A Two-Stage Identification Scheme for the Determination of the Parameters of a Model of Left Heart and Systemic Circulation

An identification scheme is developed for the determination of several parameters of a modified "Windkessel" model of the systemic arterial system for an individual patient undergoing cardiac catheterization. The scheme utilizes a modification of the Prony method [10], [11] as a "starter method" to determine good nominal values for the model parameters being varied. These values then serve as input to a well-known iterative nonlinear least-squares identification method (Marquardt method [14]) which then converges rapidly to frmal values of the parameters. Solution of the model equations with these parameter values yields the best fit in a least-squares sense of model-generated and observed aortic and brachial artery pressures. This two stage or sequential Prony-Marquardt technique represents an extension of our previous work associated with the analysis of multiexponential decay curves [18], and is applied here to the identification of parameters associated with the humam arterial system. When coupled with a method of determining the contractile mechanics of the left ventricle (eg., the ventricular elastance concept [l]-[5]), this identification scheme permits a functional characterization of the hemodynamic properties of the left ventricle and its systemic load, for an individual subject.