将左心室作为机电一体化系统的收缩期建模：心肌纤维肌节收缩特性的测定及新的性能指标

Ghista Dhanjoo N, Zhong Liang, Chua Leok P, Ng Eddie Y K, Lim Soo T, Tan Ru S, Chua Terrance S J

Bioengineering Division, School of Chemistry and Biomedical Engineering, College of Engineering, Nanyang Technological University, Singapore, 639798.

Mol Cell Biomech. 2005 Dec;2(4):217-33.

BACKGROUND

In this paper, the left ventricle (LV) is modeled as a cylinder with myocardial fibers located helically within its wall. A fiber is modeled into myocardial structural units (MSUs); the core entity of each MSU is the sarcomeric contractile element. The relationship between the sarcomere unit's contractile force and shortening velocity is expressed in terms of the LV model's wall stress and deformation, and hence in terms of the monitored LV pressure and volume. Then, the LV systolic performance is investigated in terms of a mechatronic (excitation-contraction) model of the sarcomere unit located within the LV cylindrical model wall.

METHODS

The governing equation of dynamics of the LV myocardial structural unit (MSU) is developed, involving the parameters of the series-elastic element (SE), the viscous element (VE) and the contractile element (CE). We then relate the MSU's force and displacement variables (in terms of SE, VE and CE parameters) to the LV pressure and volume, using the patient's catheterization-ventriculogram data. We thereby evaluate the MSU elements' parameters.

RESULTS

We then determine the sarcomere (CE) 'force vs. shortening-velocity' characteristics as well as the power generated by the sarcomere (or CE) element. These are deemed to be important LV functional indices. When our computed sarcomeric peak-power is compared against the traditional LV contractility indices (by linear regression), a high degree of correlation is obtained.

CONCLUSIONS

We have provided herein, a LV systolic-phase (cylindrical geometry) model whose wall contains the myocardial fibers having sarcomere units. We have expressed the LV myocardial sarcomere's CE (force vs. shortening-velocity) characteristics in terms of the LV pressure-volume data. These CE properties express the intrinsic performance capacity of the LV. Hence, indices containing these properties are deemed to reflect LV performance. In this regard, our new LV contractility index correlates very well with the traditional LV contractility index dP/dt(max).

背景

在本文中，左心室（LV）被建模为一个圆柱体，其心肌纤维呈螺旋状分布于心室壁内。一根纤维被建模为心肌结构单元（MSU）；每个MSU的核心实体是肌节收缩元件。肌节单元的收缩力与缩短速度之间的关系通过左心室模型的壁应力和变形来表示，进而通过监测到的左心室压力和容积来表示。然后，根据位于左心室圆柱模型壁内的肌节单元的机电（兴奋 - 收缩）模型来研究左心室的收缩性能。

方法

推导了左心室心肌结构单元（MSU）的动力学控制方程，该方程涉及串联弹性元件（SE）、粘性元件（VE）和收缩元件（CE）的参数。然后，利用患者的导管心室造影数据，将MSU的力和位移变量（根据SE、VE和CE参数）与左心室压力和容积相关联。从而评估MSU元件的参数。

结果

然后确定了肌节（CE）的“力与缩短速度”特性以及肌节（或CE）元件产生的功率。这些被认为是重要的左心室功能指标。当将我们计算得到的肌节峰值功率与传统的左心室收缩性指标进行线性回归比较时，得到了高度相关性。

结论

我们在此提供了一个左心室收缩期（圆柱几何形状）模型，其心室壁包含具有肌节单元的心肌纤维。我们根据左心室压力 - 容积数据表达了左心室心肌肌节的CE（力与缩短速度）特性。这些CE特性表达了左心室的内在性能能力。因此，包含这些特性的指标被认为能够反映左心室的性能。在这方面，我们新的左心室收缩性指标与传统的左心室收缩性指标dP/dt(max)具有很好的相关性。