What do your stress test results mean?

If you’ve been told that you need a stress test, you probably have some concerns. That’s understandable—being told that you need an evaluation of how your heart works can be stressful. You can rest assured that these tests are common, especially if you have any risk factors for cardiac disease. 

Still, as you prepare for your test, you may want to know what stress tests are like, and what to expect at the doctor’s office when you get the test done. You might also have questions about why you need this test, and what your stress test results will tell you about your heart and your overall health. Here, you’ll learn everything you need to know about stress tests, including why this test is done and how to interpret the results of a stress test.

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What is a stress test? 

“A stress test is a non-invasive diagnostic modality primarily to identify the presence of coronary artery disease, which involves blockages of the vessels that supply blood/oxygen to the heart,” explains Vicken Zeitjian, MD, a cardiologist in San Antonio, Texas. Stress tests can also be used to help identify other heart problems, such as irregular heart rhythms during exercise, or to help your physician determine what degree of exercise is safe for your body.

The purpose of a stress test—sometimes referred to as an exercise stress test or a cardiac stress test—is to see how your heart handles physical exertion. Physicians recommend wearing comfortable clothes and running or walking shoes to your appointment. Before your appointment, your physician will discuss any medications you regularly take, and may ask you not to take some of them in preparation for your stress test. You will likely be asked not to eat or drink two to four hours before the test, though drinking water will probably be allowed. The evaluation has two to three components:

1. Exercise
2. Electrode monitoring
3. Imaging if ordered by the healthcare provider

The exercise test usually involves working out on a treadmill or stationary bike while your heart is monitored via an electrocardiogram machine (ECG). Electrodes connected to the machine will be placed on your chest. While you exercise, the machine will monitor the electrical activity in your heart and will record measurements such as your heart rate. Your provider will place a blood pressure cuff on your arm to measure your blood pressure both before and during the treadmill test. 

During the stress test, you will be asked to exercise, starting slowly at first, and gradually working more vigorously till you reach a targeted heart rate, based on your age. The exercise portion of the stress test lasts between 10-15 minutes. If you feel out of breath or lightheaded, you can pause the test at any time.

Physical symptoms you experience while exercising, such as shortness of breath, chest pressure, and exhaustion, will also be recorded. After the test is over, your provider will continue to monitor your heart and take your blood pressure once more. Echocardiograms and nuclear imaging tests may also be used. These tests are used in addition to ECGs and can provide detailed images of the inside of your heart and your arteries. Echocardiogram or nuclear images are obtained before and immediately after exercise to look for signs of inadequate blood flow.

If exercise is not safe for you, then you can take medications that will simulate what happens in the heart during exercise, Dr. Zeitjian says. This is called a pharmacological stress test, and typically involves an intravenous drug that increases your heart rate or expands your blood vessels to simulate the stress from exercise.

What does a stress test show?

“A stress test is helpful to assess a patient’s heart and/or lung function, as to their endurance and development of symptoms,” explains Ronald Grifka, MD, chief medical officer and chief clinical quality officer for the University of Michigan Health-West. The main purpose of a stress test is to:

• Guide treatment for heart issues
• Evaluate the results of a cardiac procedure
• Demonstrate the severity of a heart condition 
• Show if your heart is capable of responding to the demands of exercise

A stress test can “help determine if a person should participate in certain types of physical activities, or if certain activities should be avoided,” says Dr. Grifka.

 A stress test can help to diagnose or further access:

• Coronary artery disease, which can involve significant blockages in your heart that could lead to heart attack
• Heart rhythm problems, known as arrhythmias
• Heart failure
• Lung conditions, like chronic obstructive pulmonary disease (COPD) and asthma
• Pulmonary hypertension

While stress tests can usually help identify major blockages, there are certain limitations. For example, they are not as helpful when it comes to identifying more minor blockages. “Smaller blockages do not usually interfere with blood flow and therefore may not be visible on the stress test,” explains Michael Goyfman, MD, chief of cardiology and director of echocardiography at Long Island Jewish Forest Hills in New York. Like all diagnostic tests, stress tests aren’t 100% accurate. After the results of your stress test are determined, you may need additional follow-up testing. 

When to get a stress test 

Stress tests are recommended to diagnose cardiac conditions, to help prevent heart attacks by identifying critical blockages, and to evaluate the heart’s fitness for surgery.

People with heart-related symptoms will often be referred for stress tests. “A person may be referred for a stress test if they are having symptoms that may be concerning for coronary artery disease or if they have heart failure,” says Dr. Zeitjian. “The main symptom we look for is called angina, which includes shortness of breath, chest pain, or lightheadedness with exertional activities.”

Additionally, patients with known multiple heart blockages may get stress tests to see which blockages are the most advanced, and to help decide which ones require intervention first, Dr. Goyfman says.

