MICROMECHANICS OF THE AORTIC VALVE

描述：(改编自研究人员摘要)生物假体心脏 阀门已被证明在短期内是成功的，但继续 长期耐久性差。尽管已经付出了相当大的努力 在新的心脏瓣膜设计中，新的瓣膜似乎只比 比旧的设计更耐用。此外，它们的终极耐用性将需要 另一个十年来证实。问题的一部分在于缺乏一个 对理想的生物人工心脏瓣膜定义的一般理解。 我们知道生物假体会在10到20年内失效，而天然瓣膜 可以持续80年，开合近30亿次。自.以来 天然瓣膜的结构矩阵尚不清楚是否需要修复和改造， 某些固有的结构和功能特征必须 对阀门非凡的耐用性负责。 这项研究的广泛目标是开发一个基本的 对瓣膜组织细观力学，特别是粘弹性的理解 这样我们就可以建立瓣膜组织的本构模型 可以预测加速加载条件下的阀门应力。是这样的 将需要信息来进行受控良好的耐久性测试 这可以确定生物心脏瓣膜的疲劳极限。在 在本研究过程中，我们还将获得材料试验数据，可以 用于比较和对比天然和生物假体的力学性能 心脏瓣膜。这些信息将使更适当的工程设计 分析了现有的生物人工心脏瓣膜，因此 设计和材料可以识别和更正。这样的数据是 将阀门设计和测试从经验过程提升到 一种控制良好的工程方法。这项研究的具体目的是： *确定纤维和脑室的自然预负荷，以及 确定鲜叶伸长过程中的载荷分担过程 和戊二醛固定阀。 *绘制Fresh和Fresh的双轴应变模式 戊二醛处理的猪主动脉瓣叶。 *开发将材料测试数据的可变性降至最低的方法 和 制定标准化的材料测试。 *描述和比较猪和人的主动脉力学 瓣膜组织。 *描述心脏瓣膜组织的粘弹性反应和 基于冯的拟线性理论建立粘弹性模型 粘弹性。 通过对材料测试数据的系统分析，我们建议 在这项研究中，我们的目标是加深对 主动脉瓣组织功能，并表征了现有的不足 生物假体组织。这些信息将成为设计的基础 新的、更耐用的、合成的和生物工程心脏瓣膜替代品。

DESCRIPTION: (Adapted from investigator's abstract) Bioprosthetic heart valves have proven to be successful in the short term, but continue to have poor long-term durability. Even though considerable effort has been put into new heart valve designs, the new valves appear to be only slightly more durable than the old designs. Moreover, their ultimate durability will take another decade to confirm. Part of the problem lies in the lack of a general understanding of what defines the ideal bioprosthetic heart valve. We know that bioprostheses fail in 10 to 20 years while the natural valve can last 8 decades, opening and closing almost 3 billion times. Since the structural matrix of natural valves is not known to repair and remodel, certain inherent structural and functional characteristics must be responsible for the valve's remarkable durability. The broad objectives of this research are to develop a fundamental understandingof valve tissue micromechanics, particularly the viscoelastic effect, so that we can formulate constitutive models of valve tissues that can predict valve stresses under accelerated loading conditions. Such information will be required to carry out well controlled durability tests that can determine the fatigue limit of bioprosthetic heart valves. In the course of this research, we will also obtain material test data that can be used to compare and contrast the mechanics of natural and bioprosthetic heart valves. This information will enable a more proper engineering analysis of existing bioprosthetic heart valves, so the deficiencies in design and materials can be identified and corrected. Data such as this is critical to elevating valve design and testing from an empirical process to a well controlled engineering method. The specific aims of this study are: *Determine the natural preload of the fibrosa and ventricularis, and define the process of load sharing during leaflet elongation of fresh and glutaraldehyde-fixed valves. *Map out the patterns of biaxial strain in fresh and glutaraldehyde-treated porcine aortic valve leaflets. *Develop means of minimizing the variability of materials test data and develop standardized material tests. *Characterize and compare the mechanics of porcine and human aortic valve tissues. *Characterize the viscoelastic response of heart valve tissues and develop a viscoelastic model based on Fung's theory of quasi-linear viscoelasticity. Through a systematic analysis of the material test data that we propose to obtain in this study, we aim to develop a much deeper understanding of aortic valve tissue function, and characterize the deficiencies of existing bioprosthetic tissues. Such information will form the basis for the design of new, more durable, synthetic and bioengineered heart valve substitutes.