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
performed.
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
test.
Overview
Doctors usually use stress testing to help diagnose
coronary
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
heart
failure.
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
pressure
- Symptoms such as shortness of breath or chest
pain
- 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,
anemia,
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
heart
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
rest.
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
magnetic
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
strongly.
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.
Other Names for Stress Testing
- Exercise test
- Treadmill test
- Exercise echocardiogram or exercise stress
echo
- Thallium stress test
- Sestamibi stress test
- Stress EKG
- Myocardial perfusion imaging
- Pharmacological stress test
- MRI stress test
- PET stress test
- Nuclear stress test
Who Needs Stress Testing?
You may need a stress test if youve had chest
pains, shortness of breath, or other symptoms of limited blood flow to your
heart. Imaging stress tests are particularly helpful in showing whether you
have coronary
artery disease (CAD) or a problem with one of the valves in your heart.
(Heart valves are like doors that let blood flow between the hearts
chambers and into the hearts arteries. So, like CAD, faulty heart valves
can limit the amount of blood reaching your heart.)
If youve been diagnosed with CAD or recently
had a
heart
attack, you may need stress testing to see whether you can tolerate an
exercise program. The testing also can show whether treatments designed to
improve blood flow in the hearts arteries are necessary and likely to
help you. These treatments include
angioplasty
(with or without
stents)
and
coronary
artery bypass grafting. After having one of these treatments, your doctor
may want you to have a stress test to see how well the treatment relieves your
signs or symptoms of CAD.
You also may need a stress test if, during exercise,
you feel faint, get a rapid heartbeat or a fluttering feeling in your chest, or
have other symptoms of an
arrhythmia
(an irregular heartbeat). The stress test can detect an arrhythmia and show
whether you need medicine or a pacemaker or implantable cardioverter
defibrillator (ICD) to correct irregular heartbeats. It also can reveal the
effectiveness of such devices.
You may need a stress test even if you dont
have chest pain when you exercise, but just get short of breath. The test can
help show whether a heart problem, rather than a lung problem or being out of
shape, is causing your breathing problems. For such testing, you breathe into a
special tube so a technician can measure the gases you breathe out.
Breathing into the special tube and monitoring of
the heart as part of a stress test also is done to assess fitness before a
heart transplant. Your doctor also may use this monitoring to figure out the
best exercise plan for you after recovery from a heart attack.
Stress testing isnt routinely done to screen
people for CAD. Usually you have to have symptoms of CAD before a doctor will
recommend that you have a stress test. But your doctor may want to use a stress
test to screen for CAD if you have diabetes, which increases your risk for
developing CAD.
What To Expect Before Stress Testing
Standard stress testing can often be done in a
doctors office. But imaging stress testing is usually done at a hospital.
Be sure to wear athletic or other shoes in which you can exercise comfortably.
You may be asked to wear comfortable clothes in which you can easily exercise,
or you may be given a gown to wear during the test.
Your doctor may ask you not to eat or drink anything
but water for a short time before the test. If youre diabetic, ask your
doctor whether you need to adjust your medicines on the day of your test.
For some stress tests, you cant drink coffee
or other caffeinated drinks for a day before the test. Certain over-the-counter
or prescribed medicines also may interfere with some stress tests. Ask your
doctor whether you can take all your medicines as usual and whether you need to
avoid certain drinks or foods.
If you use an inhaler for
asthma
or other breathing problems, bring it to the test and be sure to let the doctor
know that you use it.
What To Expect During Stress Testing
During all types of stress testing, a technician
will always be with you to closely monitor your health status.
Before you start the stress part of a
stress test, a technician will put small sticky patches called electrodes on
the skin of your chest, arms, and legs. To help an electrode stick to the skin,
the technician may have to shave a patch of hair where the electrode will be
attached.
The electrodes are connected to a machine that
records the electrical activity of your heart. This recording, which is called
an EKG
(electrocardiogram), shows how fast your heart is beating and the hearts
rhythm (steady or irregular). The machine also records the strength and timing
of electrical signals as they pass through each part of your heart.
