Yettram A L, Grewal B S, Dawson J R, Gibson D G
Department of Mechanical Engineering, Brunel University, Uxbridge, Middlesex.
J Biomed Eng. 1992 Jan;14(1):21-6. doi: 10.1016/0141-5425(92)90031-f.
The aim of the study was to investigate the relative contributions of geometrical and material factors to overall left-ventricular cavity stiffness. Left-ventricular cavity shapes were reconstructed using a computer and the variation of myocardial elastic modulus was calculated, by the finite element method, through the passive phase of diastole when rising volume coincided with rising pressure. Geometric data were obtained from biplane cineangiography, with micromanometer pressure measurements, for ten patients with left ventricular disease. Dimensional analysis was applied to the initial and derived data from which the influences of myocardial compliance, wall thickness-to-long dimension ratio, and aspect ratio (long-to-short axes) were determined. The ratio between the volume elasticity and the myocardial modulus of elasticity, the normalized stiffness ratio (NSR), is proposed as a useful index of left ventricular mechanical behaviour in diastole. The volume elasticity of the chamber is dependent not only upon the myocardium elastic modulus and the wall thickness ratio, but also on the shape of the chamber. Changes in the thickness/radius ratio of the ventricle have less effect upon its distention than those in the long dimension/radius ratio. The left ventricle becomes more spherical in shape through diastole and hence becomes stiffer by this geometric mechanism.
该研究的目的是调查几何因素和材料因素对左心室腔整体硬度的相对贡献。使用计算机重建左心室腔形状，并通过有限元方法计算心肌弹性模量在舒张期被动阶段（此时容积增加与压力增加同时出现）的变化。从十名左心室疾病患者的双平面心血管造影术中获取几何数据，并进行微测压压力测量。对初始数据和衍生数据进行量纲分析，由此确定心肌顺应性、壁厚与长径比以及纵横比（长轴与短轴之比）的影响。提出容积弹性与心肌弹性模量之比，即标准化硬度比（NSR），作为舒张期左心室力学行为的有用指标。腔室的容积弹性不仅取决于心肌弹性模量和壁厚比，还取决于腔室的形状。心室厚度/半径比的变化对其扩张的影响小于长径/半径比的变化。在舒张期，左心室形状变得更接近球形，因此通过这种几何机制变得更硬。
