Drzewiecki G M, Karam E, Li J K, Noordergraaf A
Department of Biomedical Engineering, Rutgers, State University of New Jersey, College of Engineering, Piscataway 08855-1179.
Am J Physiol. 1992 Oct;263(4 Pt 2):H1054-63. doi: 10.1152/ajpheart.1992.263.4.H1054.
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.
过去，对于给定的心脏，通过左心室对改变的静脉和动脉负荷的反应来研究其动力学。这使得研究人员提出了动静脉匹配或最佳功能点的概念。本文的模型则颠倒了这一想法，在计算由于左心室大小或形状改变（这是由平行和串联肌节数量的改变引起的）而导致的心脏功能时，固定前负荷和后负荷。引入了一个生理性肥大的数学模型。肌节的串联和并联排列构成了左心室的圆柱模型。血液从具有恒定压力的静脉储液器通过一个瓣膜充盈，而射血则通过另一个瓣膜进入体循环动脉系统的三元模型。研究发现，通过选择一种心室形状，对于任何恒定的心室负荷，都能使肌原纤维的动力学与左心室的动力学相匹配，从而使心肌耗氧量（MVO2）降至最低。如果指定了MVO2的速率，就能得到心室大小的唯一解。该模型能够正确预测由缺氧、压力（向心性）和容量（离心性）过载引起的肥大。
