Contrast enhancement of myocardial infarction: dependence on necrosis and residual blood flow and the relationship to distribution of scintigraphic imaging agents.

transmission tomography after i.v. administration of iodinated contrast material. To examine the relationship of this phenomenon to the presence of myocardial necrosis, the blood flow profile of the MIs and the distribution of radionuclide infarct imaging agents, collateralized infarcts were produced in six dogs (group A) and noncollateralized infarcts were produced in nine dogs (group B). After 48 hours of coronary occlusion, each dog received technetium-99m pyrophosphate ( mTc-PYP), thallium-201 (201T1), indium-111-labeled microspheres and meglumine sodium diatrizoate (Renografin-76) before sacrifice. Residual blood flow in the center of the MI was 3-27% in group A and less than 3% in group B. In group A, the iodine concentration in the center (1.33 mg/g myocardium), periphery (1.48 mg/g), and margin (1.09 mg/g) were several times higher than normal myocardium (0.45 mg/g). The distribution of "9mTc PYP was similar to that of iodine; the distribution of 201TI was roughly the inverse of that of iodine. In group B, the average iodine and OmTc concentrations in the margin, and periphery of the MI were several times higher than that in normal myocardium, but in the center neither concentration was significantly higher than normal. However, there was no consistent relationship between iodine and 201TI, as concentrations of iodine and 201TI were low in the center of the infarct and were inversely related at other sites. The results show that contrast material has a distribution in MI similar to that of "9mTc PYP and both are markers of ischemic myocardial necrosis. Distribution of both agents in the MI depends on a threshold level of residual myocardial blood flow.