Exercise Tolerance Test (ETT)
The exercise tolerance test (ETT) is also known as an exercise electrocardiogram (ECG). This test is done to assess the severity of coronary heart disease. In such condition, the blood vessels are narrowed due to the blockage causing irritation for free-flowing blood supply to the heart. Exercise tolerance test (ETT) assess the response of the heart to raised workload and demand of blood. This is obtained by recording the ECG whilst the patient start walking on a treadmill machine.
Once the patient starts walking on the treadmill, heart rate, blood pressure, general condition and ECG will be monitored continuously. After every 3 minutes, the speed and incline of the treadmill will be increased. The patient will be encouraged to exercise for as long as he/she can and the test will be continued until the patient reaches to the desired heart rate and/or cannot exercise anymore (usually 10 to 15 minutes). After the test, the patient will be asked to rest while his/her ECG and blood pressure are recorded and until his/her recordings reach the normal baseline heart rate. All the recordings will be analyzed by a cardiologist (a doctor with special training to treat heart-related diseases).
What is an electrocardiogram (ECG)?
An electrocardiogram (ECG) test is done by an ECG machine. It records the electrical activity of the heart. The heart produces micro electrical impulses which spread through the heart muscle to make the heart contract. The micro electrical impulses are detected by an ECG machine. The ECG machine amplifies the micro electrical impulses that occur at each heartbeat and records them on to a paper or computer.
An ECG recording is harmless since it records the electrical impulses coming from your body and it does not put any electricity into your body.
What is an exercise tolerance test (ETT)?
An exercise tolerance test (ETT) records the electrical impulses of your heart whilst you exercise. This test is very useful for a patient experiencing chest pain when they exert themselves. This test is also very useful for the detection of rhythm abnormalities.
Some decades ago this was the routine test of choice to investigate a patient for the presence of narrowing of the arteries to the heart. Nowadays it is common for scans of the heart to be done rather than an ETT. The scans that can be done for the heart include:
- Computerised tomography (CT) coronary scan/CT coronary angiography
- Cardiac magnetic resonance imaging (MRI) scan of the heart
- Myocardial perfusion scan
How is an exercise tolerance test (ETT) done?
Small electrodes are stuck on to the patient's chest. Wires from the electrodes are connected to the ECG machine. The patient is asked to walk on a treadmill and the heart rate, blood pressure, general condition and ECG is monitored continuously. After every 3 minutes, the speed and incline of the treadmill are increased. The patient is encouraged to exercise for as long as he/she can and the test is continued until the patient reaches to the desired heart rate and/or cannot exercise anymore (usually 10 to 15 minutes). After the test, the patient is asked to rest while his/her ECG and blood pressure are recorded and until his/her recordings reach the normal baseline heart rate. All the records are analyzed by a cardiologist. The whole process ends in 15-20 minutes.
Are there any risks when doing an exercise tolerance test (ETT)?
An exercise tolerance test (ETT), normally do not cause any complications since, in this procedure, micro electrical pulses are recorded produced by the heart contraction. For this purpose, ECG machine is used which does not input electricity into your body.
If you do not have coronary heart disease (CHD) then complications are rare. However, serious complications occur in a small number of people who have coronary heart disease and there are reports of, very rarely, some people who have died during an ETT.