What do You Know About Sudden Cardiac Arrest?

Sudden cardiac arrest (SCA) is a leading cause of death among adults over the age of 40 in the United States and other countries. In the U.S. alone, approximately 359,400 people of all ages experience EMS-assessed out-of-hospital non-traumatic SCA each year (about 1,000/day) and nine out of 10 victims die. In fact, the number of people who die each year from SCA is roughly equivalent to the number who die from Alzheimers disease, assault with firearms, breast cancer, cervical cancer, colorectal cancer, diabetes, HIV, house fires, motor vehicle accidents, prostate cancer and suicides combined. SCA is a life-threatening condition–but it can be treated successfully through early intervention with cardiopulmonary resuscitation (CPR), defibrillation, advanced cardiac life support, and mild therapeutic hypothermia. When bystanders intervene by giving CPR and using automated external defibrillators (AEDs) before EMS arrives, four out of 10 victims survive.Causes of Death 2012

 About Sudden Cardiac Arrest

What is sudden cardiac arrest?

SCA is a sudden and unexpected pulse-less condition attributed to cessation of cardiac mechanical activity. It is usually caused by ventricular fibrillation, an abnormality in the heart’s electrical system. When SCA occurs, blood stops flowing to the brain, the heart, and the rest of the body, and the person collapses. In fact, the victim is clinically dead and will remain so unless someone helps immediately.

Is sudden cardiac arrest the same as a heart attack? 

No. A heart attack (or a myocardial infarction) occurs when part of the heart’s blood supply is reduced or blocked, causing the heart muscle to become injured or die. It has been described as a “plumbing problem” in the heart. The heart attack victim is awake and may complain about one or more of the signs and symptoms of heart attack.1 In contrast, the SCA victim is not awake and needs immediate help. While a heart attack can lead to SCA, there are many other causes, including:

  • Thickening of the heart muscle (e.g., Hypertrophic Cardiomyopathy, Arrhythmogenic Right Ventricular Dysplasia)
  • Heart rhythm disorders (e.g., Brugada syndrome, long QT syndrome, Wolff Parkinson White syndrome)
  • Heart valve disorders (e.g., Mitral Valve Prolapse).

Other causes of SCA among people who do not have heart disease include recreational drug use, electrocution, and commotio cordis, a disruption in the heart rhythm due to a sudden blow to the chest.

When SCA occurs, the heart stops beating in an effective, organized manner. As a result, blood is no longer pumped throughout the body. The person suddenly passes out and appears lifeless, except for abnormal “gasping,” which may last for several minutes. Occasionally, SCA victims experience 10-20 seconds of seizure activity (shaking of the arms and legs) at the onset of the event, as the brain stops receiving blood and oxygen from the heart.

Why do laypersons need to know about sudden cardiac arrest?

When a person collapses, is unresponsive, and is not breathing normally, he or she most likely is experiencing SCA. Whether or not the victim survives depends largely upon the immediate intervention of bystanders. There is a brief timeframe for saving the victim’s life.


How common is sudden cardiac arrest?

Each year, 359,400 people in the U.S. (about 1,000/day) experience EMS-assessed out-of-hospital non-traumatic SCA, and nine out of 10 victims die. This is roughly equivalent to the number of people who die from Alzheimers’ disease, assault with firearms, breast cancer, cervical cancer, colorectal cancer, diabetes, HIV, house fires, motor vehicle accidents, prostate cancer and suicides combined. In fact, the incidence of sudden cardiac death is nearly 10 times higher than the incidence of death from breast cancer.2,3,4,5

Does the incidence of sudden cardiac arrest vary by race?

The age-adjusted incidence of out-of hospital cardiac arrest per 10,000 adults is 10.1 among blacks, 6.5 among Hispanics, and 5.8 among whites.6

How common is sudden cardiac arrest in youth?

Estimates of the annual incidence of SCA among youth outside hospitals vary widely. In 2012, the American Heart Association (AHA) reported there are 10,235 cases of SCA annually in youth <18.7

How common is sudden cardiac arrest among athletes?

The AHA reports that most sudden deaths in athletes may be attributed to cardiovascular disease (56%). Nearly one-third of cardiovascular deaths (29%) occur in blacks, 54% occur in high school students, and 82% occur with physical exertion during competition/training. Only 11% occur in females, though this proportion is increasing over time. According to a study by the National Collegiate Athletic Association, there is one SCA death per 22,903 athlete participant years among students 17-24 years of age participating in NCAA sports.8


How should sudden cardiac arrest be treated? 

SCA victims can survive if they receive immediate CPR and are treated quickly with defibrillators. To be effective, this treatment must be delivered quickly—ideally, within three to five minutes after collapse.