The technician will put a blood pressure cuff on
your arm to monitor your blood pressure during the stress test. (The cuff will
feel tight on your arm when it expands every few minutes.) In addition, you may
be asked to breathe into a special tube so the gases you breathe out can be
monitored.
After these preparations, you will exercise on a
treadmill or stationary bicycle. If such exercise poses a problem for you, you
may instead turn a crank with your arms. During the test, the exercise level
will get harder. But you can stop whenever you feel the exercise is too much
for you.
Stress Testing
The illustration shows a patient
having a stress test. Electrodes are attached to the patients chest and
connected to an EKG (electrocardiogram) machine. The EKG records the
hearts electrical activity. A blood pressure cuff is used to record the
patients blood pressure while he walks on a treadmill.
If you cant exercise, a technician will inject
a medicine into a vein in your arm or hand. This medicine will increase the
flow of blood through the coronary arteries and/or make your heart beat faster,
as would exercise. This results in your heart working harder, so the stress
test can be performed. The medicine may make you flushed and anxious, but the
effects disappear as soon as the test is over. The medicine may also give you a
headache.
While youre exercising or receiving medicine
to make your heart work harder, the technician will ask you frequently how
youre feeling. You should tell him or her if you feel chest pain,
shortness of breath, or dizzy. The exercise or medicine infusion will continue
until you reach a target heart rate, or until you:
- Feel moderate to severe chest pain
- Get too out of breath to continue
- Develop abnormally high or low blood pressure or
an arrhythmia
(an abnormal heartbeat)
- Become dizzy
The technician will continue to monitor your heart
functions and blood pressure for a short time after you stop exercising or stop
receiving the stress-creating medicine. The stress part of a stress
test (when youre exercising or given a medicine that makes your heart
work hard) usually lasts only about 15 minutes or less. But there is
preparation time before the test and monitoring time afterward. Both extend the
total test time to about an hour for a standard stress test, and up to 3 hours
or more for some imaging stress tests.
Exercise Stress Echocardiogram Test
For an exercise stress echocardiogram test, the
technician will take pictures of your heart using
echocardiography before you exercise and after you finish. A
sonographer (a person who specializes in using ultrasound techniques) will
apply a gel to your chest and then will briefly put a wand-like device (called
a transducer) against your chest and move it around. The transducer sends and
receives high-pitched sounds that you usually cant hear. The echoes from
the sound waves are converted into moving pictures of your heart on a
screen.
You may be asked to lie on your side on an examining
table for this test. Some stress echocardiogram tests also use a dye to improve
imaging. This dye is injected into your bloodstream while the test occurs.
Sestamibi Stress Test or Other Imaging Stress Test
Involving Radioactive Dye
For a sestamibi or other imaging stress test that
uses a radioactive dye, the technician will inject a small amount of the dye
(such as sestamibi) into your bloodstream via a needle placed in a vein of your
arm or hand. Youre usually given the dye about a half-hour before you
start exercising or are given a medicine that makes your heart work hard. 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.
Pictures will be taken of your heart at least two
timeswhen its at rest and when its working its hardest. For
such imaging, you will lie down on a table and a special camera or scanner that
can see the dye in your bloodstream will take pictures of your heart. Some
pictures may not be taken until you lie quietly for a few hours after
exercising or receiving the stress-creating medicine. Some patients may even be
asked to return in a day or so for more pictures to be taken.
Magnetic Resonance Imaging Stress Test
A magnetic resonance imaging (MRI) stress test may
use a medicine rather than exercise to get your heart to work harder. But some
facilities have you exercise on a specially made bicycle or treadmill that
allows you to exercise while lying on your back. For this test, you will be put
inside a tunnel-like MRI machine that takes pictures of your heart when
its working hard and when your body is at rest.
What To Expect After Stress Testing
After stress testing, youre able to return to
normal activities. If you had a test that involved radioactive dye, your doctor
may ask you to drink plenty of fluids to flush it out of your body. You also
shouldnt have certain other imaging tests until the dye is no longer in
your body. Your doctor can advise you about this.
What Does Stress Testing Show?
Stress testing provides your doctor with information
about how your heart works during physical stress (exercise) and how healthy
your heart is. Standard exercise stress testing uses an
EKG
(electrocardiogram) to monitor changes in the electrical activity of your
heart. Imaging stress tests take pictures of the blood flow to different parts
of your heart.
