In everyday conversation, heart attack and cardiac arrest are often used as if they mean the same thing. Medically, they are two different life-threatening emergencies, and the difference changes what you do first.

A heart attack is a circulation problem. Cardiac arrest is an electrical problem.

Heart Attack: A Circulation Crisis

A heart attack, or myocardial infarction, occurs when blood flow to part of the heart muscle becomes blocked. If the blocked artery is not reopened quickly, that portion of heart muscle begins to suffer from lack of oxygen.

During a heart attack, the heart usually does not stop beating immediately. The person is often awake, breathing, and able to speak, though they may be frightened or in severe discomfort.

Common Heart Attack Signs

• Pressure, squeezing, heaviness, fullness, or pain in the center of the chest.
• Pain spreading to the jaw, neck, back, shoulder, or arms.
• Shortness of breath, cold sweat, nausea, unusual fatigue, or lightheadedness.
• Symptoms that come and go or feel different from typical indigestion or muscle pain.

Cardiac Arrest: An Electrical Malfunction

Cardiac arrest happens when an electrical malfunction causes the heart to stop pumping effectively. Blood flow to the brain and vital organs stops almost immediately.

The person usually collapses, becomes unresponsive, and is not breathing normally. This is when immediate CPR and an AED can be lifesaving.

Comparing the Two Emergencies

What Is Happening?

• Heart attack: Blood flow is blocked to part of the heart muscle.
• Cardiac arrest: Electrical failure causes effective pumping to stop.

Is the Person Conscious?

• Heart attack: Usually conscious and breathing, though distressed.
• Cardiac arrest: Unresponsive, collapsed, and not breathing normally.

First-Aid Action

• Heart attack: Call emergency services, keep the person resting, and follow dispatcher instructions.
• Cardiac arrest: Call emergency services, start CPR immediately, and use an AED as soon as one is available.

Why the Difference Matters

A person having a heart attack can deteriorate into cardiac arrest, so fast medical care still matters. But when someone is unresponsive and not breathing normally, the priority changes to CPR and defibrillation.

This comparison is for education and emergency recognition. During an active crisis, follow your local dispatcher and emergency medical team.