Acute Coronary Syndrome

(ACS; Unstable Angina)



Acute coronary syndrome (ACS) is a set of features related to poor blood flow to the heart muscle that leads to a heart attack. This results in chest pain or angina pectoris. ACS is a serious, life-threatening condition. If you think you have ACS, seek emergency medical treatment.



ACS is caused by a sudden blockage of the coronary arteries. These blood vessels carry blood to the heart muscle. The blood flow to the heart muscle is either greatly reduced or completely blocked. This leads to heart muscle damage or death from a heart attack.

The narrowing most often happens from years of plaque build-up in an artery. This is called atherosclerosis. Blood clots may often cause of the narrowing arteries.

Coronary Artery

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Risk Factors

Risk Factors

ACS is more common in men over 45 and women over 55 years old.

Factors that increase your risk of developing ACS include:

  • A family history of heart disease
  • Being overweight or obese
  • Smoking
  • High cholesterol, especially high LDL (“bad”) cholesterol, high triglycerides, and low HDL (“good”) cholesterol
  • High blood pressure
  • Diabetes
  • Inactivity
  • Having angina, a previous heart attack, or other types of coronary artery disease



ACS is serious. It requires emergency medical treatment. Contact your doctor if you have any of these symptoms:

  • Chest pain, pressure, tightness, burning, or other discomfort that may last a few minutes, go away, and then come back
  • Pain that lasts 30 minutes or longer
  • Pain that occurs after physical exertion, emotional stress, or eating a large meal
  • Pain that occurs at rest, while sleeping, or with little exertion
  • Pain or discomfort in one or both arms, shoulders, the back, the neck, jaw, or stomach
  • Shortness of breath combined with chest pain
  • Lightheadedness
  • Nausea and vomiting
  • Sweating



You will be asked about your symptoms and medical history. A physical exam will be done. If you suspect ACS, call for emergency medical services.

Your bodily fluids may need to be tested. This can be done with blood tests.

Your heart function may need to be tested. This can be done with:

Detailed images of your heart may need to be taken. These can be done with:



If you are having a heart attack, doctors will:

  • Work quickly to restore blood flow to the heart
  • Closely monitor vital signs to detect and treat complications

To restore blood flow, the main treatments are:

  • Aspirin is given to all patients suspected of having ACS.
  • Anti-ischemic drugs, such as nitroglycerin are used to help relieve chest pain.
  • Beta blockers are given to slow the heart rate so it does not use too much energy.
  • Thrombolytic drugs are used to dissolve blood clots. When given soon after a heart attack begins, these drugs can limit or prevent permanent damage to the heart. To be most effective, they need to be given within one hour after the start of heart attack symptoms.
  • Platelet inhibitors to keep the blockage from getting worse.
  • Angioplasty—a catheter is inserted into a blocked artery. A balloon is inflated and deflated. This will allow blood to flow again. A stent may be placed to prop the artery open.
  • Coronary artery bypass surgery—arteries or veins are taken from other areas in your body. They are used to bypass the blocked arteries in your heart.
  • Oxygen is given to all patients. Hyperbaric oxygen therapy may be used.



To help reduce your chances of getting ACS:

  • Eat a well-balanced diet that is low in saturated fats. The diet should also be rich in fruits, vegetables, and whole grains.
  • Exercise regularly.
  • If you smoke, talk to your doctor about ways to quit.
  • Manage your diabetes, blood pressure, and cholesterol. This can include lifestyle changes and medication.


American College of Cardiology

American Heart Association


Canadian Cardiovascular Society

Heart and Stroke Foundation of Canada


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Last reviewed August 2015 by Michael J. Fucci, DO
Last Updated: 8/17/2015

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