Abstract：
Continuous flow (CF) left ventricular assist devices (LVAD) operate at a constant speed mode, which could result in increased risk of adverse events due to reduced vascular pulsatility. Consequently, pump speed modulation algorithms have been proposed to augment vascular pulsatility. However, the quantitative local hemodynamic effects on the aorta when the pump is operating with speed modulation using different types of CF-LVADs are still under investigation. The computational fluid dynamics (CFD) study was conducted to quantitatively elucidate the hemodynamic effects on a clinical patient-specific aortic model under different speed patterns of CF-LVADs. Pressure distribution, wall shear stress (WSS), time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), and velocity were calculated to compare their differences at constant and pulsatile speeds under centrifugal and axial LVAD support. Results showed that pulse pressure on the aorta was significantly larger under pulsatile speed mode than that under constant speed mode for both CF-LVADs, indicating enhanced aorta pulsatility, as well as the higher peak blood flow velocity on some representative slices of aorta. Pulsatile speed modulation enhanced peak WSS compared to constant speed; high TAWSS region appeared near the branch of left common carotid artery and distal aorta regardless of speed modes and CF-LVADs but these regions also had low OSI; RRT was almost the same for all the cases. This study may provide a basis for the scientific and reasonable selection of the pulsatile speed patterns of CF-LVADs for treating heart failure patients.
摘要：
连续流（CF）左心室辅助装置（LVAD）以恒定速度模式运行，这可能导致血管搏动性降低导致不良事件的风险增加。因此,已经提出了泵速度调制算法来增强血管搏动性。然而,当泵使用不同类型的CF-LVAD进行速度调节时,对主动脉的定量局部血液动力学影响仍在研究中.进行了计算流体动力学（CFD）研究，以定量阐明在CF-LVAD的不同速度模式下对临床患者特定主动脉模型的血液动力学影响。压力分布,壁面剪应力(WSS)，时间平均壁面剪应力(TAWSS)，振荡剪切指数(OSI)，相对停留时间（RRT），和速度进行了计算，以比较它们在离心和轴向LVAD支持下在恒定和脉动速度下的差异。结果表明，两个CF-LVAD在脉动速度模式下的主动脉脉压明显大于恒速模式下的脉压。表明主动脉搏动增强，以及一些代表性的主动脉切片上较高的峰值血流速度。与恒定速度相比，脉动速度调制增强了WSS的峰值；无论速度模式和CF-LVAD如何，在左颈总动脉分支和远端主动脉附近都出现了高TAWSS区域，但这些区域也具有低OSI；所有病例的RRT几乎相同。本研究可为科学合理选择CF-LVAD治疗心力衰竭患者的搏动速度模式提供依据。
