What is the difference between a sudden cardiac arrest (SCA) and heart attack?


The terms sudden cardiac arrest (SCA) and heart attack are often used interchangeably, but they’re actually two very different medical conditions. While a sudden cardiac arrest refers to the heart malfunctioning, a heart attack is a serious medical emergency in which the supply of blood to the heart is suddenly blocked, usually by a blood clot. To help distinguish between the two conditions, we’re explaining the difference between a sudden cardiac arrest and a heart attack.

What is a sudden cardiac arrest (SCA)?

A sudden cardiac arrest is when the heart suddenly stops beating, usually due to an issue with the electrical signals in your heart. When your heart stops beating, it will no longer be pumping blood around your body. This will lead to your brain being starved of oxygen, and if untreated it will be fatal.

The signs:
There are often no symptoms prior to a sudden cardiac arrest. If someone collapses suddenly and is in sudden cardiac arrest they will be:

  • Unresponsive
  • Not breathing or not breathing normally

The treatment:
If you think someone is in sudden cardiac arrest, call 999 immediately and start giving CPR. If there is someone else with you, send them to find a defibrillator. The patient will have a 70% chance of survival if defibrillation happens within three minutes of a sudden cardiac arrest. However, with every minute that passes, their chance of survival will decrease by 10%.1

Not sure how a defibrillator works? Find out more by reading our guide on how to use a defibrillator.

What is a heart attack?

What is a heart attack?
A heart attack, otherwise known as a myocardial infarction, is when the supply of blood to the heart suddenly stops, usually caused by a clot blocking the blood flow. A sustained lack of blood flow to the heart can seriously damage the organ and can cause a sudden cardiac arrest.

The signs:
There are a number of symptoms which an individual may experience if they’re suffering from a heart attack. These include:

  • Chest pain (this can feel like the chest is being squeezed or pressed by a heavy object, and can radiate to other areas of the body)
  • Shortness of breath
  • Feeling weak or lightheaded
  • Feeling very anxious

It is usually a combination of the above symptoms which indicate a heart attack.

The treatment:
If you think someone is suffering from a heart attack, call 999 immediately. If the patient is conscious, give them a 300mg tablet of aspirin to thin the blood and prevent further clots from developing. Check the patient isn’t allergic before administering.

Sudden cardiac arrest vs heart attack

Despite a sudden cardiac arrest and a heart attack being two different conditions, there is a link between them. Sudden cardiac arrest can occur after a heart attack or even during the recovery. Although most heart attacks don’t lead to a sudden cardiac arrest, they do increase a person’s risk of having one.

Both a sudden cardiac arrest and a heart attack are medical emergencies and immediate action needs to be taken if you see the signs of either. If you’d like to increase the chances of your colleagues or pupils surviving a sudden cardiac arrest, get in touch today to discuss getting a defibrillator for your school or workplace.

Learn more about sudden cardiac arrest and defibrillators in our Education hub

1 European Resuscitation Council Guidelines for Resuscitation (2015); Section 1. Executive Summary (1-80)

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