1996 Fiscal Year Final Research Report Summary
Development of a Internationally acceptable fatigue test system for prosthetic heart valve
| Project/Area Number |
06557073
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 試験 |
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| Research Field |
Thoracic surgery
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| Research Institution | Waseda University |
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Principal Investigator |
UMEZU Mitsuo Dept.of Mechanical Engineering, Waseda University, Professor, 理工学部, 教授 (90132927)
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| Co-Investigator(Kenkyū-buntansha) |
NAKANO Kiyoharu National Cardiovascular Center, 心臓血管外科, 医長 (10138919)
HAYASHI Junichi Niigata University, School of Medicine, Lectuer, 医学部・付属病院, 講師 (30164940)
KAWAZOE Kohei Iwate Medical University, School of Medicine, Professor, 外科学第3講座, 教授 (50075561)
TOMIOKA Jun Dept.of Mechanical Engineering, Waseda University, Associate Professor, 理工学部, 助教授 (40217526)
KAWADA Hiroyuki Dept.of Mechanical Engineering, Waseda University, Associate Professor, 理工学部, 助教授 (20177702)
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| Project Period (FY) |
1994 – 1996
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| Keywords | heart valve / accelerated fatigue test / durability / Jellyfish valve / creep effect / impact force / FEM analysis / Young's modulus |
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| Research Abstract |
The purpose of this study is to establish an internationally-acceptable methodology of fatigue testing for prosthetic heart valves, based on the improvement process of a Chinese-made accelerated fatigue test apparatus. This test system had four parallel water cylinders, in which valves were incorporated. Open and closing motion of each valve was controlled at a repetition speed of 10-20 Hz with a displacement of 1-2mm. The Jerryfish (JF) valve was used in this study. It had the longest implantation record in animal trials. In this case, the polyurethane membrane with the thickness of 50-70 mum was ruptured due to a creep effect observed at the middle portion between two spokes after 300days in goat.
First of all, in vitro fatigue test machine has been innovated in order to reproduce the above mentioned in-vivo fatigue test results. Dynamic conditions which enabled the identical forces between accelerated and normal cycles were determined : maximum load during valve closure was 5.2N (inc
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reased by 20% to the normal), and impulse was 2.5*10^<-2>N・s. Under this condition, valves were ruptured for 1.0*10^7 cycles, but no distinct creep was noticed. Secondary, a temperature of the test-fluid was changed from 20ﾟC to 50ﾟC,expecting a creep effect to the membrane shape. Change in shape of the membrane was observed after 3.2*10^6 cycles, however, its distortion value was only 50% of the animal experimental results. For the next step, a material of the membrane was changed from polyurethane to polystirene to achieve bigger change in shape. As a result, the identical distortion level was successfully reproduced, but a location of the ruptured area was different between in vitro and in vivo results. In order to clarify the above mentioned difference, FEM analysis was performed. The calculated result exhibited that there are three major areas of the maximum elastic strain between two spokes. Moreover, it was confirmed that the ruptured areas observed by both in vitro/in vivo results could be fully superimposed to the areas of the calculated maximum elastic strain.
Further investigation should by carried out to determine more reliable methodology for fatigue testing, based on the in vitro and FEM analysis data. Less
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