AJP - Heart and Circulatory Physiology, Vol 258, Issue 1 262-H276, Copyright © 1990 by American Physiological Society
Model-based analysis of transmural vessel impedance and myocardial circulation dynamics
J. Y. Kresh, M. Fox, S. K. Brockman and A. Noordergraaf
Department of Cardiothoracic Surgery, Hahnemann University, Philadelphia 19102-1192.
The basic structure of a model of the coronary circulation has been
developed to explain the relationship between transmural perfusion dynamics
and intramyocardial mechanics. The model is in the form of a topologically
isomorphic network representation and incorporates experimentally measured
time-varying perfusion and intramyocardial pressure sources as driving
inputs to the model. The intramyocardial vessels are treated as nonlinear
impedance elements possessing regional external pressure-dependent
resistance and capacitance. Three circuit branches, perfusing the
epicardial, subepicardial, and subendocardial muscle layers, are
mathematically modeled and are used to predict time-dependent flow within
the left ventricular myocardium. The phasic coronary blood flow
characteristics predicted by the model exhibit waveform patterns that
correlate qualitatively with those patterns measured experimentally. In
addition, the pressure-dependent vascular capacitance induces a sustained
(out of phase with arterial inflow) venous systolic flow. The model also
exhibits retrograde systolic subendocardial flow and stop-flow pressure,
which are dependent on coronary resistive and capacitive properties and on
the perfusion pressure decay time constant. Furthermore, the results
predict an abrupt decrease in subendocardial flow with perturbation of
either arteriolar or capillary bed compliance. The model describes
time-dependent intramyocardial properties that have been confusing and
controversial in the understanding of coronary circulation dynamics.
Several steps are identified that are expected to improve and refine the
model significantly.
