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Acute coronary syndrome (ACS for short) is a general term. Doctors use it to refer to three serious heart problems that can happen when your heart can't get enough oxygen:

• Unstable angina
• A type of heart attack called ST segment elevation myocardial infarction (STEMI for short)
• A type of heart attack called non-ST segment elevation myocardial infarction (non-STEMI for short).

The names STEMI and non-STEMI are based on the changes that doctors see on a test called an electrocardiogram (ECG). They use this test to diagnose these conditions. See Electrocardiogram.

The main symptom of all three conditions is chest pain or discomfort. The big difference between them is that heart attacks can damage your heart, while unstable angina does not. That's why it's important to stop unstable angina from turning into a heart attack.¹

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.