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Sudden Cardiac Arrest: 5 Things Raise Your Risk

Preventive steps to take plus what to do in an emergency

Illustration of person with cardiad arrest

You may think the most common single cause of death in the United States is heart attack. Or cancer. Or stroke.


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But it’s actually sudden cardiac arrest (SCA). SCA is a problem with your heart’s electrical system (usually called ventricular tachycardia or ventricular fibrillation).

Most SCA victims survive if they get help very quickly. But SCA is fatal 95% of the time.

“Only about 5% of those who have a sudden cardiac arrest survive long enough to get to — and then be discharged from — the hospital alive,” notes cardiologist Bruce Wilkoff, MD, an expert in heart rhythm disorders.

“They might have been alone or with someone who didn’t know CPR, or no one called 911. Or the ER squad couldn’t get there within the 10 minutes required to prevent brain death.”

What happens inside your heart during sudden cardiac arrest?

In sudden cardiac arrest, the heart typically races away in a confused, disorganized manner.

Circulation halts. Blood doesn’t reach the lungs or brain. People abruptly pass out, don’t respond, stop breathing, have no pulse.

“No one can endure this for more than about four or five seconds without passing out,” says Dr. Wilkoff.

A deadly public health crisis

About 365,000 people per year experience SCA at home or out in public. That’s roughly equivalent to the combined annual deaths from:

  • Firearms.
  • Car accidents.
  • Breast, cervical, colorectal and prostate cancers.
  • House fires.
  • Diabetes.
  • Alzheimer’s disease.
  • HIV.
  • Suicide.


SCA is one of the most frequent causes of sudden death. Others include myocardial infarction (heart attack), heart muscle rupture and stroke.

5 things that increase your risk for sudden cardiac arrest

The heart rhythm disturbances leading to SCA can result from:

  1. Scarring. Rhythm problems can often be traced to a scarred heart muscle. “Scarring causes the heart’s electrical signals to become confused and fragmented,” explains Dr. Wilkoff. The most common causes are coronary artery disease and cardiomyopathy. Heart attacks starve the heart muscle, causing tissue death and scarring. Viral infections, hereditary or autoimmune conditions and chemical toxicity can also damage and scar the heart muscle.
  2. A low ejection fraction. If you have heart failure with an ejection fraction of 35% or less, your heart can’t pump out enough blood with each beat. This disrupts your heart rhythm and increases the risk of sudden cardiac death. “Putting in an implantable cardiac defibrillator (ICD) will rescue you from these rapid and irregular heart rhythm episodes, extend your life and allow you to return to normal living,” says Dr. Wilkoff. “ICDs increase survival from sudden cardiac arrest to 98% because they respond within seconds, not minutes.”
  3. A family history. If a first-degree relative — one of your parents or siblings — died young for unknown reasons, then your risk of early, sudden death is higher too (SCA is often the cause in these cases).
  4. Smoking. Smoking dramatically increases your risks of both heart attack and sudden cardiac death. “When we put ICDs in smokers, we find they need more shocks from their devices, which means they’re having more cardiac events,” says Dr. Wilkoff.
  5. Poorly managed heart failure. “If you have heart failure symptoms (shortness of breath and exercise intolerance) with or without a low ejection fraction, you need medicine,” he says. Drugs such as ACE inhibitors and beta blockers will keep your heart from working too hard, improve its function and lower your risk of SCA.

What do to in an emergency

If someone nearby falls over and is unresponsive, with no signs of breathing or a pulse, call 911. If you know how to use an automatic external defibrillator (AED), find one and use it, says Dr. Wilkoff. If not, do CPR until the ambulance arrives.

“Defibrillation is the No. 1 thing that improves survival in sudden cardiac arrest. CPR keeps people alive long enough to be defibrillated,” he explains.

Learning both skills can save a life. The American Heart Association offers training, as do many fire departments, schools and libraries.

A word to the wise

“Most people who die suddenly either didn’t know they were going to die suddenly or didn’t pay attention to the warning signs,” says Dr. Wilkoff.

Briefly passing out is usually nothing more than a fainting spell. But it’s also possible to experience a more serious but temporary irregular heart rhythm that indicates more serious heart disease.

If you or someone you love passes out, consider whether they might be at risk of SCA and see a physician, he advises.

“If you have heart scarring or symptoms of heart failure, or a history of heart attack, or a low injection fraction and continue to smoke, you likely need an ICD,” notes Dr. Wilkoff.


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