Cardiac arrest, also known as sudden cardiac arrest, is a sudden loss of heart function. A person experiencing cardiac arrest will suddenly lose consciousness and stop breathing because the heart is no longer pumping blood and oxygen to the brain.

Signs of Cardiac Arrest

• Loss of consciousness
• No breathing or gasping for breath
• Sudden collapse
• No pulse

If you see someone with these signs, do the following immediately:

• Call 911, or ask someone else to call 911 or get emergency medical help.
• Start CPR with deep chest pushes to the center of the chest. Do this at a rate of 100 to 120 pushes a minute to get blood pumping to the body and brain until an automated external defibrillator (AED) is available or until medical help arrives. According to the American Heart Association, you can do hands-only CPR until help arrives.
• Use an AED, if available, which has step-by-step instructions and voice prompts.

The sooner you can use an AED, the better. As a rule of thumb, after every one minute that passes following cardiac arrest, the likelihood of being able to successfully defibrillate someone — or shock their heart back to a normal rhythm — goes down by about 10%. Your job is to give CPR until that time.

While treating a person in cardiac arrest, you may notice jerking body motions, which can be misdiagnosed as a seizure. A person experiencing a seizure will typically have a pulse.

Common Causes and Risk Factors

The most common cause of a cardiac arrest is an "electrical storm" in which the heart develops an abnormal rhythm called ventricular fibrillation. When this happens, the heart's bottom chambers (right and left ventricles), which pump blood to the body, start to suddenly beat so fast that the heart is no longer contracting normally. This can happen to people with no history of heart disease. However, it's more common in people with a preexisting heart condition.

You are at higher risk for cardiac arrest if you have:

• Coronary artery disease. An estimated 80% of cardiac arrest incidents in adults are caused by coronary artery disease. The main risk factors for coronary artery disease apply to cardiac arrest, including:
• Smoking
• High blood pressure
• Diabetes
• Family history of coronary artery disease
• Excess body weight
• High cholesterol
• Sedentary lifestyle
• Heavy alcohol use
• Heart attack. A heart attack can lead to cardiac arrest right away. It can also lead to cardiac arrest if you previously had a heart attack that left scar tissue on your heart. This scar tissue can interrupt the normal electrical signals in the heart, causing a life-threatening heart rhythm problem known as arrhythmia.
• Hypertrophic cardiomyopathy
• Valvular heart disease
• Congenital heart disease
• Electrical problems in the heart where the muscle is normal and healthy, but the electrical system that triggers the heart to pump is malfunctioning

Early Warning Signs

Cardiac arrest is sudden and typically does not have any warning signs. However, if you have a preexisting heart condition, you may experience these symptoms before cardiac arrest:

• Chest pain
• Difficulty breathing
• Heart palpitations
• Fainting
• Intermittent dizziness

Call 911 or seek medical care if you have any of these symptoms.

What About Commotio Cordis?

Commotio cordis is a rare cause of cardiac arrest that happens when someone goes into ventricular fibrillation because of a sudden blow to the chest. During a narrow window of time, about 40 milliseconds, a forceful blow to the chest has to be delivered to cause ventricular fibrillation. The force to the chest can cause the heart to beat electrically before it is ready to beat.

Commotio cordis is most common in contact sports and sports with projectiles, like baseballs, hockey pucks or lacrosse balls. Commotio cordis also tends to happen in younger people because their chest wall is thinner, allowing the energy of impact to be delivered to the heart.

Preventive Screening

If you have a family history of premature cardiac arrest (prior to age 50), you should be evaluated by a physician. The first step is typically an electrocardiogram (EKG).

– Bradley P. Knight, MD, Northwestern Medicine Bluhm Cardiovascular Institute, Cardiac Electrophysiology