Sudden Cardiac Arrest - At a Glance



What is sudden cardiac arrest?
During a sudden cardiac arrest, the heart is no longer able to pump blood to the rest of the body, and in over 90% of victims, death occurs– abruptly and without warning. Learn more.

Causes and Risk Factors

What are the causes and risk factors of sudden cardiac arrest?
Sudden cardiac arrest is usually caused by a problem with the electrical system of the heart, which may be the result of coronary artery disease, a heart attack or other heart problems. Learn more.


What are the symptoms of sudden cardiac arrest?
Usually SCA strikes suddenly and without warning, leaving the patient unconscious. Learn more.


How is sudden cardiac arrest diagnosed?
Sudden cardiac arrest is diagnosed after the event, and may appear as ventricular fibrillation on an electrocardiogram (ECG). Learn more.


How is sudden cardiac arrest treated?
Once a cardiac arrest occurs, cardiopulmonary resuscitation (CPR) and defibrillation are required within the first several minutes to restore electrical activity to the heart and revive the heart's pumping function. Learn more.

Success Stories

What is it like to survive sudden cardiac arrest?
The chance of surviving an SCA event is about 5% in the United States. That is one survivor and nineteen deaths. Patients who survive have amazing stories to tell. Learn more.



What is sudden cardiac arrest?
SCA is a serious and life threatening medical emergency. During a sudden cardiac arrest, heart function ceases – abruptly and without warning. This causes the person to lose consciousness quickly. If the person does not receive immediate treatment with defibrillation, brain damage can occur. The chances of surviving SCA decrease by 7-10% with every minute that passes without a life-saving shock. Few attempts at resuscitation succeed after 10 minutes.1

Of course different things can cause your heart to stop suddenly, an electrocution for example. But with SCA, your heart stops because its electrical system malfunctions.

Sudden cardiac arrest is not the same as a heart attack

A heart attack is a “plumbing” problem caused by one or more blockages in the heart’s blood vessels, preventing proper flow. Part of the heart muscle dies. The patient is awake and breathing.


Heart Attack - Watch the Video [00:31]



SCA is an electrical problem, caused by an arrhythmia that prevents the heart from pumping blood to the brain and vital organs. The patient is unconscious and not breathing.


Heart Attack to Sudden Cardiac Arrest - Watch the Video [00:13]



Did you know:
Every 38 seconds an American dies of heart disease; every minute someone dies suddenly.1


Back to top



Causes and Risk Factors

What are the causes and risk factors of sudden cardiac arrest?
SCA can strike persons of any age, gender, race, and even those who seem in good health. You may remember a world class professional athlete at the peak of fitness who died suddenly during a sporting event. This is often caused by sudden cardiac arrest.

Usually, sudden cardiac arrest is caused by a problem with the electrical system of your heart. If the electrical signals in your heart are abnormal, this can create an irregular heart rhythm called an arrhythmia.

In some cases, an arrhythmia may cause your heart rate to change to a serious fast heart rate, called ventricular tachycardia or VT. If the heart rate becomes very fast, unstable, and irregular, it may become a much more dangerous rhythm, called ventricular fibrillation or VF. With VF, the heart quivers rapidly and cannot pump blood throughout the body. This is called sudden cardiac arrest.

What triggers the heart's electrical system to malfunction? Most heart and blood vessel diseases can lead to sudden cardiac arrest.

  • Cardiac Arrest Survivors: Most people who experience a sudden cardiac arrest do not survive the first event. If you survived one sudden cardiac arrest, you are at risk for having another one.1
  • Heart Attack Survivors: A heart attack can damage your heart and create an area of scar tissue. If large enough, this scar can cause a fast, dangerous heart rhythm to occur.
  • Spontaneous fast rhythms: Normal hearts can have fast heart rhythms that cause patient symptoms. If medicine is not helpful in treating the arrhythmias, an ICD device may be recommended to treat them.2
  • Congenital heart defects: Five heart defects increase the risk of having a sudden cardiac arrest. These include tetralogy of Fallot, transposition of the great arteries, aortic stenosis, functional single ventricle, and congenital Long QT Syndrome (LQTS). The defect itself, or its surgical repair, may make the patient at risk of dangerous heart rhythm.1

Given that SCA is often linked with coronary heart disease, many of the risk factors for heart disease are also risk factors for SCA. These would include such factors as:

  • A family history of coronary heart disease
  • High blood pressure
  • High cholesterol
  • Obesity
  • Diabetes
  • Sedentary lifestyle
  • Smoking
  • Excessive alcohol intake
  • Age


Other factors increasing the risk for SCA include:

  • A personal or family history of arrhythmias
  • A personal or family history of SCA
  • Previous heart attack
  • Previous heart failure
  • Drug abuse



Michael Sorrell, SCA Survivor - Watch the Video [01:00]




Do you know:
Some heart attack survivors are at increased risk due to the extent of the scar from the attack. The scar disrupts the normal electrical conduction and can do so without warning. When this happens, it creates a fatal heart rhythm called ventricular fibrillation.



