Heart attack

A heart attack occurs when there is a sudden loss of blood flow to part of the heart muscle.

Known medically as a myocardial infarction (MI), a heart attack is a medical emergency. If not treated promptly, it can cause serious heart muscle damage.

Heart attacks are most often caused by blood clots forming on plaque inside the coronary arteries, a condition known as coronary artery disease.

Common types of heart attacks often result from blockages in the coronary arteries, but they mainly differ in the severity of the blockage and the extent of heart damage.

There are two common types of heart attacks that are caused from blockages in the coronary arteries - STEMI and NSTEMI. Both are medical emergencies.

• STEMI (full blockage): A critical, life-threatening emergency where an artery is blocked by a sudden clot. Blood flow stops completely, risking fast, permanent muscle damage.
• NSTEMI (partial blockage): A serious medical emergency where an artery is partially blocked, severely reducing blood flow. It still causes muscle damage and requires urgent care.

Increasingly, doctors are moving away from classifying a heart attack as STEMI or NSTEMI, towards the terms ACOMI and NOMI (to reflect the 2025 Australian clinical guideline for diagnosing and managing acute coronary syndromes.)

• ACOMI (Acute Coronary Occlusion Myocardial Infarction): When a coronary artery becomes suddenly and completely blocked, stopping blood flow to part of the heart. This requires urgent treatment to reopen the artery as quickly as possible.
• NOMI (Non-Occlusion Myocardial Infarction): When there is a heart attack without a sudden complete artery blockage, but the heart muscle is still not getting enough blood or oxygen and becomes damaged. This still requires urgent treatment, but the cause and management may differ.

When you arrive at the hospital, doctors will quickly test to determine whether you are having a heart attack and need immediate treatment.

There are two types of tests that you will likely undergo:

• Electrocardiogram (ECG): This records your heart’s electrical activity and checks for signs that a coronary artery may be suddenly blocked.
• Troponin Test: A troponin blood test is used to diagnose heart attacks by measuring levels of a specific protein released when the heart muscle is damaged.

Your symptoms, ECG results, troponin blood tests, and clinical information are all used to decide the best treatment.

• Chest discomfort
  Most people having a heart attack feel discomfort in the centre of the chest. It can last more than a few minutes, or it may go away and then return. It can feel like uncomfortable pressure, squeezing, fullness or pain.
• Discomfort in other areas of the upper body
  Symptoms can include pain or discomfort in the:
  • Arms (one or both)
  • Back
  • Neck
  • Jaw
  • Stomach
• Shortness of breath
  This can happen with or without chest discomfort.
• Other signs
  Other possible signs include:
  • Breaking out in a cold sweat
  • Nausea
  • Rapid or irregular heartbeat
  • Feeling unusually tired
  • Feeling lightheaded

The pain can come and go or last a long time, usually more than 20 minutes and does not change with movement or body position.

Don’t wait to get help if you have any heart attack warning signs. Some heart attacks are sudden and intense. Others start slowly with mild pain or discomfort. Pay attention to your body and call 111 if you have any symptoms of heart attack.

Women may experience any of the heart attack warning signs above, but their heart attack signs can also be slightly different to men’s. 

Chest pain or discomfort is the most common sign of a heart attack, but women are more likely than men to experience a heart attack without chest pain or discomfort.

If women do have tightness, pressure or discomfort in the chest, this may not always be severe or even the most noticeable symptom. Any pain or discomfort may come and go and can extend to the abdomen or upper back. 

If you think you are having a heart attack, call 111.