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In Vitro Hydrodynamics of Four Bileaflet Valves in Mitral Position

Department of Mechanical Engineering Umezu Biomedical Engineering Laboratory Waseda University Tokyo, Japan

For reprint information contact: Mitsuo Umezu, PhD or Feng Zhong Gang, PhD Tel: 81 3 5286 3256 Fax: 81 3 3200 2516, email: umezu{at}mn.waseda.ac.jp or iac97050{at}mn.waseda.ac.jp, Department of Mechanical Engineering, Umezu Biomedical Engineering Laboratory, Waseda University, 3-4-1 Ohkobo, Shinjuku-ku, Tokyo 169-8555, Japan.

Hydrodynamics of St. Jude Medical, Carbomedics, Advancing The Standard, and On-X bileaflet valves with an annular diameter of 25 mm were obtained using an in-vitro test system. Steady flow studies demonstrated different pressure drops due to differences in valve design, particularly the geometric orifice diameter and the opening angle. The On-X valve produced the least pressure drop, whereas the Carbomedics valve had the greatest pressure drop. In pulsatile flow experiments, the On-X and St. Jude Medical valves consistently produced the lowest mean positive pressure gradients, while the Carbomedics valve had the highest gradients. In spite of its parallel leaflets design, the On-X valve showed a closing volume as small as that of Carbomedics valve. The results indicate that a larger orifice diameter and greater opening angle can significantly reduce transvalvular pressure loss. This study also demonstrated that attempts to improve the hydrodynamic efficacy of the On-X valve were successful in reducing the pressure gradient as well as maintaining a low closing volume.