An exercise tolerance test (ETT), also known as an Exercise ECG or a stress test, is a type of electrocardiogram (ECG) test that assesses the electrical activity of your heart under physiological stress. An ETT can show you how your heart works whilst you are physically exerting yourself.
An exercise tolerance test is an important cardiac diagnostic test. During an ETT, the electrical activity of your heart is recorded while you are exercising, on a treadmill or exercise bike. Exercise makes the heart contract faster and harder. When you exercise, your heart beats faster and your coronary blood flow increases. An ETT can indirectly assess the blood flow within the coronary arteries bringing blood and oxygen to your heart. It can also assess your heart rate and your heart’s electrical activity during exercise and determine whether it is functioning correctly.
Some types of coronary artery disease show no abnormality when you are resting. This means that if you have a standard ECG that assesses your heart rate and the electrical activity of your heart at rest, your results may present as normal, and your condition may go undiagnosed.
You may be referred for an ETT for a number of reasons:
· To assess the effectiveness of your current heart treatments and to determine whether other treatments would be more effective. For example, if you have a stent, an ETT can assess how well the stent is working.
· If you have recently undergone heart surgery or had a heart attack or to determine whether you can safely have surgery.
· If you are experiencing symptoms such as chest pain, palpitations or breathlessness that could be consistent with heart disease or blocked arteries.
· If you have fainted or experienced symptoms whilst exercising, as this could be consistent with coronary artery disease.
· To determine safe levels of exercise, depending on how well your heart functions when under stress.
The exercise tolerance test assesses:
· Any changes in your heart’s electrical activity.
· Whether you have a blocked artery which is causing a reduction in blood flow and a reduction in the oxygen delivery to your heart muscle.
· Any abnormal patterns in your blood pressure, including hypertension and hypotension.
· An arrhythmia (an abnormality of the heart’s rhythm).
An ETT can help your cardiologist see whether your heart is getting enough blood from your coronary arteries when you engage in physical activity. It can show how well your heart functions when under stress and detect any problems with the blood flow in your heart.
ETTs are usually used to diagnose coronary artery diseases, where your coronary arteries become narrowed. Narrow coronary arteries will result in your heart muscle not getting enough oxygen. If you have an abnormal reading on an ETT, the most likely diagnosis will be coronary artery disease.
When you come in for your ETT, you will need to wear comfortable clothes and trainers. Small electrodes will be placed on your chest and will be connected to an ECG machine. You will then be asked to walk on a treadmill, starting at a slow pace. The incline and/or speed of the treadmill will then increase to make the exercise more difficult and increase your heartrate. You will be encouraged to exercise as hard as you can so we can see how your heart functions under stress. Make sure you tell the cardiologist if you begin to feel any chest pain or become too tired or short of breath and they will stop the test. The cardiologist will monitor you very carefully throughout the test. You may also be fitted with a blood pressure monitor so your blood pressure can be monitored at intervals. Your breathing will also be monitored throughout the test.
An exercise tolerance test (ETT) usually lasts for between 10 and 15 minutes, depending on how long it takes to increase the intensity of the exercise and how quickly your heart rate reaches a high enough rate.
In the majority of cases, there are no complications associated with an ETT. However, in very rare cases, complications such as ischaemia or a heart attack can occur. Other rare complications include an arrhythmia –an irregularity of the heartbeat - triggered by the exercise, or the test could cause excessively high or low blood pressure. However, these complications are very rare, and you will be closely monitored throughout the ETT to reduce the risk of complications.