Back to top



What are the symptoms of sudden cardiac arrest?
While there are often no warning signs before sudden cardiac arrest, some of these symptoms may come before sudden cardiac arrest:

  • Fatigue or weakness
  • Shortness of breath
  • Fainting
  • Dizziness or lightheadedness
  • Heart palpitations
  • Chest pain

Some people who are said to have died from a "massive heart attack" may instead have died from sudden cardiac death. The first and often only symptom of SCA is loss of consciousness – from lack of blood to the brain.


Back to top




How is sudden cardiac arrest diagnosed?
If you are risk for sudden cardiac arrest, your doctor may suggest one or more of the tests listed below. Some of the tests check the electrical system in your heart. Other tests check to see how your heart is pumping. The test results can also help your doctor choose the best treatment for you. In some cases you may be sent to specialists for diagnosis, testing and treatment.

  • Electrocardiogram (ECG): The ECG can show how your heart’s electrical system is working. It senses and records your heartbeats.
  • Echocardiogram: This test (also called an echo) uses ultrasound to create images of your heart as it beats. The echo helps your doctor learn about the shape and size of your heart, how well your heart valves are working, and the amount of blood pumped with each heart beat. This is called your ejection fraction (also called EF).
  • Electrophysiology study: The EP study involves checking how electrical impulses travel through the heart muscle. It can help find out about abnormal heart rhythms.

Your ejection fraction (EF)
Your doctor can determine your risk of SCA by measuring your ejection fraction, or EF. The EF is the amount of blood pumped (ejected) by your heart with each beat.

The heart normally ejects at least one-half of the blood (50-60%) it holds with each beat. One or more heart attacks can cause a decrease in the ejection fraction. When less than one-third of the blood is ejected (30-35%), the risk for sudden cardiac death increases.3


Ejection Fraction - Watch the Video [00:15]



If you have a low ejection fraction, your doctor may recommend that you visit a heart rhythm specialist. Your heart rhythm specialist may recommend that you receive a pacemaker-like device called an implantable cardioverter defibrillator that can prevent sudden cardiac death.

Back to top



How is sudden cardiac arrest treated?
Immediate treatment for SCA includes:

  • Cardiopulmonary Resuscitation (CPR) – involves chest compressions with assisted breathing (30:2 ratio) 1. This is an important step to allow external defibrillation therapy to be effective.
  • Defibrillation – sends a strong electrical shock to the heart to stop the arrhythmia and restore a normal heartbeat. There are two types of defibrillators: external defibrillators  use paddles to deliver a shock to the outside of the body, and implantable cardioverter defibrillators are implanted pacemaker-like devices that can sense arrhythmias and deliver life saving shocks. ICDs have been shown to prevent sudden cardiac death.3


Survival of sudden cardiac arrest

Sudden cardiac death kills nearly 300,000 people each year in the United States. This is more than the deaths caused by AIDS, breast cancer and lung cancer.1

Information Graphic Showing Survival Chances of SCA

Only 1 in 20 people usually survives a sudden cardiac arrest event. The other 19 people die before reaching the hospital.2


Information Graphic Showing Survival Chances of SCA with ICD

With an ICD device, 19 out of 20 people will survive SCA. ICD therapy has been shown to effectively stop 95% or more of dangerously fast heart rhythms.4


Image of Patient Matt Noble"When I talk to people about defibrillators, I tell them about the odds of surviving a dangerous arrhythmia with and without defibrillation" Matt Noble



ICD Therapy - Watch the Video [00:28]



People who are at risk for SCA – or who are SCA survivors – might also be treated with procedures or medications. However, medications alone have not proven to be very effective in reducing the risk of SCA.3

If you or someone you know is at risk for SCA, you are not alone. Only your heart doctor can determine which treatment is right for you. During your discussion with your doctor, you may want to have a list of topics and questions, such as what we list below. Also, if you take notes during your appointment, you can share this information with your family members.

  • Test results, including your ECG results
  • Arrhythmia diagnosis and condition of your heart
  • Treatment options and physician’s recommendations
  • What to expect before, during, and after the procedure
  • Follow-up visits and what to expect
  • Living with the ICD, including physical limitations and medications


Back to top


Success Stories

Image of  Patient Michael Sorrel

What is it like to survive a sudden cardiac arrest?
One in twenty victims of SCA survives to talk about it. Michael Sorrell is one person that has a story to tell.



Next: Ventricular Arrhythmias >>

Are You Heart Smart?

Find out how much you know

  Take quizzes now


Note: Individual symptoms, situations, and circumstances may vary. Please consult your physician or qualified healthcare provider regarding your condition and appropriate medical treatment. The information provided is not intended to be used for medical diagnosis or treatment, or as a substitute for professional medical advice.

1. AHA. Heart and Stroke Statistics - 2010 Update, American Heart Association.
2. National Heart, Lung, and Blood Institute 112209.
3. Huikuri H, et al. Sudden death due to cardiac arrhythmias. NEJM. 2001;345:1473.
4. Himmrich E, et al. Is ICD programming for double intraoperative defibrillation threshold energy safe and effective during long-time follow-up? Results of a prospective randomized multicenter study (Low-Energy ENDOTAK Trial - LEFT). Z Kardiol. 1999;88:103-12 [German language edition].

CRV-181504-AA SEP2013
TRUSTe European Safe Harbor certification