左心室局部心肌梗塞时的组分式模型及计算机仿真

A Two-Compartment Model of Left Ventricle with Regional Ischemia and Its Computer Simulation

为研究左心室局部心肌梗塞时心肌各部分的能量供需状况及心脏辅助装置对改善心肌能量供给的影响,我们建立了一个由左心室正常区域心肌和梗塞区域心肌两部分组成的组分式模型。我们的模型以Sunagawa的模型为基础,并在此基础上加以扩展。与Sunagawa的模型相比,我们的模型允许梗塞区域心肌的收缩性在一定范围内变化,从而可以模拟各种不同范围和不同程度的梗塞情况。 用建立好的左心室组分式模型取代我们原有的狗的心血管模型中的左心室部分,通过改变梗塞范围和梗死程度两个仿真参数,我们得到了在各种梗塞情况下的左、右心室及主动脉的血压、容积和冠脉血流在一个心拍中的变化曲线。并且,还给出了如每搏输出量,平均肺动脉压及左心室舒张末期压力等血液动力学参量随心肌梗塞的发展而变化的曲线。

In order to study the energy balance of respective area of the left ventricle with regional ischemia and the effects of assistant devices on the dynamics of the regionally ischemic left ventricle, we developed a two-compartment model that consists of both normal and ischemic myocardial regions. Our model was based on Sunagawa's work. In contrast to Sunagawa's model, we allow the change of the contractility of ischemic region in our model. Therefore both the area of ischemic region and its degree of dysfunction can be simulated. In our model, two parallel time-varying elastic elements represent the normal region and the ischemic region of the left ventricle respectively. The range of ischemic region (Rm) is defined as the ratio of the mass of ischemic myocardium to the total mass of the left ventricle. The end-systolic pressure-volume relations (ES-PVRs) of the respective region were determined based on Kass's non-linear model: Ps = a(Vs-V0)z + b(V.?V0). In this equation, a is the coefficient of curvilinearity, Vo is the volume axis intercept of the curvilinear relation. Contractility is assessed by the slope of the ESPVR at Vo (that is b in the equation). Both the extent of the ischemic region and its degree of dysfunction will be input variables of the simulation. The global P-V relation is obtained by the combination of P-V locus of the individual compartment. Finally, we used our two-compartment model to replace the lumped left ventricle model in the non-linear multi-element digital hemodynamic model developed by our yroup. By changing the simulation parameters of ischemic range and degree of dysfunction, we have obtained the varying trend of some hemodynamic variables with the development of regional ischemia, for example, the stroke volume, the average pulmonary pressure and the end-diastolic presure of the left ventricle. Meanwhile, the two-compartment model provides a useful tool for us to study the energy balance of the left ventricle with regional ischemia and the effects of assistance device.