- Introduction to stress testing
- Why do a stress test?
- Who can’t do a stress test?
- Preparing for a stress test
- What happens during a stress test?
- Risks and benefits of stress testing
- What do the results mean?
A stress test is an investigation done to measure the capacity of the heart, lungs and blood vessels to cope with the extra demands of exercise. It is often used in the diagnosis of coronary heart disease, in accordance with the Cardiac Society of Australia and New Zealand’s best practice guidelines.
During a stress test, the patient is asked to exercise by running or cycling so that they put increased demand on their heart. This increased demand may ‘unmask’ symptoms of angina or other heart disease that are not normally present at rest. The ability of the heart to cope with the extra stress is monitored using an ECG, or electrocardiogram, which looks at the electric activity of the heart.
Other types of exercise stress test exist which use chemicals or imaging techniques such as ultrasound to assess heart function during exercise. These will not be discussed here.
Stress tests are most commonly performed to help in the diagnosis of coronary heart disease. Patients who have some symptoms of coronary heart disease (such as angina) but in whom the diagnosis is not certain might be asked to have a stress test to see how their heart copes with the extra stress of exercise.
Stress tests may also be done to assess the prognosis (outlook) for patients with established coronary heart disease, to assess the effect of treatments like angioplasty on coronary heart disease symptoms, or after a heart attack to work out a safe exercise program.
While ECG stress testing is a widely used test, in may not be appropriate for some patients.
Stress testing requires that you exercise, usually on a treadmill, for an extended period of time and at moderate intensity. Patients who are unable to exercise for any reason, such as severe arthritis or other physical or mental disability, may not be able to undergo stress testing.
Certain other conditions may make the results of ECG stress testing more difficult to interpret. These including being on digoxin therapy, having pre-existing ECG changes at rest, and patients with paced ventricular rhythms (eg. on a pacemaker).
- It is usually recommended that you avoid eating, drinking, or smoking for at least two hours before the test. Your doctor may also ask you to avoid caffeine for 24 hours before the test.
- You should wear comfortable clothing and shoes that you can exercise and run in.
- Avoid using powders or lotions on your chest on the day of the test. The monitoring leads for the ECG will be placed on your chest, and these substances may interfere with the signal.
- Some cardiac medications may interfere with the results of a stress test, such as verapamil, digoxin or nitrites. You should discuss these with your doctor before the test, as you may need to stop taking them one or two days before.
- If you are a diabetic, you may need to change the amount of insulin or oral medication you take on the day of the test. Speak to your doctor about this when you schedule the test.
- Before the test begins, you will be connected up to monitors that measure your blood pressure and heart rhythm (ECG). A ‘baseline’ reading will be taken of your heart rhythm and blood pressure at rest. This allows us to compare any changes that may occur with exercise.
- You will then be asked to walk or run on a treadmill (or sometimes ride an exercise bicycle) for a period of time. The intensity of the exercise will be increased as you go, for example by increasing the speed of the treadmill.
- Any changes that occur in your blood pressure or heart rhythm during the test will be recorded. Your pulse will also be closely monitored. For the test to be effective at detecting coronary artery disease, your heart rate must increase with the exercise to 85-90% of your predicted maximum possible heart rate.
- The test will be stopped if any concerning signs are noticed on the blood pressure or heart rhythm (ECG) monitors, or if you develop symptoms such as leg pain, chest pain, or breathlessness.
- If you feel unwell at any time during the test, mention it immediately to the person in charge.
- After the test is concluded, your blood pressure and heart rhythm will continue to be monitored as they return to normal.
You should expect the test to take approximately one hour.
ECG stress testing has several benefits:
- It is a simple and widely available test;
- It is appropriate for use in most people; and
- It does not produce many false-positive results (meaning that if the test returns a positive result, it is very likely to be accurate).
However, there are some risks associated with exercise stress testing. Because it is mostly used in patients with known or suspected coronary artery disease, patients undergoing stress testing are at high risk of experiencing a cardiac ‘event’ such as a heart attack. In Australia, the risk of death is approximately 1 per 10,000 tests, while the risk of major cardiac events such as heart attack, arrhythmias (abnormal heart rhythms) or development of heart failure is approximately 2-3 per 10,000 tests. All centres offering exercise stress testing must have trained personnel and emergency resuscitation equipment available.
A summary report of the results of the exercise stress test will be prepared and sent to the doctor who ordered the test. This will include information about how your blood pressure and pulse changed during exercise, as well as any changes on the ECG that may suggest cardiac ischaemia (inadequate blood flow to the heart). These results will usually be given in comparison to other people of your age and sex.
While an exercise stress test gives an indication of the likelihood that you have coronary heart disease, it is not a definitive result. It also does not give any information about which coronary vessels are affected. If your stress test returns a positive result, your doctor may order further tests, such as coronary angiography, to gather further information.
- Freedman, B et al. ‘ Safety and Performance Guidelines for Clinical Exercise Stress Testing.’ [online]. The Cardiac Society of Australia and New Zealand: Practice guidelines. 2003. Available at URL: http://www.csanz.edu.au/guidelines/practice/STRESSGL_2003.pdf (last accessed: 8/9/06)
- Gibbons RJ et al. ‘ACC/AHA 2002 Guideline Update for Exercise Testing’ [online]. The American Heart Association. 2002. Available at URL: http://www.americanheart.org/downloadable/heart/1032279013658exercise.pdf (last accessed: 8/9/06)
- Weiner, DA. ‘Advantages and limitations of different stress testing modalities.’ [online]. UpToDate. 2005, Available at URL: http://www.uptodate.com (last accessed 9/9/06)
- Yanowitz, FG. ‘Electrocardiographic changes during exercise ECG testing.’ [online]. UpToDate. 2006, Available at URL: http://www.uptodate.com (last accessed 9/9/06)
- Yanowitz, FG. ‘ Overview of exercise ECG testing.’ [online]. UpToDate. 2005. Available at URL: http://www.uptodate.com (last accessed: 8/9/06)