A stress test is a special type of test that is used to measure the heart’s tolerance for exercise and to detect various forms of heart disease. The most common type of exercise stress test combines some form of mild exercise with an electrocardiogram (EKG) to measure the heart’s activity both at rest and while working.
This test is noninvasive, generally safe and painless. It may be administered in a number of different settings, including clinics, hospitals or physician’s offices. Exercise stress tests may be performed with echocardiography or nuclear imaging techniques. If patients are unable to exercise, another type of stress test uses drugs instead of physical activity to produce the effects of exercise during the examination.
A physician may recommend an exercise stress test for a number of reasons:
To diagnose conditions such as coronary artery disease (a chronic disease in which there is a “hardening” or atherosclerosis of the arteries) in patients with chest pain. Coronary artery disease can be diagnosed through an exercise stress test if it is causing cardiac ischemia (in which the heart is not getting enough oxygen-rich blood) and/or arrhythmias (abnormal heart rhythms).
To diagnose a heart-related cause of symptoms such as chest pain, shortness of breath or lightheadedness.
To determine a safe level of exercise among heart patients who wish to increase their level of physical activity.
To screen for coronary artery disease in some patients who do not have symptoms.
To gauge exercise capacity in heart failure patients who are being considered for a heart transplant.
To evaluate the effectiveness of a balloon angioplasty (a procedure in which plaque in the arteries is pushed back against the artery walls to make more room for blood flow), or other procedures.
To predict future risk of dangerous heart-related conditions, such as heart attack.
Depending on the results of the exercise stress test, the physician may recommend additional testing such as cardiac catheterization.
About exercise stress tests
An exercise stress test is a special type of test that is used to measure the heart’s tolerance for exercise and to detect various forms of heart disease. The most common type of exercise stress test combines some form of mild exercise with an electrocardiogram (EKG) to measure the heart’s activity both at rest and while working. This test is administered on an outpatient basis, often in a hospital, clinic or physician’s office. It is noninvasive, generally safe and painless. Exercise stress tests may also be performed with echocardiography or nuclear imaging techniques to gain additional diagnostic information.
During an EKG stress test, the EKG records the heart’s electrical activity as a graph on a moving strip of paper or video monitor. The highly sensitive electrocardiograph machine measures the heart’s rhythms and electrical impulses. The painless EKG is done while the patient is exercising in a controlled manner on a treadmill or stationary bicycle at varied speeds and elevations. This increases the heart's need for oxygenated blood, which makes it easier for physicians to provoke symptoms or signs that would indicate heart disease.
Many people with coronary artery disease will eventually have abnormal EKG readings. However, because a non-stress EKG is done while the patient is at rest, certain abnormalities that might occur during periods of exertion may not be detected. Because it is common to see this false-negative result (i.e., the EKG does not detect any damage or abnormality that is present), a non-stress EKG may not be adequate to rule out suspected heart disease, and an exercise stress test may be ordered.
During an exercise stress test, the physician will evaluate the patient’s general state of health and the heart’s reaction to exercise. As the intensity of the workout increases, the patient’s heart rate, blood pressure and general appearance are monitored both by the heart monitor (EKG) and the physician. The higher the level of exercise, the harder the heart has to work and the more blood flow is needed. This test allows the physician to evaluate whether the blood supply to the heart is sufficient during different levels of exercise intensity. Certain changes in the EKG pattern or in blood pressure will help the physician measure blood flow to the heart and evaluate the health of the coronary arteries.
EKG stress tests are noninvasive, generally quick, safe and painless. A physician may recommend an exercise stress test for a number of reasons:
To diagnose conditions such as coronary artery disease (a chronic disease in which there is a “hardening” or atherosclerosis of the coronary arteries) in patients with chest pain. Coronary artery disease can be diagnosed through an exercise stress test if it is causing cardiac ischemia (a condition in which the heart is not getting enough oxygen-rich blood) and abnormal heart rhythms (arrhythmias) that are either too fast (tachycardias) or too slow (bradycardias).
To screen for coronary artery disease in some patients who do not have symptoms. Although general screening is not usually recommended, several recent research studies indicate exercise stress tests can identify coronary problems in patients without symptoms.
To gauge exercise capacity in heart failure patients who are being considered for a heart transplant.
To diagnose heart-related causes of symptoms such as chest pain, shortness of breath or lightheadedness. Angina, a type of chest pain caused by lack of oxygen-rich blood in the heart, is a classic symptom of coronary artery disease. Stable angina occurs at predictable times, such as increased exertion. During a stress test, a physician might attempt to provoke a bout of stable angina to help determine if a patient is suffering from coronary artery disease.
