Stable and Unstable Angina Compared

Medically Reviewed By Dr. Payal Kohli, M.D., FACC
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Angina refers to chest pain from lack of blood flow to the heart. Stable angina occurs during physical activity or exertion and goes away with rest. Unstable angina happens during rest or with little physical activity. Stable angina can become unstable angina.

Angina refers to chest pain that occurs when blood flow to the heart muscle becomes restricted. Angina may follow a pattern, such as only occuring while exercising. It may also occur without warning or with no apparent trigger.

Read on to learn more about the differences between stable and unstable angina.

Stable angina vs. unstable angina

A man standing at his kitchen counter experiencing chest pain
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When angina occurs only during certain situations, it is referred to as “stable angina.” With stable angina, activities such as exercise may trigger chest pain. Stable angina is the most common type of angina. Treatment includes rest and medications such as nitroglycerin.

Sometimes, angina may occur without warning or with no apparent trigger. It may even occur when resting. This is referred to as “unstable angina.” Unstable angina is considered more serious than stable angina and can be an early indication of a heart attack. Medications and rest may not be effective for treating unstable angina.

Unstable angina is sometimes called “acute coronary syndrome.” This term is also used to describe heart attacks. Acute coronary syndrome refers to groups of diseases or conditions that can suddenly stop or restrict blood flow to the heart.

The following comparative facts are from the Heart and Stroke Foundation of Canada:

Stable anginaUnstable angina
The pain usually lasts seconds to minutes and resolves quickly with rest.The pain lasts longer a few minutes.
Common triggers include physical activity, emotional stress, heavy meals, and extreme temperatures.It can happen while you are resting.
Rest, nitroglycerin, or a combination of both usually relieve symptoms within about 5 minutes.You cannot relieve it with rest or nitroglycerin.
It feels like pain in the chest that may spread to the jaw, neck, arms, back, or other body parts.You notice sudden chest pain you did not have before.
Some people may describe it as feeling like heartburn or indigestion.The episodes may get worse with time or occur at night.

Unstable angina symptoms

The difference between stable and unstable angina depends on when symptoms occur. Both types cause chest pain or pressure. However, symptoms of unstable angina can occur when you are resting or not experiencing stress.

Onset of unstable angina is usually sudden and quickly worsens over the course of 15–20 minutes. Other symptoms of unstable angina include:

  • chest pain that does not improve when taking nitroglycerin
  • drop in blood pressure that occurs with the chest pain
  • shortness of breath

Learn about the symptoms of heart disease.

Unstable angina occurs more often in males, though the incidence in females increases with age.

Other risk factors for unstable angina include:

Learn more about chest pain and chest pressure.

What to do for stable and unstable angina

If you or someone else develops sudden, unexplained chest pain or pressure, seek emergency medical attention by calling 911. Sudden chest pain or pressure may be an indication of a heart attack.

It is important to inform any emergency medical responders if you have been diagnosed with unstable angina. Sharing this information can help them provide the best treatment for your symptoms.

If you have known stable angina

If you have periods of stable angina, take note of the following information:

  • the event that triggered your angina
  • how long the angina episode lasted
  • what helped alleviate your symptoms

Always follow your doctor’s instructions about what to do when you develop chest pain.

If angina episodes become more frequent, severe, last longer, or begin occurring without exercise, contact your doctor within 24 hours. You may need testing or adjustments to your treatment.

Learn more about when to see a doctor for chest pain.

Causes of unstable angina

Unstable angina occurs when a blood clot blocks an artery to your heart. These clots may start to form and then dissolve, but can then form again. Each time a person experiences symptoms of unstable angina, it might mean a clot is blocking blood flow in an artery.


Stable angina occurs when a person experiences chest pain from angina with physical exertion, such as during exercise. Symptoms usually improve with rest or medication such as nitroglycerin.

Unstable angina occurs when a person experiences chest pain from angina at rest and without an apparent trigger. Symptoms do not resolve with rest or medication and may worsen over time.

Unstable angina is a more serious condition and can be a sign that a clot has blocked blood flow to the heart. It may be an early sign of a  heart attack.

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Medical Reviewer: Dr. Payal Kohli, M.D., FACC
Last Review Date: 2022 Oct 29
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