Paritala Phani Kumari, Yarlagadda Prasad K D V, Kansky Rhys, Wang Jiaqiu, Mendieta Jessica Benitez, Gu YuanTong, McGahan Tim, Lloyd Thomas, Li Zhiyong
School of Mechanical, Medical and Process Engineering, Queensland University of Technology, Brisbane, QLD, Australia.
Department of Vascular Surgery, Princess Alexandra Hospital, Brisbane, QLD, Australia.
Front Bioeng Biotechnol. 2020 Feb 11;8:60. doi: 10.3389/fbioe.2020.00060. eCollection 2020.
Atherosclerotic plaque rupture is a catastrophic event that contributes to mortality and long-term disability. A better understanding of the plaque mechanical behavior is essential for the identification of vulnerable plaques pre-rupture. Plaque is subjected to a natural dynamic mechanical environment under hemodynamic loading. Therefore, it is important to understand the mechanical response of plaque tissue under cyclic loading conditions. Moreover, experimental data of such mechanical properties are fundamental for more clinically relevant biomechanical modeling and numerical simulations for risk stratification. This study aims to experimentally and numerically characterize the stress-relaxation and cyclic mechanical behavior of carotid plaque tissue. Instron microtester equipped with a custom-developed setup was used for the experiments. Carotid plaque samples excised at endarterectomy were subjected to uniaxial tensile, stress-relaxation, and cyclic loading protocols. Thirty percent of the underlying load level obtained from the uniaxial tensile test results was used to determine the change in mechanical properties of the tissue over time under a controlled testing environment (Control tests). The stress-relaxation test data was used to calibrate the hyperelastic (neo-Hookean, Ogden, Yeoh) and linear viscoelastic (Prony series) material parameters. The normalized relaxation force increased initially and slowly stabilized toward the end of relaxation phase, highlighting the viscoelastic behavior. During the cyclic tests, there was a decrease in the peak force as a function of the cycle number indicating mechanical distension due to repeated loading that varied with different frequencies. The material also accumulated residual deformation, which increased with the cycle number. This trend showed softening behavior of the samples. The results of this preliminary study provide an enhanced understanding of stress-relaxation and cyclic behavior of the human atherosclerotic plaque tissue.
动脉粥样硬化斑块破裂是一种导致死亡和长期残疾的灾难性事件。更好地了解斑块的力学行为对于识别破裂前的易损斑块至关重要。在血流动力学负荷下，斑块处于自然动态力学环境中。因此，了解斑块组织在循环加载条件下的力学响应非常重要。此外，此类力学性能的实验数据对于更具临床相关性的生物力学建模和用于风险分层的数值模拟至关重要。本研究旨在通过实验和数值方法表征颈动脉斑块组织的应力松弛和循环力学行为。实验使用配备定制装置的英斯特朗微型试验机。对在动脉内膜切除术中切除的颈动脉斑块样本进行单轴拉伸、应力松弛和循环加载试验。根据单轴拉伸试验结果获得的基础负荷水平的30%用于确定在受控测试环境下组织力学性能随时间的变化（对照试验）。应力松弛试验数据用于校准超弹性（新胡克、奥格登、杨）和线性粘弹性（普龙尼级数）材料参数。归一化松弛力最初增加，在松弛阶段结束时缓慢稳定，突出了粘弹性行为。在循环试验期间，峰值力随循环次数的增加而降低，表明由于不同频率的重复加载导致的机械扩张。材料还积累了残余变形，其随循环次数增加。这种趋势表明样本出现软化行为。这项初步研究的结果有助于增强对人类动脉粥样硬化斑块组织应力松弛和循环行为的理解。
