title: Observation of cavitation in a mechanical heart valve in a total artificial heart.
abstract: Recently, cavitation on the surface of mechanical heart valves has been studied as a cause of fractures occurring in implanted mechanical heart valves. The cause of cavitation in mechanical heart valves was investigated using the 25 mm Medtronic Hall valve and the 23 mm Omnicarbon valve. Closing of these valves in the mitral position was simulated in an electrohydraulic totally artificial heart. Tests were conducted under physiologic pressures at heart rates from 60 to 100 beats per minute with cardiac outputs from 4.8 to 7.7 L/min. The disk closing motion was measured by a laser displacement sensor. A high-speed video camera was used to observe the cavitation bubbles in the mechanical heart valves. The maximum closing velocity of the Omnicarbon valve was faster than that of the Medtronic Hall valve. In both valves, the closing velocity of the leaflet, used as the cavitation threshold, was approximately 1.3-1.5 m/s. In the case of the Medtronic Hall valve, cavitation bubbles were generated by the squeeze flow and by the effects of the venturi and the water hammer. With the Omnicarbon valve, the cavitation bubbles were generated by the squeeze flow and the water hammer. The mechanism leading to the development of cavitation bubbles depended on the valve closing velocity and the valve stop geometry. Most of the cavitation bubbles were observed around the valve stop and were generated by the squeeze flow.
authors.affiliation: Department of Artificial Organs, Research Institute, National Cardiovascular Center, 5-7-1 Fujishiro-dai, Suita, Osaka 565-8565, Japan.
authors.forename: Hwansung
authors.initials: H
authors.lastname: Lee
authors.forename: Tomonori
authors.initials: T
authors.lastname: Tsukiya
authors.forename: Akihiko
authors.initials: A
authors.lastname: Homma
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Kamimura
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Takewa
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Nishinaka
authors.forename: Eisuke
authors.initials: E
authors.lastname: Tatsumi
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Taenaka
authors.forename: Hisateru
authors.initials: H
authors.lastname: Takano
authors.forename: Soichiro
authors.initials: S
authors.lastname: Kitamura
mesh_terms: D001696:Biomechanical Phenomena; D002302:Cardiac Output; D019544:Equipment Failure Analysis / Q000379:methods; D006339:Heart Rate; D006350:Heart Valve Prosthesis; D006354:Heart, Artificial; D008943:Mitral Valve; D011474:Prosthesis Design; D011475:Prosthesis Failure