Acute Coronary Syndrome
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Acute Coronary Syndrome

(Heart Attack; Unstable Angina)

En Español (Spanish Version)


Acute coronary syndrome is a term given to a group of symptoms associated with chest pain at rest or during mild exertion. It also refers to certain types of heart attack known as unstable angina , a very serious condition that indicates a heart attack could soon occur.

Acute coronary syndrome is a potentially life-threatening condition and requires immediate medical treatment.


Coronary Artery

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Acute coronary syndrome is caused by a narrowing of the arteries, blood vessels that carry blood to the heart muscle. The blood flow to the heart muscle is either greatly reduced or completely blocked, leading to muscle damage or death.

While blood clots can sometimes cause the narrowing of the arteries, it typically happens from years of plaque build-up in an artery and is called atherosclerosis .

Risk Factors

The following factors increase your chances of developing acute coronary syndrome. If you have any of these risk factors, tell your doctor:

  • A family history of heart disease
  • You are a man over 45 years old or a woman over 55 years old
  • Being overweight or obese
  • Smoking
  • High cholesterol, especially high LDL ("bad") cholesterol and low HDL (“good”) cholesterol
  • High blood pressure
  • Diabetes
  • Being sedentary
  • Having angina, a previous heart attack, or other types of coronary artery disease


Acute coronary syndrome is very serious and requires immediate medical treatment. If you experience any of these symptoms, contact your physician.

  • Angina—chest pain, pressure, tightness, burning, or other discomfort that may last a few minutes, go away, and then come back. It usually occurs after physical exertion, emotional stress or eating a large meal.
  • Unstable angina often occurs at rest, while sleeping, or with very little exertion, and typically lasts as long as 30 minutes.
  • Pain or discomfort in one or both arms, shoulders, the back, the neck, jaw, or stomach.
  • Shortness of breath that accompanies chest pain or may occur just before it.
  • Feeling light-headed or dizzy.
  • Nausea and vomiting may occur.
  • Sweating commonly occurs.


Your doctor will ask about your symptoms and medical history, and perform a physical exam. If you suspect acute coronary syndrome, call an ambulance. At the hospital, tests may include the following:

  • Electrocardiogram (ECG or EKG)—measures the rate and regularity of your heartbeat. A 12-lead EKG is used in diagnosing a heart attack. Acute coronary syndrome is used to describe two types of heart attack:
    • Non-ST segment elevation myocardial infarction (NSTEMI)—caused by partial or temporary blockage, does not cause changes on an electrocardiogram.
    • ST segment elevation myocardial infarction (STEMI)—caused by a prolonged period of blocked blood supply, and does cause changes on an electrocardiogram.
  • Blood tests to measure different enzymes that are released when cells in the heart die. The specific tests include:
    • Troponin test—considered the most accurate test to determine if a heart attack has occurred and how much acute (new) damage was done to the heart.
    • CK or CK-MB test—measures the amount of the different kinds of creatine kinase in the blood.
    • Myoglobin test—checks for the presence of myoglobin in the blood, which is released when the heart or other muscle is injured.
  • Nuclear heart scan—uses radioactive tracers to outline heart chambers and major blood vessels leading to and from the heart. It can show any damage to your heart muscle.
  • Cardiac catheterization —a thin, flexible tube (catheter) is passed through an artery in the groin or arm to reach the coronary arteries. This can determine pressure and blood flow in the heart's chambers, collect blood samples from the heart, and examine the arteries of the heart by x-ray.
  • Coronary angiography —a test usually performed along with cardiac catheterization. A dye that can be seen using x-ray is injected through the catheter into the coronary arteries. Your doctor can see the flow of blood through the heart and see where there are blockages.
  • Echocardiogram —a test that uses sound waves to create a moving picture of your heart. Echocardiogram provides information about the size and shape of your heart and how well your heart chambers and valves are functioning. The test, used to diagnose angina, also can identify areas of poor blood flow to the heart, areas of heart muscle that are not contracting normally, and previous injury to the heart muscle caused by poor blood flow.
  • Chest x-ray —assesses heart size and lung congestion and identifies the presence of pneumonia.


If you are having a heart attack, doctors will work quickly to restore blood flow to the heart and 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 acute coronary syndrome.
  • Anti-ischemic drugs, such as nitroglycerin, are used to help relieve chest pain.
  • Thrombolytic (or “clot-busting”) drugs used to dissolve blood clots blocking blood flow to the heart. 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. Some thrombolytic drugs are:
    • Eptifibatide
    • Tirofiban
    • Glycoprotein IIb/IIIa receptor antagonist
  • Angioplasty —a catheter is inserted into a blocked artery, then a balloon is inflated and deflated to allow blood flow; a stent may be placed
  • Coronary artery bypass surgery —arteries or veins from other areas in your body to bypass your blocked coronary arteries.
  • Oxygen is given to all patients.

Based on a 2008 review, treating ACS with angiography and revascularization (restoring blood flow to the heart) may reduce the rate of being hospitalized again. But the surgery did not reduce the rate of death or heart attack.


To help reduce your chances of getting acute coronary syndrome, take the same heart-healthy lifestyle steps to prevent other forms of coronary artery disease. These include:

  • Eating a well-balanced diet, that is low in saturated fats and rich in fruits, vegetables, and whole grains.
  • Exercising regularly.
  • If you smoke, quit.
  • Managing diabetes, blood pressure , and cholesterol (with medications, if necessary).


American College of Cardiology

American Heart Association


Canadian Cardiovascular Society

Heart and Stroke Foundation of Canada


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Alexander KP, Newby LK, Cannon CP et al: Acute Coronary Care in the Elderly, Part I. Circ . 2007;115:2549-69

Cohen M, Diez JE< Levine GN et al: Pharmacoiinvasive management of acute coronary syndrome: incorporating the 2007 ACC/AHA guidelines: the cATH(cardiac catherization and antithrombotic therapy in the hospital) Clinical Consensus Panel Report-III. J Invasive Cardiol . 2007:18:525-40.

Large GA. Contemporary management of acute coronary syndrome. Postgrad Med J . 2005; 81:217-222.

National Heart, Lung, and Blood Institute website. Available at: . Accessed Oct. 29, 2006.

Swap CJ, Nagurney JT. Value and limitations of chest pain history in the evaluation of patients with suspected acute coronary syndromes. JAMA . 2005;294:2623-9.

Walker CW, Dewley cA, Fletcher SF:Aspirin combined with clopidogrel (Plavix) decreases cardiovascular events in patients with acute coronary syndrome. Am Fam Physician . 2007;7:1643-5.

*¹7/72007 DynaMed's Systematic Literature Surveillance DynaMed's Systematic Literature Surveillance : O'Donoghue M, Boden WE, Braunwald E, et al. Early invasive vs conservative treatment strategies in women and men with unstable angina and non-ST-segment elevation myocardial infarction: a meta-analysis. JAMA. 2008;300:71-80.

Last reviewed February 2008 by David Juan, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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