What is exercise stress testing?
Exercise stress testing is a procedure used by doctors to measure the performance and capacity of the heart, lungs and blood vessels during exercise. The testing is sometimes referred to as a ‘clinical exercise stress test’, a ‘cardiac stress test’, or simply a ‘stress test’.
Typically, you will be asked to walk on a treadmill during the test, while a doctor or technician measures how well your heart can cope with the increasing workload.
Why is an exercise stress test done?
Exercise stress testing is commonly used by doctors to help them make a diagnosis in people with suspected heart disease, for example to:
- diagnose significant coronary artery disease – a narrowing or blockage in the coronary arteries
- identify the cause of chest pain
- diagnose an irregular heart rhythm – some heart rhythm problems only occur on exercise.
Exercise stress testing may also be carried out in people known to have heart disease to:
- help identify those people at highest risk
- assess the progress of their heart disease
- assess the effectiveness of a particular treatment or procedure (e.g. angioplasty) or
- assess the person’s capacity to undertake physical activity safely, and to develop a safe exercise plan.
What conditions can an exercise stress test help diagnose?
You may have been suffering from dizziness, palpitations or chest pain. The exercise stress test can help doctors work out what is the cause of your symptoms.
Can a stress test show if my arteries are clogged?
A stress test cannot accurately detect whether a person’s arteries are narrowed or blocked, but it may suggest that that is the case and that further tests are needed. If the arteries are severely narrowed (say 70 per cent or more), then there will be symptoms and the stress test will detect those.
The best test to work out if heart blood vessels are clogged is a standard coronary angiogram, but this involves threading a catheter into your heart or coronary arteries. A CT coronary angiogram (CTCA) is less invasive – it involves an injection of dye and then a CT scanner takes pictures of your coronary arteries as your heart is beating.
How do I prepare for the test?
You need to wear loose comfortable clothing and shoes suitable for walking or cycling. For women, it is best to wear a shirt with non-metallic buttons.
You will normally be asked to bring a list of your medications with you.
If you are having an ECG exercise stress test, no special preparations are usually necessary. However, it is best to avoid drinking cold water or exercising straight before your test. You may be asked to avoid eating for 3 hours before the test. Similarly, avoid alcohol and smoking for at least 3 hours before the test.
If you are having an echocardiogram exercise stress test, your doctor may ask you not to eat for a few hours leading up the test.
If you are having a nuclear stress test, you will be provided with a number of specific instructions to follow leading up to the test. You will be advised not to drink or eat any liquids or foods that contain caffeine for 24 hours before the test. This includes any type of coffee (including decaffeinated), any type of tea (including herbal teas), cola drinks, chocolate drinks, bars or biscuits. The centre where you are having the test done may also require you to fast for a number of hours before your test.
A number of heart and blood pressure medicines can interfere with the testing. You will need to check with your doctor whether you should stop taking certain medicines and, if so, when.
If you have diabetes, you need to inform the centre where you are having the testing done at the time that you book your test. If you are pregnant (or may be) or you are breastfeeding you should also let the centre know, as the test is not usually performed on women in these conditions.
What happens during an exercise stress test?
If you are having an ECG exercise stress test, you will be connected to a 12-lead ECG – this involves having the electrodes attached to your arms, legs and chest. A baseline ECG (resting ECG) is usually performed first. This is normally done by the cardiac technician.
You will then be asked to walk on a treadmill (or cycle on an exercise bike). The speed and gradient (steepness) of the treadmill will be increased every 3 minutes until you reach your target exercise level. A Cardiologist (heart specialist) will usually supervise the test.
The test will be stopped if you develop symptoms such as severe fatigue, breathlessness, tired legs or chest pain. If at any time during the test you feel unwell, you need to tell the doctor immediately.
Throughout the test, and for some time after the test finishes, a doctor will monitor:
- your pulse
- blood pressure
- heart rhythm
- the electrocardiogram.
If the doctor is concerned about any changes observed during the test, it will be stopped early.
If you are having an echocardiogram stress test, the exercise part of the test will be the same as in an ECG stress test. Before and immediately after exercise, you will be asked to lie on a table. A cool gel will be spread on your chest and a device called a transducer will be pressed against your skin to produce ultrasound images of your heart.
If you are having a nuclear stress test, a small amount of a radioactive chemical will be given as an injection into a vein in your arm (thallium or technetium). The injected chemical is called a ‘tracer’. As the tracer moves through the blood vessels of your heart, a special camera or scanner will be used to take images.
The test will take place in 2 stages: at rest and during exercise. While you are being tested, you will be connected to an ECG machine and a blood pressure monitor. The exercise stage of the test will involve either walking on a treadmill, or riding an exercise bicycle. The difficulty of the exercise will be increased every few minutes. It is important that you tell the doctor immediately if you feel unwell at any time during the test, particularly if you have shortness of breath or chest pain.
How does the test measure my heart?
An electrocardiogram (ECG) stress test records electrical signals from your heart during exercise. Alternatively, an echocardiogram may be used instead of an ECG. An echocardiogram uses sound waves (ultrasound) to produce images of your heart. A third type of exercise stress test involves injecting a radioactive material and following its progress through the heart’s blood vessels. This is often called a ‘nuclear stress test’ or a ‘myocardial stress test’.
In some people, exercise stress testing is not suitable. In such cases, medicines may need to be used instead of exercise to stimulate the heart. This is called ‘pharmacological stress testing’.
Are exercise stress tests safe?
Exercise stress tests are generally safe. Every effort will be made to minimise the risk of something going wrong. However, exercise stress testing does carry a small risk of complications. Emergency equipment and trained personnel will be available to deal with any complications that may arise.
Complications of exercise stress testing may include:
- severe hypotension (drop in blood pressure);
- a major disturbance of heart rhythm, requiring resuscitation;
- heart failure or prolonged heart pain;
- heart attack (approximately 1 in 5000 chance); and
- death (approximately 1 in 10,000 chance — this may be higher in patients with known severe heart disease).
If you are having an ECG or echocardiogram exercise stress test, there is a small chance that removal of the electrodes from your skin may cause irritation, redness or swelling.
Your doctor will have taken all these risks into account when recommending the testing for you. However, you should feel free to discuss these issues before agreeing to the testing.
When will the results be available?
A full report of the test will be sent by the Cardiologist to your referring doctor, usually the day after the test.
If the test results are normal, no further testing may be needed. However, if the results indicate a problem and your doctor suspects you have heart disease, you may be required to repeat the same test, or undergo further testing with other diagnostic procedures. In some cases, you may be referred to a Cardiologist.
Further information and support
Talk to your doctor if you have any questions or concerns about the testing. You may also like to contact the hospital or centre where you will be having the test done.