Both types of stress testing are used to look for
signs that your heart isnt getting enough blood flow during exercise.
Abnormal results on stress testing may be due to
coronary
artery disease (CAD), but also can be due to other factors such as a lack
of physical fitness.
If you have a standard exercise stress test and the
results are normal, no further testing or treatment may be needed. But if your
standard exercise stress test results are abnormal, or if youre
physically unable to exercise, your doctor may want you to have an imaging
stress test or undergo other testing. Even if your standard exercise stress
test results are normal, your doctor may want you to have an imaging stress
test if you continue having symptoms (such as shortness of breath or chest
pain).
Standard exercise stress testing isnt equally
accurate in men and women. Normal results from a standard exercise stress test
usually accurately rule out CAD in both men and women. But a standard exercise
stress test can show abnormal results even when the patient doesnt have
CAD (these results are called false positives). False positive exercise stress
tests happen more often in women than in men.
Imaging stress tests are more accurate than standard
exercise stress tests (in men and women) because they directly show how well
blood is flowing in heart muscle and reveal parts of the heart that arent
contracting strongly. But imaging stress tests are much more expensive than
standard exercise stress tests.
Imaging stress tests can show the parts of the heart
not getting enough blood, as well as dead tissue in the heart, where no blood
flows. (A
heart
attack can cause some tissue in the heart to die.) If your imaging stress
test suggests significant CAD, your doctor may want you to have more testing
and/or treatment.
What Are the Risks of Stress Testing?
Theres little risk of being seriously harmed
from any type of stress testing. The chance of these tests causing a
heart
attack or death is about 1 in 5,000. More common but less serious side
effects linked to stress testing include:
- Arrhythmia
(an irregular heartbeat). This often will go away quickly once youre at
rest. But if it persists, you may need to go to the hospital and be monitored
or get treatment.
- Low blood pressure, which can cause you to feel
dizzy or faint. This will go away once your heart stops working hard; it
doesnt usually require treatment.
- Jitteriness or discomfort while getting medicine
to make your heart work harder (you will be given medicine if you cant
exercise). These side effects usually disappear shortly after you stop getting
the medicine, but in some cases may last a few hours.
Key Points
- A stress test helps show whether enough blood
flows to your heart when its working hard. Doctors usually use stress
testing to help them diagnose
coronary
artery disease (CAD) or to see how serious this disease is in those who are
known to have it.
- During a stress test, 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.
- Standard exercise stress tests use
EKGs
(electrocardiograms) and breathing and blood pressure monitoring to assess
blood flow in the heart. Imaging stress tests, such as those that use
echocardiography, radioactive dyes, or magnetic resonance
imaging (MRI), show how well blood is flowing in heart muscle. Imaging stress
tests tend to be more accurate than standard exercise tests.
- You may need a stress test if you have CAD
symptoms, such as chest pain and shortness of breath. If youve been
diagnosed with CAD or recently had a
heart
attack, you may have stress testing to see whether treatments aimed at
improving blood flow in the hearts arteries are needed and likely to help
you. Stress testing also is done on people who have signs of an
arrhythmia
(irregular heartbeat).
- Stress testing may be done at a doctors
office or at a hospital. It will usually take between 1 and 3 hours.
- You may have to restrict your diet or not take
certain medicines before a stress test. Be sure to wear shoes in which you can
exercise comfortably during the stress test.
- Your health status will always be closely
monitored during a stress test, and you will not have to exercise more than you
think you can handle. Stress tests are safe and have few side effects. The
chance of a stress test causing a heart attack or death is only about 1 in
5,000.
- Youre able to return to all your normal
activities after a stress test.
- If test results are normal, no further testing or
treatment is usually needed unless your CAD symptoms persist. If there are
abnormal results on your standard exercise stress test, your doctor will
probably want you to have an imaging stress test or undergo other testing. But
imaging may not be needed if factors other than CAD could explain the abnormal
results. Abnormal results on an imaging stress test will require more testing
and/or treatment.
Links to Other Information About Stress
Testing
NHLBI Resources
Non-NHLBI Resources
Clinical Trials
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