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Acute Coronary Syndrome

Conditions Basics

What is acute coronary syndrome?

Acute coronary syndrome is an emergency. It happens when the heart muscle is not getting enough blood and oxygen.

Acute coronary syndrome includes unstable angina and heart attack.

  • Unstable angina happens when blood flow to the heart is suddenly slowed by narrowed coronary arteries. Or small blood clots can form in these arteries and slow blood flow. There may be no damage to the heart muscle.
  • A heart attack occurs when part of the heart muscle does not get enough blood and oxygen. This part of the heart starts to die. This most often happens because blood flow through one or more of the coronary arteries is blocked.

Any type of acute coronary syndrome needs to be treated right away.

What causes it?

Acute coronary syndrome happens when not enough blood and oxygen reach part of the heart muscle. This most often happens because blood flow in one or more of the coronary arteries is suddenly slowed or blocked.

This slowing or blockage is most often the result of coronary artery disease. In this disease, fatty deposits called plaque (say "plak") build up inside the coronary arteries. If the plaque breaks open, the body tries to repair the artery. A blood clot may form and slow or block blood flow.

There are other less common causes. These can include a blocked stent or a sudden tear or spasm in the artery. Sometimes acute coronary syndrome is caused by heart surgery.

What are the symptoms?

Symptoms of acute coronary syndrome include:

  • Chest pain or pressure, or a strange feeling in the chest.
  • Shortness of breath.
  • Sweating.
  • Nausea or vomiting.
  • Pain, pressure, or a strange feeling in the back, neck, jaw, or upper belly or in one or both shoulders or arms.
  • Lightheadedness, sudden weakness, or passing out.
  • A fast or irregular heartbeat.

The most common symptom is chest pain or pressure. But many people have other symptoms like shortness of breath, tiredness, nausea, and back or jaw pain. People may have more than one symptom.

People also describe the symptoms as discomfort, pressure, squeezing, or heaviness in the chest. The pain may spread down the left shoulder and arm and to other areas.

People with unstable angina often describe their symptoms as different from their typical pattern of stable angina. For example, symptoms might happen when they're at rest, feeling stressed, or not using much energy.

How is it diagnosed?

A doctor will take your history, do a physical exam, and check your heart rate, blood pressure, and breathing rate. You will have tests that can help diagnose a heart attack. The tests include:

  • Electrocardiogram (EKG, ECG). This test measures the electrical signals of the heart. It helps show whether you are having a heart attack.
  • Troponin test. This is a blood test that looks for a rise in cardiac proteins. The heart muscle releases these proteins when it is damaged.
  • Imaging tests. These tests provide images that show how well the heart is working and how well blood is flowing to the heart muscle. Examples include a CT angiogram, an echocardiogram, and an MRI.
  • Coronary angiogram. This test can check blood flow in the coronary arteries.

How is acute coronary syndrome treated?

If you call 911, treatment will start in the ambulance. You may be given aspirin, oxygen, and pain medicine.

In the hospital, the doctor will work right away to return blood flow to your heart. You may be given:

  • Medicine for blood clots. Some medicine prevents blood clots from getting bigger so blood can flow to the heart. Other medicines break up blood clots to increase blood flow.
  • Nitroglycerin. It opens up the arteries of the heart to help blood flow back to the heart.

You may be given other medicine, such as a beta-blocker.

Your test results will help your doctor decide about more treatment. You might have angioplasty or bypass surgery to improve blood flow to your heart.

Your doctors will start you on medicines that lower your risk of having acute coronary syndrome again. Or you may get medicines that lower your risk of having other problems and that help you live longer. They include medicine to:

  • Lower blood pressure.
  • Lower cholesterol.
  • Lower the heart's workload.
  • Prevent blood clots from forming and causing a heart attack.

Cardiac rehabilitation (rehab) might be started in the hospital or soon after you go home. It can help you have a heart-healthy lifestyle which can lead to a stronger heart and better health. Cardiac rehab can help you feel better and reduce your risk for future heart problems. If cardiac rehab has not already been offered to you, ask your doctor if it's right for you.

How can you prevent it?

You can help prevent acute coronary syndrome by taking medicine and having a heart-healthy lifestyle. This lifestyle includes being active, eating healthy, and not smoking. You can manage other health problems, including diabetes, high blood pressure, and high cholesterol. If you think you may have a problem with drug use, talk to your doctor.


Current as of: June 24, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

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