School of Mechanical Engineering, University of Birmingham, Birmingham B15 2TT, UK.
Cardiothoracic Surgery, Aberdeen Royal Infirmary, Aberdeen AB25 2ZD, UK.
J Mech Behav Biomed Mater. 2014 Feb;30:186-95. doi: 10.1016/j.jmbbm.2013.11.013. Epub 2013 Nov 25.
This study aimed to characterise viscoelastic properties of different categories of chordae tendineae over a range of frequencies. Dynamic Mechanical Analysis (DMA) was performed using a materials testing machine. Chordae (n=51) were dissected from seven porcine hearts and categorised as basal, marginal, strut or commissural. Chordae were loaded under a sinusoidally varying tensile load at a range of frequencies between 0.5 and 5Hz, both at a standardised load (i.e. same mean load of 4N for all chordae) and under chordal specific loading (i.e. based on in vivo loads for different chordae). Storage modulus and stiffness were frequency-dependent. Loss modulus and stiffness were frequency-independent. Storage and loss moduli, but not stiffness, decreased with chordal diameter. Therefore, strut chordae have the lowest moduli and marginal chordae the highest moduli. The hierarchy of dynamic storage and loss moduli is: marginal, commissural, basal and strut. In conclusion, viscoelastic properties of chordae are dependent on both frequency and chordal type. Future/novel replacement chordal materials should account for frequency and diameter dependent viscoelastic properties of chordae tendineae.
本研究旨在研究不同类型的腱索在一定频率范围内的粘弹性特性。使用材料试验机进行动态力学分析（DMA）。从七只猪心中解剖出腱索（n=51），并将其分类为基底部、边缘部、支柱部或连合部。腱索在一定频率范围内（0.5 至 5Hz），在标准负荷（即所有腱索的平均负荷相同，均为 4N）和腱索特定负荷（即基于不同腱索的体内负荷）下，承受正弦变化的拉伸负荷。储存模量和刚度随频率而变化。损耗模量和刚度与频率无关。储存模量和损耗模量随腱索直径的减小而降低。因此，支柱腱索的模量最低，边缘腱索的模量最高。动态储存和损耗模量的层次结构为：边缘部、连合部、基底部和支柱部。总之，腱索的粘弹性特性既取决于频率，又取决于腱索类型。未来/新型替代腱索材料应考虑腱索的粘弹性特性，这种特性依赖于频率和直径。
