May-Newman Karen, Moon Juyeun, Ramesh Varsha, Montes Ricardo, Campos Josue, Herold Brian, Isingoma Paul, Motomura Tadashi, Benkowski Robert
From the *Bioengineering Program, San Diego State University, San Diego, California; †Evaheart, Inc., Houston, Texas; and ‡B-Squared Medical Device Solutions, Fort Worth, Texas.
ASAIO J. 2017 Sep/Oct;63(5):592-603. doi: 10.1097/MAT.0000000000000559.
Left ventricular assist device (LVAD) inflow cannula malposition is a significant risk for pump thrombosis. Thrombus development is influenced by altered flow dynamics, such as stasis or high shear that promote coagulation. The goal of this study was to measure the intraventricular flow field surrounding the apical inflow cannula of the Evaheart centrifugal LVAD, and assess flow stasis, vortex structures, and pulsatility for a range of cannula insertion depths and support conditions. Experimental studies were performed using a mock loop with a customized silicone left ventricle (LV) and the Evaheart LVAD. A transparent inflow cannula was positioned at 1, 2, or 3 cm insertion depth into the LV and the velocity field in the LV midplane was measured for 2 levels of LVAD support: 1800 and 2300 rpm. The LV velocity field exhibits a diastolic vortex ring whose size, path, and strength are affected by the flow conditions and cannula position. During diastole, the large clockwise midplane vortex grows, but its circulation and kinetic energy are reduced with cannula insertion depth. The counterclockwise vortex is smaller and exhibits more complex behavior, reflecting a flow split at 3 cm. Overall, the 1 cm cannula insertion depth produces the flow pattern that exhibits the least apical flow stasis and greatest pulsatility and should correlate to a lower risk of thrombus formation.
左心室辅助装置（LVAD）流入插管位置不当是泵血栓形成的重大风险。血栓形成受血流动力学改变的影响，如促进凝血的血流淤滞或高剪切力。本研究的目的是测量Evaheart离心式LVAD心尖流入插管周围的心室内流场，并评估一系列插管插入深度和支持条件下的血流淤滞、涡旋结构和搏动性。使用带有定制硅胶左心室（LV）的模拟回路和Evaheart LVAD进行实验研究。将透明流入插管以1、2或3厘米的插入深度置于左心室内，并针对LVAD的两个支持水平（1800和2300转/分钟）测量左心室中平面的速度场。左心室速度场呈现出一个舒张期涡旋环，其大小、路径和强度受血流条件和插管位置的影响。在舒张期，大的顺时针中平面涡旋增大，但其环流和动能随插管插入深度而降低。逆时针涡旋较小，表现出更复杂的行为，反映了在3厘米处的血流分裂。总体而言，1厘米的插管插入深度产生的流型表现出最少的心尖血流淤滞和最大的搏动性，并且应该与较低的血栓形成风险相关。
