Radionuclide methods in the evaluation of myocardial ischemia and infarction.

Radionuclide techniques that assess regional myocardial perfusion and detect acute myocardial infarction promise to provide critical information in the detection and evaluation of coronary artery disease and in the assessment of therapies aimed at limiting the degree of ischemia and the extent of tissue necrosis. Radioindicators such as 99mTc-tetracycline and 99mTc-pyrophosphate which are sequestered by acutely infarcted myocardium provide a direct method to detect an infarct and to determine its size. Regional alterations in myocardial perfusion can be assessed by myocardial scintigraphy performed after the injection of radiopotassium or one of its analogues with the patient either at rest or at exercise. A somewhat more accurate evaluation of the extent of altered perfusion can be obtained after the intracoronary injection of macro-aggregated particles. A quantitative index of altered perfusion can be obtained after the intracoronary injection of an inert gas such as 133Xe.