Why is bystander action so important?

Even the best emergency medical services may not be able to reach a victim within three to five minutes. This is why prompt action by bystanders is so critical and why it is so important for laypersons learn CPR and how to use automated external defibrillators (AEDs).

What is an automated external defibrillator?

An AED is a portable user-friendly electronic device that automatically diagnoses potentially life-threatening heart rhythms. If the AED detects a problem that may respond positively to an electric shock, it permits a shock to be delivered to restore a normal heart rhythm. AEDs provide simple audio and visual instructions and are designed for use by laypersons. Some AEDs advise the operator to press a button to deliver the shock. Other AEDs automatically provide a shock if the heart is in a fatal rhythm.

Do most sudden cardiac arrest victims receive immediate CPR and treatment with an automated exernal defibrillator?

Unfortunately, only one-third (32%) of SCA victims receive bystander CPR and only 2% are treated with AEDs by bystanders.9

Who can use an automated external defibrillator?

AEDs may be used by any motivated bystander, regardless of training.

Is a rescuer protected from legal liability risks if he or she uses an automated external defibrillator? 

The overwhelming majority of U.S. jurisdictions afford some type of legal liability protection for AED users. Often, these protections are provided by Good Samaritan statutes. Typically, AED users are protected from liability so long as they act in a reasonable and rational manner. Liability protections generally don’t cover gross negligence or willful or wanton misconduct, such as consciously seeking to injure the patient or using an AED in a non-accepted, non-standard way.12

 Can a rescuer accidentally hurt the victim with an automated external defibrillator? 

No. The victim is already clinically dead and the rescuer’s actions can only help. AEDs are designed to resuscitate people whose hearts have stopped working effectively. AEDs will only shock victims whose hearts need to be shocked to restore a healthy rhythm.

Can a rescuer hurt himself or others with an automated external defibrillator? 

No, not if the AED is used properly. The therapeutic shock is programmed to go from one electrode pad to the other through the victim’s chest. Basic precautions, such as not touching the victim during the shock, ensure the safety of rescuers and other bystanders.

Can automated external defibrillators be used to treat children? 

Yes. For children under age eight, a pediatric dose of electrical therapy should be used if possible. Some AEDs have pediatric capabilities. If a child’s heart rhythm is potentially fatal and a device with pediatric capabilities is not available, a standard AED should be used.

Survival and Follow-Up Care

Do most sudden cardiac arrest victims survive?

On average, only 11.4% of EMS-treated non-traumatic SCA victims survive.10 Survival rates among young SCA victims is somewhat lower (8.6%). However, when victims are treated quickly, their chances of survival improve dramatically. If bystanders provide CPR and use an AED to treat the victim before EMS arrives, survival rates increase to 38%.11 In other words, lay bystanders who take action by calling 9-1-1, starting CPR, and using the nearest AED can mean the difference between life and death for victims of sudden cardiac arrest. For every minute without CPR and defibrillation, the victim’s chance of survival decreases by 7-10%.

What happens once the victim is resuscitated?

Subsequent care by healthcare professionals includes administration of medications and other advanced cardiac life support techniques. In patients who have been successfully resuscitated, mild therapeutic hypothermia can improve the chances of survival with good brain function.  SCA survivors should see heart specialists (cardiologists and electrophysiologists) for follow-up care. Many survivors use wearable cardioverter defibrillators (WCDs) and later undergo implantable cardioverter defibrillation (ICD) therapy to reduce the risk of death from future SCA incidents.

What is a wearable cardioverter defibrillator?

The wearable cardioverter defibrillator (WCD) is a device worn by patients at risk for SCA that provides protection as changing conditions are assessed and permanent SCA risk is established. The WCD allows a patient’s physician time to assess long-term arrhythmic risk and make appropriate plans.

What is an implantable cardioverter defibrillator?

An ICD is a small, computerized device that is implanted in the upper chest of patients who are at risk for SCA. The ICD detects abnormal heart rhythms, delivers electrical energy to the heart muscle, and restores a normal heartbeat.

After resuscitation, will the victim be able to resume a normal life? 

Most people who survive sudden cardiac arrest return to their previous level of functioning. All survivors need follow-up care with physicians who specialize in heart conditions (cardiologists and electrophysiologists). Survivors and their loved ones should expect that psychological support will also be needed.

Risk Factors and Prevention

Who is at risk for sudden cardiac arrest?

