Scintigraphy of acute myocardial infarction with ligands of sup(99m)Tc-phosphate

Of the wide range of radiopharmaceuticals which accumulate in acutely infarcted myocardial tissue and subsequently enable its scintigraphic detection compounds of sup(99m)technetium phosphate have proven clinically practicable in numerous investigations. As opposed to the similarly non-invasive method of myocardial scintigraphy with ionic tracers (201thallium scintigraphy), infarct detection through positive delineation is possible, at the earliest, six to twelve hours after the onset of pain and meaningful for those in whom the classical ECG and enzyme changes are equivocally diagnostic and for patients with delayed hospital admissions. After approximately one week the concentration of activity in the necrotic zone and, in turn, its detectability, declines. Persistent activity is indicative of extensive infarction and poor prognosis. The sensitivity of the infarct scintigram, which is primarily carried out with sup(99m)Tc-pyrophosphate or sup(99m)Tc-methylendiphosphonate, is about 86% with small and subendocardial infarcts more frequently eluding detection. The method corresponds with electrocardiographic assessment of localization. The combination with 201thallium scintigraphy is useful in differentiating remote from acute infarction and in detection of right ventricular involvement associated with inferior infarction. In spite of a good correlation between the experimentally-determined infarct weight and scintigraphic findings, clinical investigations employing conventional methods of measurement (scintillation camera) have not been able to yield an early and accurate quantification of the infarcted area. (orig.)