What Is Stress Testing?

Stress testing gives your doctor information about how your heart works during physical stress. Some heart problems are easier to diagnose when your heart is working hard and beating fast.

During a stress test, you exercise (walk or run on a treadmill or pedal a bicycle) to make your heart work hard and beat fast. Tests are done on your heart while you exercise.

You may have arthritis or another medical problem that prevents you from exercising during a stress test. If so, your doctor may give you medicine to make your heart work hard, as it would during exercise. This is called a pharmacological (FAR-ma-ko-LOJ-i-kal) stress test.

Overview

Doctors usually use stress testing to help diagnose coronary heart disease (CHD), also called coronary artery disease. They also use stress testing to see how severe CHD is in people who have it.

CHD is a condition in which a fatty material called plaque (plak) builds up in the coronary arteries. These arteries supply oxygen-rich blood to your heart.

Plaque narrows the arteries and reduces blood flow to your heart muscle. It also makes it more likely that blood clots will form in your arteries. Blood clots can partly or completely block blood flow. This can lead to chest pain or a heart attack.

You may not have any signs or symptoms of CHD when your heart is at rest. But when your heart has to work harder during exercise, it needs more blood and oxygen. Narrowed arteries can't supply enough blood for your heart to work well. As a result, signs and symptoms of CHD may only occur during exercise.

A stress test can detect the following problems, which may suggest that your heart isn't getting enough blood during exercise.

• Abnormal changes in your heart rate or blood pressure
• Symptoms such as shortness of breath or chest pain, which are particularly important if they occur at low levels of exercise
• Abnormal changes in your heart's rhythm or electrical activity

During a stress test, if you can't exercise for as long as what's considered normal for someone your age, it may be a sign that not enough blood is flowing to your heart. However, other factors besides CHD can prevent you from exercising long enough (for example, lung disease, anemia, or poor general fitness).

A stress test also may be used to assess other problems, such as heart valve disease or heart failure.

Types of Stress Testing

There are two main types of stress testing: a standard exercise stress test and an imaging stress test.

Standard Exercise Stress Test

A standard exercise stress test uses an EKG (electrocardiogram) to detect and record the heart's electrical activity.

An EKG shows how fast your heart is beating and the heart's rhythm (steady or irregular). It also records the strength and timing of electrical signals as they pass through each part of your heart.

During a standard stress test, your blood pressure will be checked. You also may be asked to breathe into a special tube during the test. This allows your doctor to see how well you're breathing and measure the gases that you breathe out.

A standard stress test shows changes in your heart's electrical activity. It also may show signs that your heart isn't getting enough blood during exercise.

Imaging Stress Test

Some stress tests take pictures of the heart when you exercise and when you're at rest. These imaging stress tests can show how well blood is flowing in various parts of your heart and/or how well your heart squeezes out blood when it beats.

One type of imaging stress test involves echocardiography (echo). This test uses sound waves to create a moving picture of your heart. An exercise stress echo can show how well your heart's chambers and valves are working when your heart is under stress.

The test can identify areas of poor blood flow to your heart, dead heart muscle tissue, and areas of the heart muscle wall that aren't contracting normally. These areas may have been damaged during a heart attack, or they may not be getting enough blood.

Other imaging stress tests use radioactive dye to create pictures of the blood flow to your heart. The dye is injected into your bloodstream before the pictures of your heart are taken. The pictures show how much of the dye has reached various parts of your heart during exercise and while you're at rest.

Tests that use radioactive dye include a thallium or sestamibi stress test and a positron emission tomography (PET) stress test. The amount of radiation in the dye is thought to be safe and not a danger to you or those around you. However, if you're pregnant, you shouldn't have this test because of risks it might pose to your unborn child.

Imaging stress tests tend to be more accurate at detecting CHD than standard (nonimaging) stress tests. Imaging stress tests also can predict the risk of a future heart attack or premature death.

