What Is Stress Testing?
Stress testing provides your doctor with 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 a
stress test, you exercise (walk or run on a treadmill or pedal a bicycle) or
are given a medicine to make your heart work harder while heart tests are
During these tests, your heart is monitored using
images or through dime-sized electrodes attached to your chest, arms, or legs.
You may be asked to breathe into a special tube during the test. This will
allow your doctor to see how well youre breathing.
You may have arthritis or another medical problem
that prevents you from exercising during a stress test. If so, your doctor can
give you a medicine that makes your heart work harder, as it would if you were
exercising. This is called a pharmacological (FAR-ma-ko-LOJ-i-kal) stress
Doctors usually use stress testing to help diagnose
artery disease (CAD) or to see how serious this disease is in those who are
known to have it. Its sometimes used to assess other problems such as
heart valve abnormalities or
CAD occurs when the arteries that supply blood to
the heart muscle (the coronary arteries) become hardened and narrowed with a
material called plaque (plak). Plaque is made up of fat, cholesterol, calcium,
and other substances found in the blood. Plaque builds up on the insides of the
arteries, narrowing them and restricting blood flow to your heart.
You may not have any signs or symptoms of CAD when
your heart is at rest. But when your heart has to work harder during exercise,
it needs more blood and oxygen, and narrowed arteries arent able to
supply enough blood for your heart to work well. Thus, the signs and symptoms
may occur only during exercise.
A stress test can detect the following indications
that your heart may not be getting enough blood during exercise.
- Abnormal changes in your heart rate or blood
- Symptoms such as shortness of breath or chest
- Abnormal changes in your heart rhythm or the
electrical activity of your heart
During the stress test, if you cant exercise
for as long as whats considered normal for someone your age, it may be a
sign that not enough blood is flowing to your heart. But other factors besides
CAD can prevent you from exercising long enough (for example, lung diseases,
or poor general fitness).
Stress Testing Using Imaging
Some stress tests take pictures of the heart when
you exercise and when youre at rest. These imaging stress tests can show
how well blood is flowing in the different parts of your heart and/or how well
your heart squeezes out blood when it beats
One type of imaging stress test involves
echocardiography, which is a test that uses sound waves to
create a moving picture of your heart. An echocardiogram stress test can show
how well your hearts chambers and valves are working when your heart is
under stress. The test can identify areas of poor blood flow to your heart,
dead heart muscle tissue, and areas of the heart muscle wall that arent
contracting normally. These areas may have been damaged during a
attack or may be getting too little blood.
Other imaging stress tests use a radioactive dye to
create images of the blood flow to your heart. The dye is injected into your
bloodstream before pictures are taken of your heart. The pictures show how much
of the dye has reached various parts of your heart during exercise and at
Tests that use a 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 safe and not a danger to you or those
around you. However, if youre pregnant, you shouldnt have this test
because of risks it might pose to your unborn child.
Some doctors may use
resonance imaging (MRI) to take pictures of the heart when its
working hard. This test doesnt use a radioactive dye or sound waves.
Instead, it uses radio waves and magnetic fields to create images that show
blood flow in the heart and whether all parts of the heart wall are contracting
Imaging stress tests tend to be more accurate at
detecting CAD than standard (nonimaging) stress tests. An imaging stress test
may be done first if you:
- Cant exercise for enough time to get your
heart working its hardest. (Medical problems, such as arthritis or leg arteries
clogged by plaque, may prevent you from exercising enough.)
- Have abnormal heartbeats or other problems that
will cause a standard exercise stress test to be inaccurate.
- Are a woman. Standard stress tests are less
accurate in women than in men. If youre a woman and live far from a
testing facility, your doctor may want you to skip a standard stress test and
get an imaging stress test instead. That way, you dont have to make a
second trip for the imaging stress test if there are any questions about the
results from the standard stress test.