If you are at risk of suffering from coronary heart disease, a treadmill test will help to assess this risk and determine whether your heart is functioning normally. People who are known to suffer from conditions such as hypertension, diabetes, and high cholesterol, people who are heavy smokers, and people who have a family history of heart disease may be advised to undergo this test once they reach a certain age or if they experience certain symptoms. The sensitivity and accuracy of a regular treadmill stress test is rather limited, and in some cases additional data may be needed. This can be provided by using a thallium treadmill stress test instead of a regular stress test. A thallium treadmill test can detect regional areas of decreased blood flow, and is able to determine the presence and severity of a coronary artery blockage. Sometimes this test may be done after cardiac surgery in order to determine how successful it was.
You mainly need to ask your doctor whether you need to discontinue any medication that you are currently on, especially if you are taking any medication for your heart. Beyond this, all you need is to wear clothes and shoes that are suitable for walking and running.
Typically, the doctor will attach the electrodes from the electrocardiogram (ECG) machine to your chest, after which you will need to use the treadmill. You will begin at a low speed, and at set intervals, the intensity of the exercise will be increased. Eventually, the treadmill will be stopped, and you will be given the injection of thallium. You will then need to lie down on an examination table so that a special camera called a gamma ray camera can take pictures of you. The camera detects the radioactive thallium in your body, and thus takes pictures of your heart. Usually, you are then allowed to leave, but you will need to return after a few hours, during which you should not exercise or consume any caffeine. When you return, you will get another thallium injection, and the camera will once again photograph your heart, this time while you are at rest.