Lumens Joost, Delhaas Tammo, Kirn Borut, Arts Theo
Department of Physiology, Maastricht University, Universiteitssingel 50, Maastricht, P.O. Box 616, The Netherlands.
Pac Symp Biocomput. 2008:378-89.
Direct ventricular interaction via the interventricular septum plays an important role in ventricular hemodynamics and mechanics. A large amount of experimental data demonstrates that left and right ventricular pump mechanics influence each other and that septal geometry and motion depend on transmural pressure. We present a lumped model of ventricular mechanics consisting of three wall segments that are coupled on the basis of balance laws stating mechanical equilibrium at the intersection of the three walls. The input consists of left and right ventricular volumes and an estimate of septal wall geometry. Wall segment geometry is expressed as area and curvature and is related to sarcomere extension. With constitutive equations of the sarcomere, myofiber stress is calculated. The force exerted by each wall segment on the intersection, as a result of wall tension, is derived from myofiber stress. Finally, septal geometry and ventricular pressures are solved by achieving balance of forces. We implemented this ventricular module in a lumped model of the closed-loop cardiovascular system (CircAdapt model) The resulting multiscale model enables dynamic simulation of myofiber mechanics, ventricular cavity mechanics, and cardiovascular system hemodynamics. The model was tested by performing simulations with synchronous and asynchronous mechanical activation of the wall segments. The simulated results of ventricular mechanics and hemodynamics were compared with experimental data obtained before and after acute induction of left bundle branch block (LBBB) in dogs. The changes in simulated ventricular mechanics and septal motion as a result of the introduction of mechanical asynchrony were very similar to those measured in the animal experiments. In conclusion, the module presented describes ventricular mechanics including direct ventricular interaction realistically and thereby extends the physiological application range of the CircAdapt model.
通过室间隔的心室直接相互作用在心室血流动力学和力学中起着重要作用。大量实验数据表明，左、右心室泵血力学相互影响，且间隔几何形状和运动取决于跨壁压力。我们提出了一个心室力学集总模型，该模型由三个壁段组成，这三个壁段基于平衡定律耦合，该平衡定律表明在三个壁的交点处存在力学平衡。输入包括左、右心室容积以及间隔壁几何形状的估计值。壁段几何形状用面积和曲率表示，并与肌节伸展相关。利用肌节的本构方程计算肌纤维应力。每个壁段由于壁张力在交点处施加的力由肌纤维应力推导得出。最后，通过实现力的平衡来求解间隔几何形状和心室压力。我们将这个心室模块应用于闭环心血管系统的集总模型（CircAdapt模型）中。由此产生的多尺度模型能够对肌纤维力学、心室腔力学和心血管系统血流动力学进行动态模拟。通过对壁段进行同步和异步机械激活的模拟来测试该模型。将心室力学和血流动力学的模拟结果与在犬急性诱导左束支传导阻滞（LBBB）前后获得的实验数据进行比较。引入机械不同步后模拟的心室力学和间隔运动变化与动物实验中测量的结果非常相似。总之，所提出的模块逼真地描述了包括心室直接相互作用在内的心室力学，从而扩展了CircAdapt模型的生理学应用范围。
