Exercise Stress Testing - Diagnostic test for heart diseases

An exercise stress test is sometimes known as an exercise tolerance test (ETT) or stress electrocardiogram. It is a method of measuring how your heart and blood vessels respond to physical exertion.

During this diagnostic test, you will wear electrodes which are connected by leads to a monitor. By observing this monitor, the physician can record your heartbeat during the test. The exercise you will perform consists of walking on a treadmill.

Why does my doctor want me to undergo this test?
You may have presented your doctor with symptoms of heart disease such as chest or arm pain, shortness of breath, dizziness, fatigue or swelling of your feet and ankles. Based upon your symptoms, your doctor may want to determine whether you have heart disease such as coronary artery disease (CAD).

Coronary artery disease or atherosclerosis, occurs when a build up of fat, cholesterol and other substances on the inner walls of the coronary arteries, block the flow of oxygen rich blood. If blood flow is completely blocked, the heart doesn't get the oxygen it requires, and the heart muscle may become permanently damaged. If you have known CAD, the stress test can also provide some information to your physician as to the severity of the disease.

An ETT can also be used to objectify your exercise capacity, if you have disease of your heart valves or if you have heart failure.

Your doctor may order a stress test after you have undergone corrective surgery such as coronary bypass surgery or balloon angioplasty, to help him/her design a safe rehabilitation program for you.

Is it a risky or dangerous test?
An exercise stress test is extremely safe. There are some risks associated with the test. Complications are very rare. The clinician performing the test will explain the risks and benefits of the procedure and obtain your informed consent before the test.

You should not undergo exercise stress testing if you have any of the following conditions: severe congestive heart failure; life threatening abnormal heart rhythms, heart infection, severe valve disease; severe hypertension; or any medical condition that precludes you from walking safely on a treadmill.

What preparations should I make before the test?
Do not eat three to four hours before the test. If you have diabetes, ask your physician what you may eat.

Discuss any medications you are currently taking with your doctor. You may take approved medications with water.

Wear comfortable clothing and comfortable shoes or sneakers.

How long will the test take?
The entire test, including preparation, takes about 45 minutes. Allow extra time for check in.

Do I have any additional responsibilities during the test?
You should tell the doctor if you feel any of the following symptoms during the test: chest, arm, or jaw discomfort; severe shortness of breath; fatigue; dizziness; or leg cramps or soreness during the test.

What will happen during the test?
The areas where the electrodes will be placed are first cleaned with alcohol and then with a slightly abrasive material. 12 electrodes will be placed on your chest. A blood pressure cuff will be placed around your arm so that your blood pressure can be measured throughout the test

Before the test, a resting ECG, blood pressure, and pulse levels are taken. ECG leads are kept in place during the exercise and for several minutes after the test.

The physician will show you how to use the treadmill. During the test, the treadmill's speed and incline will increase every 3 minutes. If you're at high risk for coronary artery disease or in poor physical condition, the grade and speed may be increased in smaller increments. Most stress tests last 6 to 10 minutes.

While you exercise, the supervising clinician will monitor changes in ECG and in your blood pressure which may indicate that your heart is not getting enough oxygen. Other signs include chest pain and unusual shortness of breath.

Feelings of fatigue, shortness of breath and sweating are normal during testing. The clinician will terminate the test early if he/she believes it's unsafe for you to continue.

At the end of the test the clinician may provide a cool down phase of approximately three minutes.

What happens after the test?
When the test is over, you may eat, drink, and return to your normal routine. Ask your doctor about resuming your medication(s).

You doctor may order another exercise stress test called a "nuclear" stress test.

What is "nuclear" stress testing?
A nuclear stress test allows your doctor to see pictures of your heart when you are at rest and immediately after you have exercised. The test can give information about the size of the heart's chambers, the pumping action of the heart, and the blood supply to the heart muscle.

This test is very similar to the exercise stress test, but differs in a few ways. You will receive an intravenous injection of a small amount of a radioactive substance (Thallium or Sestamibi) during the exercise.

As in the exercise stress test, you will have electrodes placed on your chest, and you will walk on a treadmill.

After the exercise portion of the test, you will leave the treadmill, and go into another room where you will lie flat on a narrow bed. A nuclear camera will be used to take pictures of your heart. The radioactive substance, also known as a nuclear tracer, is taken up by your heart muscle and allows the heart muscle to be visible for the nuclear camera. The camera moves around your body as it takes pictures. This part of the test takes about 15 to 20 minutes.

In most cases, it will also be necessary to take pictures of your heart muscle at rest. Depending on the kind of nuclear tracer being used, these pictures will be taken either before the exercise portion or after the exercise portion of the test using the same nuclear camera.

Your doctor will discuss the results of the nuclear stress test with you in a day or two. If the test shows that blood flow is normal during rest but abnormal during exercise, then the heart isn't receiving enough blood when you work harder than usual. If the test is abnormal during both exercise and rest segments, there probably is limited blood flow to a part of the heart at all times. If no radioactive substance is seen in a part of the heart muscle, it is indicative of a prior heart attack.

What if I am unable to exercise?
If you are disabled or too sick to perform an exercise tolerance test using a treadmill, a drug can be administered that increases blood flow to the heart and thus "mimics" exercise. Then the nuclear portion of the test can be performed as usual.

If you are having a "pharmacological" stress test, as described above, you should not eat, drink, smoke or have any caffeine for four hours before the test. Some over-the-counter pain relievers may contain caffeine. If you have diabetes, consult your physician about eating.

What is a stress echocardiogram?
An echocardiogram is a diagnostic test which employs ultrasound (high frequency sound waves) to obtain moving and still pictures of your heart. It is a safe and painless procedure.

A transducer wand is moved across your chest, to produce the sound waves and receive the echoes as they "bounce" off the heart and reflect as images on a television-like screen. The pictures are similar to X-ray images, but the process doesn't involve exposure to radiation. The pictures are recorded on videotape and paper.

Some of the information that stress echocardiography can provide includes: size measurements of the heart's four chambers, pictures of the appearance and motion of the heart valves, and indications as to how forcefully the heart contracts and forces blood throughout the body.

What happens during the stress echocardiogram?
The treadmill portion of the test resembles that of the exercise tolerance test. In this case, after your heart rate reaches a certain limit, you will be asked to lie down for the echocardiography portion of the test.

The echocardiograph operator will place three electrodes on your chest, and attach them by leads to an ECG machine so that your heart rhythm can be monitored throughout the test.

The operator will put a harmless, odorless gel on your chest. The gel will feel a little cool and moist at first. The gel helps the transducer pick up the sound waves from your heart. This device looks like a wand or a microphone. The transducer both generates and receives the sound signals.

The operator will put the transducer on your chest, directly above the structures your doctor wants to visualize. He will press firmly as he moves the transducer in arcs across your chest. This does not hurt.

You may be asked to participate by inhaling, exhaling or holding your breath at various times during the test. For the remainder of the time, you should remain still.

A stress echocardiogram takes approximately 60 minutes to perform.

What is a Dobutamine stress echocardiogram?
If you are unable to exercise, you may be given a drug such as Dobutamine which mimics the effect of stress on the body. The echocardiogram procedure is the same as above, except that slowly you will be given Dobutamine intravenously.

As in the drug-induced ETT, you should refrain from eating, drinking or ingesting caffeine for four hours before test. Again, if you have diabetes, consult your physician about eating.