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When is exercise stress test ordered?
Patients with coronary artery diseases may have minimal symptoms and an unremarkable or unchanged EKG upon rest. However, symptoms and signs of heart disease may become unmasked by exposing the heart to the stress of exercise. During exercise, healthy coronary arteries dilate more than an artery that has a blockage. This unequal dilation causes more blood to be delivered to the heart muscle supplied by normal arteries. The heart muscle supplied by the blocked artery becomes ‘starved’. This starvation may produce symptoms like chest discomfort or acute shortness of breath and EKG may produce characteristic abnormalities. Most commonly, a motorized treadmill is used for exercise, while a stationary bicycle is used in some laboratories.
When is exercise stress test ordered?
A regular exercise test is considered in the following circumstances:
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Patients with symptoms or signs that is suggestive of coronary artery disease (CAD) |
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Patients with significant risk factors for CAD |
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To evaluate exercise tolerance when patients have unexplained fatigue and shortness of breath |
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To evaluate blood pressure response to exercise in patients with borderline hypertension |
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To look for exercise-induced seriously irregular heart beats |
How is the treadmill stress test performed?
The patient is brought to the exercise laboratory where the heart rate and blood pressure are recorded at rest. Electrodes are attached to the chest, shoulders and hips which are in turn connected to the EKG portion of the stress machine. A 12-lead EKG is recorded. The treadmill is then started at a relatively slow ‘warm up’ speed. The speed and slope or inclination of the treadmill are increased every 3 minutes according to the protocol used. The patient’s blood pressure is recorded in each stage. The EKG is constantly displayed on the monitor and recorded. The treadmill is finally stopped when the patient has achieved the targeted heart rate. This test may be stopped period to achieving target heart rate if the patient develops significant chest discomfort, shortness of breath, dizziness, an unsteady gait or if the EKG shows alarming changes or serious irregular heart beats. It may also be stopped if the blood pressure rises or falls beyond acceptable levels.
Preparing for the test:
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No eating or drinking for 3 hours prior to the procedure. This reduces the likelihood of nausea that may accompany strenuous exercise after a heavy meal. |
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Special heart medicine may need to be stopped 1 or 2 days prior to this test. |
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Wear comfortable clothing and shoes that are suitable for exercise. |
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An explanation of the test is provided and the patient must be asked to sign a consent form. |
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A patient should allow approximately 1 hour for the entire test, including preparation process. |
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How safe is the regular treadmill stress test?
The risk of the stress portion of the test is very small and similar to what anyone would expect from any strenuous forms of exercise. An experienced medical staff is in attendance to manage rare complications that may arise like sustained irregular heart beats, unrelieved chest pains or even a heart attack.
How reliable is this test?
If a patient is able to achieve the target heart rate, a regular treadmill stress test is capable of diagnosing important diseases in approximately 67% or 2/3 of patients with coronary artery diseases. The accuracy is lower when patients have narrowing in a single coronary artery or higher when all three major coronary arteries are involved. Approximately 10% of patients may have a ‘false-positive’ test result.
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