Myocardial clearance of technetium-99m-teboroxime in reperfused injured canine myocardium

摘要

Background Recent technical developments using solid-state technology have enabled rapid image acquisition with single photon emission computed tomography (SPECT) and have led to a renewed interest in technetium-99m-teboroxime (Tc-99m-teboroxime) as a myocardial imaging agent. Tc-99m-teboroxime has demonstrated high myocardial extraction, linear myocardial uptake relative to flow even at high flow rates, rapid uptake and clearance kinetics, and differential clearance in the setting of ischemia. However, the myocardial clearance kinetics of Tc-99m-teboroxime in a model of myocardial injury has not been previously reported. Thus, the purposes of this study were to use a canine model of ischemia-reperfusion to (1) compare Tc-99m-teboroxime clearance kinetics in normal and ischemic-reperfused myocardium and (2) assess the utility of Tc-99m-teboroxime clearance kinetics in determining the severity of injury following ischemia-reperfusion. Methods Thirteen dogs underwent left circumflex coronary artery (LCx) occlusion for either 30min (IR30, n?=?6) or 120min (IR120, n?=?7), followed by reperfusion, and finally Tc-99m-teboroxime administration 120min after reperfusion. Microsphere blood flows were determined at baseline, during occlusion, after reperfusion, and before euthanasia. Post-mortem, area at risk was determined using Evans blue dye, and viability was determined using triphenytetrazolium chloride (TTC) staining. The hearts were then subdivided into 24 pieces and Tc-99m activity was measured in a well counter. Results TTC-determined infarct area as a percentage of total left ventricular myocardium was 1.1%?±?0.3% for the IR30 group and 7.5%?±?2.9% for the IR120 group (p?p?Conclusions Tc-99m-teboroxime demonstrates moderate differential clearance in a model of severe injury with 120min of ischemia-reperfusion, but only minimal differential clearance in a model of mild injury with 30min of ischemia-reperfusion. Thus, Tc-99m-teboroxime clearance kinetics may be helpful in differentiating normal and minimally injured from severely injured myocardium.