To determine a safe level of exercise in cardiac patients who wish to increase their level of physical activity.
To check the effectiveness of a balloon angioplasty (a procedure in which plaque in the arteries is pushed back against the artery walls to make more room for blood flow), or other procedures that have been performed.
To predict future risk of dangerous heart-related conditions, such as heart attack.
To provide an objective assessment of functional capacity in patients whose symptoms do not match the severity of the underlying heart disease.
Although the exercise stress test is generally safe, it is not without a small risk to certain patients. According to a 2001 statement by the American Heart Association, an exercise stress test should not be ordered for patients who have:
Experienced a heart attack in the previous two days
Unstable angina, or chest pain that occurs at unpredictable times and is considered a very serious warning sign of an impending heart attack
Uncontrolled arrhythmias, or abnormal heart rhythms
Severe aortic heart valve disease with symptoms
Uncontrolled heart failure with symptoms
Endocarditis, acute myocarditis or pericarditis
Acute aortic dissection
Acute pulmonary embolism
Other non-cardiac disorders that may be aggravated by exercise
Other types of stress tests
Although the EKG exercise stress test is the most common, there are a number of others, including:
Pharmacological stress test (or chemical stress test). A type of stress test used with patients who are unable to perform physical activity. A drug such as dobutamine or adenosine is given to the patient, which causes the heart to react as if the person were exercising, even though the patient is actually at rest. Some drugs increase the heart rate, and other drugs increase blood flow by causing the coronary arteries to widen.
Stress echocardiogram. An echocardiogram is performed while the patient exercises in a controlled manner on a treadmill or stationary bicycle at varied speeds and elevations. The reaction of the heart under exertion can be measured, and the heart’s structure and function can be evaluated. This type of test can also be performed with the help of certain drugs that create stress in patients who are unable to exercise.
Nuclear stress test. A stress test that is performed in conjunction with a nuclear imaging test, such as a SPECT scan or PET scan. In these tests, a radionuclide tracer is introduced into the bloodstream and the rate of uptake is monitored. In the case of a SPECT test, a special gamma camera will measure how quickly the radionuclide tracer is taken into heart muscle on a blood cell. In the case of a PET scan, special sensors measure how quickly a carrier molecule, usually glucose, is absorbed into the heart muscle. In either case, physicians are able to see how healthy heart muscle is by determining its ability to absorb blood or glucose. These tests are frequently ordered after a heart attack to help doctors determine how much of the heart tissue has been damaged, and whether damaged areas are truly dead or if they are stunned or hibernating. Because the overall radiation exposure is low, these tests are considered very safe.
Before and during an exercise stress test
Patients are advised to refrain from eating or drinking anything other than water after midnight before a morning test, or after the morning before an afternoon test. It is easier to evaluate the heart’s performance when the patient’s stomach is empty because intense exercise can lead to nausea or cramping. Physicians may also reduce or stop certain medications prior to the test. Certain medications, such as beta blockers and digitalis, will reduce the target heart rate for the test or otherwise affect the results.
Patients should wear comfortable, loose clothing and appropriate shoes. Some patients may be asked to remove their clothes from the waist up and put on a gown. Also, it may be necessary for the patient to sign a consent form before beginning the test.
Depending on the physician, an exercise stress test will take place either in the physician’s office or at a facility such as a hospital. Once the patient has removed his or her clothes from the waist up, a nurse or technician will thoroughly clean about a dozen small areas on the patient’s body – usually the chest, arms and legs. Usually the technician will apply a conductive gel to these areas. About 10 to 12 small metal devices (electrodes) are then taped to the skin and attached by wires to the electrocardiograph machine. Each electrode produces a “tracing” or “lead” of a particular area of the heart and its activity.
The patient will sit down and the technician will enter the following information about the patient into the computer:
Age
Sex
Height
Weight
Current medications
Using this information, the physician can determine the patient’s maximum heart rate. This yields a target goal during the test. The patient then sits perfectly still for about one minute while the resting heart rate and blood pressure are measured and recorded. Blood pressure will be monitored throughout the test, and oxygen levels in the blood may also be measured by a small pulse oximeter on the finger, nose or ear.
If the patient is scheduled for a pharmacological stress test, he or she will then be given an injection that mimics the effects of exertion on the heart. If the patient is scheduled for a standard exercise stress test, he or she will complete the exercise component of the test.
