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ACS encompasses signs and symptoms that typically indicate a person is having a cardiac event, such as a heart attack. There are three main types of ACS.

  • STEMI (ST-elevation myocardial infarction): This is a heart attack caused by a sudden and prolonged blockage of blood supply to the heart. A large area of the heart is affected, so in an electrocardiogram (ECG), a segment is elevated compared to normal. The blood levels of key chemical markers in the body are also elevated.
  • Non-STEMI: This is a heart attack where the blockage of blood supply to the heart may be partial or temporary, so the damage to the heart is relatively small. It may not cause changes on an ECG, but key chemical markers in the blood will be elevated.
  • Unstable angina: Angina is a type of pain or discomfort in the chest that is a symptom of an underlying problem with the heart. Unstable angina is a change from stable angina – the angina may occur more frequently or easily, feel more severe, or last longer. It is treated as seriously as a confirmed heart attack.

The most common cause of ACS is development of a clot in a coronary artery that blocks the supply of blood to the heart.

ACS is respon­si­ble for over 83,000 admis­sions to hos­pi­tals in the UK every year.

The symptoms

Symptoms of ACS include:

  • Pain, pressure or an aching sensation in the chest or arms that can spread to the neck, jaw or back
  • Shortness of breath
  • Nausea, indigestion, heartburn or abdominal pain
  • Lightheadedness or sudden dizziness
  • Fatigue
  • Cold sweat.

If you experience these symptoms, immediately call emergency services. If a heart attack is occurring, it is vital to get treatment as soon as possible to restore blood flow to the heart and prevent further damage to the heart.

The risk

People are more likely to experience ACS if they have certain risk factors. While some of these can’t be changed, such as a family history of heart disease or stroke, the following can:

Visit the risk factors page for more information.

What is HRI doing?

HRI is conducting innovative research to develop new therapies for detecting, preventing and treating ACS.

Our Thrombosis Group is undertaking research to understand how blood clot formation occurs in healthy individuals. This research is crucial for developing safer and more effective therapies for heart attacks, amongst other cardiovascular diseases.


Every donation to the Heart Research Institute is an investment into the lives of millions.

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