What Is Sudden Cardiac Arrest (SCA)?

Cardiac arrest is the sudden and unexpected loss of cardiac function. It’s often wrongly referred to as a heart attack. SCA usually occurs after an electrical disturbance of the heart’s normal rhythm (activity) occurs. A heart attack (MI) is when blood flow to a section of the heart muscle becomes blocked.

During cardiac arrest, the heart stops beating, the person will lose consciousness, stop breathing and will have the loss of blood pressure. The vital organs within the body quickly become starved of blood and life sustaining oxygen. Without immediate defibrillation, permanent brain damage and death will occur within minutes. This is often referred to as sudden cardiac death or SCD.

Survival is directly linked to the time interval between the SCA and the defibrillation (shock from an AED) to the victim. Each minute that elapses without defibrillation decreases a victim's chance of survival by 7-10%. Defibrillation within the first three minutes increases one’s chance of survival to 70%. Cardiopulmonary resuscitation (CPR) is a vital step in the chain of survival, only defibrillation can restore the heart’s normal rhythm, as known as ventricular fibrillation (VF).

Heart attack is the most common cause of VF. Despite how common sudden cardiac arrest is, doctors know little about what predisposes one person to it and not another.