Positron Emission Tomography Analysis of [1-C]Acetate Kinetics in Short-term Hibernating Myocardium

Background—Modeling of the time-[1-C]acetate activity curve assumes a constant concentration of labeled tricarboxylic acid cycle intermediates and associated metabolites, such as glutamate and aspartate, which may, however, decrease in short-term hibernating myocardium. Methods and Results—In 12 anesthetized pigs, [1-C]acetate was injected as a bolus into the cannulated left anterior descending coronary artery during normoperfusion, inotropic stimulation, and early (5 to 45 minutes) and prolonged ischemia (60 to 90 minutes). Regional myocardial oxygen consumption (MV̇O2, microliters per minute per gram) was measured, and the absence of necrosis was verified by triphenyl tetrazolium chloride staining. Inotropic stimulation increased MV̇O2 from 52.567.4 to 195.4636.2 (mean6SD) and the rate constant (kmono, minutes ) of [1-C]acetate clearance from 0.09460.018 to 0.32260.076. During early ischemia, MV̇O2 and kmono were decreased to 24.368.5 and 0.06160.011, respectively. Kmono closely correlated to MV̇O2 during normoperfusion, inotropic stimulation, and early ischemia. In short-term hibernating myocardium, however, at an unchanged MV̇O2, kmono increased toward control values (0.08060.014). Myocardial glutamate and aspartate concentrations (biopsies) decreased to 47626% and 77618%; the peak count rate decreased to 66622% of its respective control value. After correction for the decreases in glutamate and aspartate or in peak count rate, kmono was again decreased (0.05060.016 or 0.05260.014, respectively), and a close relationship to MV̇O2 was restored. Conclusions—Kmono correlates to MV̇O2 in short-term hibernating myocardium when the decreases in aspartate and glutamate or in peak count rate are considered. (Circulation. 1998;97:1009-1016.)