Feline left ventricular oxygen consumption is not affected by volume expansion, ejection or redevelopment of pressure during relaxation

We studied the dependency of myocardial oxygen consumption on the mechanical events during left ventricular relaxation in isolated supported cat hearts. The volume of the left ventricle was controlled by means of a balloon connected to a membrane pump. Oxygen consumption ( $M\dot VO_2 $ in cm³·min⁻¹·100 g⁻¹) for three protocols (PROT) performed at peak isovolumic pressure, was studied: (1) rapid ejection to zero pressure, (2) partial rapid ejection followed by redevelopment of pressure, (3) volume expansion during relaxation, and compared with oxygen consumption of isovolumic (ISOV) beats. We found (mean±SD):