When she passed out at 38, doctors blamed stress. The problem was her heart.

By the time Sheena Fannin and her two sons, ages 6 and 9, arrived home from soccer practice it was already getting late. She rushed to get them to bed. Her husband, Michael, was traveling, so she tucked them in alone.

Sheena went downstairs to check her calendar for the following day. Suddenly she felt lightheaded. Her heart started beating rapidly.

These were not new sensations. Sheena had been having similar episodes for the past month or so. Because she was 38 and fit, she figured it was hormonal. She had an appointment with her general physician for a checkup later that week.

On this evening, in October 2020, Sheena's symptoms were stronger than ever. She grabbed the kitchen counter to steady herself. Knowing she couldn't make it to a chair, she started to lower herself to the floor.

The next thing Sheena remembers is being on the floor. She'd bumped her head hard on the floor, which she thinks might have jolted her back to consciousness. Only a few seconds had passed.

She called one friend to watch the boys and another friend to take her to the emergency room. Michael made arrangements to return to their home in Carrollton, Texas, the next day.

At the hospital, all test results came back normal. A doctor said her symptoms were likely stress-related but advised her to see a cardiologist.

Sheena returned home after midnight, exhausted. She couldn't sleep. She feared she might never wake up.

A couple days later, she saw a cardiologist. He also blamed her symptoms on stress and anxiety. He was so sure that he performed no tests.

She disagreed with his assessment. He insisted she was fine.

Seeking more insight, Sheena and Michael scheduled an appointment with an electrophysiologist.

"I know my body," she told the doctor. "Something is wrong."

He performed an echocardiogram and had her wear a heart monitor that would automatically send the output to his office.

A few days later, she and Michael were in a carpool line, waiting to pick up the kids from school. Sheena had stopped driving by this point because she was afraid she'd pass out behind the wheel. The phone rang; it was the doctor.

"Sheena, what are you doing right now?" he asked. "You need to get to the hospital now."

Readings from the heart monitor showed that her heart was going in and out of ventricular tachycardia, or V-tach. That's an abnormal heart rhythm, or arrhythmia, that occurs when the lower chamber of the heart beats too fast and the body doesn't receive enough oxygenated blood. While brief episodes can be harmless, longer ones can cause sudden cardiac arrest, which is often fatal.

Sheena was petrified. She'd been waiting so long for a diagnosis, but never expected anything so serious.

After several days of additional testing and being hooked up to an electrocardiogram machine in the hospital, doctors concluded Sheena was at high risk for sudden cardiac arrest because her heart continued to go in and out of V-tach. They thought it could be related to scarring from a mild heart murmur she'd been diagnosed with as a child.

On her fourth day in the hospital, doctors called a meeting with Sheena and Michael, with her sister and father joining by phone.

Doctors told Sheena she would need to have an implantable cardioverter defibrillator placed in her chest. The small battery-powered device detects and stops dangerously irregular heartbeats. If needed, it delivers electric shocks to restore a regular heart rhythm. She would also be on medication for the rest of her life.

After they spoke, the room went silent. Sheena couldn't make eye contact with the doctor or Michael. If she did, she would lose control, and she was trying to stay strong.

"If this is what I need to do to live longer and see my boys grow, this is what I will do," she thought.

When they wheeled her away for surgery, she felt she was being taken away from the life she knew, the person she'd been.

Two days later, she was home, exhausted but resolved.

"I'm going to get back to being Sheena," she said.

She and Michael joke about how on her first morning home she set the alarm to make the children's breakfast, as she always had.

"That's Sheena to a T," Michael said. "She's such a strong-willed person. It's tough to articulate how emotionally, mentally and physically challenging all this was, but then for her to say, 'I'm not going to let this change us, how we are,' that's so her."

Sheena also told Michael, "I'm going to take this diagnosis and make something out of this."

Within six months, Sheena had connected with the American Heart Association for her own support but also to do advocacy work. Last year, she was among the nation's top Woman of Impact fundraisers.

"Being able to spread that advocacy and raise funds gives other survivors hope," she said. "It's really my way of taking back that control and being able to make something positive out of all of this."

More than two years since she passed out, Sheena understands that the defibrillator is not a cure.

"My heart goes in and out of V-tach once a month," she said. "I can feel when it happens, and I don't think it's something I'll ever get used to. But the device hasn't shocked me, which means my heart goes back into a normal rhythm."

She's grateful to have the lifesaving piece of equipment, which she received only because of her persistence.

"If I had trusted what that first doctor said, I wouldn't be here today," she said. "You have to listen to your body."

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