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What Is Sudden Cardiac Arrest (SCA)?

Posted Jun 23 2009 6:54pm

Sudden cardiac arrest (SCA) is acondition in which the heart suddenly and unexpectedly stops beating. When this happens, blood stops flowing to the brain and other vital organs.

SCA usually causes death if it's not treated within minutes.


Ninety-five percent of people who have SCA die from it—most within minutes. Rapid treatment of SCA with a defibrillator can be lifesaving. A defibrillator is a device that sends an electric shock to the heart to try to restore its normal rhythm.

Automated external defibrillators (AEDs), which often are found in public places like airports and office buildings, can be used by bystanders to save the lives of people who are having SCA.


Most cases of sudden cardiac arrest (SCA) are due to ventricular fibrillation (v-fib). V-fib is a type of arrhythmia (for this please see my article on Wolff-Parkinson-White Syndrome (Arrhythmia) . In v-fib, the ventricles (the heart's lower chambers) don't beat normally. Instead, they quiver very rapidly and irregularly.

Who Is At Risk?

Each year, between 250,000 and 450,000 Americans have sudden cardiac arrest (SCA). SCA occurs most often in people in their mid-thirties to mid-forties. It appears to affect men twice as often as women.

SCA rarely occurs in children unless they have inherited problems that make them likely to have SCA. Only a very small number of children have SCA each year.

Other Risk Factors

Other risk factors for SCA include:

  • A personal or family history of SCA or of inherited disorders that make you prone to arrhythmias
  • A history of having arrhythmias
  • Heart attack
  • Heart failure
  • Drug abuse or excessive alcohol intake

How Is Sudden Cardiac Arrest Diagnosed?

Sudden cardiac arrest (SCA) happens without warning. It requires immediate emergency treatment. Doctors rarely can diagnose SCA with medical tests as it's happening.

Instead, SCA often is diagnosed after it happens. Doctors do this by ruling out other causes of a person's sudden collapse.

How Is Sudden Cardiac Arrest Treated?

Emergency Treatment

Sudden cardiac arrest (SCA) requires immediate treatment with a defibrillator. This device sends an electric shock to the heart. The electric shock may restore a normal rhythm to a heart that's stopped beating.

To work well, defibrillation must be done within minutes of SCA. With every minute that passes, the chances of surviving SCA drop rapidly.

Police, emergency medical technicians, and other first responders usually are trained and equipped to use a defibrillator. Call 9–1–1 right away if someone has signs or symptoms of SCA. The sooner help is called, the sooner potentially lifesaving treatment can be done.

How Can Death Due to Sudden Cardiac Arrest Be Prevented?

Ways to prevent death due to sudden cardiac arrest (SCA) differ depending on whether:

  • You've already had SCA
  • You've never had SCA but are at high risk for the condition
  • You've never had SCA and have no known risk factors for the condition

For People Who Have Survived Sudden Cardiac Arrest

If you've already had SCA, you're at high risk of having it again. Research shows that an implantable cardioverter defibrillator (ICD) reduces the chances of dying from a second SCA.

An ICD is surgically placed under the skin in your chest or abdomen. The device has wires with electrodes on the ends that connect to your heart's chambers. The ICD monitors your heartbeat.

If the ICD detects a dangerous heart rhythm, it gives an electric shock to restore the heart's normal rhythm. Your doctor may give you medicine to limit irregular heartbeats that can trigger the ICD.

The illustration shows the location of an implantable cardioverter defibrillator in the upper chest. The electrodes are inserted into the heart through a vein.

The illustration shows the location of an implantable cardioverter defibrillator in the upper chest. The electrodes are inserted into the heart through a vein.

An ICD isn't the same as a pacemaker. The devices are similar, but have some differences. Pacemakers only give off low-energy electrical pulses. They're often used to treat less dangerous heart rhythms, such as those that occur in the upper chambers of the heart. Most new ICDs work as both pacemakers and ICDs.

For People at High Risk for a First Sudden Cardiac Arrest

If you have severe coronary artery disease (CAD), you're at increased risk for SCA. This is especially true if you've recently had a heart attack.

Your doctor may prescribe a type of medicine called a beta blocker to help lower your risk for SCA. Other treatments for CAD, such as angioplasty or coronary artery bypass grafting, also may lower your risk for SCA.

Your doctor also may recommend an ICD if your risk for SCA is very high.

For People Who Have No Known Risk Factors for Sudden Cardiac Arrest

CAD seems to be the cause of most cases of SCA in adults. CAD also is a major risk factor for angina (chest pain or discomfort) and heart attack, and it contributes to other heart problems.

Following a healthy lifestyle can help you lower your risk for CAD, SCA, and other heart problems.

A healthy diet is an important part of a heart healthy lifestyle. Choose a variety of fruits, vegetables, and grains; half of your grains should come from whole-grain products.

Choose foods that are low in saturated fat, trans fat, and cholesterol. Healthy choices include lean meats, poultry without skin, fish, beans, and fat-free or low-fat milk and milk products.

Choose and prepare foods with little sodium (salt). Too much salt can raise your risk for high blood pressure. Recent studies show that following the Dietary Approaches to Stop Hypertension (DASH) eating plan can lower blood pressure.

Choose foods and beverages that are low in added sugar. If you drink alcoholic beverages, do so in moderation.

Aim for a healthy weight by staying within your daily calorie needs. Balance the calories you take in with the calories you use while doing physical activity. Be as physically active as you can.

Some people should get medical advice before starting or increasing physical activity. For example, talk to your doctor if you have a chronic (ongoing) health problem, are on medicine, or have symptoms such as chest pain, shortness of breath, or dizziness. Your doctor can suggest types and amounts of physical activity that are safe for you.

For more information on following a healthy diet, see the National Heart, Lung, and Blood Institute's (NHLBI's) Aim for a Healthy Weight Web site, "Your Guide to a Healthy Heart," and "Your Guide to Lowering Your Blood Pressure With DASH." All of these resources provide general information about healthy eating.

For more information about physical activity, see NHLBI's "Your Guide to Physical Activity and Your Heart."

Other Lifestyle Changes

Other lifestyle changes also can help lower your risk for SCA. Examples include:

  • Quitting smoking. Talk to your doctor about programs and products that can help you quit. Also, try to avoid secondhand smoke.
  • Losing weight if you're overweight or obese.
  • Treating other health problems, such as high blood pressure, high blood cholesterol, and diabetes.

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