Cardiac adaptation of sarcomere dynamics to arterial load: a model of hypertrophy.
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.
Drzewiecki
G M
GM
Department of Biomedical Engineering, Rutgers, State University of New Jersey, College of Engineering, Piscataway 08855-1179.
Karam
E
E
Li
J K
JK
Noordergraaf
A
A
D000222:Adaptation, Physiological; D000818:Animals; D001011:Aorta / Q000502:physiology; D001158:Arteries / Q000502:physiology*; D001794:Blood Pressure; D006332:Cardiomegaly / Q000209:etiology*; D005544:Forecasting; D006321:Heart / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism; D012518:Sarcomeres / Q000502:physiology*; D016277:Ventricular Function, Left