Prediction of durability of artificial organs using an accerelated fatigue tester

为了预测心脏瓣膜的耐久性，采用了两种市售(ISU-Standard)相关的疲劳试验，同时提高了水母聚合物瓣膜的寿命。在常规囊状血泵中加入水母瓣膜超过300天的慢性动物实验表明，这种柔性膜上存在断裂和钙化。因此，较长的耐用性(约1年保修期)的水母阀门一直在开发中。在明确问题原因的同时，首先对水母阀门进行了设计改进。对水母瓣膜关闭阶段的有限元分析结果表明，在动物实验中，瓣膜破裂和钙化产生了机械应变。此外，进一步的分析表明，在半径为7.0 mm处增加一个圆形轮缘对于避免应变集中是非常有效的。体外稳态和脉动试验表明，半径为70 mm、宽度为0.5 mm的改进型水母阀具有与原水母阀相当的水动力性能。下一步，采用了两种商用加速疲劳试验。疲劳试验成功地表明，改进型瓣膜的寿命比原来的水母瓣膜延长了7倍。因此，将改良型瓣膜植入常规囊式血泵进行了长达数月的慢性动物实验。未观察到与应用改良瓣膜相关的溶血。这是由于附加轮缘的锥形结构，流入侧宽度为0.1 mm。从以上数据可以看出，改进后的聚合物瓣膜在临床人工心脏应用中具有很大的前景，同时也澄清了我们的抗疲劳试验机可以提供聚合物瓣膜的比较耐久性数据。

In order to predict a durability of heart valve prostheses, two types of commercially available (ISU-Standard) accerelated fatigue tests were employed, while improving a life time of Jellyfish polymer valve.A chronic animal experiment of Jellyfish valves incorporated into conventional sac-type blood pumps for over 300days exhibited that there were a fracture and calcification on this flexible membrane. Therefore, a long durability (approx. 1 year guarantee) of Jellyfish valve has been developing. while clearing a cause of the problems.First of all, design improvement of Jellyfish valve was attempted. Results of finite element analysis during closed phase of Jellyfish valve indicated that mechanical strain generated on valve membrane fracture and calcification in the animal experiment. Moreover further analysis suggested that an additional circular rim located at 7.0mm in radius was quite effective to avoid strain concentration. In vitro steady and pulsatile tests demonstrated that a modified valve with 0.5mm width rim located at 70mm in radius had a comparable hydrodynamic performance to the original Jellyfish valve.For the next step, commercially available two types of accelerated fatigue tests were employed. Fatigue tests successfully revealed that a durability of the modified valve was much more extended than the original Jellyfish valve by 7 times.Thus, chronic animal experiment with conventional sac-type blood pumps in which the modified valves were incorporated was performed for months. Hemolysis related to the application of the modified valve was not observed. This would be owing to the tapered configuration of the additional rim with 0.1mm width of inflow side.From the data above, the modified polymer valve showed great promise for clinical artificial heart application, and it was also clarified that our prevent fatigue tester could provide comparative durability data of polymer valves.