Interaction between heart as a pump and artery as a load

For a better understanding of the functional roles of the heart as a pump system, an analogy with an industrial fluid-pump system is beneficial. In this paper, the use of the ventricular pressure-volume relationship was shown to provide one of the most useful descriptions of the heart as a pump system. This description included the pump function of the ventricle as well as the interrelation between cardiac mechanics and energetics. In describing the heart only as a pump, Thévenin's network model consisting of a source of pressure with a series source resistance (or impedance) is useful in analysing the complex interactions of the equilibrium mechanism for determining cardiac output and arterial pressure, and the matching conditions under the ventriculo-arterial coupling during the ejection period for a given set of ventricular and arterial system parameters. The analytical results using this model explained previous experimental results by other investigators. It was also suggested that the ventriculo-arterial-coupled system appears to be matched. From the engineering point of view, it is desirable also for the ventricle as a pump to behave under such an optimum matching condition for delivering a maximum power to the arterial load.