Mitral heart valve cavitation in an artificial heart environment.
Mitral heart valve cavitation in an artificial heart environment.
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发表时间：
1996-03
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通讯作者：
D. S. Sneckenberger;D. Stinebring;S. Deutsch;D. Geselowitz;J. Tarbell
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作者：
D. S. Sneckenberger;D. Stinebring;S. Deutsch;D. Geselowitz;J. Tarbell
研究的背景和目的瓣膜关闭时机械心脏瓣膜周围流体中蒸汽腔的形成和随后的塌陷可产生足够大的应力以损伤瓣膜本身和血细胞。对气蚀机理的进一步了解将有助于降低未来阀门设计中气蚀的可能性。材料和方法本研究比较了两种不同几何形状（Monostrut和Medtronic Hall）、封堵器外壳间隙（紧密、中等和泄漏）和封堵器材料（Delrin和热解碳）的8个机械二尖瓣。在模拟循环回路内运行的宾夕法尼亚州立大学电动心室辅助装置（EVAD）的模型心室中评价瓣膜。EVAD代表整个人工心脏的一半。模拟回路由硅胶管组成，硅胶管连接到设计用于模拟自然循环的顺应性和阻力特性的元件。通过改变心室充盈程度来控制空化：低充盈导致较高的瓣膜关闭速度，从而导致比心室完全充盈更大的空化强度。使用从空化事件期间瓣膜周围发生的二尖瓣压力的高频波动导出的参数来量化空化的强度。除了空化强度参数之外，还使用空化压力信号的形状和空化压力信号的功率谱的形状来进行阀之间的比较。结果在研究的三种瓣膜特性中，封堵器材料对空化强度的影响最显著：热解碳封堵器瓣膜的空化强度大于Delrin圆盘瓣膜。结论瓣膜上的空化主要形式与涡流形成有关，封堵器材料通过瓣膜关闭时产生的张力波强度影响空化强度，几何形状和间隙仅起次要作用。未来的研究计划在体内环境中采用这种技术。
BACKGROUND AND AIMS OF THE STUDY The formation and subsequent collapse of vaporous cavities in the fluid around mechanical heart valves at valve closure can create stresses large enough to damage both the valve itself and blood cells. Improved understanding of cavitation mechanisms should lead to a reduction in the cavitation potential of future valve designs. MATERIALS AND METHODS This study compares eight mechanical mitral valves of two different geometries (Monostrut and Medtronic Hall), occluder housing gaps (tight, medium, and leaky), and occluder materials (Delrin and pyrolytic carbon). The valves were evaluated in a model ventricle of the Penn State Electric Ventricular Assist Device (EVAD) operating within a mock circulatory loop. The EVAD represents one half of a total artificial heart. The mock loop consisted of silicone tubing connected to elements designed to mimic the compliant and resistant properties of the natural circulation. Cavitation was controlled by varying the degree of filling of the ventricle: low filling caused higher valve closing velocities resulting in greater cavitation intensities than complete filling of the ventricle. The intensity of cavitation was quantified using a parameter derived from the high frequency fluctuations in the mitral pressure that occur around the valve during cavitation events. The shape of the cavitation pressure signature and that of the power spectrum of the cavitation pressure signature were used in addition to the cavitation intensity parameter to make comparisons between valves. RESULTS Of the three valve characteristics studied, occluder material showed the most significant influence on cavitation intensity: valves with pyrolytic carbon occluders demonstrated greater cavitation than did those with Delrin discs. CONCLUSION It is hypothesized that the dominant form of cavitation on the valves studied is related to vortex formation and that occluder material influences the intensity of cavitation through the strength of the tension wave generated at valve closure, while geometry and gap have only secondary effects. Future studies are planned to incorporate this technique in an in vivo environment.