Arts T, Bovendeerd P H, Prinzen F W, Reneman R S
Department of Biophysics, University of Limburg, Maastricht, The Netherlands.
Biophys J. 1991 Jan;59(1):93-102. doi: 10.1016/S0006-3495(91)82201-9.
Pumping power as delivered by the heart is generated by the cells in the myocardial wall. In the present model study global left-ventricular pump function as expressed in terms of cavity pressure and volume is related to local wall tissue function as expressed in terms of myocardial fiber stress and strain. On the basis of earlier studies in our laboratory, it may be concluded that in the normal left ventricle muscle fiber stress and strain are homogeneously distributed. So, fiber stress and strain may be approximated by single values, being valid for the whole wall. When assuming rotational symmetry and homogeneity of mechanical load in the wall, the dimensionless ratio of muscle fiber stress (sigma f) to left-ventricular pressure (Plv) appears to depend mainly on the dimensionless ratio of cavity volume (Vlv) to wall volume (Vw) and is quite independent of other geometric parameters. A good (+/- 10%) and simple approximation of this relation is sigma f/Plv = 1 + 3 Vlv/Vw. Natural fiber strain is defined by ef = In (lf/lf,ref), where lf,ref indicates fiber length (lf) in a reference situation. Using the principle of conservation of energy for a change in ef, it holds delta ef = (1/3)delta In (1 + 3Vlv/Vw).
心脏所产生的泵血动力由心肌壁中的细胞产生。在本模型研究中，以心腔压力和容积表示的左心室整体泵功能与以心肌纤维应力和应变表示的局部壁组织功能相关。基于我们实验室早期的研究，可以得出结论，在正常左心室中，肌纤维应力和应变是均匀分布的。因此，纤维应力和应变可以用对整个壁有效的单个值来近似。当假设壁内机械负荷具有旋转对称性和均匀性时，肌纤维应力（σf）与左心室压力（Plv）的无量纲比值似乎主要取决于心腔容积（Vlv）与壁容积（Vw）的无量纲比值，并且与其他几何参数相当独立。该关系的一个良好（±10%）且简单的近似式为σf/Plv = 1 + 3Vlv/Vw。自然纤维应变由ef = In（lf/lf,ref）定义，其中lf,ref表示参考情况下的纤维长度（lf）。利用能量守恒原理来描述ef的变化，可得δef = (1/3)δIn(1 + 3Vlv/Vw)。
