液氮保存3个月至8年人类同种主动脉瓣叶和主动脉壁的生物力学特性对比研究

INFLUENCE OF CRYOPRESERVED TIME UPON BIOMECHANICAL CHARACTERISTICS OF AORTIC VALVE LEAFLETS AND WALL HOMOGRAFTS

目的 :研究液氮保存时间对人类同种主动脉瓣叶和主动脉管壁的生物力学特性的影响 ,从力学性能角度探讨同种瓣的有效使用期限 ,指导临床应用。方法 :将同种主动脉瓣叶和管壁随机分为 10组 ,Ⅰ组为新鲜组 ,Ⅱ组为新鲜冷冻组 ,Ⅲ～Ⅹ组分别为液氮保存 3个月、6个月、1年、1.5年、2年、3年、4年和 8年组。每组 6个瓣叶和管壁。测量瓣叶及管壁的厚度、宽度 ,分别进行应力应变试验和破坏试验 ,比较各组瓣叶和管壁的厚度、截面积、应力应变曲线参数、破坏应力有无差异。结果 :各组瓣叶和管壁的平均厚度、截面积、破坏应力和同一应力下的伸长比之间无明显差异。Ⅱ～Ⅷ组的应力应变曲线有集中趋势 ,而Ⅸ、Ⅹ组的应力应变曲线呈离散趋势。主动脉壁的横向破坏应力明显强于纵向破坏应力 (P <0 .0 5 )。结论 :程控降温、液氮保存法对同种瓣生物力学性能无明显影响。液氮保存 3年以内的主动脉瓣叶和主动脉壁的生物力学特性更趋于稳定 ,个体之间差异明显减小 ,可用于手术 ;液氮保存 4年以上的同种瓣个体间差异明显增加 ,不宜应用于临床。术中应用同种主动脉壁加宽右室流出道时应注意其生物力学各向异性的特点。

Objective: This investigation aims to study the influence of cryopreserved time upon biomechanical characteristics of human aortic valve homograft (AVH); discuss the useful life-span of the homograft from the angle of biomechanics. Methods: Sixty AVH were randomly divided into 10 groups: Fresh AVH in group 1, fresh cryopreserved AVH in group 2, the others were cryopreserved in liquid nitrogen for 3months (group 3), 6months (group 4), 1 year (group 5), 1.5 years (group 6), 2 years (group 7), 3 years (group 8), 4 years (group 9), 8 years (group 10). There were 6 aortic valve leaflets and walls in each group. After measuring the width and height, we carried out tests for stress-strain and intensity to compare differences groups. Results: There were no significant differences in average height, cross sectional area, destroying stress and parameters of stress-strain curve among different groups. Stress-strain curves showed tendenties to concentrate in group 2 to 8 and discrete in group 9 and 10. The transverse strength of the aortic wall was stronger than that of the longitudinal one. (P < 0.05) Conclusion: Controlled freezing and cryopreservation in liquid nitrogen will not produce obvious mechanical effects on AVH. The biomechanical characteristics of AVH cryopreserved for less than 3 years are stabler than those stored for more than 4 years. AVH cryopreserved for more than 4 years may be not applicable to clinical use.