It is common to confuse a cardiac arrest with a heart attack, as both are medical emergencies affecting the heart. However, they are not the same thing. A heart attack involves an interruption in the blood supply to the heart. It may lead to cardiac arrest, which is when the heart stops pumping.

The American Heart Association (AHA) describes the difference between a heart attack and a cardiac arrest as a circulation issue compared with an electrical problem.

With a heart attack, a blocked artery prevents blood flow to the part of the heart that the artery serves. This causes that part of the heart to begin to die.

With a cardiac arrest, the heart has an electrical malfunction and stops beating suddenly.

This article explains the differences between a heart attack, cardiac arrest, and heart failure. It also discusses the symptoms of each and explains what to do in an emergency.

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A cardiac arrest happens suddenly, usually without warning, when the heart stops pumping blood around the body. A person can fall unconscious and die within minutes if they do not receive immediate treatment.

Many cardiac arrests occur because a person has had a heart attack, which causes an abnormal heart rhythm, known as arrhythmia.

A common cause of cardiac arrest is an arrhythmia called ventricular fibrillation (VFib). VFib happens when the heart’s electrical circuitry becomes chaotic. Instead of beating, the heart fibrillates, meaning that it quivers.

Symptoms of a cardiac arrest

In most cases, the first symptom of a cardiac arrest is loss of consciousness.

Sometimes, a person experiences warning signs of a cardiac arrest within the hour before the cardiac arrest.

Warning signs include:

  • racing heartbeat
  • lightheadedness or dizziness
  • chest pain
  • shortness of breath
  • nausea
  • vomiting

If someone has already had a cardiac arrest, they may be:

  • not breathing or breathing abnormally
  • making gasping sounds
  • unconscious
  • unresponsive

If a bystander tries to find a pulse, they will not be able to locate one.

Cardiac arrest: What to do in an emergency

Cardiac arrest is an emergency, and witnesses should take immediate action. If more than one person is available, one should begin cardiopulmonary resuscitation (CPR) while the other calls 911 and looks for an automated external defibrillator (AED).

AEDs are programmed to give an electric shock to the heart if they detect a dangerous heart rhythm, such as VFib. It is often possible to find an AED mounted on the exterior of prominent public buildings or inside buildings such as shopping malls, schools, hotels, and grocery stores.

Defibrillation with an AED must happen within seconds to minutes of a person having a cardiac arrest, as their chance of surviving decreases rapidly with time.

Learn how to perform CPR.

In the United States, someone has a heart attack every 40 seconds.

A heart attack happens when there is an interruption in the blood supply to the heart. This usually happens when a blood clot blocks one of the coronary arteries.

The heart still pumps blood around the body, but the part of the heart that usually receives blood from the blocked artery begins to die.

A heart attack can cause serious damage to the heart and be fatal.

The most common cause of heart attack is coronary artery disease (CAD), in which the artery walls become clogged with atheroma, a buildup of fatty deposits. If a piece of atheroma breaks off, a clot forms around it, which can block the blood flow.

Symptoms of a heart attack

Although the symptoms of a heart attack can appear suddenly, this is not always the case. Some people’s symptoms are mild and gradual, developing over days to weeks.

The symptoms can differ between the sexes and even among heart attacks in the same person.

However, typical symptoms of a heart attack include:

  • chest pain or discomfort
  • heavy or burning pain that spreads to one or both arms or the back, neck, jaw, or stomach
  • shortness of breath
  • lightheadedness
  • nausea
  • a rapid or irregular heartbeat
  • sweating

Some people may experience a silent heart attack, which is one that happens either without symptoms or with very mild symptoms. According to one estimate, silent heart attacks account for almost 50% of heart attacks.

Being older and having conditions that cause nerve damage, such as diabetes, can affect how a person experiences pain. As a result, a person may have a heart attack without feeling pain.

Learn how to spot and treat a heart attack.

Heart attack: What to do in an emergency

If a person thinks that they or the person they are with is having a heart attack, they should maximize the chance of a good outcome by:

  • calling 911 immediately
  • sitting down and staying calm
  • chewing and swallowing 325 milligrams of aspirin, if possible
  • waiting for the emergency medical services (EMS)

The AHA suggests calling an ambulance rather than going by car to the emergency room (ER), as EMS staff can begin treatment as soon as they reach the person. Individuals arriving at the ER by ambulance will, therefore, usually receive treatment sooner than those arriving by car. The quicker a person receives treatment, the better their outlook.

A person with heart failure has a weakened heart that cannot pump blood around the body properly. The heart can sustain damage during a heart attack or as a result of high blood pressure.

The symptoms of heart failure include:

  • shortness of breath
  • fatigue
  • swelling in the ankles and feet
  • bloating
  • exercise intolerance
  • shortness of breath when lying down

With the right medication and lifestyle changes, a person with heart failure can live a normal, active life.

Learn about congestive heart failure.

The most significant risk factor for cardiac arrest is having CAD, a history of heart attack, or heart failure. A person with CAD may have no symptoms before experiencing cardiac arrest or a heart attack. Sometimes, people have silent heart attacks before they experience cardiac arrest.

The following factors increase a person’s risk of cardiac arrest and heart attack:

  • Age: The risk increases with age.
  • Sex: The risk of cardiac arrest is higher for males.
  • Race: African American people have an increased risk of cardiac arrest. At particular risk are those with conditions such as diabetes, high blood pressure, chronic kidney disease, and heart failure.

Additional risk factors for cardiac arrest and heart attack include:

  • a personal or family medical history of cardiac arrest
  • a personal or family medical history of inherited disorders that may cause arrhythmias or cardiomyopathy
  • drug use disorder
  • alcohol use disorder
  • heart failure
  • tobacco smoking
  • high blood cholesterol
  • high blood pressure
  • physical inactivity
  • obesity
  • diabetes
  • stress
  • a nonnutritious diet
  • an electrolyte imbalance
  • kidney failure

Heart attack and cardiac arrest can lead to complications that range from mild to fatal.

Heart attack complications

If a person does not get treatment for a heart attack, it can cause cardiac arrest. People may also experience the following complications after a heart attack:

Cardiac arrest complications

If a person does not get immediate treatment following a cardiac arrest, it can lead to permanent brain and organ injury or disability. It can even be fatal. The risk increases the longer the delay in restoring a heart rhythm and blood flow.

During cardiac arrest, the brain can become starved of oxygen, leading to long-term effects that include:

  • personality changes
  • memory problems
  • fatigue
  • problems with speech and language
  • dizziness
  • balance issues
  • involuntary movements
  • permanent brain injury

People often have no memory of having a cardiac arrest.

People who survive a heart attack have a higher chance of experiencing another one. About 200,000 people each year have a subsequent heart attack.

With the right medication and lifestyle changes, people can reduce the likelihood of a subsequent heart attack.

The AHA notes that out of the 350,000 or so people who have a cardiac arrest outside of a hospital each year, fewer than 12% of people will survive and go home. CPR can double or triple the chances of survival.

Both heart attack and cardiac arrest are medical emergencies.

A heart attack happens when blood flow to the heart becomes blocked. A person will usually remain conscious during a heart attack unless it is very severe. It is essential to call 911 immediately so that a person can receive treatment. A heart attack can lead to cardiac arrest.

A cardiac arrest happens when the heart stops pumping blood without warning, causing a person to fall unconscious. It is vital to call 911 immediately, give the person CPR, and use an AED to deliver an electric shock to the heart.

A person can manage their risk factors for both events by adopting lifestyle changes and taking medication as a doctor has prescribed it.