Duncan A C, Boughner D
J.P. Robarts Research Institute, University of Western Ontario, London, Canada.
Biomaterials. 1998 Apr-May;19(7-9):777-83. doi: 10.1016/s0142-9612(97)00215-9.
We have previously proposed dynamic fixation as an alternative method to fix a porcine aortic heart valve xenograft with better tissue fixation and better preservation of its natural biomechanical properties. Bovine pericardium was fixed under dynamic conditions, low pressures (< 4 mmHg) and low vibration rate (1.2 Hz) in a 0.5% glutaraldehyde phosphate buffer (pH 7.4, 0.2 M). After fixation, tensile testing (i.e. relaxation and stress-strain curves) was performed at low and high extension rates (3 and 30 mm s(-1)) and tissue denaturation temperatures were determined by the hydrothermal isometric tension method. Conventional fresh and statically fixed pericardium were used as controls. In this instance, we found no significant biomechanical differences between the dynamically and statically fixed pericardial tissue (e.g. moduli and stress relaxation). However, differences in tissue extensibility were delineated, since the extensibility of the dynamically fixed tissue was closer to that of the fresh tissue compared to that of the statically fixed tissue. The final relaxation rate of the dynamically fixed tissue (-3.5 +/- 1.0% of stress remaining per log(second)) was similar to that of the statically fixed tissue (-3.2 +/- 0.60% log(s(-1))) and significantly lower than the fresh tissue(-9.5 +/- 1.2% log(s(-1))). The denaturation temperatures of the dynamically fixed pericardial tissue (mean +/- SD) (86.0 +/- 1.2 degrees C) and the statically fixed (85.2 +/- 1.6 degrees C) were similar but significantly higher than that of the untreated (fresh) valves (69.3 +/- 0.4 degrees C). The results suggest a similar degree of internal cross-linking for both statically and dynamically fixed pericardium. Although fundamental structural differences exist between both porcine and bovine xenograft tissue, how these differences contribute to biomechanical differences in the effects of dynamic versus static fixation remain to be explained.
我们之前曾提出动态固定作为一种替代方法，用于固定猪主动脉心脏瓣膜异种移植物，以实现更好的组织固定并更好地保留其天然生物力学特性。牛心包在动态条件下，于0.5%戊二醛磷酸盐缓冲液（pH 7.4，0.2 M）中，在低压（<4 mmHg）和低振动频率（1.2 Hz）下进行固定。固定后，在低和高延伸率（3和30 mm s⁻¹）下进行拉伸测试（即松弛和应力-应变曲线），并通过水热等长张力法测定组织变性温度。使用传统的新鲜和静态固定心包作为对照。在这种情况下，我们发现动态和静态固定的心包组织之间没有显著的生物力学差异（例如模量和应力松弛）。然而，组织伸展性存在差异，因为与静态固定组织相比，动态固定组织的伸展性更接近新鲜组织。动态固定组织的最终松弛率（每对数（秒）剩余应力的-3.5±1.0%）与静态固定组织（-3.2±0.60% log（s⁻¹））相似，且显著低于新鲜组织（-9.5±1.2% log（s⁻¹））。动态固定心包组织的变性温度（平均值±标准差）（86.0±1.2℃）和静态固定的（85.2±1.6℃）相似，但显著高于未处理（新鲜）瓣膜的变性温度（69.3±0.4℃）。结果表明静态和动态固定的心包内部交联程度相似。尽管猪和牛异种移植组织之间存在基本结构差异，但这些差异如何导致动态与静态固定效果的生物力学差异仍有待解释。
