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What is Myocardial Perfusion Imaging
A radionuclide procedure that allows cardiologists to observe the flow of BLOOD from the CORONARY ARTERIES into the tissues of the MYOCARDIUM (HEART MUSCLE). The test usually involves a resting and an exercise component, to provide a comprehensive picture of how much blood the heart receives to assess the extent to which CORONARY ARTERY DISEASE (CAD) is reducing cardiac function. The procedure takes about an hour and requires little preparation (namely, abstaining from STIMULANTS such as CAFFEINE and NICOTINE for 48 hours before the procedure).
The cardiologist administers a small amount of a radioactive substance, called a radionuclide or radioisotope (most commonly thallium), into a VEIN in the back of the hand or in the arm. The radionuclide is mixed in a solution, usually GLUCOSE, that the blood carries to the cells. The radionuclide rides along as a “tag” on the glucose molecules, accompanying them into the cells. The radionuclide rapidly disintegrates, releasing a pattern of electromagnetic energy called gamma-rays. A special device called a gamma camera detects the gamma rays, and presents them as images. The concentrations of energy tell cardiologists where myocardial blood flow is strong and where it is restricted, helping identify areas of ischemia (oxygen-deprived tissue).
When actual physical exercise is not feasible, the cardiologist may use a DRUG (often dipyridamole) to chemically simulate the effects of exercise on the heart. People who have ANGINA PECTORIS or significant CAD may feel temporary discomfort during this simulation. There are no side effects from myocardial perfusion imaging. The radionuclides cardiologists use emit minimal radioactivity and are gone from the body within a few hours.
See also COMPUTED TOMOGRAPHY (CT) SCAN; ECHOCARDIOGRAM; MAGNETIC RESONANCE IMAGING (MRI); POSITRON EMISSION TOMOGRAPHY (PET) SCAN; SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT) SCAN.