A stress test can be used to test for heart disease and may be recommended for some people with diabetes. Stress tests are tests performed by a doctor and/or trained technician to determine the amount of stress that your heart can manage before developing either an abnormal rhythm or evidence of ischemia (not enough blood flow to the heart muscle). The most commonly performed stress test is the exercise stress test.
What Is an Exercise Stress Test?
The exercise stress test -- also called a stress test, exercise electrocardiogram, treadmill test, graded exercise test, or stress ECG -- is a test used to provide information about how the heart responds to exertion. It usually involves walking on a treadmill or pedaling a stationary bike at increasing levels of difficulty, while your electrocardiogram, heart rate, and blood pressure are monitored.
Why Do I Need a Stress Test?
Your doctor uses the stress test to:
- Determine if there is adequate blood flow to your heart during increasing levels of activity.
- Evaluate the effectiveness of your heart medications to control angina and ischemia.
- Determine the likelihood of having coronary heart disease and the need for further evaluation.
- Check the effectiveness of procedures done to improve blood flow within the heart vessels in people with coronary heart disease.
- Identify abnormal heart rhythms.
- Help you develop a safe exercise program.
What Types of Stress Tests Are There?
Besides the exercise stress test, there are several different types of stress tests, including:
- Pharmacologic Stress Test: This test is used in people who are unable to exercise. A drug such as adenosine, dobutamine or dipyridamole is given to make the heart respond as if the person were exercising. This way the doctor can still determine how the heart responds to stress, but no exercise is required.
- Stress echocardiogram: An echocardiogram (often called "echo") is a graphic outline of the heart's movement. A stress echo can accurately visualize the motion of the heart's walls and pumping action when the heart is stressed; it may reveal a lack of blood flow that isn't always apparent on other heart tests.
- Nuclear stress test: This test helps to determine which parts of the heart are healthy and function normally and which are not. A very small and harmless amount of radioactive substance is injected into the patient. Then the doctor uses a special camera to identify the rays emitted from the substance within the body; this produces clear pictures of the heart tissue on a monitor. These pictures are done both at rest and after exercise. Using this technique, a less than normal amount of the substance will be seen in those areas of the heart that have a decreased blood supply.
Preparation for these types of stress test will vary from preparation for the exercise stress test. Ask your doctor about any specific instructions.
How Should I Prepare for the Exercise Stress Test?
Your doctor will give you specific instructions on what to do before your stress test. These may include:
- Do not eat or drink anything except water for four hours before the test.
- Do not drink or eat foods containing caffeine for 12 hours before the test. Caffeine can interfere with the results of your test.
- You may be told not to take certain heart or blood pressure medications the morning of the test that may interfere with the results. If you have any questions about your medications, ask your doctor. Do not discontinue any medication without first talking with your doctor.
- If you use an inhaler for your breathing, you may need to bring it to the test.
What If I Have Diabetes?
If you have diabetes and are scheduled for a stress test, ask your doctor about your medication:
- If you take insulin to control your blood sugar, ask your doctor what amount of your medication you should take the day of the test and if you should eat a light meal.
- If you take pills to control your blood sugar, you may be told to wait and take your medication after the test is complete.
- Do not take your diabetes medication and skip a meal before the test.
- If you own a glucose monitor, bring it with you to check your blood sugar levels before and after your exercise stress test. If you think that your blood sugar is low, tell the lab personnel immediately.
What Should I Wear the Day of the Test?
Wear soft-soled shoes suitable for walking and comfortable clothes. Do not bring valuables.
What Happens During the Exercise Stress Test?
During an exercise stress test, a technician will first gently clean 10 small areas on your chest and place electrodes (small, flat, sticky patches) on these areas. The electrodes are attached to an electrocardiograph monitor (ECG or EKG) that charts your heart's electrical activity during the test.
Before you start exercising, the technician will perform an EKG, to measure your heart rate at rest and will take your blood pressure.
You will begin to exercise by walking on a treadmill or pedaling a stationary bicycle. The rate of exercise, or degree of difficulty will gradually increase. You will be asked to exercise until you reach a target heart rate, feel exhausted or start having any symptoms.
At regular intervals, the lab personnel will ask how you are feeling. Please tell them if you feel chest, arm, or jaw pain or discomfort, short of breath, dizzy, lightheaded, or any other unusual symptoms. It is normal for your heart rate, blood pressure, breathing rate, and perspiration to increase during the test. The lab personnel will watch for any symptoms or changes on the ECG monitor that suggest the test should be stopped.
After the test you will walk or pedal slowly for a couple of minutes to cool down. Your heart rate, blood pressure, and ECG will continue to be monitored until the levels begin returning to normal.
Although the appointment lasts about 60 minutes, the actual exercise time is usually between seven and 12 minutes.
Ask your doctor if you have any questions about the exercise stress test.