Lim K O, Boughner D R
Can J Physiol Pharmacol. 1975 Jun;53(3):330-9. doi: 10.1139/y75-048.
A knowledge of the mechanical properties of valve tissue is a necessary prerequisite for a better understanding of valvular behavior and design of prosthetic heart valves. Elastic response of chordae tendineae under strain rates of 0.05 cm min(-1)(6.25% min(-1)) to 12.7 cm min(-1)(1600% min(-1)) were obtained by the application of an uniaxial tensile stress using an Instron machine. The chordae exhibited viscoelastic properties in that extensibility decreased with increasing strain rates. The approximate maximum physiological strain rate of the chordae was estimated from echocardiographic traces at the instant of valve closure, and a high value of 29 (S.D. equals 9) cm s(-1) (2000% s(-1)) was found. The breaking strain and stress were found to have values of 21.4 plus or minus 0.5% and 3.1 plus or minus 0.1 times 10(8) dyn cm(-2) respectively, and were independent of strain rates (1 dyn equals 10(-5) N). These values are typical of collagen fibers. The final modulus, before the proportional limit, was found to be about 10(9) dyn cm(-2), which is again typical of collagen fibers. In addition, smaller chordae exhibited less extensibility than the larger chordae. This behavior could be due to structural and functional differences and allows the more centrally inserted chordae to maintain an even valve surface during valve closure.
了解瓣膜组织的力学特性是更好地理解瓣膜行为和设计人工心脏瓣膜的必要前提。使用英斯特朗材料试验机施加单轴拉伸应力，获得了腱索在0.05 cm min⁻¹（6.25% min⁻¹）至12.7 cm min⁻¹（1600% min⁻¹）应变率下的弹性响应。腱索表现出粘弹性特性，即随着应变率增加，伸长率降低。根据瓣膜关闭瞬间的超声心动图轨迹估算出腱索的近似最大生理应变率，发现其值高达29（标准差为9）cm s⁻¹（2000% s⁻¹）。发现断裂应变和应力值分别为21.4±0.5%和3.1±0.1×10⁸ dyn cm⁻²，且与应变率无关（1 dyn等于10⁻⁵ N）。这些值是胶原纤维的典型特征。比例极限之前的最终模量约为10⁹ dyn cm⁻²，这同样是胶原纤维的典型特征。此外，较小的腱索比较大的腱索伸长性更小。这种行为可能是由于结构和功能差异导致的，使得更靠近中心插入的腱索在瓣膜关闭期间能够维持瓣膜表面平整。
