Mussivand T, Day K D, Naber B C
Cardiovascular Devices Division, University of Ottawa Heart Institute, Ontario, Canada.
ASAIO J. 1999 Jan-Feb;45(1):25-31. doi: 10.1097/00002480-199901000-00007.
Thrombus formation and resulting thromboembolism are major risks that can impede the widespread use of ventricular assist devices (VADs). Adverse flow patterns (turbulence and stasis) have been implicated in thrombogenesis. This study focuses on optimization of VAD geometry, port orientation, and fluid dynamics to reduce thrombus formation. Particle image velocimetry with cross-correlation was performed using Amberlite particles suspended in distilled water. The transparent VADs were illuminated by halogen lamps. Four different VADs were tested in an iterative approach toward optimization. A peak shear stress of 9,100 dynes/cm2 was noted in the first configuration immediately after the end of systole at the outlet port. Modifications in chamber geometry, port diameters and orientation, and valve enclosure design yielded shear stresses in the two subsequent geometries of 5,100 dynes/cm2 and 1,900 dynes/cm2, respectively. For the third iteration, a region of stasis occurred during the transition between the inlet port and the blood chamber. Further modifications were implemented, including a reduction in port diameters and further smoothing of the port entry region. This eliminated stasis and yielded a maximum shear level of 4,100 dynes/cm2. In conclusion, optimization was achieved through geometric modification of the VAD, thus minimizing adverse flow conditions.
血栓形成及由此导致的血栓栓塞是阻碍心室辅助装置（VAD）广泛应用的主要风险。不利的血流模式（湍流和淤滞）与血栓形成有关。本研究聚焦于优化VAD的几何形状、端口方向和流体动力学，以减少血栓形成。使用悬浮在蒸馏水中的Amberlite颗粒进行互相关颗粒图像测速。透明的VAD由卤素灯照亮。采用迭代方法对四种不同的VAD进行测试以实现优化。在第一种配置中，收缩期末尾刚结束时，出口端口处的峰值剪应力为9100达因/平方厘米。对腔室几何形状、端口直径和方向以及瓣膜外壳设计进行修改后，在随后的两种几何形状中，剪应力分别为5100达因/平方厘米和1900达因/平方厘米。在第三次迭代中，在入口端口和血腔之间的过渡过程中出现了一个淤滞区域。进一步实施了修改措施，包括减小端口直径并进一步平滑端口入口区域。这消除了淤滞，产生的最大剪应力水平为4100达因/平方厘米。总之，通过对VAD进行几何形状修改实现了优化，从而将不利的血流状况降至最低。
