Parameter Estimates of a Left Ventricular Model During Ejection

How to quantify pump function of the heart. The value of variables derived from measurements on isolated muscle.

“…They used mean values to obtain this relationship. Buoncristiani et al (1973) averaged the left ventricular pressure over the ejection period only and plotted that value against mean flow, whereas Weber et al (1974) and McGregor et al (1974) made graphs of peak ventricular pressure against stroke volume. Although different in a number of experimental and theoretical details, all these studies had the same objective: the description of the pump function of the heart by relating the amount of blood it ejects to the pressure it has to overcome.…”

Source parameters of the left ventricle related to the physiological characteristics of the cardiac muscle

“…Numerous attempts at modeling the cardiovascular system have led to the development of a large number of analog and digital models of the left ventricle (LV). A group of electrically oriented analogies for the LV performance are based on a pressure source that is combined, in series, with an internal source resistance, or impedance, Westerhof, 1973, 1978;Westerhof et al, 1977;Abel 1966Abel , 1971Fich et al, 1973;Min et al, 1976Min et al, , 1978Buonochristiani et al, 1973;Shroff et al, 1983;Hunter et al, 1983). These concepts of source parameters have evolved from the Thevenin-Norton Equivalence theorem for electrical circuits that define an open circuit voltage for the electrical source, analogous to the isovolumic pressure of the LV.…”

“…The in-series resistance of the system is defined as the source resistance. While the experimental data provided by Westerhof (1973, 1978) and Buonochristiani et al (1973) deal with the average values of the LV pressure and the internal resistance, Welkowitz (1977Welkowitz ( , 1981 and Min (1978), have used the instantaneous pres-Please address reprint requests to R. Beyar, M.D., D.Sc., Department of Cardiology, Johns Hopkins University Hospital, 720 Ruthland Avenue, Baltimore, MD 21205. sure and flow values to characterize the LV internal impedance rather than its resistance.…”