Bachmann Christopher, Kini Vinayak, Deutsch Steven, Fontaine Arnold A, Tarbell John M
The Bioengineering Department, The Pennsylvania State University, University Park, USA.
J Heart Valve Dis. 2002 Jan;11(1):105-13.
Transcranial Doppler studies performed on patients with the Björk-Shiley Monostrut mechanical heart valve have detected signals typical of gaseous emboli.
In this study, a high-speed digital imaging system was used to examine the closure event of the Björk-Shiley Monostrut valve in vitro.
Observations support the hypothesis that cavitation occurs before the formation of stable gas bubbles. Bubble cavitation occurs at the instant of valve closure and lasts on the order of 0.3 ms. The rebounding motion of the occluder initiates the development of a vortex which induces vortex cavitation. Vortex cavitation begins approximately 0.5 ms after impact of the occluder and the valve housing (approximately 0.2 ms after bubble cavitation has subsided), and lasts for approximately 1 ms. The formation of stable bubbles occurs later, along the center of the vortex that persists throughout much of the first rebound.
It is hypothesized that the low-pressure region at the center of the vortex contributes to the formation of stable bubbles by collecting expanded nuclei that arise from both bubble and vortex cavitation, and providing a low-pressure environment in which the nuclei combine and continue to grow.
对植入Björk-Shiley单叶机械心脏瓣膜的患者进行经颅多普勒研究时，检测到了典型的气体栓塞信号。
在本研究中，使用高速数字成像系统在体外检查Björk-Shiley单叶瓣膜的关闭过程。
观察结果支持以下假设，即空化现象在稳定气泡形成之前就已发生。气泡空化在瓣膜关闭瞬间发生，持续时间约为0.3毫秒。封堵器的回弹运动引发了一个漩涡的形成，进而导致漩涡空化。漩涡空化在封堵器与瓣膜外壳碰撞后约0.5毫秒开始（在气泡空化消退后约0.2毫秒），持续约1毫秒。稳定气泡的形成稍后发生，沿着在首次回弹的大部分时间里持续存在的漩涡中心。
据推测，漩涡中心的低压区域通过收集由气泡空化和漩涡空化产生的膨胀核，并提供一个使这些核结合并继续生长的低压环境，从而有助于稳定气泡的形成。
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