Myocardial metabolism during increased work states in the porcine left ventricle in

It is not known whether myocardial energy requirements can be increased to the degree that they exceed myocardial 02 avail-ability in the absence of abnormalities of coronary blood flow or coronary reserve. To determine whether this form of "demand ischemia " occurs, 10 swine were subjected to pressure overload induced by aortic constriction, inotropic and chronotropic stimn-ulation by dobutamine, and the combination of these interven-tions. In an additional 9 animals, intravenous adenosine was administered during the combination of constriction and dobu-tamine to determine whether further increases in coronary flow could be achieved and if they would attenuate the metabolic changes. Left ventricular anterior wall transmural blood flow was measured by radioactive microspheres. Energy phosphates were assessed by 31P magnetic resonance spectroscopy using the Fourier series window technique to increase the proportion o