Medically reviewed on March 29, 2018
A stress test, also called an exercise stress test, shows how your heart works during physical activity. Because exercise makes your heart pump harder and faster, an exercise stress test can reveal problems with blood flow within your heart.
A stress test usually involves walking on a treadmill or riding a stationary bike your heart rhythm, blood pressure and breathing are monitored. Or you'll receive a drug that mimics the effects of exercise.
Your doctor may recommend a stress test if you have signs or symptoms of coronary artery disease or an irregular heart rhythm (arrhythmia). The test may also guide treatment decisions, measure the effectiveness of treatment or determine the severity if you've already been diagnosed with a heart condition.
Why it's done
Your doctor may recommend a stress test to:
- Diagnose coronary artery disease. Your coronary arteries are the major blood vessels that supply your heart with blood, oxygen and nutrients. Coronary artery disease develops when these arteries become damaged or diseased — usually due to a buildup of deposits containing cholesterol and other substances (plaques).
- Diagnose heart rhythm problems (arrhythmias). Heart arrhythmias occur when the electrical impulses that coordinate your heart rhythm don't function properly, causing your heart to beat too fast, too slowly or irregularly.
Guide treatment of heart disorders. If you've already been diagnosed with a heart condition, an exercise stress test can help your doctor find out how well treatment is working. It may also be used to help establish the treatment plan for you by showing how much exercise your heart can handle.
Your doctor may use a stress test to help determine the timing of cardiac surgery, such as valve replacement. In some people with heart failure, stress test results may help the doctor determine whether you need a heart transplant or other advanced therapies.
Your doctor may recommend a test with imaging, such as a nuclear stress test or echocardiographic stress test, if an exercise stress test doesn't pinpoint the cause of your symptoms.
A stress test is generally safe, and complications are rare. But, as with any medical procedure, there is a risk of complications, including:
- Low blood pressure. Blood pressure may drop during or immediately after exercise, possibly causing you to feel dizzy or faint. The problem should go away after you stop exercising.
- Abnormal heart rhythms (arrhythmias). Arrhythmias brought on by an exercise stress test usually go away soon after you stop exercising.
- Heart attack (myocardial infarction). Although exceedingly rare, it's possible that an exercise stress test could cause a heart attack.
How you prepare
Your doctor will give you specific instructions on how to prepare for your stress test.
Food and medications
You may be asked not to eat, drink or smoke for a period of time before a stress test. You may need to avoid caffeine the day before and the day of the test.
Ask your doctor if it's safe for you to continue taking all of your prescription and over-the-counter medications before the test, because they might interfere with certain stress tests.
If you use an inhaler for asthma or other breathing problems, bring it to the test. Make sure your doctor and the health care team member monitoring your stress test know that you use an inhaler.
Clothing and personal items
Wear or bring comfortable clothes and walking shoes. If you're having a nuclear stress test, don't apply oil, lotion or cream to your skin that day.
What you can expect
Your stress test will take around an hour, including both your prep time and the time it takes to perform the actual test. The actual test takes only around 15 minutes. You may have an exercise stress test in which you walk on a treadmill or pedal a stationary bicycle. If you aren't able to exercise, you'll receive a drug through an IV that mimics exercise by increasing blood flow to your heart.
Before a stress test
First, your doctor will ask you some questions about your medical history and how often and strenuously you exercise. This helps determine the amount of exercise that's appropriate for you during the test. Your doctor will also listen to your heart and lungs for any abnormalities that might affect your test results.
During a stress test
A nurse or technician will place sticky patches (electrodes) on your chest, legs and arms. Some areas may need to be shaved to help them stick. The electrodes have wires connected to an electrocardiogram machine, which records the electrical signals that trigger your heartbeats. A cuff on your arm checks your blood pressure during the test. You may be asked to breathe into a tube during the test to show how well you're able to breathe during exercise.
If you're not exercising, your doctor will inject the drug into your IV that increases blood flow to your heart. You might feel flushed or short of breath, just as you would if you were exercising. You might get a headache.
You'll probably exercise on a treadmill or stationary bike, starting slowly. As the test progresses, the exercise gets more difficult. You can use the railing on the treadmill for balance. Don't hang on tightly, as this may skew the results.
You continue exercising until your heart rate has reached a set target or until you develop symptoms that don't allow you to continue. These signs and symptoms may include:
- Moderate to severe chest pain
- Severe shortness of breath
- Abnormally high or low blood pressure
- An abnormal heart rhythm
- Certain changes in your electrocardiogram
You and your doctor will discuss your safe limits for exercise. You may stop the test anytime you're too uncomfortable to continue exercising.
After a stress test
After you stop exercising, you may be asked to stand still for several seconds and then lie down for a period of time with the monitors in place. Your doctor can watch for any abnormalities as your heart rate and breathing return to normal.
When your exercise stress test is complete, you may return to your normal activities unless your doctor tells you otherwise.
In an exercise stress test, electrodes are taped to your chest to detect your heart's rhythm. A nurse or technician will watch your heartbeat on a monitor while you exercise. If your doctor orders a nuclear stress test, you'll also receive a shot of radioactive dye that shows the blood flow to your heart muscle.
If the information gathered during your exercise stress test shows your heart function to be normal, you may not need any further tests.
However, if the results are normal and your symptoms continue to worsen, your doctor might recommend a nuclear stress test or another stress test that includes an echocardiogram before and after exercise or medications to increase blood flow to your heart. These tests are more accurate and provide more information about your heart function, but they are also more expensive.
If your stress test results suggest that you might have coronary artery disease or show an arrhythmia, your doctor will use the information to develop a treatment plan. You may need additional tests, such as a coronary angiogram.
If you had a stress test to help determine treatment for a heart condition, your doctor will use the results to plan or change your treatment.