AJP - Heart and Circulatory Physiology, Vol 263, Issue 4 1054-H1063, Copyright © 1992 by American Physiological Society
Cardiac adaptation of sarcomere dynamics to arterial load: a model of hypertrophy
G. M. Drzewiecki, E. Karam, J. K. Li and A. Noordergraaf
Department of Biomedical Engineering, Rutgers, State University of New Jersey, College of Engineering, Piscataway 08855-1179.
In the past, the dynamics of the left ventricle were studied by its
response to altered venous and arterial load for a given heart. This led
researchers to propose the concept of an arterioventricular match or
optimal point of function. The model of this paper reverses that idea by
fixing preload and afterload while computing cardiac function due to
altered left ventricular size or shape, resulting from modification of the
number of parallel and series sarcounits. A mathematical model of
physiological hypertrophy is introduced. Series and parallel arrangements
of sarcounits constitute a cylindrical model of the left ventricle. Filling
occurs from a venous reservoir with constant pressure through a valve,
while ejection takes place into a three-element model of the systemic
arterial system through another valve. It is found that the dynamics of the
myofibrils can be matched to those of the left ventricle by choosing a
ventricular shape that results in a minimum in myocardial O2 consumption
(MVO2) for any constant ventricular load. A unique solution for the size of
the ventricle results if the rate of MVO2 is specified. The model is able
to predict correctly hypertrophy due to hypoxia and due to pressure
(concentric) and volume (eccentric) overloads.
