A 24-year-old thought numbness on one side of her body was job stress. She almost died from a cardiac arrest days later.

• Brittany Williams was visiting New York City when she collapsed from cardiac arrest.
• Bystanders performed CPR before paramedics took her to the hospital and saved her life.

Brittany Williams was working in an accounting firm in Tallahassee, Florida, at age 24 when she felt the left side of her body go numb. She Googled her symptom, and learned that stroke, heart attack, and cardiac arrest were possible culprits. "I started to panic," Williams, now 32, told Insider.

But when she told her boss how she was feeling and what it could mean, her boss told Williams she was overreacting — and Williams agreed.

"I was like, 'You're right. I'm only 24. I'm running five miles every day, eating extremely healthy, living a healthy lifestyle,'" Williams, who now lives in St. Petersburg, Florida, said. So she brushed it off as stress from tax season and working a retail job on the side.

But a few days later, while on a family trip to New York City, Williams collapsed at a Times Square bar. She'd suffered a cardiac arrest due to an undiagnosed heart condition. She credits bystanders and an automated external defibrillator, or AED, with her survival.

Now a volunteer for the American Heart Association's Go Red For Women "Real Women" campaign, Williams is sharing her story to encourage people to seek help at the first signs of heart disease.

"I just wanna kick myself because maybe I could have prevented this," she said, "but I just didn't know."

Williams says quick-thinking bar patrons saved her life

The day Williams went into cardiac arrest, her family was cheering on the Florida State Seminoles, Williams' alma mater, in the ACC Championships at a Times Square bar partial to the team.

But within minutes of their arrival, Williams' eyes rolled back in her head and she collapsed, her parents later told her. Two ophthalmologist patrons sprung into action, performing CPR after they couldn't detect a pulse.

"It went from a lively, energetic football game to complete silence," Williams said. She only remembers hearing her mom's voice saying, "Brittany, we love you. Don't leave us."

After eight minutes of CPR, paramedics arrived and shocked Williams' heart with an AED before rushing her to the hospital. Some bar patrons blocked traffic to clear the ambulance's way, and others walked to a nearby cathedral to pray. "New York is the city that saved my life," Williams said.

At the hospital, Williams was put in a medically-induced coma. When providers woke her up two days later, she didn't know where she was or why her parents were sobbing.

A doctor told her she'd suffered a cardiac arrest, an electrical problem that stops the heart from beating. Cardiac arrest is different from a heart attack, which occurs from a blockage in a coronary artery. About 90% of people who suffer from a cardiac arrest outside of a hospital die, according to the Centers for Disease Control and Prevention.

"I was in disbelief," Williams said. "I just thought heart disease happened to the elderly or heavy smokers and heavy drinkers, not young adult athletes like me. I just never in a million years would picture myself going into cardiac arrest."

Williams was diagnosed with a disorder that causes her heart to beat irregularly

Williams stayed in the hospital for eight days, where she was diagnosed with long QT syndrome, a heart signaling disorder that causes "fast, chaotic heartbeats," according to the Mayo Clinic. The National Organization for Rare Diseases estimates that about 1 in 2,000 people are born with the condition.

Williams underwent a procedure to implant an internal defibrillator, which monitors her heartbeat and shocks it back into a normal rhythm in the case of another cardiac event.

When she returned to Florida, Williams struggled to adjust to life with the device. "There was a huge fear that anything I did was going to make my heart race or go into cardiac arrest or was I going to get shocked," she said.

Once, while at her desk, her heart rate exceeded 350 beats per minute, but the device failed to shock her.

She's since had another pacemaker wire implanted in her other heart chamber. While she has episodes of a chaotic heart beat "all the time," Williams said, the device has only needed to shock her once. "It definitely feels like a horse kicks you," she said.

Now, she tries to focus on what she can control — like maintaining a healthy lifestyle with moderate, but not vigorous, exercise — and advocating for heart disease awareness. She specifically wants people to learn how to recognize the signs of cardiac arrest and to perform CPR if necessary.

"People lose their lives every day due to somebody not knowing CPR," she said. "But I'm here today because somebody did."