Load tests can be used to check for heart disease and may be recommended for some patients with diabetes. A stress test is a test performed by a physician and/or trained technician to determine the load the heart can carry before it develops an abnormal rhythm or ischemia (not enough blood flowing to the heart muscle). The most commonly performed stress test is the exercise stress test.
What is an exercise stress test?
An exercise stress test, also known as a stress test, exercise ECG, treadmill test, graded exercise test, or stress ECG, is a test that examines how the heart responds to exercise. It usually involves the patient walking on a treadmill or pedaling a stationary bike (with progressively increasing difficulty) while monitoring the ECG, heart rate, and blood pressure.
Why is a stress test needed?
Physicians typically use a stress test for the following goals.
- To determine if there is enough blood flow to the heart at increased activity levels.
- To assess the effectiveness of cardiac medications to control angina and ischemia.
- To determine the risk of developing coronary heart disease and the need for further evaluation.
- Examine the effectiveness of cardiac endovascular-related procedures (improving blood flow) to improve coronary artery disease.
- Identify heart rhythm abnormalities.
- Help develop a safe exercise program.
How do I prepare for an exercise load test?
Your doctor will tell you exactly what to prepare for before the load test. This may include the following.
- Fasting and abstaining from drinking anything other than water for 4 hours before the test.
- No alcohol or caffeine-containing foods for 24 hours before the test. Caffeine can affect test results.
- The physician may advise that certain heart disease or blood pressure medications that may interfere with the results are prohibited on the morning the test is performed. If you have any questions about your medication, talk to your doctor. Do not stop taking your medication without consulting your doctor.
- If an inhaler is required for breathing, it may be necessary to bring it to the test site.
What if I have diabetes?
If you have diabetes and plan to do a loading test, ask your doctor about medications.
- If taking insulin to control your blood sugar, ask your doctor about the dose of medication you should take on the day of the trial and if you should eat less.
- If controlling blood glucose by taking medication, your doctor may tell you not to take the medication for now and to take it after the trial is complete.
- Do not take your diabetes medication or eat one less meal before the trial.
- If you have a blood glucose monitor, take it with you and check your blood glucose levels before and after the exercise stress test. If you feel your blood sugar is extremely low, tell the staff right away.
What clothing should I wear on the day of the test?
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Wear soft-soled shoes suitable for walking and comfortable clothing. Do not bring valuables.
What does the exercise load test procedure involve?
During an exercise stress test, the examiner first gently cleans localized areas of the chest and places electrodes (tiny, flat, adhesive patches) in these areas. The electrodes are connected to an electrocardiogram monitor (ECG or EKG) to show the electrical activity of the heart during the test.
Before starting exercise, the examiner does an ECG to measure the heart rate and blood pressure at rest.
Exercise will then begin with walking on a treadmill or riding a stationary bike. The speed or difficulty of the exercise will gradually increase. The doctor will ask for continued exercise until the target heart rate is reached, fatigue is felt, or any symptoms begin to develop.
At regular intervals, the examiner will ask the patient how he or she feels. If you feel pain or discomfort in the chest, arm or jaw, shortness of breath, dizziness, vertigo or any other unusual symptoms, inform the examiner. It is normal to experience an increase in heart rate, blood pressure, respiratory rate and sweating during the test. Laboratory personnel will observe any symptoms or changes on the cardiac monitor, and the monitor will prompt the test to be stopped.
After the test, it is necessary to walk or pedal slowly for a few minutes to gradually return to a calm state. The monitor will still continue to monitor heart rate, blood pressure, and ECG until it begins to return to normal.
The actual exercise time is usually between 7 and 12 minutes.
If you have any questions about the exercise stress test, ask your doctor.
What other types of loading tests are available?
There are several different types of stress tests in addition to the exercise stress test.
- Drug stress test: This test is used in people who are unable to exercise. The patient is given a drug (such as adenosine, dobutamine, or dipyridamole) that causes the heart to respond as if the person were exercising. This way the doctor can still determine how the heart is responding to the load without having to exercise.
- Stress echocardiography: An echocardiogram (often called an “echo”) is an image of the heart’s movement. The echocardiographic stress test allows precise visualization of wall motion and pumping action of the heart under stress. Echocardiographic stress tests can also show inadequate blood flow, an abnormality that may be difficult to detect in other cardiac tests.
- Nuclear stress test: This test helps determine which parts of the heart are healthy, which parts are functioning normally, and which parts are abnormal. The test involves injecting a very small amount of harmless radioactive material into the body. The doctor then uses a special camera to identify the rays emitted by the substance in the body; this in turn produces images of blood flow to the heart muscle, both at rest and after exercise. With this technique, it is possible to detect less than normal amounts of material emitting rays from areas of the heart where the blood supply is reduced.
Preparation for different loading tests depends on how they are performed. Ask your doctor for specific requirements.