Mechanical performance and oxygen utilization of the isovolumic rabbit heart

Abstract

The force of isovolumic contraction, the velocity of contractile element shortening (Vce), and the myocardial O2 consumption (O2C) were measured in the perfused rabbit heart subjected to changes in perfusion pressure (PP), volume loading, heart rate (HR), and increased Ca and catecholamine administration. Coronary flow (CF) is a linear function of PP, and the cardiac performance and O2C are mutually related and independent of PP, provided PP is maintained above a critical level. A clear difference in the linear regression coefficients relating O2C to the product of heart rate and developed tension was seen that is dependent on the manner of augmenting cardiac performance. Catecholamine administration and increased Ca were associated with larger regression slopes than were increases in HR or volume loading. The velocity of force development may influence the relationship between O2C and cardiac performance.