Kronborg Joel, Svelander Frida, Eriksson-Lidbrink Samuel, Lindström Ludvig, Homs-Pons Carme, Lucor Didier, Hoffman Johan
Department of Computational Science and Technology, School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden.
Laboratoire Interdisciplinaire des Sciences du Numérique (LISN), CNRS, Université Paris-Saclay, Orsay, France.
Front Physiol. 2022 Jun 30;13:806534. doi: 10.3389/fphys.2022.806534. eCollection 2022.
Cardiac disease and clinical intervention may both lead to an increased risk for thrombosis events due to a modified blood flow in the heart, and thereby a change in the mechanical stimuli of blood cells passing through the chambers of the heart. Specifically, the degree of platelet activation is influenced by the level and type of mechanical stresses in the blood flow. In this article we analyze the blood flow in the left ventricle of the heart through a computational model constructed from patient-specific data. The blood flow in the ventricle is modelled by the Navier-Stokes equations, and the flow through the mitral valve by a parameterized model which represents the projected opening of the valve. A finite element method is used to solve the equations, from which a simulation of the velocity and pressure of the blood flow is constructed. The intraventricular blood flow is complex, in particular in diastole when the inflow jet from the atrium breaks down into turbulent flow on a range of scales. A triple decomposition of the velocity gradient tensor is then used to distinguish between rigid body rotational flow, irrotational straining flow, and shear flow. The triple decomposition enables the separation of three fundamentally different flow structures, that each generates a distinct type of mechanical stimulus on the blood cells in the flow. We compare the results in a simulation where a mitral valve clip intervention is modelled, which leads to a significant modification of the intraventricular flow. Further, we perform a sensitivity study of the results with respect to the positioning of the clip. It was found that the shear in the simulation cases treated with clips increased more compared to the untreated case than the rotation and strain did. A decrease in valve opening area of 64% in one of the cases led to a 90% increase in rotation and strain, but a 150% increase in shear. The computational analysis opens up for improvements in models of shear-induced platelet activation, by offering an algorithm to distinguish shear from other modalities in intraventricular blood flow.
心脏疾病和临床干预都可能因心脏内血流改变而导致血栓形成事件风险增加，进而使流经心脏腔室的血细胞机械刺激发生变化。具体而言，血小板激活程度受血流中机械应力的水平和类型影响。在本文中，我们通过基于患者特定数据构建的计算模型来分析心脏左心室的血流情况。心室中的血流由纳维 - 斯托克斯方程建模，通过二尖瓣的血流则由代表瓣膜投影开口的参数化模型建模。采用有限元方法求解方程，从而构建出血流速度和压力的模拟。心室内血流复杂，尤其是在舒张期，此时来自心房的流入射流会分解为一系列尺度上的湍流。然后使用速度梯度张量的三重分解来区分刚体旋转流、无旋应变流和剪切流。这种三重分解能够分离出三种根本不同的流动结构，每种结构都会在血流中的血细胞上产生独特类型的机械刺激。我们比较了模拟二尖瓣夹合干预的结果，该干预会导致心室内血流发生显著改变。此外，我们针对夹子的定位对结果进行了敏感性研究。结果发现，与未处理情况相比，夹子处理的模拟案例中剪切力的增加幅度比旋转和应变更大。其中一个案例中瓣膜开口面积减少64%，导致旋转和应变增加90%，但剪切力增加150%。该计算分析通过提供一种区分心室内血流中剪切力与其他形式的算法，为改进剪切诱导血小板激活模型开辟了道路。
