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Heart Disease Health Center

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Acute Coronary Syndrome - Topic Overview

What is acute coronary syndrome?

Acute coronary syndrome happens when the heart is not getting enough blood. It is an emergency. It includes unstable angina and heart attack.

The coronary arteries supply oxygen-rich blood to the heart muscle. If these arteries are narrowed or blocked, the heart does not get enough oxygen. This can cause angina or a heart attack.

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  • Unstable angina happens when blood flow to the heart is suddenly slowed by narrowed coronary arteries. Or small blood clots form in the coronary arteries and slow blood flow. Typically, there is no damage to the heart muscle. It often happens when you are at rest. You may have had stable angina before. You knew when to expect your symptoms, such as when you exercised. Stable angina usually goes away when you rest or take your angina medicine. But the symptoms of unstable angina may not go away with rest or medicine. It may get worse or happen at times that it didn't before. Unstable angina is not a heart attack. But it is a warning that a heart attack could happen soon, so it needs to be treated right away.
  • A heart attack means a coronary artery has been blocked and the heart has been damaged. Without blood flow and oxygen, part of the heart starts to die.

Any type of acute coronary syndrome is very serious and needs to be treated right away.

What causes acute coronary syndrome?

Acute coronary syndrome happens because blood flow has slowed or stopped in the arteries that supply blood to the heart. Acute coronary syndrome is typically caused by coronary artery disease. Coronary artery disease, also called heart disease, is caused by atherosclerosis, or hardening of the arteries.

Atherosclerosis causes a substance called plaque to build up in the coronary arteries. Plaque causes angina by narrowing the arteries. The narrowing limits blood flow to the heart muscle. A heart attack happens when blood flow is completely blocked.

What are the symptoms?

Call 911 or other emergency services immediately if you have symptoms of acute coronary syndrome. These may include:

After you call 911, the operator may tell you to chew 1 adult-strength or 2 to 4 low-dose aspirin. Wait for an ambulance. Do not try to drive yourself.

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