Exercise Tolerance Test (ETT)

What is an exercise tolerance test?
An exercise tolerance test (ETT) records the electrical activity of your heart whilst you exercise.

How is an exercise tolerance test done?
Small electrodes are stuck on to your chest. Wires from the electrodes are connected to the ECG machine. You will then be asked to exercise on a treadmill or on an exercise bike. The exercise starts at a very easy pace, and is gradually made more strenuous by increasing the speed and incline of the treadmill, or by putting some resistance on the bike wheel.
Whilst you exercise, ECG tracings are made and you will also have your blood pressure measured from time to time. The test lasts about 15-20 minutes.

ETT might be prematurely stopped for any of the following:

• Development of chest pain,
• Presence of ST elevation,
• Very deep ST depression,
• Arrhythmias,
• Hypotension
• The patient becomes tired and is unable to continue.
• Elevation of blood pressure to dangerous levels such as >170/120 mm Hg should also lead to termination of the test.

Note: Beta-blockers and digoxin can interfere with the results so are usually stopped before the ETT.

Preparation for the test?

You should not have a heavy meal within one hour of the test. Otherwise, there is no special preparation needed. For the test, wear loose-fitting clothes and shoes that are comfortable to walk in. Continue to take your usual medication unless advised otherwise by a doctor. If you have hair on the parts of your body where the electrodes will be placed, the technician may need to shave the hair so that the electrodes stick properly.

Why is an exercise tolerance test done?

The ETT helps to diagnose and assess the severity of ischemic heart disease (sometimes called coronary heart disease or coronary artery disease). This disease is due to narrowing of the coronary arteries. It can cause angina (chest pains) and other problems. So, if you develop chest pains you may be advised to have an ETT to help to clarify the cause.

If you already have ischemic heart disease, the degree of abnormality on the ECG tracing from the ETT can give a good idea of the severity of the disease. Therefore, ETT is often done to help to decide if you need further investigations or treatment.