A heart stress test can be useful in identifying partial blockages in your coronary arteries.

Many times, the presence of coronary artery disease (CAD) is 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 heart stress test is used to evaluate the heart and vascular system during exercise. It helps answer to two general questions: 1) Is CAD present that only becomes apparent when the heart is stressed by exercise? 2) If there is underlying heart disease, how severe is it likely to be?

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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 your symptoms (chest pain, shortness of breath, or lightheadedness) prevent further exercise, or until changes on your ECG indicate a cardiac problem. Maximal stress tests should be performed when the goal is to diagnose the presence or absence of CAD.

With a "submaximal" stress test, you will exercise only until a pre-determined level of exercise is attained. Submaximal tests are used in patients with known CAD, in order to measure whether a specific level of exercise can be performed safely.

After the test, you will be monitored until any symptoms disappear, and until your pulse, blood pressure and ECG return to baseline.