IBiTech-BioMMedA, Ghent University, Ghent, Belgium.
Department of Mechanical Engineering, KU Leuven, Leuven, Belgium.
Comput Biol Med. 2024 Jun;176:108604. doi: 10.1016/j.compbiomed.2024.108604. Epub 2024 May 14.
In young patients, aortic valve disease is often treated by placement of a pulmonary autograft (PA) which adapts to its new environment through growth and remodeling. To better understand the hemodynamic forces acting on the highly distensible PA in the acute phase after surgery, we developed a fluid-structure interaction (FSI) framework and comprehensively compared hemodynamics and wall shear-stress (WSS) metrics with a computational fluid dynamic (CFD) simulation.
The FSI framework couples a prestressed non-linear hyperelastic arterial tissue model with a fluid model using the in-house coupling code CoCoNuT. Geometry, material parameters and boundary conditions are based on in-vivo measurements. Hemodynamics, time-averaged WSS (TAWSS), oscillatory shear index (OSI) and topological shear variation index (TSVI) are evaluated qualitatively and quantitatively for 3 different sheeps.
Despite systolic-to-diastolic volumetric changes of the PA in the order of 20 %, the point-by-point correlation of TAWSS and OSI obtained through CFD and FSI remains high (r > 0.9, p < 0.01) for TAWSS and (r > 0.8, p < 0.01) for OSI). Instantaneous WSS divergence patterns qualitatively preserve similarities, but large deformations of the PA leads to a decrease of the correlation between FSI and CFD resolved TSVI (r < 0.7, p < 0.01). Moderate co-localization between FSI and CFD is observed for low thresholds of TAWSS and high thresholds of OSI and TSVI.
FSI might be warranted if we were to use the TSVI as a mechano-biological driver for growth and remodeling of PA due to varying intra-vascular flow structures and near wall hemodynamics because of the large expansion of the PA.
在年轻患者中，主动脉瓣疾病通常通过放置肺动脉移植物 (PA) 来治疗，PA 通过生长和重塑来适应新的环境。为了更好地了解手术后急性阶段作用于高度可伸展的 PA 的血流动力学力，我们开发了一个流固耦合 (FSI) 框架，并使用计算流体动力学 (CFD) 模拟全面比较了血流动力学和壁切应力 (WSS) 指标。
FSI 框架使用内部耦合代码 CoCoNuT 将预应力非线性超弹性动脉组织模型与流体模型耦合。几何形状、材料参数和边界条件基于体内测量值。对 3 只不同绵羊进行了定性和定量评估血流动力学、时均壁切应力 (TAWSS)、振荡剪切指数 (OSI) 和拓扑剪切变化指数 (TSVI)。
尽管 PA 的收缩期到舒张期容积变化在 20%左右，但通过 CFD 和 FSI 获得的 TAWSS 和 OSI 的逐点相关性仍然很高(r>0.9，p<0.01)，对于 TAWSS(r>0.8，p<0.01)。对于 OSI)。尽管 PA 的大变形导致 FSI 和 CFD 分辨的 TSVI 的相关性降低(r<0.7，p<0.01)，但瞬时 WSS 发散模式在定性上仍保持相似性。对于低 TAWSS 和高 OSI 和 TSVI 阈值，FSI 与 CFD 之间存在中度的局部化。
如果我们要将 TSVI 用作 PA 生长和重塑的机械生物学驱动因素，因为 PA 的大量扩张导致血管内流动结构和近壁血流动力学发生变化，那么 FSI 可能是合理的。
