Acute coronary syndrome (ACS) is an umbrella term that refers to different conditions that suddenly disrupt or completely stop blood flow to your heart. This is usually called a heart attack.

ACS is considered a medical emergency, and immediate treatment is needed to help prevent life threatening complications. If you or your loved one has a history of heart disease or related risk factors, it’s important to know about ACS and its possible symptoms.

Learn more about the types of ACS, as well as the causes, risk factors, and treatments you can discuss with your doctor.

The term ACS refers to many conditions that suddenly stop blood from flowing to your heart. It can also result in damaged heart muscle tissues.

While you may not be as familiar with ACS, you may have heard of the different types of conditions that fall under this umbrella term. Below are the three main types of ACS, along with their key differences.

Unstable angina

Also called acute coronary insufficiency, unstable angina causes platelet clots in the arteries due to plaque buildup. A key characteristic of unstable angina is that chest pain and other symptoms tend to develop and worsen during periods of rest. If left untreated, it may lead to a heart attack.


ST-segment elevation myocardial infarction (STEMI) is a type of heart attack that involves the blockage of one or more arteries in your heart. It may cause serious injury to the heart muscle, including loss of tissues and cells.


Non-ST-segment elevation myocardial infarction (NSTEMI) is the second type of heart attack associated with ACS. While still a serious event, NSTEMI usually involves partial or near-complete artery blockage.

Also, compared with unstable angina and STEMI, NSTEMI has a lower mortality rate after 6 months.

What is a myocardial infarction (MI)?

A myocardial infarction (MI) is the clinical term for “heart attack.“ It is most often the result of coronary artery disease.

An MI deprives a portion of the heart muscle of oxygen. This can destroy heart tissues and lead to a sudden onset of symptoms, such as chest pain.

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If you suspect symptoms of ACS, you need to seek emergency medical help right away.

Chest pain and discomfort are perhaps the first and most common sign of ACS. You may notice sharp or dull pain, along with pressure and fullness. Like other types of chest pains, such as muscle spasms or anxiety, you may also feel a squeezing sensation.

Chest pain from ACS may come on suddenly, such as with MI, or gradually worsen at rest, such as with unstable angina. Chest pain from MI typically lasts longer than 20 minutes.

During ACS, chest pain and discomfort may also radiate to other areas of your body, particularly your:

  • arm(s)
  • back
  • stomach
  • neck
  • jaw

Other common symptoms seen in ACS include:

  • dizziness
  • feeling lightheaded
  • weakness
  • nausea
  • sweating
  • shortness of breath

ACS develops as a result of having coronary heart disease (CHD). CHD is the most common cause of death in the United States.

While “heart disease” can refer to a variety of conditions that affect the function and overall structure of your heart muscle, CHD develops when plaque blocks your coronary arteries.

Even a small amount of plaque can make it difficult for blood to flow through these large arteries. You won’t likely know this is even happening until you start experiencing symptoms, such as chest pain.

Sometimes, plaque can build up for a very long time without causing symptoms. This is known as stable ischemic heart disease (SIHD) and can lead to stable angina. While ACS is acute (sudden), SIHD is chronic (long term).

It’s important to be aware of the risk factors so you may take preventive measures to reduce your chances of having a heart attack or cardiac arrest from ACS.

The risk factors of ACS are similar to CHD. You may be at a higher risk if you:

To diagnose ACS, your doctor will perform blood tests to look for signs of heart damage and to help rule out other possible conditions. They might measure the following items:

Diagnosis of unstable angina requires a negative blood test. A positive test suggests a myocardial infarction.

Your doctor will also order an electrocardiogram (EKG) test, which measures the electrical activity inside your heart. An EKG can also confirm a suspected heart attack and help your doctor tell the difference between STEMI and NSTEMI.

To help rule out ACS or CHD, you might need additional tests, such as a:

Additionally, your doctor will take a physical assessment and ask you questions about your personal and family heart health history. It’s important to tell your doctor about your medical history, including any medications and supplements you currently take.

ACS is a medical emergency that requires treatment in a hospital.

If you’re not currently experiencing an ACS event but have a history of ACS or CHD, your doctor may recommend the following treatments to help reduce your risk factors.


Immediately after an ACS event, you may be given medications that help dissolve blood clots, such as:

For overall management, you may be prescribed the following:

Surgical procedures

Surgery for ACS may involve percutaneous coronary intervention (PCI). During this procedure, your doctor will open up your blocked artery by inflating a specialized balloon. To help keep it open, a stent and mesh tube may be placed.

To treat multiple affected arteries, your doctor may recommend coronary artery bypass grafting (CABG) to increase overall blood flow to your heart.

Lifestyle changes

Adopting health-promoting lifestyle changes is just as important after an ACS event. You can help improve your overall heart health by:

  • eating whole foods and plant-based products
  • staying physically active
  • maintaining a moderate weight
  • quitting smoking if you smoke
  • managing stress when possible
  • getting 7 to 9 hours of sleep every night

If you need help getting started with any of these lifestyle changes, talk with your doctor or a dietitian for advice.

After you’ve experienced an ACS event, it’s important to stay in touch with your doctor and carefully follow your treatment plan. Aside from follow-up care, you may also benefit from cardiac rehabilitation to help prevent future ACS events while improving your quality of life.

To support your heart health, you might consider stress management to improve your mental health. You might also consider seeing an exercise physiologist and dietitian to make sure you know about the best lifestyle habits for your particular situation.

Finally, you can empower yourself by having a plan in case of any other future ACS events. Tell your loved ones about the above symptoms so they will know when to call 911 or your local emergency services for help.

Seek emergency medical care for any signs of a heart attack, such as chest pain, shortness of breath, and faintness.