ANASTOMOSIS OF A LEFT VENTRICULAR ASSIST DEVICE

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 左心辅助装置(LVAD)已被广泛用于辅助或替代衰竭的左心功能。左前降支通常通过左前降支流入导管与左心室心尖部之间的天然心脏相连，通过左前降支流出导管与主动脉相连。根据心脏状态的不同，LVAD既可以串联工作，也可以并行工作。主动脉中的血流可能会受到吻合口的高度干扰。降主动脉流出道吻合术通常不被采用，因为它有可能在主动脉瓣附近产生停滞血流和血栓形成(DiGiorgi等人，2004年)。然而，升主动脉吻合术可在主动脉内产生高度扰动的流动，导致在特定操作条件下对主动脉弓的射流冲击，主要次级血管之间不可预知的流动分配，主动脉根部附近的停滞流动，甚至是湍流。这些高切变的湍流可能会导致血小板活化和溶血。因此，研究基于不同LVAD吻合口形态的主动脉内流动模式具有重要意义。本研究的目的是利用面向对象的CFD软件工具包OpenFOAM(Open Field Operation And Manipment)对连续和脉动流动条件下的流出道套管吻合口的流场进行计算。研究了层流和湍流在串联和平行两种条件下的流动。假设主动脉只在一个平面上弯曲。次级血管之间的流量分配通过应用阻力流出边界条件来建模(Figueroa等人，2006；Vignon-Clementel等人，2006)。考虑了两种不同的流出管吻合方式，包括近端和远端位置。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Left ventricular assist devices (LVADs)have been used extensively to assist or replace the function of a failing left heart. The LVAD is usually connected to the native heart between the apex of the left ventricle by the LVAD inflow cannula and to the aorta by the LVAD outflow cannula. Depending on the state of the heart, the LVAD can work in either serial or parallel conditions.Blood flow in the aorta can be highly disturbed by the anastomosis. A descending aortic outflow anastomosis is usually not employed due to its potential to generate stagnant flows associated thrombosis near the aortic valves (DiGiorgi et al., 2004). An ascending aortic anastomosis, however, can produce highly disturbed flows in the aorta, resulting in jet impingement on the aortic arch, unpredictable flow partitioning between the major secondary vessels, stagnant flow near the aortic root, and even turbulent flow under specific operating conditions. These high shear turbulent flows might cause platelet activation and hemolysis. Therefore, it is important to study flow patterns in the aorta based on different LVAD anastomotic configurations.The goal of the present study is to understand the influence of the outflow cannula anastomosis, in continuous and pulsatile flow conditions, using an object-oriented CFD software toolkit OpenFOAM (Open Field Operation and Manipulation) to compute the flow field. Both laminar and turbulent flows are studied under serial and parallel conditions. The aorta is assumed to be curved in one plane only. The flow partitioning between the secondary vessels is modeled by applying a resistance outflow boundary condition (Figueroa et al., 2006; Vignon-Clementel et al., 2006). Two different outflow cannula anastomotic configurations, including both proximal and distal positions, are considered.