A numerical model of left ventricular (LV) pump function, incorporating cardiac muscle mechanics and LV geometry, was used to derive a simple linear model of local LV contractile properties. This simplified model views the ventricle as a pressure generator (related to isovolumic contraction) coupled with two time-varying elements: 1) a viscous term (related to the dissipative properties of the myocardium), and 2) an elastic term (related to the tension-length curve of activated fiber and to LV geometry). Pressures and flows generated from the model, under a wide variety of circulatory conditions, were used in a complex-to-simple model check to clarify the connections between the parameters of the simplified model and the underlying physiological mechanisms, suggesting the physical interpretations of these parameters. Published data from experiments on the isolated rabbit heart were used for parameter estimation. The results of the simulations were consistent with the conclusion that both viscosity and stiffness vary with time in linear proportion to isovolumic pressure. Changes with preload and afterload agree favorably with conclusions drawn from organ-level physiology. Copyright © 1985 by The Institute of Electrical and Electronics Engineers, Inc.
Time-varying mechanical properties of the left ventricle--a computer simulation
Cevese A.
1985-01-01
Abstract
A numerical model of left ventricular (LV) pump function, incorporating cardiac muscle mechanics and LV geometry, was used to derive a simple linear model of local LV contractile properties. This simplified model views the ventricle as a pressure generator (related to isovolumic contraction) coupled with two time-varying elements: 1) a viscous term (related to the dissipative properties of the myocardium), and 2) an elastic term (related to the tension-length curve of activated fiber and to LV geometry). Pressures and flows generated from the model, under a wide variety of circulatory conditions, were used in a complex-to-simple model check to clarify the connections between the parameters of the simplified model and the underlying physiological mechanisms, suggesting the physical interpretations of these parameters. Published data from experiments on the isolated rabbit heart were used for parameter estimation. The results of the simulations were consistent with the conclusion that both viscosity and stiffness vary with time in linear proportion to isovolumic pressure. Changes with preload and afterload agree favorably with conclusions drawn from organ-level physiology. Copyright © 1985 by The Institute of Electrical and Electronics Engineers, Inc.
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