Very Early Noninvasive Detection of Acute Experimental Nonreperfused Myocardial Infarction With 99m Tc-Labeled Glucarate

Abstract

Background 99m Tc glucarate has recently been reported to be an infarct-avid agent. The feasibility of imaging with 99m Tc glucarate was evaluated for the early diagnosis of nonreperfused and reperfused myocardial infarction and compared with localization of simultaneously administered 111 In anti-myosin. Methods and Results Four groups of six rabbits each were studied. The left anterior descending coronary artery (LAD) was kept persistently occluded (n=6) or reperfused after 40 minutes (n=6) in rabbits. After confirmation of LAD occlusion by 201 Tl scintigraphy, a mixture of 99m Tc glucarate (15.7±1.6 mCi) and 111 In anti-myosin (0.53±0.03 mCi) was administered intravenously. Another group of rabbits (n=6) with 5 or 15 minutes of LAD occlusion were used to assess the affinity of 99m Tc glucarate for the ischemic myocardium. The remaining 6 rabbits with reperfused myocardial infarction were used for the assessment of subcellular localization of 99m Tc glucarate. 99m Tc glucarate cleared rapidly from circulation (elimination t 1/2 , 36 minutes). Infarcts were visualized within 10 minutes in reperfused and within 30 minutes in nonreperfused coronary territories after intravenous administration. 111 In anti-myosin delineated reperfused infarcts within 1 to 3 hours, but no uptake was seen in persistently occluded rabbits. 99m Tc glucarate uptake in reperfused and nonreperfused infarct centers was 28 and 12 times greater, respectively, than that in normal myocardium ( P =.0001). A direct correlation between glucarate and anti-myosin localization ( r =.60 for nonreperfused; 0.76 for reperfused; P <.0001) was observed. Ischemic hearts showed no glucarate uptake. Subcellularly, 99m Tc glucarate localized predominantly in the nuclear fraction of the infarct, with lesser extents in the mitochondrial and cytoplasmic fractions. Conclusions Noninvasive imaging of myocardial infarcts with 99m Tc glucarate is possible within minutes in persistently occluded or reperfused myocardial infarcts. Early detectability results from the rapid blood clearance and high avidity of glucarate for the acutely necrotic myocardial tissue.