Microflow fields in the hinge region of the CarboMedics bileaflet mechanical heart valve design
Microflow fields in the hinge region of the CarboMedics bileaflet mechanical heart valve design
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DOI：
10.1067/mtc.2002.125206
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发表时间：
2002-09-01
影响因子：
6
通讯作者：
Yoganathan, AP
中科院分区：
文献类型：
--
作者：
Leo, HL;He, ZM;Yoganathan, AP
目的：双叶机械心脏瓣膜的设计包括瓣膜关闭时的一定程度的泄漏流，用于逆流冲洗瓣膜的铰链和枢轴区域。据信，这种反向流动有助于防止淤滞区域并抑制微血栓形成。然而，这种逆向流动的幅度也可能引起不可接受的血液成分损伤水平，并由于通过铰链区的流速增加而导致血小板活化或溶血。本研究旨在评价23 mm CarboMedics双叶机械瓣膜（Sulzer CarboMedics Inc，Austin，Tex）的铰链流动力学，然后将结果与之前研究的St Jude Medical 23 mm Regent（St Jude Medical Inc，Minneapolis，Minn）和Medtronic Parallel（Medtronic，Inc，Minneapolis，Minn）瓣膜的结果进行比较。这种比较允许新的洞察到铰链区域内的CarboMedics双叶机械瓣膜，这还没有以前评估在其临床history.Methods：二维激光多普勒测速仪的微流场被用来测量铰链区域的速度和湍流剪切应力场。为了进行这些测量，双叶铰链区域的精确尺寸模型由透明塑料材料铸造或机加工而成。实验在脉动流回路中进行，在枢轴和铰链区域内的不同水平进行测量。在23-mm CarboMedics瓣膜铰链中，在平坦水平和平坦上方190 μ m和390 μ m以及平坦下方1 mm的水平处获得的相位平均向前速度为0.54 m/s、0.77 m/s、0.3 m/s和1.0 m/s，分别相应的峰值相位平均泄漏速度分别为3.17 m/s、2.91 m/s、2.52 m/s和0.5 m/s。相应的湍流剪切应力分别为5510 dyne/cm（2）、5640 dyne/cm（2）、4380 dyne/cm（2）和4810 dyne/cm（2）。结论：CarboMedics双叶设计的铰链流动动力学介于St Jude Medical和Medtronic平行瓣膜设计之间。研究瓣膜的流体动力学与St Jude Medical瓣膜相似，但泄漏速度和湍流剪切应力略高。这种差异可能是由于与CarboMedics瓣膜铰链设计相关的尖角造成的。也可能是由于St Jude Medical Regent设计的内瓣口面积逐渐增大。
Objective: The design of bileaflet mechanical heart valves includes some degree of leakage flow on valve closure for the reverse flow to wash the hinge and pivot region of the valve. It is believed that this reverse flow helps to prevent areas of stasis and inhibit microthrombus formation. However, the magnitude of this retrograde flow may also give rise to unacceptable levels of blood element damage and lead to platelet activation or hemolysis as a result of the increased flow velocities through the hinge region. The purpose of this study was to evaluate the hinge flow dynamics of a 23-mm CarboMedics bileaflet mechanical valve (Sulzer CarboMedics Inc, Austin, Tex) and then to compare the results with those of the St Jude Medical 23-mm Regent (St Jude Medical Inc, Minneapolis, Minn) and Medtronic Parallel (Medtronic, Inc, Minneapolis, Minn) valves studied earlier. This comparison allows new insight into the microflow fields within the hinge region of the CarboMedics bileaflet mechanical valve, which have not been previously assessed during its clinical history.Methods: Two-dimensional laser Doppler velocimetry was used to measure the velocity and turbulent shear stress fields in the hinge regions. To conduct these measurements, exact dimensional models of the bileaflet hinge regions were cast or machined from transparent plastic materials. The experiment was conducted in a pulsatile flow loop with measurements taken at different levels within the pivot and hinge regions.Results: In the 23-mm CarboMedics valve hinge, the phase-averaged forward velocity obtained at the flat level and levels of 190 mum and 390 mum above flat and 1 mm below flat were 0.54 m/s, 0.77 m/s, 0.3 m/s, and 1.0 m/s, respectively. Corresponding values of the peak phase-averaged leakage velocities were 3.17 m/s, 2.91 m/s, 2.52 m/s, and 0.5 m/s, respectively. Corresponding turbulent shear stresses were 5510 dyne/cm(2), 5640 dyne/cm(2), 4380 dyne/cm(2), and 4810 dyne/cm(2), respectively.Conclusions: The hinge flow dynamics of the CarboMedics bileaflet design lie somewhere in between those of the St Jude Medical and the Medtronic Parallel valve designs. The fluid dynamics of the investigated valve were found to be similar to those of the St Jude Medical valves, although with slightly higher leakage velocities and turbulent shear stresses. This discrepancy may be a result of the sharper corners associated with the hinge design of the CarboMedics valve. It could also be due to the incremental enlargement of the internal orifice area of the St Jude Medical Regent design.