Ross Colton, Laurence Devin, Wu Yi, Lee Chung-Hao
Biomechanics and Biomaterials Design Laboratory (BBDL), School of Aerospace and Mechanical Engineering, The University of Oklahoma.
Biomechanics and Biomaterials Design Laboratory (BBDL), School of Aerospace and Mechanical Engineering, The University of Oklahoma; Institute for Biomedical Engineering, Science and Technology (IBEST), The University of Oklahoma;
J Vis Exp. 2019 Apr 9(146). doi: 10.3791/59170.
Extensive biaxial mechanical testing of the atrioventricular heart valve leaflets can be utilized to derive optimal parameters used in constitutive models, which provide a mathematical representation of the mechanical function of those structures. This presented biaxial mechanical testing protocol involves (i) tissue acquisition, (ii) the preparation of tissue specimens, (iii) biaxial mechanical testing, and (iv) postprocessing of the acquired data. First, tissue acquisition requires obtaining porcine or ovine hearts from a local Food and Drug Administration-approved abattoir for later dissection to retrieve the valve leaflets. Second, tissue preparation requires using tissue specimen cutters on the leaflet tissue to extract a clear zone for testing. Third, biaxial mechanical testing of the leaflet specimen requires the use of a commercial biaxial mechanical tester, which consists of force-controlled, displacement-controlled, and stress-relaxation testing protocols to characterize the leaflet tissue's mechanical properties. Finally, post-processing requires the use of data image correlation techniques and force and displacement readings to summarize the tissue's mechanical behaviors in response to external loading. In general, results from biaxial testing demonstrate that the leaflet tissues yield a nonlinear, anisotropic mechanical response. The presented biaxial testing procedure is advantageous to other methods since the method presented here allows for a more comprehensive characterization of the valve leaflet tissue under one unified testing scheme, as opposed to separate testing protocols on different tissue specimens. The proposed testing method has its limitations in that shear stress is potentially present in the tissue sample. However, any potential shear is presumed negligible.
对房室心脏瓣膜小叶进行广泛的双轴力学测试，可用于推导本构模型中使用的最佳参数，这些模型提供了这些结构力学功能的数学表示。本文介绍的双轴力学测试方案包括：（i）组织采集，（ii）组织标本制备，（iii）双轴力学测试，以及（iv）采集数据的后处理。首先，组织采集需要从当地食品药品监督管理局批准的屠宰场获取猪或羊的心脏，以便稍后解剖以取出瓣膜小叶。其次，组织制备需要在小叶组织上使用组织标本切割器，以提取用于测试的清晰区域。第三，小叶标本的双轴力学测试需要使用商用双轴力学测试仪，该测试仪由力控制、位移控制和应力松弛测试方案组成，以表征小叶组织的力学性能。最后，后处理需要使用数据图像相关技术以及力和位移读数，以总结组织在外部加载下的力学行为。一般来说，双轴测试结果表明，小叶组织呈现非线性、各向异性的力学响应。本文介绍的双轴测试程序比其他方法更具优势，因为与在不同组织标本上进行单独测试方案不同，本文提出的方法允许在一个统一的测试方案下更全面地表征瓣膜小叶组织。所提出的测试方法有其局限性，即组织样本中可能存在剪应力。然而，任何潜在的剪应力都被认为可以忽略不计。
