Noninvasive quantitation of regional myocardial oxygen consumption in vivo with [1-11C]acetate and dynamic positron emission tomography

Abstract

The usefulness of [1-11C]acetate as a tracer of overall myocardial oxidative metabolism for use with positron emission tomography has been investigated in 12 closed-chest dogs. Myocardial 11C activity clearance kinetics after intravenous administration of [1-11C]acetate in dogs have been determined noninvasively by positron emission tomography. Biexponential fitting of regional myocardial 11C time-activity curves was performed to give clearance half-times and fractional distribution. The rate constant k1 for the early rapid phase of 11C activity clearance was found to correlate linearly with myocardial oxygen consumption (y=0.0156x+0.039; SEE=0.023; r=0.95). k1 was approximately 7% lower in septal sectors compared with the left ventricular free wall, suggesting that regional oxygen consumption in the septum was lower; a concomitant regional attenuation of blood flow in the septum relative to the left ventricular free wall was also observed. In dogs using carbohydrates as the predominant fuel, k1:oxygen consumption was somewhat more than in dogs using predominantly free fatty acids (0.021±0.002 compared with 0.018±0.002, p<0.01), indicating that increased carbohydrate consumption is associated with a small increase in k1 at constant oxygen consumption. It is concluded that measurement of myocardial [1-11C]acetate kinetics allows noninvasive determination of cardiac oxygen consumption by positron emission tomography and that the technique is relatively insensitive to myocardial fuel selection.