Exercise will begin at a slow pace. Typically after three minutes (one stage), blood pressure is remeasured and recorded, and the speed and elevation of the treadmill or bicycle is increased. Throughout the test, the physician will speak with the patient, regularly monitoring and observing his or her physical condition, heart rate and EKG. Oxygen and carbon dioxide levels in the patient’s exhaled air may be measured. Generally, these measurements are taken at least once during each stage, and usually for about 30 seconds each.
Because patients are asked to exercise rather vigorously during the exercise phase of the test, some patients may experience symptoms including:
Lightheadedness
Discomfort or cramping
Tiredness or fatigue
If the patient experiences severe pain at any time or significant change in his or her physical state, the test will most likely be stopped.
The exercise portion of the test (up to 15 minutes) is ended either by the patient’s signal that he or she is too uncomfortable to continue (due to fatigue, pain or breathlessness), or because the patient’s heart rate has reached the target heart rate. The test may also be stopped if the physician discovers any serious abnormalities in the EKG or blood pressure measurements. A cool-down period of a few minutes will follow. Upon returning to a resting state, the patient’s EKG will once again be monitored, recorded and compared to the initial at-rest measurement.
After the exercise stress test
After the test, the patient is usually advised that he or she can eat, drink and resume normal activities immediately. The physician may then offer the patient a preliminary report and will usually provide a complete report within a day or two.
Some patients may experience mild to moderate chest pain (angina), tiredness, muscle aches and shortness of breath (dyspnea) after the test.
Overall, exercise stress test results are very accurate, depending on the patient and the variety of stress text. However, results can be affected by any of the following:
Abnormal resting EKGs
Anxiety that some patients may experience
Failure to finish or reach maximum heart rate
Faulty equipment (rare)
Women are more likely than men to be told that their exercise stress test was abnormal when no problem was actually present (a false-positive result).
Based on the results, the physician may order additional testing, such as a nuclear stress test. A more invasive procedure such as a cardiac catheterization may also be ordered.
Recent research on exercise stress tests
Studies continue to show that stress testing can reveal coronary artery disease (CAD) before the onset of any symptoms, or in the absence of overt symptoms (e.g., silent cardiac ischemia). According to the American Heart Association, stress testing is not recommended for general screening of people who do not have symptoms of heart disease unless those people are considered at high risk. However, several recent research studies have indicated that stress testing can identify potential heart problems in apparently healthy people with no symptoms.
Ultrafast computed tomography (also called electron beam computed tomography or EBCT) may be an alternative to exercise stress testing in identifying clogged arteries. A feature of EBCT is that it can detect even low percentages of calcified plaque that has formed in coronary arteries. This can be useful in younger individuals who have early, but asymptomatic heart disease. However, EBCT has little application in the elderly, who typically have greater degrees of calcification. Moreover, because EBCT involves exposure to radiation, it is not recommended as a general screening tool by the American Heart Association.
Nuclear stress testing is also becoming more available. Currently, the most common form of nuclear stress test is the SPECT test, which relies on a thallium tracer that is relatively easy to produce and store. However, this test results in a higher rate of false positives than the more sensitive PET test. Until recently, though, PET testing was more limited because of the difficulty associated with obtaining the radionuclide tracers. In recent years, the availability of tracers and the cost has come down, so PET testing has become more common.
Nuclear stress testing is also becoming more available. Currently, the most common form of nuclear stress test is the SPECT test, which relies on a thallium tracer that is relatively easy to produce and store. However, this test results in a higher rate of false positives than the more sensitive PET test. Until recently, though, PET testing was more limited because of the difficulty associated with obtaining the radionuclide tracers. In recent years, the availability of tracers and the cost has come down, so PET testing has become more common.
Questions for your doctor
Preparing questions in advance can help patients have more meaningful discussions with their physicians about their conditions. Patients may wish to ask their doctor the following questions related to stress tests:
Why are you recommending a stress test for me?
What type of stress test will I have?
Do I need to follow any special preparations?
Will any of my current medications affect the results of the test?
How long will the test take?
How will I be monitored for problems during the test?
What professionals are present during a stress test?
What will happen if I cannot perform the exercises?
Am I a candidate for a chemical stress test?
When and from whom will I receive the results of my test?
What will the test tell you about my heart health?
What are the risks associated with stress tests?
Should any other family members have this test for prevention reasons?