An imaging stress test may be done first (as opposed to a standard exercise stress test) if you:

• Can't exercise for enough time to get your heart working at its hardest. (Medical problems, such as arthritis or leg arteries clogged by plaque, may prevent you from exercising enough.)
• Have abnormal heartbeats or other problems that will cause a standard exercise stress test to be inaccurate.
• Had a heart procedure in the past, such as coronary artery bypass grafting or placement of a stent in a coronary artery.

Other Names for Stress Testing

• Exercise echocardiogram or exercise stress echo
• Exercise test
• Myocardial perfusion imaging
• Nuclear stress test
• PET stress test
• Pharmacological stress test
• Sestamibi stress test
• Stress EKG
• Thallium stress test
• Treadmill test

Who Needs Stress Testing?

You may need stress testing if you've had chest pains, shortness of breath, or other symptoms of limited blood flow to your heart.

Imaging stress tests, particularly, can show whether you have coronary heart disease (CHD) or a heart valve problem. (Heart valves are like doors that let blood flow between the heart's chambers and into the heart's arteries. So, like CHD, faulty heart valves can limit the amount of blood reaching your heart.)

If you've been diagnosed with CHD or recently had a heart attack, a stress test can show whether you can tolerate an exercise program. If you've had angioplasty (AN-jee-oh-plas-tee) with or without stents or coronary artery bypass grafting, a stress test can show how well the treatment relieves your CHD symptoms.

You also may need a stress test if, during exercise, you feel faint, get a rapid heartbeat or a fluttering feeling in your chest, or have other symptoms of an arrhythmia (an abnormal heartbeat).

If you don't have chest pain when you exercise, but still get short of breath, you may need a stress test. The test can help show whether a heart problem, rather than a lung problem or being out of shape, is causing your breathing problems.

For such testing, you breathe into a special tube. This allows a technician to measure the gases you breathe out. Breathing into the special tube and checking the heart as part of a stress test also is done before a heart transplant to help assess whether you're a candidate for the surgery.

Stress testing isn't used as a routine screening test for CHD. Usually you have to have symptoms of CHD before a doctor will recommend stress testing.

However, your doctor may want to use a stress test to screen for CHD if you have diabetes. This disease increases your risk for CHD. Currently, though, no evidence shows that having a stress test will improve your outcome if you have diabetes.

What To Expect Before Stress Testing

Standard stress testing often is done in a doctor's office. Imaging stress testing usually is done at a hospital. Be sure to wear athletic or other shoes in which you can exercise comfortably. You may be asked to wear comfortable clothes, or you may be given a gown to wear during the test.

Your doctor may ask you not to eat or drink anything but water for a short time before the test. If you're diabetic, ask your doctor whether you need to adjust your medicines on the day of your test.

For some stress tests, you can't drink coffee or other caffeinated drinks for a day before the test. Certain over-the-counter or prescription medicines also may interfere with some stress tests. Discuss with your doctor whether you need to avoid certain drinks or food or change how you take your medicine before the test.

If you use an inhaler for asthma or other breathing problems, bring it to the test. Make sure you let the doctor know that you use it.

What To Expect During Stress Testing

During all types of stress testing, a technician or nurse will always be with you to closely check your health status.

Before you start the "stress" part of a stress test, the technician or nurse will put sticky patches called electrodes on the skin of your chest, arms, and legs. To help an electrode stick to the skin, the technician or nurse may have to shave a patch of hair where the electrode will be attached.

The electrodes are connected to an EKG (electrocardiogram) machine. This machine records your heart's electrical activity and shows how fast your heart is beating and the heart's rhythm (steady or irregular). An EKG also records the strength and timing of electrical signals as they pass through each part of your heart.

The technician or nurse will put a blood pressure cuff on your arm to check your blood pressure during the stress test. (The cuff will feel tight on your arm when it expands every few minutes.) Also, you may be asked to breathe into a special tube so the gases you breathe out can be measured.

After these preparations, you'll exercise on a treadmill or stationary bicycle. If such exercise poses a problem for you, you may instead turn a crank with your arms. During the test, the exercise level will get harder. You can stop whenever you feel the exercise is too much for you.