Sudden cardiac arrest often occurs in active people who seem to be healthy and have no known medical conditions. In these patients, SCA is the first indication of a heart condition. However, some people can be identified in advance as being at risk for SCA. Risk factors include:

  • A previous heart attack
  • Coronary artery disease (and risk factors for CAD including smoking, high blood pressure, diabetes, elevated LDL cholesterol, family history of heart disease, sedentary lifestyle)
  • Heart failure from other causes
  • Episodes of fainting of unknown cause
  • A thickened heart muscle (cardiomyopathy)
  • Heart rhythm disorders
  • Heart valve disorders
  • Blood vessel abnormalities
  • A low ejection fraction (EF) (<35%).13

A family history of cardiac arrest in a close blood relative (i.e., a parent, full sibling, or child) is associated with a two-fold increase in risk of SCA.

Other risk factors for SCA among people who do not have heart disease include recreational drug use, electrocution, and commotio cordis, a disruption in the heart rhythm due to a sudden blow to the chest.

Can sudden cardiac arrest be prevented? 

Living a healthy lifestyle—exercising regularly, eating healthy foods, maintaining a reasonable weight, and avoiding smoking—can help prevent sudden cardiac arrest. Monitoring and controlling blood pressure, cholesterol levels and diabetes is also important. If abnormal heart rhythms or arrhythmias are detected, they can be treated through implantable cardioverter defibrillator (ICD) therapy, use of medications such as ACE inhibitors, beta blockers and calcium channel blockers, and catheter ablation.

Take Home Message

Be prepared

Take a CPR-AED class through the American Heart Association, American Red Cross, Health & Safety Institute, National Safety Council, a local training agency, fire department, hospital, or community college. Too busy to take a class? Check out HeartRescueNow.com for a quick tutorial. Learn how to save a life. The life you save will most likely be that of a friend, relative, or co-worker.

Be on the lookout for AEDs

Become familiar with the location of AEDs in public places so you can quickly retrieve one if it is needed. If AEDs are not readily available in public places such as schools, workplaces, and places of worship, advocate for change. Consider purchasing an AED for your home/car. About 80% of cases of SCA occur in the home.

How to save a life

If you come across someone who has collapsed, is unresponsive and is not breathing normally, here’s what to do:

  • Act fast. Call 9-1-1 and send for the nearest AED. Use the AED as soon as possible.

While waiting for professional the AED and professional help to arrive:

  • If you are not trained in CPR, push down hard and fast in the center of the chest (2” depth, 100 pumps/minute). Continue. Think “Stayin’ Alive” by the BeeGees
  • If you are trained in CPR, push down hard and fast in center of chest (2” depth, 100 pumps/minute).

Do not be concerned about harming the person. He or she is clinically dead and can only benefit from your help.


  1. 1.       Signs and symptoms of a heart attack include intermittent chest discomfort; pain or discomfort in one or both arms, spreading to the shoulders, upper back, neck or jaw; shortness of breath; nausea; sweating; and a general sense of anxiety. In women, additional symptoms can include stomach or abdominal pain, weakness or overwhelming fatigue, and swelling of the ankles or lower legs.
  2. 2.       Go AS, Mozaffarian D, Roger VL, et al. Heart disease and stroke statistics–2013 update: A report from the American Heart Assoociation. Circulation. Published online December 12, 2012. 
  3. 3.       CDC National Vital Statistics Report, Vol. 60, No. 3, Dec. 29, 2011.
  4. 4.       CDC Fire Deaths and Injury Fact Sheet
  5. 5.       39,520 deaths from breast cancer were projected for 2011. U.S. Breast Cancer Statistics,www.breastcancer.org, retrieved October 24, 2012.
  6. 6.       Roger VL, et al. Heart disease and stroke statistics-2012 update: A report from the AHA. Circulation. 2012:125(1):188-197.
  7. 7.       Roger VL, et al. (Ibid.)
  8. 8.       Harmon KG, et al. Incidence of sudden cardiac arrest in national collegiate athletic association athletes. Circulation 2011;123(15):1594-600.
  9. 9.       Roger VL, et al (Ibid.)
  10. 10.    Roger VL, et al. (Ibid.)
  11. 11.    Weisfeldt ML, Sitlani CM, Ornato JP, et al. Survival after application of automated external defibrillators before arrival of the emergency medical system: Evaluation in the Resuscitation outcomes consortium population of 21 million. J Am Coll Cardiol. 2010;55(16): 1,713-1,720.
  12. 12.    Personal communication from Andrew Roszak, JD, MPA, EMT-P, Member, SCA Foundation Advisory Council
  13. 13.    The ejection fraction (EF) is a measurement of how much blood is pumped by the ventricles with each heartbeat. A healthy heart pumps 55 percent or more of its blood with each beat.
What do You Know About Sudden Cardiac Arrest?

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