Myocardial uptake of Tc-99m-tetrofosmin, sestamibi, and Tl-201 in a model of acute coronary reperfusion

Background To investigate whether tetrofosmin uptake is affected by myocardial viability as has been noted for Tl-201 and sestamibi, we analyzed the initial and delayed distribution patterns of tetrofosmin in a rat coronary artery occlusion-reperfusion model. Methods and Results Animals were intubated and ventilated, and their arterial pressures were monitored. A left thoracotomy was performed. After 1-hour occlusion and 1-hour reperfusion of a major branch of the circumflex artery, Tl-201 and either tetrofosmin or sestamibi were injected intravenously. Radiolabeled microspheres were used to document the area at risk and reperfusion. Five minutes or 1 hour after administration of the diffusible tracers, the animals were killed. Tracer distribution was determined by use of segmental tissue analysis, and tissue viability was determined by use of histochemical staining. Both the initial and delayed retention of tetrofosmin were sensitive to myocardial viability, as shown by significantly lower uptake (30+/-14%) and retention (24+/-12%) of tetrofosmin in the nonviable segments compared with the viable segments. In addition, the initial myocardial distribution of tetrofosmin was similar to that noted for Tl-201, but after 1 hour of tracer circulation, the tetrofosmin tissue distribution appeared unchanged compared with the initial regional blood flow distribution. This is in direct contrast to our present observations of significant Tl-201 redistribution and some changes in sestamibi distribution as well. Conclusions The clinical implication of these observations suggests that initial and delayed imaging after tetrofosmin administration would reflect both the initial regional blood flow pattern and myocardial viability.