A fatty substance called plaque can build up in the arteries that bring oxygen-rich blood to your heart. Plaque is made up of cholesterol, fat, cells, and other substances.

Plaque can block blood flow in two ways:

• It can cause an artery to become so narrow over time that it becomes blocked enough to cause symptoms.
• The plaque tears suddenly and a blood clot forms around it, severely narrowing or blocking the artery.

Many risk factors for heart disease may lead to an ACS.

The most common symptom of ACS is chest pain. The chest pain may come on quickly, come and go, or get worse with exercise or rest. Other symptoms can include:

• Pain in the shoulder, arm, neck, jaw, back, or belly area
• Discomfort that feels like tightness, squeezing, crushing, burning, choking, or aching
• Discomfort that occurs at rest and does not easily go away when you take medicine
• Shortness of breath
• Anxiety
• Nausea
• Sweating
• Feeling dizzy or lightheaded
• Fast or irregular heartbeat

Women and older people often experience these other symptoms, although chest pain is common for them as well.

Your health care provider will do an exam, listen to your chest with a stethoscope, and ask about your medical history.

Tests for ACS include:

• Electrocardiogram (ECG) -- An ECG is usually the first test your provider will run. It measures your heart's electrical activity. During the test, you will have small pads taped to your chest and other areas of your body.
• Blood test -- Some blood tests help show the cause of chest pain and see if you are at a high risk for a heart attack. A troponin blood test can show if the cells in your heart have been damaged. This test can confirm you are having a heart attack.
• Echocardiogram -- This test uses sound waves to look at your heart. It shows if your heart has been damaged and can find some types of heart problems.

Coronary angiography may be done right away or when you are more stable. This test:

• Uses a special dye and x-rays to see how blood flows through your heart
• Can help your provider decide which treatments you need next

Other tests to look at your heart that may be done while you are in the hospital include:

• Exercise stress test
• Nuclear stress test
• Stress echocardiography

Your provider may use medicines, surgery, or other procedures to treat your symptoms and restore blood flow to your heart. Your treatment depends on your condition and the amount of blockage in your arteries. Your treatment may include:

• Medicine -- Your provider may give you one or more types of medicine, including aspirin, beta blockers, statins, blood thinners, clot dissolving medicines (thrombolytics), angiotensin converting enzyme (ACE) inhibitors, or nitroglycerin. These medicines may help prevent or break up a blood clot, treat high blood pressure or angina, relieve chest pain, and stabilize your heart.
• Angioplasty -- This procedure opens the clogged artery using a long, thin tube called a catheter. The tube is placed in the artery and the provider inserts a small deflated balloon. The balloon is inflated inside the artery to open it up. Your doctor (usually a heart specialist called a cardiologist) may insert a wire tube, called a stent, to keep the artery open.
• Bypass surgery -- This is surgery to route the blood around the artery that is blocked.

How well you do after an ACS depends on:

• How quickly you get treated
• The number of arteries that are blocked and how bad the blockage is
• Whether or not your heart has been damaged, as well as the extent and location of the damage, and where the damage is

In general, the quicker your artery gets unblocked, the less damage you will have to your heart. People tend to do best when the blocked artery is opened within a few hours from the time symptoms start.

In some cases, ACS can lead to other health problems including:

• Abnormal heart rhythms
• Death
• Heart attack
• Heart failure, which happens when the heart cannot pump enough blood
• Rupture of part of the heart muscle causing tamponade or severe valve leakage
• Stroke

An ACS is a medical emergency. If you have symptoms of an ACS, call 911 or the local emergency number quickly.

Do not:

• Try to drive yourself to the hospital.
• Wait - If you are having a heart attack, you are at greatest risk for sudden death in the early hours.

There is a lot you can do to help prevent ACS.

• Eat a heart-healthy diet. Have plenty of fruits, veggies, whole grains, and lean meats. Try to limit foods high in cholesterol and saturated fats, since too much of these substances can clog your arteries.
• Get exercise. Aim to get at least 30 minutes of moderate exercise most days of the week.
• Lose weight, if you are overweight.
• Quit smoking. Smoking can damage your heart. Ask your doctor if you need help quitting.
• Get preventive health screenings. You should see your doctor for regular cholesterol and blood pressure tests and learn how to keep your numbers in check.
• Manage health conditions, such as high blood pressure, high cholesterol, or diabetes.

Heart attack - ACS; Myocardial infarction - ACS; MI - ACS; Acute MI - ACS; ST elevation myocardial infarction - ACS; Non ST-elevation myocardial infarction - ACS; Unstable angina - ACS; Accelerating angina - ACS; Angina - unstable-ACS; Progressive angina

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Updated by: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.