IDENTIFICATION OF THE VENTRICULAR PUMP PARAMETERS DURING THE EJECTION PHASE OF THE CARDIAC CYCLE.

Abstract

Cardiac function and measures of cardiac quality have been investigated in a number of ways. The conventional approach is to represent the cardiac pump in terms of one or more physical parameters either as constants or, more recently, in terms of their time variation. Cardiac parameters representing all energy components (inertance, resistance, compliance), however, have thus far not been reported. In this project we estimate all time varying parameters in an unbiased manner; the end diastolic volume is also estimated. Nonlinear and linear estimation methods are used to identify the unknowns. The problem is analyzed for the ejection phase using pressure and flow measured at the root of the aorta or main pulmonary trunk. Sensitivity of the identified parameters to chronotropic and inotropic changes are studied using nonparametric statistical methods. The Resistance parameter emerges as the parameter that best reflects alterations of inotropic state. An equivalent area (related to inertia) is correlated with the cross section of the ventricular outflow tract. The Inertial parameter is shown to contribute significantly to the pressure development. Thus it can not be ignored in a detailed study of the dynamics of the ventricles during ejection. Compliance, represented as the major source of energy during contraction, is related to ATP concentration changes. The results of this study do not fully support all previous related findings and it is likely that resolution of differences will require considerable effort