Hemocompatibility Evaluation With Experimental and Computational Fluid Dynamic Analyses for a Monopivot Circulatory Assist Pump *Masahiro Nishida, *Osamu Maruyama, *Ryo Kosaka, *Takashi Yamane, †Hisato Kogure, †Hiroshi Kawamura, ‡Yoshihiro Yamamoto, ‡Katsuyuki Kuwana, §Yoshiyuki Sankai, and ¶Tatsuo Tsutsui *Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology Tsukuba, Ibaraki; †Department of Mechanical Engineering,Tokyo University of Science, Noda, Chiba; ‡Senko Medical Instrument Mfg. Co. Ltd., Kasukabe, Saitama; §Institute of Engineering Mechanics and Systems, University of Tsukuba; and ¶Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan Abstract: The hemocompatibility of a newly developed monopivot circulatory assist pump was evaluated by the computational fluid dynamic (CFD) analyses with the par- ticle tracking velocimetry measurement. Results were com- pared with those of the hemolysis test and in vitro antithrombogenic test to prevent hemolysis and thrombus formation inside the pump. The results of the CFD analysis and the particle tracking velocimetry had a good agree- ment with each other. The flow distributions by the CFD analysis indicated that the radial jet out of the impeller was adequately weak so that the wall shear stress was lower than 300 Pa on the volute casing wall. It corresponded with the hemolysis tests results, indicating that the hemolysis level was lower than that of the commercially available pump. However, the flow distributions also indicated that the pivot that was easy to stagnate was washed out, not only by the secondary flow through the back gap of the impeller, but also by the vortices generated by the secondary vanes. It corresponded with the in vitro antithrombogenic test results, indicating that thrombus formation could be removed only by redesigning the geometry of the second- ary vanes. Key Words: Centrifugal blood pump— Computational fluid dynamics—Flow visualization—Shear stress—Hemolysis—Thrombogenesis. We have been developing monopivot centrifugal pumps (Senko Medical Instrument Mfg. Co. Ltd., Kasukabe, Saitama, Japan) for cardiopulmonary bypass and heart operation, the impeller of which is supported by a permanent magnet suspension and a pivot bearing. Because the impeller contacts the pump casing only at a pivot bearing, thrombus for- mation should be prevented around the bearing. The centrifugal-type impeller restrains low impeller rota- tional speed that prevents hemolysis, and realizes a small priming volume and high efficiency. In pump development, it is important to obtain hemocompatibility because there is a good relation- ship between blood flow and the hemocompatibility of the pump. Certain researchers have investigated the effect of high shear on hemolysis in the devel- oping of the pump using computational fluid dynamic (CFD) analysis (1–14). It was found that hemolysis depends on flow behavior because degra- dation of erythrocytes are caused by their exposure to excessively high shear flow. In centrifugal blood pumps, a high-shear region is likely to be generated near the casing wall, which causes a high hemolysis level because the outflow from the impeller collides with the volute casing wall. Based on a correlation study of quantitative flow visualization analysis, CFD analysis, and hemolysis tests, our group has suggested that high shear near the volute casing wall causes a high hemolysis level in the centrifugal pump (6,15,16). doi:10.1111/j.1525-1594.2009.00730.x Received March 2008; revised July 2008. Address correspondence and reprint requests to Dr. Masahiro Nishida, National Institute of Advanced Industrial Science and Technology, 1-2-1, Namiki, Tsukuba, Ibaraki 305-8564, Japan. E-mail: masahiro.nishida@aist.go.jp Artificial Organs 33(4):378–386, Wiley Periodicals, Inc. © 2009, Copyright the Authors Journal compilation © 2009, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc. 378