Informational analysis of left-ventricle/systemic-arterial interaction

Abstract

Studies of left ventricle (LV) and systemic arterial (SA) interaction can be grouped into four categories: 1) prediction of pressure and flow waveforms, 2) changes in LV/SA function with changes in SA properties, 3) identification of criteria that reveal matching between LV and SA properties, 4) definition of LV afterload. Whereas results from studies in categories 1, 2, and 3 reveal the consequences of interaction, results from studies in category 4 come closest to revealing the true character of LV/SA interaction. A useful description arising from category 4 is that of a circular feedback path connecting LV outflow, SA input-impedance, LV pressure, and LV pump properties. The identification of a node in this scheme results in the separation of LV functions into active functions and loading functions and the separation of LV/SA load into LV load and SA loading elements. The time-varying LV elastance participates in both LV active functions and LV loading functions, with the former dominating the latter. Total peripheral resistance dominates all other LV and SA loading elements in its loading effects. Although an elastance-resistance LV model coupled with a simple second-order SA load model accounts for many reported observations on LV/SA interaction, data from sudden aortic occlusion studies indicate a need to consider yet another interaction action. Evidence is presented to suggest the existence of an LV pump element that couples ejection events with relaxation and filling events.

Development of a Numerical Simulation Model of the Cardiovascular System

“…The characteristic behavior of the left ventricle can be approximated by a resistance, R L , and an elastance (2,3,5), E(t), which represents the ratio of pressure and volume. The LV elastance is the input of the model and enables the left ventricle to develop a certain pressure.…”

Downstream from the Heart Left Ventricle

“…Thus, the L was considered a further degree of freedom that allows improvement of data fit. Campbell et al [42] used the W4P model and made the observation that R c and L combine to determine the characteristic impedance and do not, in themselves, represent physiologic entities. Stergiopulos et al [16] attributed to L the physiological meaning of total arterial inertance.…”

A Preload and Afterload Sensitive Artificial Ventricle to Test Cardiovascular Prostheses

“…The ventricle is modeled by the time varying differential elastance model with internal resistance (Arabia et al, 2003), (Vollkron et al, 2002) and (Campbell et al, 1984). This model links the instantaneous ventricular pressure with the instantaneous ventricular volume in one cardiac cycle.…”