Chong Mei Yan, Gu Boram, Chan Bee Ting, Ong Zhi Chao, Xu Xiao Yun, Lim Einly
Department of Biomedical Engineering, University of Malaya, Kuala Lumpur, Malaysia.
Department of Chemical Engineering, Imperial College London, London, UK.
Int J Numer Method Biomed Eng. 2020 Dec;36(12):e3399. doi: 10.1002/cnm.3399. Epub 2020 Sep 28.
A monolithic, fully coupled fluid-structure interaction (FSI) computational framework was developed to account for dissection flap motion in acute type B aortic dissection (TBAD). Analysis of results included wall deformation, pressure, flow, wall shear stress (WSS), von Mises stress and comparison of hemodynamics between rigid wall and FSI models. Our FSI model mimicked realistic wall deformation that resulted in maximum compression of the distal true lumen (TL) by 21.4%. The substantial movement of intimal flap mostly affected flow conditions in the false lumen (FL). Flap motion facilitated more flow entering the FL at peak systole, with the TL to FL flow split changing from 88:12 in the rigid model to 83:17 in the FSI model. There was more disturbed flow in the FL during systole (5.8% FSI vs 5.2% rigid) and diastole (13.5% FSI vs 9.8% rigid), via a λ -criterion. The flap-induced disturbed flow near the tears in the FSI model caused an increase of local WSS by up to 70.0% during diastole. This resulted in a significant reduction in the size of low time-averaged WSS (TAWSS) regions in the FL (113.11 cm FSI vs 177.44 cm rigid). Moreover, the FSI model predicted lower systolic pressure, higher diastolic pressure, and hence lower pulse pressure. Our results provided new insights into the possible impact of flap motion on flow in aortic dissections, which are particularly important when evaluating hemodynamics of acute TBAD. NOVELTY STATEMENT: Our monolithic fully coupled FSI computational framework is able to reproduce experimentally measured range of flap deformation in aortic dissection, thereby providing novel insights into the influence of physiological flap motion on the flow and pressure distributions. The drastic flap movement increases the flow resistance in the true lumen and causes more disturbed flow in the false lumen, as visualized through the λ criterion. The flap-induced luminal pressure is dampened, thereby affecting pressure measures, which may serve as potential prognostic indicators for late complications in acute uncomplicated TBAD patients.
开发了一种整体式、完全耦合的流固相互作用（FSI）计算框架，以解释急性B型主动脉夹层（TBAD）中夹层瓣的运动。结果分析包括壁变形、压力、流量、壁面剪应力（WSS）、冯·米塞斯应力，以及刚性壁模型和FSI模型之间的血流动力学比较。我们的FSI模型模拟了逼真的壁变形，导致远端真腔（TL）最大压缩21.4%。内膜瓣的大幅移动主要影响假腔（FL）中的血流状况。瓣的运动促使更多血流在收缩期峰值进入假腔，真腔与假腔的血流分流比从刚性模型中的88:12变为FSI模型中的83:17。通过λ准则，在收缩期（FSI为5.8%，刚性为5.2%）和舒张期（FSI为13.5%，刚性为9.8%），假腔内的血流紊乱更多。FSI模型中瓣引起的靠近撕裂处的紊乱血流在舒张期使局部WSS增加高达70.0%。这导致假腔内低时间平均WSS（TAWSS）区域的大小显著减小（FSI为113.11平方厘米，刚性为177.44平方厘米）。此外，FSI模型预测收缩压较低、舒张压较高，因此脉压较低。我们的结果为瓣运动对主动脉夹层血流的可能影响提供了新的见解，这在评估急性TBAD的血流动力学时尤为重要。新颖性声明：我们的整体式完全耦合FSI计算框架能够重现主动脉夹层中通过实验测量的瓣变形范围，从而为生理瓣运动对血流和压力分布的影响提供新的见解。如通过λ准则所见，剧烈的瓣运动增加了真腔内的流动阻力，并在假腔内引起更多紊乱血流。瓣引起的腔内压力受到抑制，从而影响压力测量，这可能作为急性非复杂性TBAD患者晚期并发症的潜在预后指标。
