Brenneisen Jochen, Daub Anna, Gerach Tobias, Kovacheva Ekaterina, Huetter Larissa, Frohnapfel Bettina, Dössel Olaf, Loewe Axel
Institute of Biomedical Engineering, Karlsruhe Institute of Technology, Karlsruhe, Germany.
Institute of Fluid Mechanics, Karlsruhe Institute of Technology, Karlsruhe, Germany.
Front Cardiovasc Med. 2021 Dec 23;8:768548. doi: 10.3389/fcvm.2021.768548. eCollection 2021.
The human heart is a masterpiece of the highest complexity coordinating multi-physics aspects on a multi-scale range. Thus, modeling the cardiac function to reproduce physiological characteristics and diseases remains challenging. Especially the complex simulation of the blood's hemodynamics and its interaction with the myocardial tissue requires a high accuracy of the underlying computational models and solvers. These demanding aspects make whole-heart fully-coupled simulations computationally highly expensive and call for simpler but still accurate models. While the mechanical deformation during the heart cycle drives the blood flow, less is known about the feedback of the blood flow onto the myocardial tissue. To solve the fluid-structure interaction problem, we suggest a cycle-to-cycle coupling of the structural deformation and the fluid dynamics. In a first step, the displacement of the endocardial wall in the mechanical simulation serves as a unidirectional boundary condition for the fluid simulation. After a complete heart cycle of fluid simulation, a spatially resolved pressure factor (PF) is extracted and returned to the next iteration of the solid mechanical simulation, closing the loop of the iterative coupling procedure. All simulations were performed on an individualized whole heart geometry. The effect of the sequential coupling was assessed by global measures such as the change in deformation and-as an example of diagnostically relevant information-the particle residence time. The mechanical displacement was up to 2 mm after the first iteration. In the second iteration, the deviation was in the sub-millimeter range, implying that already one iteration of the proposed cycle-to-cycle coupling is sufficient to converge to a coupled limit cycle. Cycle-to-cycle coupling between cardiac mechanics and fluid dynamics can be a promising approach to account for fluid-structure interaction with low computational effort. In an individualized healthy whole-heart model, one iteration sufficed to obtain converged and physiologically plausible results.
人类心脏是一个高度复杂的杰作，在多尺度范围内协调多物理方面。因此，对心脏功能进行建模以再现生理特征和疾病仍然具有挑战性。特别是血液血流动力学及其与心肌组织相互作用的复杂模拟需要基础计算模型和求解器具有高精度。这些苛刻的方面使得全心全耦合模拟在计算上成本高昂，因此需要更简单但仍然准确的模型。虽然心动周期中的机械变形驱动血流，但关于血流对心肌组织的反馈知之甚少。为了解决流固耦合问题，我们建议对结构变形和流体动力学进行逐周期耦合。第一步，力学模拟中心内膜壁的位移用作流体模拟的单向边界条件。在流体模拟完成一个完整的心动周期后，提取空间分辨压力因子（PF）并返回固体力学模拟的下一次迭代，从而闭合迭代耦合过程的循环。所有模拟均在个体化的全心几何模型上进行。通过诸如变形变化等全局测量以及作为诊断相关信息示例的粒子停留时间来评估顺序耦合的效果。第一次迭代后机械位移高达2毫米。在第二次迭代中，偏差在亚毫米范围内，这意味着所提出的逐周期耦合仅一次迭代就足以收敛到耦合极限环。心脏力学和流体动力学之间的逐周期耦合可能是一种以低计算量考虑流固耦合的有前途的方法。在个体化的健康全心模型中，一次迭代就足以获得收敛且符合生理的合理结果。
