How does a Regular Stress Test Work?
Patients with coronary artery blockages may have minimal symptoms and an unremarkable ECG while at 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 (develop a more open channel) than an artery that has a blockage. This unequal dilation causes more blood to be delivered to heart muscle supplied by the normal artery. In contrast, narrowed arteries end up supplying reduced flow to it’s area of distribution. This reduced flow causes the involved muscle to “starve” during exercise. The “starvation” may produce symptoms (like chest discomfort or inappropriate shortness of breath), and the ECG may produce characteristic abnormalities. Most commonly, a motorized treadmill is used for exercise.
When is a Regular Stress Test ordered?
A regular stress test is considered in the following circumstances:
- Patients with symptoms or signs that are suggestive of coronary artery diseases (CAD).
- Patients with significant risk factors for CAD.
- To evaluate exercise tolerance when patients have unexplained fatigue and shortness of breath.
- To evaluate blood pressure response to exercise in patients with borderline hypertension.
- To look for exercise-induced serious irregular heart beats.
How is a Regular Treadmill Stress Test Performed?
The patient is brought to the exercise laboratory where the heart rate and blood pressure are recorded at rest. Sticky electrodes are attached to the chest, shoulders and hips and connected to the ECG portion of the stress test machine. A 12-lead ECG is recorded on paper. Each lead of the ECG represents a different portion of the heart.
The treadmill is then started at a relatively slow “warm-up” speed. The treadmill speed and it’s slope or inclination are increased every three minutes according to a preprogrammed protocol. The protocol dictates the precise speed and slope. Each three minute interval is known as a Stage (Stage 1, Stage 2, Stage 3, etc. Thus a patient completing Stage 3 has exercised for 3 x 3 = 9 minutes). The patient’s blood pressure is usually recorded during the second minute of each Stage. However, it may be recorded more frequently if the readings are too high or too low.
Dr. Wolfson pays particular attention to the heart rate, blood pressure, changes in the ECG pattern, irregular heart rhythm, and the patient’s appearance and symptoms. The treadmill is typically stopped when the patient achieves a target heart rate (this is 85% of the maximal heart rate predicted for the patient’s age). The test may be stopped if the patient develops significant chest discomfort, shortness of breath, dizziness, unsteady gait, etc., or if the ECG shows alarming changes or serious irregular heart beats. It may also be stopped if the blood pressure (BP) rises or falls beyond acceptable limits.
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. Patients with diabetes, particularly those who use insulin, will need special instructions from the office.
- Dr. Wolfson prefers you take all current medications and supplements on the day of your test.
- 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.
- How long does the entire test take? A patient should allow approximately one hour for the entire test, including the preparation.
How safe is a Regular Treadmill 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.
How quickly will I get the results and what will it mean?
Dr. Wolfson will be able to give you the results before you leave the exercise laboratory. 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 Dr. Wolfson’s decision to change your treatment or recommend additional testing such as a stress echocardiogram or cardiac catheterization.