Nuclear Stress Test
Nuclear (Thallium) Stress Test
What is it?
A nuclear stress test lets doctors see pictures of your heart while you are resting and shortly after you have exercised. A nuclear stress test helps to determine which parts of the heart are healthy and function normally and which are not.
How does it work?
This test is similar to an exercise stress test, except a very small and harmless amount of radioactive substance is injected into the patient towards the end of the exercise portion. The doctor uses a special camera to identify the rays emitted from the substance within the body; this produces clear pictures of the heart tissue on a monitor. These pictures are done both at rest and after exercise. Using this technique, a less than normal amount of thallium will be seen in those areas of the heart that have a decreased blood supply.
Reasons for an Exercise Stress Test
The test can give information about the size of the heart's chambers, how well the heart is pumping blood, and whether the heart has any damaged or dead muscle. Nuclear stress tests can also give doctors information about the arteries and whether they might be narrowed or blocked because of coronary artery disease.
What to expect
The entire test takes about five to six hours in total. A technician will clean the chest and back areas on the skin where the electrodes will be placed. The electrodes are attached to an electrocardiograph machine, which records the heart's electrical activity. A blood pressure cuff will be placed on the arm, which will be used to monitor blood pressure during the test.
During the test, the patient will be asked to walk on a treadmill or to ride a stationary bike. Every 2 or 3 minutes, the technician will increase the speed and slope of the treadmill or stationary bike, which will make it feel like the patient is walking or pedaling uphill. The technician will look for changes in the electrocardiogram patterns and blood pressure levels, and other signs of coronary artery disease include chest pain or unusual shortness of breath while you are exercising.
After your doctors have the information they need from the exercise portion of the test, the patient will come off of the treadmill and be given an injection of a radioactive substance. The patient will lie on an examination table, which has a gamma-ray camera above it which is used to take pictures of the heart. The camera can pick up traces of the radioactive substance in the body and then send a picture to a television monitor.
Once this part of the test is over, the patient will be asked to come back in three to four hours and not to exercise or drink or eat anything with caffeine. Upon returning to the exam room, doctors will give another injection of the radioactive substance to the patient and once again the gamma-ray camera will take pictures of the heart while you are resting. This provides information on how the heart works during both exercise and rest.
This radioactive substance is not harmful to your body or your organs. After the test is over the patient may resume normal activities.