What is it?
A stress test shows how the heart works during physical activity or conditions of stress. Because exercise makes the heart pump harder and faster, an exercise stress test can reveal problems with blood flow within the heart.
A stress test usually involves walking on a treadmill while the heart rhythm, blood pressure and breathing are monitored. Or the patient will receive a drug that mimics the effects of exercise.
The doctor may recommend a stress test if there are signs or symptoms of coronary artery disease or an abnormal heart rhythm (arrhythmia).
It may also be done in patients with established diagnosis of coronary heart disease. The test helps to evaluate the heart’s circulation, either for recurring symptoms or for the evaluation of prior angioplasty / surgical bypass procedure.
Types of Stress Tests
The simplest form of stress test utilizes a treadmill for exercise. Sometimes this is combined with the use of an injected imaging agent.
In patients who cannot exercise to the required level to make a diagnosis, other means of “stress” are employed to simulate the effects of exercise demands on the heart. This involves injecting or infusing a chemical to simulate exercise, followed by an imaging agent.
Before the test
The patient is asked not to eat, drink or smoke for a period of time before the stress test, and will need to avoid caffeine the day before and the day of the test.
Some medications might interfere with certain stress tests. The patient should inquire if any of the existing medications need to be held for the test.
For patients with breathing problems who use an inhaler, need to bring the inhaler for the test. It is important to notify the medical team about inhaler use.
Comfortable clothes and walking shoes are recommended for the test.
How is it done?
A treadmill stress test usually takes about an hour, including both prep time and the time it takes to do the actual test. The actual exercise test takes only around 15 minutes.
For patients that are not able to exercise, will receive a drug, through an IV that mimics the effect of exercise on the heart.
When nuclear imaging is combined with the stress, additional time is required for two sets of image acquisition.
A nurse or technician will place sticky patches (electrodes) on the patient’s chest, legs and arms. Body hair may be shaved to help them stick. Wires connect the sensors to a computer, which records the heart's electrical activity. A cuff on the arm checks the blood pressure during the test.
The treadmill exercise starts slowly. As the test continues, the speed and incline increase progressively making it harder. The patient can use the railing on the treadmill for balance, but not too tightly, as this may affect the results.
The patient continues exercising until the heart rate has reached a target level or until there are conditions that terminate the test. These conditions may include:
- Moderate to severe chest pain
- Severe shortness of breath
- Abnormally high or low blood pressure
- An abnormal heart rhythm
- Certain changes in the electrocardiogram
The patient and doctor will discuss the safe limits for exercise. The patient may stop the test any time it becomes too uncomfortable. The doctor will watch the heart activity and stop the test if there are any concerns.
If the patient cannot exercise during the stress test, they will be given a drug through an IV that increases blood flow to the heart. This may produce shortness of breath, headache, feeling flushed or racing of the heart.
Why is it done?
Diagnose coronary artery disease. The coronary arteries are the major blood vessels that supply the 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 signals that coordinate the heartbeat do not work properly. An arrhythmia can cause the heart to beat too fast, too slowly or irregularly.
Guide treatment of heart disorders. For already diagnosed heart conditions, an exercise stress test can help the doctor determine if the current treatment is working. The test results also helps the doctor decide on the best treatment.
Checking the heart before surgery. The doctor may use a stress test to determine when it is safe for a patient to have surgery, such as valve replacement or orthopedic surgery.
The physician will review the data and generate a report.
The findings will be reported to the referring physician or surgeon and will be discussed with the patient on follow up.
If the stress test results suggest that there may be coronary artery disease or show an arrhythmia, the doctor will use the information to develop a treatment plan. This may require additional tests, such as a coronary angiogram.
If a stress test was performed to help determine treatment for a heart condition, the doctor will use the results to plan or change the treatment.