What Is Stress Testing?
Stress testing provides information about how your heart works during physical stress. Some heart problems are easier to diagnose when your heart is working hard and beating fast.
During stress testing, you exercise (walk or run on a treadmill or pedal a stationary bike) to make your heart work hard and beat fast. Tests are done on your heart while you exercise.
Doctors usually use stress testing to help diagnose coronary heart disease (CHD). They also use stress testing to find out the severity of CHD.
CHD is a disease in which a waxy substance called plaque (plak) builds up in the coronary arteries. These arteries supply oxygen-rich blood to your heart.
Plaque narrows the arteries and reduces blood flow to your heart muscle. The buildup of plaque also makes it more likely that blood clots will form in your arteries. Blood clots can mostly or completely block blood flow through an artery. This can lead to chest pain called angina (an-JI-nuh or AN-juh-nuh) or a heart attack.
You may not have any signs or symptoms of CHD when your heart is at rest. But when your heart has to work harder during exercise, it needs more blood and oxygen. Narrow arteries can’t supply enough blood for your heart to work well. As a result, signs and symptoms of CHD may occur only during exercise.
A stress test can detect the following problems, which may suggest that your heart isn’t getting enough blood during exercise:
- Abnormal changes in your heart rate or blood pressure
- Symptoms such as shortness of breath or chest pain, especially if they occur at low levels of exercise
- Abnormal changes in your heart’s rhythm or electrical activity
During a stress test, if you can’t exercise for as long as what is considered normal for someone your age, it may be a sign that not enough blood is flowing to your heart. However, other factors besides CHD can prevent you from exercising long enough (for example, lung disease, anemia, or poor general fitness).
Types of Stress Testing
The two main types of stress testing are a standard exercise stress test and an imaging stress test.
Standard Exercise Stress Test
A standard exercise stress test uses an EKG (electrocardiogram) to detect and record the heart’s electrical activity.
An EKG shows how fast your heart is beating and the heart’s rhythm (steady or irregular). It also records the strength and timing of electrical signals as they pass through your heart.
During a standard stress test, your blood pressure will be checked. You also may be asked to breathe into a special tube during the test. This allows your doctor to see how well you’re breathing and measure the gases that you breathe out.
A standard stress test shows changes in your heart’s electrical activity. It also can show whether your heart is getting enough blood during exercise.
Imaging Stress Test
As part of some stress tests, pictures are taken of your heart while you exercise and while you’re at rest. These imaging stress tests can show how well blood is flowing in your heart and how well your heart pumps blood when it beats.
One type of imaging stress test involves echocardiography (echo). This test uses sound waves to create a moving picture of your heart. An exercise stress echo can show how well your heart’s chambers and valves are working when your heart is under stress.
A stress echo also can show areas of poor blood flow to your heart, dead heart muscle tissue, and areas of the heart muscle wall that aren’t contracting well. These areas may have been damaged during a heart attack, or they may not be getting enough blood.
Other imaging stress tests use radioactive dye to create pictures of blood flow to your heart. The dye is injected into your bloodstream before the pictures are taken. The pictures show how much of the dye has reached various parts of your heart during exercise and while you’re at rest.
Tests that use radioactive dye include a thallium or sestamibi stress test and a positron emission tomography (PET) stress test. The amount of radiation in the dye is considered safe for you and those around you. However, if you’re pregnant, you shouldn’t have this test because of risks it might pose to your unborn child.
Imaging stress tests tend to detect CHD better than standard (nonimaging) stress tests. Imaging stress tests also can predict the risk of a future heart attack or premature death.
An imaging stress test might be done first (as opposed to a standard exercise stress test) if you:
- Can’t exercise for enough time to get your heart working at its hardest. (Medical problems, such as arthritis or leg arteries clogged by plaque, might prevent you from exercising long enough.)
- Have abnormal heartbeats or other problems that prevent a standard exercise stress test from giving correct results.
- Had a heart procedure in the past, such as coronary artery bypass grafting or angioplasty (AN-jee-oh-plas-tee) and stent placement.
Information provided by National Heart Lung and Blood Institute