Myocardial uptake of a Tc-99m-nitroheterocycle in a swine model of occlusion and reperfusion

The purpose of this study was to evaluate the window for scan positivity of the radiolabeled nitroheterocycle (TC)-T-99m-BRU-59-21 in the peri-ischemi c period using a swine model of occlusion and reperfusion. Methods: A ballo on catheter was placed in the left anterior descending coronary artery in e ach of 19 domestic swine. Blood flow and hemodynamic measurements were made at baseline, during occlusion, and at 15 and 180 min after reperfusion. A dose of approximately 925 MBq Tc-99m-BRU-59-21 was injected before a brief (6 min) period of coronary occlusion at the following times: 15 min (n = 2) , 5 min (n = 2), and 2.2 min (n = 5), In 5 experiments the dose was injecte d 15 min after reperfusion. Animals underwent SPECT imaging 3 h later. Anim als were then killed, and hearts were removed, sliced, stained with triphen yl tetrazolium chloride, and imaged on the detector. Results: The risk regi on became ischemic during occlusion on the basis of severe reduction in blo od flow and lactate production, but necrosis occurred in only 3 experiments . Focal tracer uptake was seen in the risk region in animals injected 5 and 2.2 min before occlusion but not in animals injected 15 min before occlusi on and 15 min after reperfusion. Conclusion: The window for scan positivity for Tc-99m-BRU-59-21 injected in the peri-ischemic period is short using t his model of balloon occlusion and reperfusion in swine.