膨体聚四氟乙烯人工二尖瓣的体外加速疲劳实验

In vitro accelerative fatigue test of expanded polytetrafluoroethylene mitral valve prothesis

目的:测试膨体聚四氟乙烯人工二尖瓣的体外耐久性。方法:实验于2004-11/2005-06在湖南心脏研究所完成。符合GB12279-90标准。疲劳实验前后进行体外脉动流流体力学实验。实验在20℃恒温条件下进行,采用生理盐水作为实验液体。以TH-2200型瓣膜体外加速疲劳寿命实验台对6个膨体聚四氟乙烯人工二尖瓣进行体外加速疲劳实验,总计4亿次,实验中每2500万次停机检查1次,每5000万次测量腱索长度。实验结束时观察瓣膜的大体情况。以TH-1200型人工心脏瓣膜体外脉动流试验台测试瓣膜于疲劳实验前后的流体力学参数,并进行对比,以测试膨体聚四氟乙烯人工二尖瓣的耐久性。结果:①瓣膜大体观察:6个膨体聚四氟乙烯人工二尖瓣在每个周期的循环中均能够完全开放与闭合,每个膨体聚四氟乙烯人工二尖瓣的腱索均处于张紧状态,瓣膜大小瓣间对合严密,无肉眼可见的缝隙。②腱索长度变化:腱索长度随时间(实验次数)的增加而增加,但增加速度逐渐减慢,0.5亿次时平均增加(0.795±0.037)mm,1亿次时增加(0.587±0.044)mm,以后增加缓慢,不超过(0.168±0.021)mm。由实验开始到结束时各腱索总计增加长度均值为1.86mm。总体上随时间变化腱索增长差异有显著性意义(F=5025.909,P=0.000)。腱索长度增加各腱索间差异无显著性意义(F=2.119,P=0.067)。③平均跨瓣压差:疲劳实验后平均跨瓣压差略高于实验前,差异无显著性意义[分别为(4.540±1.846),(4.498±1.430)mmHg,F=0.013,P=0.912]。④瓣膜有效开口面积:疲劳实验后瓣膜有效开口面积略高于实验前,差异无显著性意义[分别为(2.633±1.077),(2.474±1.074)cm2,F=0.651,P=0.427]。⑤瓣膜反流量:疲劳实验后瓣膜反流量低于实验前,差异有显著性意义[分别为(1.291±1.028),(2.128±1.250)mL,F=8.606,P=0.007]。⑥瓣膜反流率:疲劳实验后瓣膜反流率低于实验前,差异有显著性意义[分别为(3.491±2.998)%,(5.147±1.736)%,F=5.849,P=0.023]。结论:膨体聚四氟乙烯人工二尖瓣具有良好的体外耐久性及流体力学特性。

AIM： To study the durability of expanded polytetrafluoroethylene mitral valve prothesis （ePTFEMVP）. METHODS ： The experiment was conducted in the laboratory of Hunan Angiocardiopathy Institute from November 2004 to June 2005, and the experimental processes wore consistent with the specifications of GB12279-90. In vitro pulsing hydromechanical experiment was performed before and after fatigue experiment. The experiment was carried on at 20℃ with normal sodium as the work fluid. Six ePTFEMVPs wore tested for 400 million times with accelerative fatigue with TH-2200 artificial heart valve exosomatic accelerative fatigue instrument. The valves wore checked every 25 million times and the length of chorda tendineaes was checked every 50 million times during the test. The general condition of mitral valve was observed when the experiment was completed. Hydromechanical parameters before and after the accelerative fatigue test wore tested with TH-1200 artificial heart valve exosomatic pulsatile stream instrument and compared to estimate the durability of the ePTFEMVP. RESULTS ： ①General observation results： All six ePTFEMVPs could open and close completely in every cycle. All chorda tendineaes wore tensive and the big and small cusps wore jointed tightly without macroscopic crevices. ② Length changes of chorda tendineaes： The length was increased with time （experimental times）, but the increase rate gradually slowed down. At 50 million times the mean length increase was （0.795±0.037） mm and at 100 million times it was （0.587±0.044） mm, then it gradually slowed down, and did not excess （0.168±0.021） mm. From the beginning to the end of the accelerated fatigue test the mean total length increase was 1.86 mm. Generally the differences of the length increase with time wore extremely statistically significant （F =5 025.909, P =0.000）. The length increase differences among chorda tendineaes wore not statistically significant （F =2.119, P =0.067）. ③Mean pressure difference： It slightly increased compared with that before the test, but the difference was not statistically significant [（4.540± 1.846）, （4.498±1.430） mm Hg, F =0.013,. P =0.912]. ④Effective orifice area： It slightly increased compared with that before the fatigue test, but the difference was not statistically significant [（2.633±1.077）, （2.474±1.074） cm^2, F =0.651, P =0.427]. ⑤Regurgitation volume： The regurgitation volume was diminished after the accelerative fatigue test and the differencec wore statistically significant [（1.291±1.028）, （2.128±1.250） mL, F=8.606, P =0.007]. ⑥Regurgitation rate： It was lower than that before the accelerative fatigue test and the differencec wore statistically significant [（3.491±2.998）%, （5.147±1.736）%, F =5.849, P =0.023]. CONCLUSION： The ePTFEMVP has favorable exosomatic durability and hydromechanical characteristics.