Stress Tests

What are stress tests?

Stress tests show how well your heart works when under stress. To do this, a health care provider will usually monitor your heart while you exercise on a treadmill or stationary bicycle.

Most stress tests monitor your heart using electrodes that your provider places on your body. This is called an electrocardiogram (or EKG/ECG). It can record the electrical activity your heart makes when it beats. However, there are other types of stress tests, including:

• Stress echocardiograms, which take moving pictures of your heart using doppler ultrasound. These pictures show the size and shape of your heart and the blood flow through your heart before and after your heart has worked its hardest.
• Nuclear stress tests, which take pictures of your heart using a small amount of a radioactive substance called a “tracer” and a special camera that scans your heart. A provider injects the tracer into your bloodstream so that your heart and blood vessels can absorb it. Once they do, they will show up more clearly in the pictures your provider will take before and after your heart has worked its hardest.
• Cardiac MRI stress tests, which take the most detailed pictures of your heart using radio waves, magnets, and a computer. These newer tests are mostly used for very serious heart problems.
• Adenosine stress tests, which use a medicine (adenosine) to make your heart work as if you were exercising. Your provider can use this type of stress test if you aren't able to exercise.

Though these tests differ in some ways, each of them checks:

• Blood flow in your heart
• Your blood pressure
• The rate and rhythm of your heartbeat
• The strength of the electrical signals that control your heartbeat

Some stress tests also take pictures of your heart at rest and when it's working hard. The pictures provide more detail about how your heart is working.

Other names: exercise stress test, treadmill test, stress EKG, stress ECG, exercise tolerance test, exercise EKG, stress echocardiogram, nuclear stress test, thallium stress test, sestamibi stress test, cardiac MRI stress test, myocardial perfusion imaging test, cardiac single photon emission computed tomography (SPECT), stress perfusion test

What are they used for?

A provider may use a stress test if you have symptoms of certain types of heart problems. These can include:

• Coronary artery disease (CAD)
• Angina
• Arrhythmia
• Heart failure
• Heart valve diseases
• Cardiomyopathy

These heart conditions are often easier to find when your heart is working its hardest to pump blood through your body. This is why your provider may use a stress test when looking for CAD or arrhythmia instead of an EKG or echocardiogram.

Your provider may also use stress testing to:

• Find out how serious a known heart condition is, including the chance that you'll have a heart attack in the future.
• Help make treatment decisions for a heart condition.
• See if your heart is healthy enough for an upcoming surgery.
• Monitor your heart health if you're getting treated for heart disease. This test can also show whether heart surgery was effective.

Why do I need a stress test?

You may need a stress test if you have symptoms that could be from a heart condition. Symptoms may include:

• Chest pain or discomfort without a known cause
• Shortness of breath
• Irregular or rapid heartbeat that may feel like a fluttering in your chest
• Feeling dizzy or lightheaded

You may also need a stress test to check your heart health if you:

• Have a heart condition with new or worsening symptoms.
• Have an upcoming surgery, and your provider wants to see if your heart is healthy enough for the procedure.
• Are being treated for heart disease.
• Have a high risk for heart disease. Your risk may be higher than normal if you have a family history of heart disease and/or certain conditions, such as diabetes, that are linked to heart disease.
• Plan to start an exercise program. If you have a heart condition or a high risk for a heart condition, a stress test can show what level of exercise is safe for you. (Always talk with your provider before starting any strenuous, new exercise.)
• Have a high-risk job. For example, you might need a stress test if you are a pilot.

What happens during a stress test?

Stress tests may be done with or without imaging (pictures of your heart). The most common type is an exercise stress test. It doesn't include pictures. However, the main steps of this type of test are the same for all stress tests:

You'll have a blood pressure cuff on your arm to check your blood pressure.

Electrodes will be placed on your body for an electrocardiogram test. These electrodes are small sensors that stick to your skin. They rarely cause any pain or discomfort. Wires connect the electrodes to a computer or an EKG machine that records the electrical activity in your heart during the stress test.

