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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 is not getting enough blood.

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 unstable angina or a 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 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 needs to be treated right away.

What causes it?

Acute coronary syndrome happens because blood flow has slowed or stopped in the arteries that supply blood to the heart muscle. It's most often caused by coronary artery disease (sometimes called heart disease).

Coronary artery disease is caused by atherosclerosis (sometimes called hardening of the arteries).

With atherosclerosis, a substance called plaque builds up in the coronary arteries. Plaque leads to angina by making the arteries more narrow. This narrowing limits blood flow to the heart muscle. A heart attack happens when blood flow is completely blocked.

What are the symptoms?

Symptoms of acute coronary syndrome include:

  • Chest pain or pressure, or a strange feeling in the chest.
  • Sweating.
  • Shortness of breath.
  • 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.
  • Light-headedness or sudden weakness.
  • A fast or irregular heartbeat.

For men and women, the most common symptom is chest pain or pressure. But women are somewhat more likely than men to have other symptoms like shortness of breath, tiredness, nausea, and back or jaw pain.

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 and they're not using much energy or feeling stressed.

How is it diagnosed?

A doctor will do a physical examination and ask about your symptoms and past health. The doctor will ask about your family's health. You'll have tests to find what is causing your symptoms.

An electrocardiogram can help show whether you have angina or have had a heart attack. This test measures the electrical signals that control your heart's rhythm.

A blood test will look for a rise in cardiac proteins. The heart releases these substances when it's damaged.

You may have imaging tests that show how well your heart is working and how well blood is flowing to the heart muscle. Examples include a CT angiogram, an echocardiogram, and an MRI. A coronary angiogram may be done to check blood flow from inside the coronary arteries.

How is acute coronary syndrome treated?

If you call 9-1-1, treatment will start in the ambulance. You may be given aspirin and other medicines.

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

  • Medicines to break up and prevent blood clots.
  • Nitroglycerin and other medicines that make your arteries wider. This helps improve blood flow and relieve symptoms, such as chest pain or pressure.
  • Pain medicine.
  • Oxygen.

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.

When you get out of the hospital, you will keep taking medicines that lower your risk for a heart attack. These may include:

  • Beta-blockers.
  • Aspirin or other medicines to prevent blood clots.
  • Blood pressure medicine.
  • Cholesterol medicine.

A heart-healthy lifestyle also helps lower your chance of a heart attack. This lifestyle includes taking steps to quit smoking, eat heart-healthy foods, get regular exercise, and stay at a healthy weight. Manage other health problems such as diabetes, high cholesterol, and high blood pressure. Also, if you think you may have a problem with alcohol or drug use, talk with your doctor.

Talk to your doctor about trying a cardiac rehab program. Ask your doctor if it is right for you. In cardiac rehab, you get education and support that help you make new, healthy habits. For example, it can help you find ways to eat a healthy diet and get more exercise.

How can you prevent it?

A heart-healthy lifestyle and medicine can help prevent acute coronary syndrome. This includes being active, staying at a healthy weight, not smoking, and eating heart-healthy foods. Managing other health problems, such as diabetes, high blood pressure, and high cholesterol, can also help.


Current as of: September 7, 2022

Author: Healthwise Staff
Medical Review:
Rakesh K. Pai MD, FACC - Cardiology, Electrophysiology
E. Gregory Thompson MD - Internal Medicine
Martin J. Gabica MD - Family Medicine
Adam Husney MD - Family Medicine
Kathleen Romito MD - Family Medicine
George Philippides MD - Cardiology