Exercise Stress Test
The exercise stress test is a means of measuring the heart’s work capacity while exercising at increasing levels of exertion. Specifically, it is a way to gauge the heart’s ability to deliver oxygen-rich blood to the muscles as they work progressively harder. The test results also help your doctor estimate the ability of the blood vessels (coronary arteries) surrounding the heart to supply blood to the working heart muscle.
The stress test consists of monitoring the heart's electrocardiogram (ECG) pattern, rhythm, pulse rate and blood pressure while you perform a series of increasingly demanding physical exercises; these usually involve walking on a treadmill or pedaling a stationary bicycle.
At the beginning of the test, the doctor or staff member takes an ECG while you are in a resting position. The ECG shows, among other things, the electrical activity of your heart. After the resting measurements are obtained, the stress test is begun.
Every few minutes, at regular intervals, the speed and/or inclination of the treadmill or stationary bicycle is increased until your heart rate reaches a predetermined level.
The results of this test are evaluated by your doctor to determine the state of your heart and any treatment you may require.
Nuclear Stress Test
An additional form of exercise testing is called a nuclear stress test. The nuclear stress test is also performed on a treadmill or stationary bicycle to find out how well the coronary arteries are delivering blood to the heart muscle in a stress situation.
A temporary intravenous (IV) line is set up in one arm before beginning the exercise. When the stress test is nearly complete, the agent, which contains a small amount of radioactivity, is painlessly injected through the IV. The narrowed arteries can then be detected with a scanning camera. Shortly thereafter, several pictures of the heart are obtained so that your doctor can review the results and determine which treatment is best for you.
Pharmacologic Stress Test
For those patients unable to exercise adequately because of general weakness or advanced age, or those recovering from surgery, detection of coronary artery disease must be assessed by other means. Stress tests may be performed using a pharmacological drug in combination with a nuclear agent.
During the first part of the stress test, an intravenous (IV) medication is administered to expand or dilate the coronary arteries, as they would normally during vigorous exercise. Arteries that have narrowed because of coronary artery disease are not able to expand as much as normal arteries.
A nuclear agent is given intravenously after a few minutes. This agent flows freely through the normal arteries that have been expanded by the medication and less freely through the arteries that have narrowed. Because the nuclear agent is a radioisotope, scanning with a nuclear camera detects the narrowed arteries. By studying the ECG and the scans, your doctor is able to determine which areas of the heart may not receive a sufficient supply of blood and oxygen, and can decide the best course of treatment for you.
A stress echocardiogram is a stress test that includes ultrasound imaging with the exam. The test allows your doctor to see the heart muscle at work during exercise. For those patients that are unable to exercise adequately, a medication may be given to simulate exercise conditions. The pictures are obtained painlessly by placing a small ultrasound probe on the chest wall over the heart. No injections are required. Your doctor will analyze these images to obtain added information about your heart’s circulation pattern.