Stress Testing

The illustration shows a patient having a stress test. Electrodes are attached to the patient's chest and connected to an EKG (electrocardiogram) machine. The EKG records the heart's electrical activity. A blood pressure cuff is used to record the patient's blood pressure while he walks on a treadmill.

If you can't exercise, medicine may be injected into a vein in your arm or hand. This medicine will increase blood flow through your coronary arteries and/or make your heart beat fast, as would exercise. The stress test can then be done.

The medicine may make you flushed and anxious, but the effects go away as soon as the test is over. The medicine also may give you a headache.

While you're exercising or getting medicine to make your heart work harder, the technician will frequently ask you how you're feeling. You should tell him or her if you feel chest pain, short of breath, or dizzy.

The exercise or medicine infusion will continue until you reach a target heart rate, or until you:

• Feel moderate to severe chest pain
• Get too out of breath to continue
• Develop abnormally high or low blood pressure or an arrhythmia (an abnormal heartbeat)
• Become dizzy

The technician will continue to check your heart functions and blood pressure after the test until they return to your normal levels.

The "stress" part of a stress test (when you're exercising or given medicine that makes your heart work hard) usually lasts about 15 minutes or less.

However, there's prep time before the test and monitoring time afterward. Both extend the total test time to about an hour for a standard stress test, and up to 3 hours or more for some imaging stress tests.

Exercise Stress Echocardiogram Test

For an exercise stress echocardiogram (echo) test, the technician will take pictures of your heart using echocardiography before you exercise and as soon as you finish.

A sonographer (a person who specializes in using ultrasound techniques) will apply gel to your chest. Then, he or she will briefly put a transducer (a wand-like device) against your chest and move it around.

The transducer sends and receives high-pitched sounds that you usually can't hear. The echoes from the sound waves are converted into moving pictures of your heart on a screen.

You may be asked to lie on your side on an exam table for this test. Some stress echo tests also use a dye to improve imaging. This dye is injected into your bloodstream while the test occurs.

Sestamibi or Other Imaging Stress Tests Involving Radioactive Dye

For a sestamibi stress test, or other imaging stress tests that use radioactive dye, the technician will inject a small amount of dye (such as sestamibi) into your bloodstream. This is done through a needle placed in a vein in your arm or hand.

You're usually given the dye about a half-hour before you start exercising or take medicine to make your heart work hard. The amount of radiation in the dye is thought to be safe and not a danger to you or those around you. However, if you're pregnant, you shouldn't have this test because of risks it might pose to your unborn child.

Pictures will be taken of your heart at least two times: when it's at rest and when it's working its hardest. You'll lie down on a table, and a special camera or scanner that can see the dye in your bloodstream will take pictures of your heart.

Some pictures may not be taken until you lie quietly for a few hours after the stress test. Some patients may even be asked to return in a day or so for more pictures.

What To Expect After Stress Testing

After stress testing, you'll be able to return to your normal activities. If you had a test that involved radioactive dye, your doctor may ask you to drink plenty of fluids to flush it out of your body. You also shouldn't have certain other imaging tests until the dye is no longer in your body. Your doctor can advise you about this.

What Does Stress Testing Show?

Stress testing gives your doctor information about how your heart works during physical stress (exercise) and how healthy your heart is.

A standard exercise stress test uses an EKG (electrocardiogram) to monitor changes in your heart's electrical activity. Imaging stress tests take pictures of blood flow in various parts of your heart. They also show your heart valves and the movement of your heart muscle.

Both types of stress tests are used to look for signs that your heart isn't getting enough blood flow during exercise. Abnormal test results may be due to coronary heart disease (CHD) or other factors, such as a lack of physical fitness.

If you have a standard exercise stress test and the results are normal, no further testing or treatment may be needed. But if your test results are abnormal, or if you're physically unable to exercise, your doctor may want you to have an imaging stress test or other tests.

Even if your standard exercise stress test results are normal, your doctor may want you to have an imaging stress test if you continue having symptoms (such as shortness of breath or chest pain).