Even if you don’t have a known heart condition or upcoming surgery, you might be given a stress test if you have an underlying condition or previous health history that puts you at high risk of developing a serious cardiac disorder. People who are more likely to need a stress test include:

• People with diabetes, high cholesterol, or high blood pressure
• People who have a family history of heart disease
• People who’ve had previous heart surgeries
• Older individuals who are starting a new exercise program

Stress test results

The results of a stress test provide an abundance of useful clinical information, says Dr. Grifka. “It determines how rapidly a person’s heart rate and blood pressure increase with exercise, and to what level of maximum heart rate and blood pressure are achieved,” he explains. Additionally, stress tests check the heart rate and blood pressure response during the “cool down” period of exercise, after your stress test is done, Dr. Grifka says.

Importantly, stress test results can alert your medical team to any potential severe blockages in your heart or other heart conditions that you might not be aware of. After your healthcare provider reads your stress test results, further testing may be necessary to get a more complete picture of your heart health.

Your test results will vary based on which equipment was used. For example, all stress tests have an ECG component, but some people also use echocardiograms or nuclear tests. Here’s what to know about each of these tests:

• Electrocardiograms (EKG): This test measures the electrical activity in the heart. It can determine if blood is moving freely through your arteries and if any blockages may be present. It can also diagnose heart structure abnormalities, heart damage, and heart rhythm problems.
• Echocardiograms: This test uses ultrasound images (sound waves) to view the inside of your heart. Echocardiograms can help diagnose coronary artery disease, heart failure, cardiomyopathy, and heart valve conditions.
• Nuclear tests: During this test, your healthcare provider injects a small amount of radioactive substance (called a “tracer”) into your bloodstream. A special camera is then used to take images as the tracer moves through the structures of your heart. These images can help determine if there are any blockages in your arteries, how well your blood is moving, how well your heart is pumping blood, and whether you have any heart damage.

After you are finished with your stress test, a report will be generated. Stress test results are categorized as either “normal” or “abnormal.” This report will list the various factors the test was looking at, along with the results of these tests. These factors usually include:

• Electrocardiogram, echocardiogram, and nuclear test results—before you exercise (baseline) and during exercise
• Your baseline heart rate, which is your heart rate when you are resting
• Your baseline blood pressure, which is your blood pressure when you are resting
• Your heart rate during exercise, which will show your provider how your heart handles exertion
• Your blood pressure during exercise, which will also show your provider how your heart handles exertion
• Your heart rhythm
• Any symptoms you experienced during exercise, which will help your healthcare provider determine what type of exercise is right for your body and your heart

 The report will come with medical advice from your provider.

By age 

Age is a major factor in interpreting stress test results. It impacts what’s considered a normal heart rate. Your maximum heart rate is determined by subtracting your age from 220. So for example, a 20-year-old would have a maximum heart rate of 200, with a target heart rate (85% of max) of 170. For a 70-year-old, the maximum heart rate decreases to 150, with a target heart rate of 128. 

Additionally, the likelihood of having an abnormal stress test result increases as you get older as more cholesterol and calcium build up in your blood vessels. “When the blockages become greater than 70%-80%, then we start to see blood flow limitations which is when symptoms begin and when the stress testing becomes positive,” explains Dr. Zeitjian.

“Age comes into play when we are deciding what to do with the results of the stress test,” Dr. Zeitjian says. For example, a 90-year-old with an abnormal test may not have an invasive surgery like coronary bypass surgery, as the risks of the surgery may outweigh the benefits, Dr. Zeitjian suggests. However, for a younger person, these more invasive surgeries are more appropriate. 

Abnormal results

The results of your stress tests will be reviewed and interpreted by your cardiologist. Normal stress test results mean that no serious blockages were detected by the testing equipment. “Abnormal results may mean that there are significant blockages of the coronary arteries which may be accounting for the angina symptoms or heart failure,” says Dr. Zeitjian.

Specifically, an “abnormal” result predicts that one or more of your coronary arteries is 70% or more blocked, whereas a “normal” result predicts that none of your arteries are experiencing a blockage of 70% or more. 

If you receive abnormal stress test results, there will be certain steps that will follow. First, you may need additional testing to understand what is causing your condition. For example, if you got a basic screening test with an EKG, more sophisticated imaging tests, such as nuclear stress tests or echocardiogram assessment might be recommended, says Dr. Goyfman. In addition to any further testing, your healthcare provider may also recommend heart medication or treatments to manage your blood pressure or cholesterol. Or, certain medical procedures, like cardiac catheterization may be necessary.

Finally, it will be vital that you live a heart-healthy lifestyle. Steps that can help reduce stress on the heart include:

• Staying physically active
• Eating a healthy diet with plenty of fruits, veggies, whole grains, and fiber
• Maintaining a healthy weight
• Quitting smoking
• Limiting alcohol intake
• Managing your stress levels

The bottom line 

The results of your stress test will give you and your medical team valuable information about the health of your heart. If your test results are abnormal, indicating that there is reduced blood flow to your heart, you may feel distressed. Keep in mind that although this may not be the result you wanted, you are now armed with the information you need to make positive steps toward better health.