Stress exercise thallium scan: A method of examining the heart to obtain information about the blood supply to the heart muscle. Special cameras take a series of pictures of the heart. A radioactive substance is injected into the bloodstream and serves as a tracer. The tracer attaches to certain cells and makes them visible to the special camera. The tracer attaches to the muscle cells of the heart so the imaging camera can take pictures of the heart muscles. If an area of the heart does not receive an adequate flow of blood, the cells in the underserved area do not receive as much tracer and it appears as a darker area on the picture taken by the camera.
The patient has an IV (intravenous) line placed in the arm, EKG patches are applied to chest and connected to an EKG machine to monitor the heart. Then the patient exercises as hard as possible on the treadmill to give information about how well the heart functions with exercise. One minute before stopping exercise, the tracer, sestamibi, is injected IV to give the tracer time to circulate through the bloodstream. Then one lies flat on a table with arms above the head. A large imaging camera is brought close to the chest for the first set of scans. This part of the scan lasts about 25 minutes.
A second set of pictures is taken approximately 3 hours after the injection. The patient should not eat but can drink fluids that do not contain caffeine. The entire test takes approximately 5 to 6 hours.
To prepare for the stress exercise sestamibi scan, the patient should not drink or eat anything containing caffeine for 24 hours before the test (this includes decaf coffee and chocolate) and should not eat or drink after midnight and not smoke on the day of the test. Most medications are taken as usual; however, one should check in advance with the doctor or nurse. Diabetics also should seek special instructions from the doctor or nurse.
The amount of radiation from the scan is no more than from other x-ray tests. However, if there is any chance the patient might be pregnant, she should notify the doctor or nurse before the test is done.