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About Sudden Cardiac Arrest

Sudden cardiac arrest, is when the heart abruptly stops pumping without warning. When cardiac arrest occurs, no blood can be pumped to the rest of the body. It is responsible for half of all heart disease deaths.

Cardiac arrest occurs when the heart’s electrical system malfunctions. It is not a heart attack (myocardial infarction). A heart attack is when a blockage in a blood vessel interrupts the flow of oxygen-rich blood to the heart, causing heart muscle to die.

The most common cause of cardiac arrest is a heart rhythm disorder or arrhythmia called ventricular fibrillation (VF). The heart has a built-in electrical system. In a healthy heart, the heart's natural pacemaker (the sinoatrial node) triggers the heartbeat, then electrical impulses run along pathways in the heart, causing it to contract in a regular, rhythmic way. When a contraction happens, blood is pumped.

But in VF, the electrical signals that control the pumping of the heart suddenly become rapid and chaotic. As a result, the lower chambers of the heart, the ventricles, quiver or fibrillate instead of contracting, and they can no longer pump blood from the heart to the rest of the body. If blood cannot flow to the brain, the brain becomes starved of oxygen, and the person loses consciousness in seconds. Unless an emergency shock is delivered to the heart to restore its regular rhythm using a machine called a defibrillator, death occurs within minutes. It's estimated more than 70% of VF victims die before reaching hospital.

Who is at risk?

Cardiac Arrest often occurs in active, outwardly healthy people with no known heart disease or other health problems, but it is not a random event. Most victims do have heart diseases or other health problems, but may not know it.

There are numerous contributors to cardiac arrest, but two of the most important ones are:

  • Coronary Artery Disease: This is a condition in which the arteries that supply blood to the heart are narrowed or blocked. 75% of people who die of SCD show signs of a previous heart attack.
  • A low ejection fraction (EF): The ejection fraction is a measurement of how much blood is pumped by the left ventricle (the heart's main pumping chamber) with each heart beat. A healthy heart pumps 55% or more of its blood out to the body with each beat. People at highest risk for SCD have ejection fractions of less than 35.

Diagnosis

The following tests are used to predict risk of SCD:

Prevention

There are a number of ways people can decrease their likelihood of becoming a victim of cardiac arrest:

  • Maintaining a healthy lifestyle, including a healthy, balanced diet, regular exercise, maintaining a reasonable weight and not smoking.
  • Treating and monitoring diseases and conditions that can contribute to heart problems, including high blood pressure, high cholesterol and diabetes.
  • Controlling or stopping an arrhythmia (abnormal heart rhythm) that may trigger ventricle fibrillation (VF).

Treatment

A number of treatment options are available, including: