Cardiac stress testing, also called exercise testing, can be useful in identifying partial blockages in your coronary arteries. Many times, the presence of coronary artery disease (CAD) are easily missed when a person is at rest, because at rest there may be no sign of a problem either on physical examination or on the ECG. In these cases, cardiac abnormalities may become apparent only when the heart is asked to perform at increased workloads.
The stress test is used to evaluate the heart and vascular system during exercise. It helps answer to two general questions:
- Is CAD present that only becomes apparent when the heart is stressed by exercise?
- If there is underlying heart disease, how severe is it likely to be?
How is a stress test performed?
First, you will have leads (wires) to an ECG machine attached to your chest, and a blood pressure cuff is placed on your arm. A clothespin-like sensor may be placed on your finger to measure the amount of oxygen in your blood. After a baseline ECG is obtained, you will be asked to begin performing a low level of exercise, either by walking on a treadmill, or pedaling a stationary bicycle.
The exercise is “graded” – that is, every three minutes, the level of exercise is increased. At each “stage” of exercise, your pulse, blood pressure and ECG are recorded, along with any symptoms you may be experiencing. With a “maximal” stress test, the level of exercise is gradually increased until you cannot keep up any longer because of fatigue, or until you experience symptoms (chest pain, shortness of breath, or lightheadedness) that prevent further exercise, or until changes on your ECG indicate a cardiac problem. Maximal stress tests should be performed when the goal is to look for any evidence of CAD.
What are the limitations of the stress test?
In some patients, ECG changes suggestive of ischemia can occur even in the absence of CAD (In other words, “false positive” stress tests are not uncommon). In other patients, no significant ECG changes are seen even in the presence of CAD (So “false negative” stress tests can be seen). False positive and false negative studies can significantly limit the usefulness of the stress test in many patients. By adding a nuclear perfusion study to the stress test, this limitation is minimized, and the diagnostic capacity of the stress test is greatly improved.
What are the risks of having a stress test?
The stress test has proven to be remarkably safe. It poses about the same level of risk as taking a brisk walk or walking up a hill. While it is possible that the ischemia provoked by such stress can lead to a myocardial infarction or to serious heart rhythm disturbances, in practice this event is rare. Further, when these serious events do occur during a stress test, they occur in the presence of trained medical personnel who can deal with them immediately.
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