she did, would anyone be there at the time to help?

Last October – three years after Virginia's episode – Sara was studying interior design at Stephen F. Austin University in Nacogdoches, Texas. She was enjoying karaoke night at a sports bar, about to belt out "Come As You Are" by Nirvana, when she passed out on stage.

Someone called 911. A bystander started CPR. When paramedics arrived minutes later, they shocked Sara with an AED and got a sustained heartbeat.

At the hospital, doctors determined Sara had experienced cardiac arrest. They induced a coma and used a cooling method to lower her body temperature. It's a treatment called therapeutic hypothermia that's sometimes used right after cardiac arrest to help reduce damage to the brain.

Sara woke up two days later with no memory of what happened to her. A week later, she got her own ICD. Back at school, Sara wore her backpack on one shoulder to keep it from rubbing her surgical scar. It was a constant reminder of what happened and her new limitations. She, too, couldn't let her adrenaline get too high.

But the scar healed. Sara, 22, is enjoying one of her favorite activities again, roller skating. "If I'm careful with it, I'm OK," she said. "You have to figure out the activities you can still do, just at a lower impact."

In recent months, the Krejci family had additional genetic testing done. This time, the results showed that Virginia has a genetic mutation that causes catecholaminergic polymorphic ventricular tachycardia, or CPVT It's an inherited cardiac condition that causes sudden heart rhythm disturbances called arrhythmias, which most commonly show up during childhood.

It's not clear why Virginia was fine as a child. Joe's testing showed the same results. The family's waiting for Sara's results. Virginia's brother and his daughter also are getting tested.

It's not lost on the Krejcis that only around 9% of people who experience a sudden cardiac arrest survive. "The fact that three of us in the same family did, I don't think there even are statistics on that," Virginia said. "It's a true miracle, and we know that and value that."

Virginia, who has a home remodeling business, pays forward her appreciation by volunteering with local non-profit Living for Zachary, started by a mother who lost her teenage son to sudden cardiac arrest during football practice.

Virginia's work, her volunteering, and her daily walks to stay active keep her positive and from dwelling on the "what-ifs," she said. "I call that `the dark side,'" she said. "We made a decision just to never live in a state of worry."

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