Imaging stress tests are more accurate than standard exercise stress tests, but they're much more expensive.

Imaging stress tests show how well blood is flowing in the heart muscle and reveal parts of the heart that aren't contracting strongly. They also can show the parts of the heart that aren't getting enough blood, as well as dead tissue in the heart, where no blood flows. (A heart attack can cause some tissue in the heart to die.)

If your imaging stress test suggests significant CHD, your doctor may want you to have more testing and/or treatment.

What Are the Risks of Stress Testing?

There's little risk of serious harm from any type of stress testing. The chance of these tests causing a heart attack or death is about 1 in 5,000. More common, but less serious side effects linked to stress testing include:

• Arrhythmia (an abnormal heartbeat). Often, an arrhythmia will go away quickly once you're at rest. But if it persists, you may need monitoring or treatment in a hospital.
• Low blood pressure, which can cause you to feel dizzy or faint. This problem may go away once your heart stops working hard; it usually doesn't require treatment.
• Jitteriness or discomfort while getting medicine to make your heart work harder (you may be given medicine if you can’t exercise). These side effects usually go away shortly after you stop getting the medicine. In some cases, the symptoms may last a few hours.

Also, some of the medicines used for pharmacological stress tests can cause wheezing, shortness of breath, and other asthma-like symptoms. In some cases, these symptoms may be severe and require treatment.

Key Points

• Stress testing gives your doctor information about how your heart works during physical stress. Some heart problems are easier to diagnose when your heart is working hard and beating fast.
• During a stress test, you exercise (walk or run on a treadmill or pedal a bicycle) to make your heart work hard and beat fast. Tests are done on your heart while you exercise.
• If you're unable to exercise, your doctor may give you medicine to make your heart work hard, as it would during exercise. This is called a pharmacological stress test.
• Doctors usually use stress testing to help diagnose coronary heart disease (CHD), also called coronary artery disease. They also use stress testing to see how severe CHD is in people who have it.
• Some stress tests take pictures of the heart when you exercise and when you’re at rest. These imaging stress tests can show how well blood is flowing in various parts of your heart and/or how well your heart squeezes out blood when it beats. Imaging stress tests tend to be more accurate at detecting CHD than standard (nonimaging) stress tests.
• You may need a stress test if you’ve had chest pains, shortness of breath, or other symptoms of limited blood flow to your heart.
• Standard stress testing often is done in a doctor’s office. Imaging stress testing usually is done at a hospital. Be sure to wear athletic shoes in which you can exercise comfortably. Your doctor may ask you not to eat or drink for a short time before the test. You also may have to adjust how you take certain medicines before the test.
• During all types of stress testing, a technician or nurse will be with you to closely check your health status.
• Standard exercise stress tests use EKGs (electrocardiograms) and breathing and blood pressure monitoring to check blood flow in the heart. Imaging stress tests, such as those that use echocardiography and radioactive dyes, show how well blood is flowing in your heart muscle.
• After stress testing, you’ll be able to return to your normal activities. If you had a test that involved radioactive dye, your doctor may ask you to drink plenty of fluids to flush it out of your body.
• If your test results are normal, no further testing or treatment may be needed unless your CHD symptoms persist. If your test results are abnormal, your doctor may recommend other tests.
• There's little risk of serious harm from any type of stress testing. The chance of these tests causing a heart attack or death is about 1 in 5,000. More common, but less serious side effects may include arrhythmias (abnormal heartbeats), low blood pressure, and jitteriness or discomfort (if you get medicine to make your heart work hard).

Links to Other Information About Stress Testing

NHLBI Resources

• Coronary Heart Disease/Coronary Artery Disease (Diseases and Conditions Index)
• Echocardiography (Diseases and Conditions Index)
• Electrocardiogram (Diseases and Condition Index)
• "Your Guide to Living Well With Heart Disease"

Non-NHLBI Resources

• Echocardiography Stress Test (MedlinePlus)
• Exercise Stress Test (MedlinePlus)

Clinical Trials

• Current Research (ClinicalTrials.gov)