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Bjork–Shiley valve
The Björk–Shiley valve is a mechanical prosthetic heart valve. The valve was co-invented by American engineer Donald Shiley and Swedish heart surgeon Viking Björk.
Beginning in 1971, it has been used to replace aortic valves and mitral valves. It was the first successful tilting-disc valve. It was manufactured first by Shiley Laboratories, then later by Pfizer after that company purchased Shiley. One model of the Bjork–Shiley valve became the subject of a famous lawsuit and recall after it was shown to malfunction.
==Construction==
The Björk–Shiley valve consists of a single carbon-coated disc in a metal housing. The disc is held in place by two metal struts, an inflow and an outflow strut. The housing is made from the alloy Haynes 25,〔Bronzino, Joseph D. (ed.) ''The Biomedical Engineering Handbook'' 2nd Edition. (pg. 127-20 )〕 which is composed of 51% cobalt, 20% chromium, 15% tungsten, and 10% nickel.〔(''ALLOYS AT A GLANCE: HAYNES® 25 Alloy'' ) Haynes International.〕 The Björk–Shiley valve was considered very durable and was widely used in the 1970s.〔(【引用サイトリンク】title=Valves )〕 However, later research indicated it was susceptible to long-term wear problems, and could shed microscopic metal fragments.〔(Black Holes on MR Images of the Brain of Patients with Björk-Shiley Heart Valves: Additional Observation in Three Cases ) MJ van Gorp et al, ''American Journal of Neuroradiology'', 24:512–514, March 2003〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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