ERI: Fluid dynamics of non-Newtonian blood substitutes in heart valve

人工心脏瓣膜的植入改变了心脏中的血流，这使得植入后的血流评估至关重要。为了了解主动脉瓣置换术后的结局，特别是与凝块形成相关的结局，已经建立了模拟心血管性能和操作的实验方案。由于与使用全血进行实验室实验相关的挑战，通常使用血液替代品。大多数血液替代品是牛顿混合物，而血液是非牛顿混合物。非牛顿流体是以粘度随剪切速率变化为特征的流体。这种效应在流动停滞并因此血栓形成的区域变得重要，目前的实验没有充分考虑到这一点。因此，本项目的目的是了解非牛顿行为对周围流动动态环境的影响。该项目还将包括重要的教育活动，包括本科生参与和当地社区学生的推广计划。本项目的目标是找到一种具有非牛顿特性的适当血液替代品，以准确模拟血液与周围主动脉根部解剖结构（主要是窦和新生窦）在台式流量测试室中的各种生理条件下的相互作用。然后，将使用粒子图像测速组成的高保真成像工具进行实验，以表征主动脉根部的流动特性。非牛顿流变学对脉动生理条件下流动停滞评估的影响，如心血管应用，是一个未充分探索的领域。我们的目标是使用两个具体目标来解决这个问题：（i）制备和开发非牛顿血液模拟溶液并测试其流变学特性，以及（ii）评估瓣膜植入后脉动条件下非牛顿特性对血流停滞的影响。本提案中描述的研究是新颖的，因为将使用非牛顿血液类似物对瓣膜置换术后的窦和新窦流动进行实验评价，并将建立与牛顿流体与非牛顿流体中血栓形成相关的所得流动停滞特性（如速度、剪切应力和洗脱）之间的比较。该项目将有助于进一步了解止血相关血栓形成，这是一个不断发展的科学领域。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估。

The implantation of an artificial heart valve alters the blood flow in the heart, which makes flow assessment post-implant of utmost importance. To understand outcomes after aortic valve replacement procedures, especially related to clot formation, experimental protocols to emulate cardiovascular performance and operation have been established. Because of the challenges associated with performing laboratory experiments with whole human blood, blood substitutes are generally used. The majority of blood substitutes are Newtonian mixtures, whereas blood is non-Newtonian. A non-Newtonian fluid is a fluid that is characterized by a viscosity that varies with shear rate. This effect becomes important in areas that are subjected to flow stagnation and therefore thrombosis, which current experiments do not fully consider. Therefore, the aim of this project is to understand the impact of non-Newtonian behavior on the surrounding flow dynamic environment. The project will also encompass significant educational activities, including undergraduate involvement and an outreach program for students in local communities. The goal of this project is to find an adequate blood substitute with non-Newtonian properties to accurately model blood’s interactions with the surrounding aortic root anatomy, mainly the sinus and neo-sinus, under various physiological conditions in benchtop flow testing chambers. Then, experiments to characterize the resulting flow properties in the aortic root will be performed using high-fidelity imaging tools consisting of particle image velocimetry. The influence of non-Newtonian rheology on flow stagnation assessment under pulsatile physiological conditions, such as cardiovascular applications, is an underexplored territory. We aim to address that using two specific aims: (i) preparing and developing a non-Newtonian blood analog solution and testing its rheological properties and (ii) assessing the effects of non-Newtonian properties on flow stasis under pulsatile conditions after valve implantation. The research described in this proposal is novel in that, the sinus and neo-sinus flows after valve replacement will be experimentally evaluated using non-Newtonian blood analogs and a comparison between resulting flow stasis properties such as velocity, shear stress, and washout that are associated with thrombosis in Newtonian versus non-Newtonian fluids will be established. The project would contribute to further the understanding of hemostasis-related thrombosis, a scientific area that is constantly growing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.