A treadmill test or cardiac stress test is performed to assess the heart's response to stress or exercise. This method is one of the simplest and fastest procedures used to evaluate the heart. During the test, electrodes (small, plastic patches) are placed at certain locations on the chest, arms, and legs. When the electrodes are connected to an electrocardiogram (ECG or EKG) machine by lead wires, the electrical activity of the heart is measured, interpreted, and printed out for the physician's information and further interpretation. This test is also known as cardiac SPECT, myocardial perfusion SPECT, nuclear stress test, and stress perfusion test.
An ECG tracing will be taken at certain points during the test in order to compare the effects of increasing stress on the heart. Periodically, the incline and treadmill speed will be increased in order to make exercise more difficult for the person being tested. If the person is riding a bicycle, he/she will pedal faster against increased resistance. In either circumstance, the person will exercise until reaching a target heart rate (determined by the physician based on age and physical status) or until unable to continue due to fatigue, shortness of breath, chest pain, or other symptoms.
Other related procedures that may be used to assess the heart include resting electrocardiogram (ECG), Holter monitor, signal-averaged ECG, cardiac catheterization, chest X-ray, computed tomography (CT scan) of the chest, echocardiography, electrophysiological studies, magnetic resonance imaging (MRI) of the heart, myocardial perfusion scans, radionuclide angiography, and ultrafast CT scan.
Reasons for the procedure
Reasons for your physician to request a treadmill test or cardiac stress test include, but are not limited to the following:
- To determine limits for safe exercise in patients who are entering a cardiac rehabilitation program and/or those who are recovering from a cardiac event, such as a heart attack (myocardial infarction, or MI) or heart surgery
- To assess leg pain with exercise (also called intermittent claudication) in patients with suspected occlusion in the legs' circulatory system
- To evaluate blood pressure during exercise
- To assess stress or exercise tolerance in patients with known or suspected coronary artery disease
There may be other reasons for your physician to recommend an exercise ECG.
Risks of the procedure
Because of the stress the heart incurs during a cardiac stress test, there is a small chance for chest pain, heart attack, high blood pressure, irregular heartbeats, dizziness, nausea and extreme fatigue. Notify your physician if you have the following conditions:
- Aneurysm – a dilation of a part of the heart muscle or the aorta (the large artery that carries oxygenated blood out of the heart to the rest of the body) which may cause a weakness of the tissue at the site of the aneurysm
- Unstable angina (uncontrolled chest pain)
- Severe heart valve disease
- Severe congestive heart failure
- Recent myocardial infarction (also called MI, or heart attack)
- Severe hypertension (high blood pressure)
- Uncontrolled irregular heartbeats
- Pericarditis (an inflammation or infection of the sac which surrounds the heart)
- Severe anemia (low red blood cell count)
If you are pregnant or suspect that you may be pregnant, you should notify your physician.
Prolonged application of the adhesive electrode patches may cause tissue breakdown or skin irritation at the application site.
There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your physician prior to the procedure.
Certain factors or conditions may interfere with or affect the results of the test. These include, but are not limited to, the following:
- Intake of a heavy meal, caffeine, and/or smoking prior to the procedure
- High blood pressure
- Electrolyte abnormalities, such as too much or too little potassium, magnesium, and/or calcium in the blood
- Certain medications
- Heart valve disease
- Enlarged left ventricle