FLUID DYNAMICS OF RIGHT HEART BYPASS OPERATIONS

描述：(改编自申请者的摘要)手术成功 采取干预措施改善婴幼儿肺血流量 导致肺循环中断的先天缺陷取决于 选定的程序和材料以及干预的能力 适应患者的成长。修复选项包括创建Atrio- 腔-肺连接和深低温保存瓣膜植入术 同种异体移植或心外管道。然而，管道和同种异体移植物不 增长，连接的最佳位置是有争议的，而且结果很晚 来自临床和尸检的研究表明管道故障的发生率很高 到纤维肌内长、瓣膜退变和假性内膜剥离 队形。因此，尽管取得了重大进展，但仍需要答案来 关于如何1)防止管道故障的许多重要问题，2) 保持足够的能量以通过低压系统输送血液，3) 适当地将流量分配到两个肺，以及4)准备合理的 成长。要回答这些一般问题，需要回答Basic 关于流体力学与相关学科关系的几个问题 几何：1)管道设计和形状如何影响剪切应力， 二次流和流分离，2)曲线、扭结、凹陷和弯曲 影响能量损失，3)吻合口几何形状影响流量分布？ 这项研究将通过一系列体内、在 现场实验和计算实验。(A)在体内阶段，血流动力学 研究将在1个月和3个月大的羔羊身上进行， 植入心外分流术或建立房室或腔肺 联系。呼吸和心房收缩对血液的重要性 将对运输进行评估。(B)下腔静脉硅橡胶模型 连接右心和近端肺动脉将在 SITE。(C)体外研究将以不同的流动方式进行 使用染料注入和激光可视化的模型、速度模式 以及用激光和脉冲多普勒设备测量的速度。离体 研究提供体内没有的灵活性；导管设计特点 将在一系列血流动力学和心肺几何参数中进行测试 条件。(D)将对就地制作的铸件进行CT扫描，以便 可以重建计算机化的3D图像，并提取关键特征。这个 计算机化的图像将为定义几何图形提供基础 立体光刻法，解剖学上正确的流动模型和 计算研究。模拟肺组织的有限元技术 将开发血液流动，扩大In提供的灵活性 体外研究，包括预测预期增长的能力。(E)先生 Fontan患者的图像和CT扫描将用于生成可比的 体外流动模型和有限元模型及计算 学习。统一所获得的结果应有助于确定原因 移植失败并协助外科医生选择干预措施以建立 最佳的肺血流模式，并适当考虑 患者的成长。

DESCRIPTION: (Adapted from the applicant's abstract) Success of surgical interventions performed to improve pulmonary blood flow in infants with congenital defects that interrupt the pulmonary circulation depends on the procedures and materials selected and the ability of the intervention to accommodate for patient growth. Repair options include creation of atrio- and cavopulmonary connections and implantation of cryopreserved valve homografts or extracardiac conduits. However, conduits and homografts don't grow, optimal positions for connections are controversial, and late results from clinical and autopsy studies show high incidence of conduit failure due to fibromuscular ingrowth, valvular degeneration and pseudointimal peel formation. Thus, despite significant advances, answers are still needed to many important questions concerning how to 1) prevent conduit failure, 2) maintain sufficient energy to move blood through a low pressure system, 3) appropriately distribute flow to both lungs, and 4) prepare for reasonable growth. Answers to these general questions require answers to basic questions regarding relationships between fluid mechanics and the involved geometries: How do 1) conduit design and shape affect shear stresses, secondary flow and flow separation, 2) curves, kinks, pouches and bends affect energy losses, 3) anastomotic geometries influence flow distribution? This study will address pertinent issues through a series of in vivo, in situ, and computational experiments. (A) In the in vivo phase, hemodynamic studies will be performed in 1-month and 3-month old lambs before and implanting an extracardiac shunt or establishing an atrio- or cavopulmonary connection. The importance of respiration and atrial contractions to blood transport will be evaluated. (B) Silicone rubber casts of the vena cava connections, right heart and proximal pulmonary arteries will be made in situ. (C) In vitro studies will be performed in various flow through models, velocity patterns visualized using dye injections and laser light and velocity measured with laser and pulsed Doppler devices. In vitro studies provide flexibility not available in vivo; conduit design features will be tested in a range of hemodynamic and cardiopulmonary geometric conditions. (D) Casts made in situ will be CT scanned such that computerized 3D images can be reconstructed and key features extracted. The computerized images will provide the basis for defining geometry for stereolithographic, anatomically correct flow-through models and for computation studies. Finite element techniques for simulating pulmonary blood flow will be developed, expanding the flexibility provided by the in vitro studies, including the ability to project for expected growth. (E) MR images and CT scans of Fontan patients will be used to generate comparable flow-through and finite element models for in vitro and computational studies. unification of results obtained should help identify causes of graft failure and assist surgeons in selecting interventions to establish optimal pulmonary blood flow patterns and make appropriate allowances for patient growth.