Tang Dalin, Yang Chun, Kobayashi Shunichi, Zheng Jie, Woodard Pamela K, Teng Zhongzhao, Billiar Kristen, Bach Richard, Ku David N
Department of Mathematical Sciences, Worcester Polytechnic Institute, Worcester, MA 01609, USA.
J Biomech Eng. 2009 Jun;131(6):061010. doi: 10.1115/1.3127253.
Heart attack and stroke are often caused by atherosclerotic plaque rupture, which happens without warning most of the time. Magnetic resonance imaging (MRI)-based atherosclerotic plaque models with fluid-structure interactions (FSIs) have been introduced to perform flow and stress/strain analysis and identify possible mechanical and morphological indices for accurate plaque vulnerability assessment. For coronary arteries, cyclic bending associated with heart motion and anisotropy of the vessel walls may have significant influence on flow and stress/strain distributions in the plaque. FSI models with cyclic bending and anisotropic vessel properties for coronary plaques are lacking in the current literature. In this paper, cyclic bending and anisotropic vessel properties were added to 3D FSI coronary plaque models so that the models would be more realistic for more accurate computational flow and stress/strain predictions. Six computational models using one ex vivo MRI human coronary plaque specimen data were constructed to assess the effects of cyclic bending, anisotropic vessel properties, pulsating pressure, plaque structure, and axial stretch on plaque stress/strain distributions. Our results indicate that cyclic bending and anisotropic properties may cause 50-800% increase in maximum principal stress (Stress-P1) values at selected locations. The stress increase varies with location and is higher when bending is coupled with axial stretch, nonsmooth plaque structure, and resonant pressure conditions (zero phase angle shift). Effects of cyclic bending on flow behaviors are more modest (9.8% decrease in maximum velocity, 2.5% decrease in flow rate, 15% increase in maximum flow shear stress). Inclusion of cyclic bending, anisotropic vessel material properties, accurate plaque structure, and axial stretch in computational FSI models should lead to a considerable improvement of accuracy of computational stress/strain predictions for coronary plaque vulnerability assessment. Further studies incorporating additional mechanical property data and in vivo MRI data are needed to obtain more complete and accurate knowledge about flow and stress/strain behaviors in coronary plaques and to identify critical indicators for better plaque assessment and possible rupture predictions.
心脏病发作和中风通常由动脉粥样硬化斑块破裂引起，这种情况大多时候没有任何预兆。基于磁共振成像（MRI）的具有流固相互作用（FSI）的动脉粥样硬化斑块模型已被引入，用于进行流动和应力/应变分析，并识别可能的力学和形态学指标，以准确评估斑块易损性。对于冠状动脉，与心脏运动相关的周期性弯曲以及血管壁的各向异性可能会对斑块内的流动和应力/应变分布产生重大影响。目前的文献中缺乏针对冠状动脉斑块的具有周期性弯曲和各向异性血管特性的FSI模型。在本文中，将周期性弯曲和各向异性血管特性添加到三维FSI冠状动脉斑块模型中，以使模型更符合实际情况，从而更准确地进行计算流体力学和应力/应变预测。使用一个离体MRI人体冠状动脉斑块标本数据构建了六个计算模型，以评估周期性弯曲、各向异性血管特性、脉动压力、斑块结构和轴向拉伸对斑块应力/应变分布的影响。我们的结果表明，周期性弯曲和各向异性特性可能会使选定位置的最大主应力（应力-P1）值增加50%-800%。应力增加随位置而异，当弯曲与轴向拉伸、不光滑的斑块结构和共振压力条件（零相位角偏移）相结合时，应力增加更高。周期性弯曲对流动行为的影响较小（最大速度降低9.8%，流速降低2.5%，最大流动剪应力增加15%）。在计算FSI模型中纳入周期性弯曲、各向异性血管材料特性、准确的斑块结构和轴向拉伸，应该会显著提高冠状动脉斑块易损性评估中计算应力/应变预测的准确性。需要进一步开展研究，纳入更多的力学性能数据和体内MRI数据，以更全面、准确地了解冠状动脉斑块中的流动和应力/应变行为，并识别关键指标，以更好地评估斑块和预测可能的破裂情况。
