Lee Hwansung, Taenaka Yoshiyuki, Kitamura Soichiro
Department of Artificial Organs, Research Institute, National Cardiovascular Center, Suita, Osaka, Japan.
ASAIO J. 2005 May-Jun;51(3):208-13. doi: 10.1097/01.mat.0000159383.40133.92.
Until now, we have estimated cavitation for mechanical heart valves (MHV) mounted in an electrohydraulic total artificial heart (EHTAH) with tap water as a working fluid. However, tap water at room temperature is not a proper substitute for blood at 37 degrees C. We therefore investigated MHV cavitation using a glycerin solution that was identical in viscosity and vapor pressure to blood at body temperature. In this study, six different kinds of monoleaflet and bileaflet valves were mounted in the mitral position in an EHTAH, and we investigated the mechanisms for MHV cavitation. The valve closing velocity, pressure drop measurements, and a high-speed video camera were used to investigate the mechanism for MHV cavitation and to select the best MHV for our EHTAH. The closing velocity of the bileaflet valves was slower than that of the monoleaflet valves. Cavitation bubbles were concentrated on the edge of the valve stop and along the leaflet tip. It was established that squeeze flow holds the key to MHV cavitation in our study. Cavitation intensity increased with an increase in the valve closing velocity and the valve stop area. With regard to squeeze flow, the Björk-Shiley valve, because it is associated with slow squeeze flow, and the bileaflet valve with low valve closing velocity and small valve stop areas are better able to prevent blood cell damage than the monoleaflet valves.
到目前为止，我们已经对安装在以自来水作为工作流体的电动液压全人工心脏（EHTAH）中的机械心脏瓣膜（MHV）的空化现象进行了评估。然而，室温下的自来水并非37摄氏度血液的合适替代品。因此，我们使用了一种在粘度和蒸气压方面与体温下的血液相同的甘油溶液来研究MHV的空化现象。在本研究中，将六种不同类型的单叶瓣和双叶瓣瓣膜安装在EHTAH的二尖瓣位置，我们研究了MHV空化的机制。利用瓣膜关闭速度、压降测量以及高速摄像机来研究MHV空化的机制，并为我们的EHTAH选择最佳的MHV。双叶瓣瓣膜的关闭速度比单叶瓣瓣膜慢。空化气泡集中在瓣膜限位器的边缘以及瓣叶尖端沿线。在我们的研究中确定，挤压流是MHV空化的关键所在。空化强度随着瓣膜关闭速度和瓣膜限位器面积的增加而增大。关于挤压流，由于与缓慢的挤压流相关，Björk-Shiley瓣膜以及关闭速度低且瓣膜限位器面积小的双叶瓣瓣膜比单叶瓣瓣膜更能防止血细胞损伤。
