These are tests in which radioactive molecules are injected intravenously to demonstrate damages and evaluate the function of the heart. As the injected radionuclide circulates to the heart, the presence of radioactivity in the ventricles of the heart or the myocardium is measured. Thallium scan: Thallium is taken up by normal cells, in which case the scan shows an evenly distributed pattern of radioactivity. Ischemic areas or infarcted areas take up less thallium and appear as cold spots on the scan. Technetium-99m pyrophosphate scintigraphy: This is used to diagnose acute myocardial infarction at least 18 hours postinfarction. Areas of damaged myocardium contain calcium which complexes with the Technetium-99m. Therefore infarcted areas appear as hot spots. Thallium Stress Testing: Evaluates heart function. This is the observation of thallium distribution in the myocardium during exercise. Ischemic areas induced by stress will appear as cold spots. Persantine Thallium Scan: Evaluates heart function. For patients who cannot exercise, the persantine-thallium scan can be used to reveal ischemic areas. Persantine is the trademark for the drug dipyridamole which is a coronary vasodilator. Persantine dilates normal coronary vessels more than the occluded vessels. Blood would preferentially flow to the normal vessels; a sort of "steal" phenomenon. A thallium scan can then reveal the ischemic areas by demonstrating reduced perfusion.
Selected cardiac scans links:
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