Sudden Cardiac Arrest (SCA)

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Sudden Cardiac Arrest, or SCA, is a frequently misunderstood worldwide killer. It can affect anyone, anywhere, anytime. It occurs when the heart's electrical system malfunctions and the heart suddenly stops beating. It's unpredictable. Almost 40,000 Canadians die each year of Sudden Cardiac Arrest.

Yet few people are familiar with Sudden Cardiac Arrest. SCA occurs when the heart's electrical system malfunctions and the heart suddenly stops beating. It's unpredictable. It can happen to anyone, anywhere, anytime and it is fatal unless treated quickly.

Did you know?
Cardiopulmonary resuscitation (CPR) will not restart a heart in Sudden Cardiac Arrest. CPR is just a temporary measure used to continue a minimal supply of oxygen to the brain and other organs. When someone is in Sudden Cardiac Arrest, defibrillation is the only way to re-establish a regular heartbeat.


What is Sudden Cardiac Arrest?

Sudden Cardiac Arrest (SCA) is a condition in which the heart stops beating suddenly and unexpectedly due to a malfunction in the heart's electrical system. The malfunction that causes SCA is a life-threatening abnormal rhythm, or arrhythmia. The most common arrhythmia is ventricular fibrillation (VF).


When in VF, the heart's rhythm is so chaotic (called "fibrillating") that the heart merely quivers, and is unable to pump blood to the body and brain. These graphics show a heart with a normal rhythm and a heart experiencing ventricular fibrillation (VF). Once a heart has entered VF, Sudden Cardiac Arrest occurs.


Heart beating normally
Heart in VF

A victim in SCA first loses his or her pulse, then consciousness, and finally the ability to breathe. But all of this happens quickly -- in a matter of seconds. Without immediate treatment from a defibrillator, 90-95 percent of SCA victims will die.

The only effective treatment for SCA is to deliver an electrical shock using a device called a defibrillator (to de-fibrillate the heart), which stops the chaotic rhythm of a heart in VF, giving it the chance to restart beating with a normal rhythm.

Did you know?
Cardiopulmonary resuscitation (CPR) will not restart a heart in Sudden Cardiac Arrest. CPR is just a temporary measure used to continue a minimal supply of oxygen to the brain and other organs. When someone is in Sudden Cardiac Arrest, defibrillation is the only way to re-establish a regular heartbeat.


Who can be affected by SCA?

Unfortunately, anyone can suffer Sudden Cardiac Arrest. SCA is unpredictable and can happen to anyone, anytime, anywhere-even teenagers. Although pre-existing heart disease is a common cause of cardiac arrest, many victims have never had a heart problem. Risk does increase with age.

Without immediate treatment, only 5-10 percent of people survives a SCA. But survival rates above 50 percent have been achieved in places that have successfully implemented AED programs. Survival rates can climb even higher when the person is treated within three minutes of cardiac arrest.

These statistics are impressive, but they're still just numbers. It's not until you save a life, or meet someone whose life has been saved by an AED, that the remarkable power of an AED program becomes evident.


Is Sudden Cardiac Arrest the same as a heart attack?

Sudden Cardiac Arrest (SCA) is not the same thing as a heart attack, although a person suffering a heart attack has an increased risk of SCA.

Here's how they differ:

 

  Heart Attack

Sudden Cardiac Arrest 
Cause
Caused by a blockage in an artery that supplies blood to the heart. The affected heart muscle then begins to die due to lack of oxygen.

Caused by an abnormal heart rhythm, usually ventricular fibrillation.
Warning
Signs

Often preceded by chest, arm, upper abdomen, or jaw pain; nausea and sweating are common.

Rarely a warning.
Victim's Response
Usually remains conscious and alert.

Always loses consciousness.
Risk of
Death

With proper treatment, many people survive.

A person experiencing a heart attack is at a much higher risk for Sudden Cardiac Arrest. This increases his/her risk of death.
90-95% will die, unless a defibrillation shock is delivered within 10 minutes of collapse.

 

It's not always easy to tell if someone is suffering from SCA, but the victim will typically:

  • Be unconscious
  • Have no signs of circulation (e.g. no pulse)
  • Not be breathing

Why is it important to know the difference between SCA and a heart attack? Because the treatment for each is very different:

  • For a heart attack, medical professionals must administer medications, other life-saving procedures, and sometimes surgery, to unblock blood flow to the heart muscle. Time is important, with the best results occurring if treatment is received in the first hour of symptoms.
  • For SCA, an electrical shock from a defibrillator must be delivered, the sooner the better, otherwise the victim will likely die. Laypersons can be easily trained to use an AED, thus dramatically increasing the odds of saving someone's life.

How is Sudden Cardiac Arrest treated?

The only way to effectively treat Sudden Cardiac Arrest (SCA) is with an electrical shock delivered by a defibrillator. Voltage stored by the defibrillator pushes electrical current through the heart by means of the electrodes or paddles placed on the chest. This brief pulse of current halts the chaotic activity of the heart, giving it a chance to start beating again with a normal rhythm. Delivering a shock that returns the heart to a normal rhythm is called defibrillation.

Early defibrillation is the key to surviving SCA.

Survival rates for SCA are highest when defibrillation occurs within the first few minutes. The person has the best chance of survival if the defibrillation shock is given within the first three minutes of collapsing.

But if a defibrillator is not immediately available, the outlook is grim. For each minute defibrillation is delayed, survival rates drop by about 7-10 percent even if CPR is started immediately.

  • The rate of survival for SCA victims averages less than two percent when defibrillation is delayed ten minutes or more.
  • The average time it takes emergency crews to arrive is between 6-12 minutes.
  • If the heart isn't restarted within the first four to six minutes after the arrest, the victim may sustain irreversible brain damage.



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