The exercise stress test, also known as the treadmill test or exercise tolerance test, indicates whether your heart gets enough blood flow and oxygen when it’s working its hardest, such as during exercise. Often, stress tests are given to people with chest pain or other symptoms who appear to have coronary artery disease, based on a medical exam and EKG. In addition, these tests are sometimes used for other purposes, from assessing the effectiveness of heart disease treatment to gauging the safety of a proposed exercise program.
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Stress tests are among the best tools for diagnosing heart disease, and some research suggests that they may also be useful in estimating disease risk in people who don’t have symptoms but have risk factors such as high cholesterol. If you are over age 40 and are at risk for coronary artery disease because you smoke or have high blood pressure or other risk factors, ask your doctor if you should have this test.
Preparing for the Regular Stress Test:
The following recommendations are “generic” for all types of cardiac stress tests:
*Do not eat or drink for three hours prior to the procedure. This reduces the likelihood of nausea that may accompany strenuous exercise after a heavy meal. Diabetics, particularly those who use insulin, will need special instructions from the physician’s office.
*Specific heart medicines may need to be stopped one or two days prior to the test. Such instructions are generally provided when the test is scheduled.
*Wear comfortable clothing and shoes that are suitable for exercise.
*An explanation of the test is provided and the patient is asked to sign a consent form.
*Wear comfortable, loose-fitting clothing and athletic shoes. Let the doctor performing the test know if you think that you won’t be able to walk on a treadmill for any health reason, such as arthritis. Also let the doctor know if you have diabetes; since exercise can lower blood sugar, he or she may want to check your blood sugar level before the test begins, to be sure it is not too low (see “Diabetes alert,” below). It’s also important to tell the doctor or other health professional in the testing room if you’ve had any chest pain or pressure on the day of the test. Try to avoid eating a large meal right before the test, which could make exercising uncomfortable.
Total timing is approximately one hour for the entire test, including the preparation.
What happens when the test is performed?
First you have an EKG both while lying down and standing up. Your blood pressure is taken. Several plasticcoated wires, or leads, are taped to your arms and one leg so that your heart’s electrical pattern can be detected while you exercise.Your blood pressure and heart rate also are monitored during the test. You are asked to walk on a treadmill for about 10 minutes. The speed and steepness of the treadmill will increase several times while you exercise. Let the person who is monitoring you know immediately if you feel chest pain or heaviness, shortness of breath, leg pain or weakness, or other unusual symptoms, or if you think you can’t continue exercising.After the exercise period is completed, your blood pressure will be checked again.
A variation of this test uses a radionuclide to visualize parts of the heart that are not getting enough blood. This test is called either an exercise-thallium test or exercise-MIBI test (depending on the radionuclides used). If you have this test, you will probably need to repeat it on a day when you have not been exercising hard, for the sake of comparison.
An exercise stress test strongly suggests coronary artery disease if walking on the treadmill produces symptoms such as chest discomfort, shortness of breath, or dizziness, and these symptoms are accompanied by EKG changes that indicate inadequate blood flow to parts of the heart. A test is considered normal if you can perform a normal amount of exercise without symptoms or EKG changes. Many people have chest discomfort but no EKG changes, or vice versa. In these cases, the exercise test is of less help, and the result will be interpreted as consistent with coronary artery disease, but not conclusive. Further testing may then be required.
Must you do anything special after the test is over?
If your blood pressure becomes unusually high, or if it suddenly drops during exercise, a nurse will recheck your blood pressure a few minutes after the test and may continue to monitor your EKG. If you develop chest pain, you might be given some nitroglycerin tablets to relieve the pain and lower the demand on your heart by dilating your blood vessels.
What is the reliability of a Regular Stress Test?
If a patient is able to achieve the target heart rate, a regular treadmill stress test is capable of diagnosing important disease in approximately 67% or 2/3 rd of patients with coronary artery disease. The accuracy is lower (about 50%) when patients have narrowing in a single coronary artery or higher (greater than 80%) when all three major arteries are involved. Approximately 10% of patients may have a “false-positive” test (when the result is falsely abnormal in a patient without coronary artery disease).
How quickly will you may get the results and what will it mean?
The physician conducting the test will be able to give you the preliminary results before you leave the exercise laboratory. However, the official result may take a few days to complete. The results of the test may help confirm or rule out a diagnosis of heart disease. In patients with known coronary artery disease (prior heart attack, known coronary blockages, previous treatment with angioplasty, stents or bypass surgery, etc.), the study will help confirm that the patient is in a stable state, or that a new blockage is developing. The results may influence your physician’s decision to change your treatment or recommend additional testing such as cardiac catheterization, Echo Stress test, or a nuclear stress test.
The risk of the stress portion of the test is very small and similar to what you would expect from any strenuous form of exercise (jogging in your neighborhood, running up a flight of stairs, etc.). As noted earlier, experienced medical staff is in attendance to manage the rare complications like sustained irregular heart beats, unrelieved chest pain or even a heart attack.
If you have cardiac disease, you might develop chest pain during the test. Because this is a sign that your heart isn’t getting enough oxygen and could be in danger of damage, it’s important that you alert the medical staff immediately so that the test can be stopped. While many people worry that an exercise stress test could be dangerous to someone with heart disease, it is extremely safe if doctors examine patients beforehand to make sure that they are healthy enough for it.
How long is it before the result of the test is known?
It usually takes several days for the doctor to completely evaluate the printout of your heart’s electrical pattern.