Heart Attack vs Cardiac Arrest: What Is the Difference?

People often use the words heart attack and cardiac arrest as if they mean the same thing. They do not. Both are emergencies, but they happen in different ways and need different first steps. This article uses information from MedlinePlus and the NHS.

What is a heart attack?

A heart attack happens when blood flow to the heart is blocked, so the heart cannot get the oxygen it needs. MedlinePlus explains that, in a heart attack, the heart usually keeps beating. Without quick treatment, though, heart muscle begins to die.

What is sudden cardiac arrest?

Sudden cardiac arrest is when the heart suddenly stops beating. Blood then stops flowing to the brain and other vital organs. MedlinePlus says that without prompt treatment it usually causes death within minutes.

How are they linked?

The two can be connected. A heart attack can trigger cardiac arrest, and cardiac arrest can happen during or after recovery from a heart attack. But cardiac arrest can also happen without a heart attack.

What causes cardiac arrest?

MedlinePlus explains that cardiac arrest is caused by an electrical problem that makes the heartbeat irregular. Most often this is a rhythm called ventricular fibrillation, in which the lower chambers of the heart beat very fast and irregularly and cannot pump blood.

Other things that can play a part include:

• Coronary artery disease
• Physical stress, such as intense exertion, very low potassium or magnesium, major blood loss or a severe lack of oxygen
• Certain inherited conditions
• Changes in the structure of the heart, such as an enlarged heart from high blood pressure or advanced heart disease
• Heart infections

What does each look like?

Heart attack: chest pain or discomfort, pain in the arms, back, neck or jaw, shortness of breath, feeling sick, sweating and light-headedness. The person is usually awake and able to respond.

Cardiac arrest: MedlinePlus says the usual first sign is fainting, meaning loss of consciousness. Some people have a racing heartbeat, dizziness or light-headedness just before they faint. Some have chest pain, breathlessness or nausea in the hour before.

What to do in each emergency

For a suspected heart attack, call emergency services at once. The NHS says not to drive yourself to hospital, and advises resting in a comfortable position while you wait.

For suspected cardiac arrest, MedlinePlus advises to:

1. Call emergency services right away.
2. Start CPR (cardiopulmonary resuscitation) immediately and keep going until a defibrillator is ready.
3. If you have not been trained in CPR, do hands-only CPR by pushing hard and fast on the centre of the chest.
4. Use an automated external defibrillator (AED) if one is nearby. They can be used by people with no training, give voice instructions and deliver a shock only if a dangerous rhythm is detected.

MedlinePlus explains that CPR keeps blood moving to the brain and organs until the heart rhythm can be restored, and a defibrillator must be used within minutes to work.

After a cardiac arrest

People who survive are usually treated in hospital. MedlinePlus says treatment targets the underlying cause, for example with angioplasty or bypass surgery for coronary artery disease, and an implantable cardioverter defibrillator (ICD) is often recommended to help control dangerous rhythms. Doctors decide what each person needs.

When to see a doctor

If you have had fainting, a racing heartbeat, chest pain or breathlessness, see a doctor promptly, even if it passed. Call emergency services at once if someone collapses and is not responding normally, has chest pain with sweating or breathlessness, or has pain spreading to the arms, neck or jaw.

In an emergency, call your local emergency number (112 in India, 911 in the United States).