If you're unable to exercise:

• An intravenous (IV) line will be inserted into a vein in your arm.
• You'll get medicine through the IV. The medicine will make your heart work harder for 10 to 20 minutes while an EKG records your heart's electrical activity.
• Your provider will measure your heart rate as your heart works harder.

If you can exercise:

• You'll walk on a treadmill or ride a stationary bicycle.
• On a treadmill, the speed will slowly increase. The treadmill may also tilt so you feel like you're walking uphill.
• On a bicycle, the resistance will slowly increase, so it's harder to pedal.
• You'll exercise for about 10 to 15 minutes until you reach a target heart rate based on your age and fitness level.
• You should stop the test sooner if you develop chest pain, shortness of breath, dizziness, fatigue, or other symptoms. Your provider may stop the test if an EKG shows a problem with your heart.

After all types of stress tests, you'll be monitored for 10–15 minutes or until your heart rate returns to normal.

Other types of stress tests may have additional steps.

For a stress echocardiogram:

• You'll lie on your left side on a table before you exercise. While you are on the table, your provider will move an ultrasound device on your chest.
• You will then exercise. If you exercise on a bicycle, your provider will take another set of pictures using the ultrasound while you're pedaling. If you run on a treadmill, they may instead take a second set of pictures right after you've finished running.

For a nuclear stress test:

• Your provider will inject a small amount of a radioactive substance called a “tracer” into your bloodstream. Your heart and blood vessels absorb the tracer, which makes them show up more clearly in the pictures.
• You will then lie on a table so that your provider can take the first set of pictures of your heart.
• After your provider has taken the first set of pictures, you will exercise. Once your heart rate gets to its highest, your provider will inject more of the tracer.
• After you've exercised, you will lie on a table again so that your provider can take the second set of pictures of your heart.

For a cardiac MRI stress test:

• A provider may inject dye into your bloodstream through an IV line placed in your arm. Some cardiac MRIs, but not all, use dye to help show very small details on the pictures.
• The provider may then take a picture of your heart before you exercise. To do this, your provider will ask you to lie on a table that slides into a large, tunnel-like MRI machine. You'll hear loud sounds as the machine takes pictures.
• You may then exercise. If you do, you may use a treadmill near the MRI or you may exercise while lying in the MRI machine using special devices to move your arms and legs.
• After you exercise, your provider may again ask you to lie on the MRI machine's table. They will then take the second set of pictures.

For an adenosine stress test:

• Your provider will place two IVs in your arm and several electrodes on your chest. They will inject the medicine (adenosine) into your bloodstream using the IVs.
• Instead of exercising, you will be asked to lie on a table. Your provider may have you enter an MRI machine. This can take about 45 minutes.
• Your provider may also ask you to hold your breath for short periods while you're in the MRI scanner.

Will I need to do anything to prepare for the test?

Wear comfortable shoes and clothing for exercise. Your provider will tell you what else to do before a stress test. You'll usually need to fast (not eat or drink) and stop smoking for at least a few hours before the test. You may need to avoid drinks with caffeine, such as coffee, tea, and colas, for a longer period of time.

If you take medicines or supplements, ask your provider if you should take them as usual. Don't stop taking any medicine unless your provider tells you to. You may also want to tell your provider if you have asthma and/or bring your inhaler in case you need it during the test. If your test uses MRI, tell your provider about any metal you have in your body. An MRI can heat certain metal and cause burns.

Are there any risks to the test?

Stress tests are usually safe. You will be closely watched during the test. If a problem develops, you'll be treated quickly. Medicines that make your heart work harder sometimes cause symptoms such as chest pain, dizziness, or nausea. An IV may bruise your arm.

The tracers and dyes used in nuclear and MRI stress tests may cause an allergic reaction, but this is rare. If you are or could become pregnant or are breastfeeding, talk with your provider before you have these tests.

What do the results mean?

A normal test result means no blood flow problems were found. Your heart is working well.

If your test result was not normal, it may mean you have heart disease. Ask your provider to explain what condition you may have. You may need more tests to find out how serious your condition is.

Learn more about laboratory tests, reference ranges, and understanding results.