SIMULTANEOUS MEASUREMENT OF MYOCARDIAL OXYGEN-CONSUMPTION AND BLOOD-FLOW USING [1-CARBON-11]ACETATE

[1-Carbon-11]acetate has been used as a racer-for oxidative metabolism with PET; The aim of this study was to validate, in humans, a previou sly proposed two-compartment model for [1-C-11]acetate for the noninva sive measurement of myocardial oxygen consumption (MVO2) and myocardia l blood flow (MBF) with PET. Methods: Twelve healthy volunteers were s tudied with [N-13]ammonia, [1-C-11]acetate and PET. Myocardial oxygen consumption was invasively determined by the Fick method from arterial and coronary sinus O-2 concentrations and from MBF obtained by [N-13] ammonia PET. Results: Directly measured MVO2 ranged from 5.2 id 11.1 m l/100 g/min, and MBF ranged from 0.48 to 0.88 ml/g/min. Oxidative flux through the tricarboxylic acid cycle, reflected by the rate constant k(2), which correlated linearly with measured MVO2 [k(2) = 0.0071 + 0. 0074(MVO2); r = 0.74, s.e.e. = 0.015]. With this correlation, MVO2 cou ld-be estimated from the model-derived k(2) value by MVO2 = 135(k(2)) -0.96, The slope of this relationship was close to that previously obt ained in rats and implies that the tricarboxylic acid cycle intermedia te metabolite pool sizes are comparable. The net extraction (K-1) of [ 1-C-11]acetate, measured by PET, from blood into myocardium correlated closely with MBF by K-1 = 0.15 + 0.73(MBF) (r = 0.93, s.e.e. = 0.033) and, thus, provided noninvasively obtainable measures of blood flow. C onclusion: The proposed compartment model for [1-C-11]acetate fits the measured kinetics well and, with proper calibration, allows estimatio n of absolute MVO, rather than only an index of oxidative metabolism. Furthermore, [1-C-11]acetate-derived estimates of MBF are feasible.