What is an Exercise Treadmill Test
The exercise treadmill test is used for several reasons including evaluation of heart or cardiac symptoms and as a functional assessment of the interrelationship of cardiopulmonary, musculoskeletal, and neuropsychological systems. The test goes by different names. It is sometimes referred to simply as a stress test and sometimes referred to as a graded exercise test. We will refer to it as the exercise treadmill test.
The test is primarily performed to see if one’s heart is receiving enough blood flow and oxygen when being physically stressed.
During the exercise treadmill test physiological changes are monitored in response to incremental changes in exercise intensity. The intensity can be increased either by changing the speed the treadmill belt moves and/or by increasing the grade or steepness of the treadmill platform. Various protocol have been developed. You may have heard of the Bruce Protocol or the Balke Protocol.
Reasons to Perform an Exercise Treadmill Test
Exercise treadmill tests are performed in a doctor’s office, hospital, and some fitness centers or health clubs.
Is used to determine if your:
- chest pain or difficulty breathing are related to a problem with your heart.
- to assess if heart treatments are effective
- determine if you an irregular heart beat.
- determine how hard you can safely exercise either as part of a fitness program or cardiac rehabilitation program.
- determine the need for addition cardiac testing to rule out narrowed or blocked coronary arteries.
Preparing for Exercise Treadmill Test
- Your doctor may tell you to hold or not take certain medications leading up to the treadmill test as some medications (some blood pressure medications) can interfere with the interpretation of the test.
- Wear comfortable clothing and walking or running shoes.
- Let your physician know if you have an orthopedic problems that may limit your ability to walk or run on a treadmill. The test can be performed on a cycle if necessary.
What to Expect During the Exercise Test
- Prior to the start of the treadmill test, a resting EKG will be obtained.
- You will remain hooked up to the EKG monitor.
- You will walk on the treadmill at first but the speed and grade/elevation of the treadmill will increase (how fast this happens depend the particular protocol being used).
- If you do not have any known cardiac issues, you are normally asked to stay on the treadmill as long as you can. This is called a maximal exercise test. If you have an underlying heart condition or if an abnormality is detected, the test may be stopped prior to you achieving maximal exertion. This is called a sub-maximal stress test.
- Once the test is stopped you will enter the recovery phase and continue to walk in the treadmill for a few minutes, and then you will sit or lie down. During this time your blood pressure and heart rate is being monitored.
- EKG tracings are obtain periodically throughout the exercise and recovery phases. Also, your breathing is monitored as well as any symptoms you may report like chest pain, fatigue, palpitations, or shortness of breath.
Risks of Exercise Treadmill Test
Since exercise treadmill tests are conducted in a controlled environment and supervised by health care professional, they are considered generally safe. Below are some of the risks.
- Development of chest pain
- Irregular heart beat.
- Fainting or passing out.
- Heart attack,
- Collapse (death).
The risk of death, heart attack, or serious ventricular arrhythmia is about 1 in 10,000 tests.
How Accurate is an Exercise Treadmill Test?
When we talk about the accuracy of any test we want to know how sensitive a test is and how specific a test is. Sensitivity is how well a test detects the disease being screened for in those who actually have the disease. Specificity is how well a test accurately identifies those who are normal or do not have a disease.
A exercise treadmill test by itself has a sensitivity of 70% and specificity of 75%. This means if 100 patients of critical restriction of blood flow to the heart the exercise treadmill test will pick/detect this problem in 70 of those 100 patients. If 100 patients do not have any critical restriction of blood flow the test will identify 75 of those 100 as having a normal test.
This leads us to define four other terms.
- True positive: the person has the disease and the test is positive.
- True negative: the person does not have the disease and the test is negative.
- False positive: the person does not have the disease but the test is positive.
- False negative: the person has the disease but the test is negative.
A test that is highly sensitive will have few false negatives and a test that is highly specific will have few false positives. The exercise treadmill test is more accurate when performed in conjunction with some type of imaging study like a nuclear scan or cardiac echo.
Overall, the sensitivity and specificity of an exercise treadmill test is decent, but not great, but it is has many advantages. It less costly than other cardiac tests, can be done in an outpatient setting, and it provides a lot of useful information of the physiology of the body when under physical stress – how the blood pressure changes, how the heart changes, changes in the EKG, how well and quickly one recovers from exercise and more. All of this helps in designing a safe exercise program for patients.