Cardiac Arrest vs. Heart Attack: What’s the difference?

We often use the terms “heart attack” and “cardiac arrest” interchangeably. However, these are 2 different conditions. While they are at times interlinked, they differ in cause and progression.

What is a cardiac arrest?

It is estimated that around 1000 Singaporeans die from cardiac arrest each year. It is known as an “electrical” problem — a sudden condition that occurs as a result of an electrical malfunction in the heart.

Our heartbeat starts with an electrical signal that commands the heart muscles to contract and pump blood to the heart itself and also the rest of our body in a coordinated fashion. When an abnormal electrical signal is produced, it causes an irregular heartbeat, clinically referred to as arrhythmia. When this happens, the normal pumping action of the heart is disrupted or even completely stopped. Consequently, this leads to a lack of blood flow to the brain, lungs, and other organs, which may cause immediate death. A fatal arrhythmia causing cardiac arrest is ventricular fibrillation; when not treated immediately the heart will stop.

diagram of healthy heart and heart with CAD

What is a heart attack?

Conversely, a heart attack is known as a “circulation” problem that progresses over time. A heart attack happens when parts of the heart are damaged due to a lack of blood flow.

The lack of blood flow is caused when the arteries supplying blood to your heart are blocked or narrowed. This is often caused by a buildup of fat and cholesterol, referred to as plaque. When a part of your heart muscle does not receive enough blood, that part starts to die. The longer it is left untreated, the more extensive the damage will be.

Heart attacks occur more frequently than sudden cardiac arrest. In fact, in 2018, there were 3.5 heart attacks per 1000 population in Singapore.

How are they linked?

Sudden cardiac arrest may happen during a heart attack or during recovery from a heart attack. Even if a cardiac arrest does not occur immediately, a heart attack increases the risk of sudden cardiac arrest.

Most heart attacks do not lead to cardiac arrest. But when a sudden cardiac arrest occurs, a heart attack is a common cause. Other causes include:

Why do I need to know the difference?

Understanding the differences will help you discern the best way to help someone who is experiencing a cardiac arrest or a heart attack. What is important for these conditions is that every single second matters. If you suspect someone experiencing either condition, immediately call 995.

So, how can I tell the difference between a heart attack and cardiac arrest?

Both these conditions may present similarly and as such your first response should be calling 995 to ensure that the person will get emergency medical help as soon as possible.

A cardiac arrest victim may turn unresponsive and stop breathing (or appear to be gasping for air) within a few seconds. This can happen suddenly and without prior warning signs or symptoms. Other signs include:

  • Loss of consciousness
  • The appearance of a seizure with the jerking of limbs
  • Rolling-up of the eyes

In contrast, a heart attack victim may have some warning symptoms. In the majority of cases, the symptoms may appear and build up over a few minutes to hours; some may even have warning symptoms days or weeks before the actual attack. These symptoms include:

  • Chest pain
  • Pain or intense discomfort around the upper body
  • Shortness of breath
  • Choking sensation
  • Nausea/vomiting
  • Heartburn/indigestion
  • Cold sweats
  • Feeling weak/lethargic
  • Palpitations
  • Giddiness
  • Back or jaw pain

Reacting to a cardiac arrest

A cardiac arrest is reversible, especially if it is treated within a few minutes. After calling 995, start CPR immediately. Most buildings in Singapore should also have an Automated External Defibrillator (AED), usually near the lift lobbies. You can also use the myResponder App to find the nearest AED. Use the AED as soon as possible while continuing to perform CPR until the ambulance arrives.

If not attended to promptly, within minutes, a cardiac arrest could quickly result in brain damage or even death.

Reacting to a heart attack

In the case of a heart attack, immediately call 995 to get an ambulance as soon as possible. Whenever possible, communicate the exact location so that medical help can be rendered immediately and during the journey to the hospital. Heart attack patients need emergency lifesaving treatment at the hospital as soon as possible.

If the patient develops a cardiac arrest, then start CPR immediately and get someone to fetch an AED while continuing to perform CPR until the ambulance arrives.


Recognising the signs and differences between cardiac arrest and a heart attack are a matter of life and death. Fast action is vital as every minute of delay in CPR and/or defibrillation via AED leads to a 7-10% decrease in survival.

As a guide, this is how you should respond:

  • Sudden unconsciousness 🡪 most likely a cardiac arrest
    • Call 995
    • Start CPR immediately
    • Attract attention and get someone to find an AED as soon as possible
  • Conscious with symptoms 🡪 most likely a heart attack
    • Call 995
    • Stay with patient until emergency help arrives

Remember, fast action saves lives.

How can we help you?

We offer consultation for a comprehensive range of cardiac diagnostic tests and treatment plans.

Dr Joshua Loh

Senior Consultant Interventional Cardiologist

Medical Director at Capital Heart Centre, Dr Joshua Loh has more than 15 years of experience in the field of cardiology.

He is experienced in the treatment of complex coronary and interventional procedures.



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