Bioprosthetic valves are widely used for aortic valve replacements for patients with severe aortic diseases. However, tissue-engineered leaflets normally deteriorate over time due to calcification, leading to life-threatening conditions that would require re-operation. The hemodynamics induced by a prosthetic stenosis is complicated and not fully understood. This in vitro experimental study focuses on the fluid dynamics of two aortic valve models with different prosthetic stenosis conditions. An in vitro cardiovascular flow simulator was utilized to provide the pulsatile physiological flow conditions. Phase-locked particle image velocimetry (PIV) and high-frequency pressure sensors were employed to measure the flow fields and pressure waveforms. Pressure data were evaluated for the two models representing moderate and severe stenosis conditions, respectively. The severe prosthetic stenosis induced a prolonged ejection period and increased acceleration time ratio. PIV results suggest the severe prosthetic stenosis resulted in a two-fold increase in peak jet velocity and a three-fold increase in peak turbulence kinetic energy compared to the moderate stenosis case. The severe stenosis also caused rapid expansion of the jet downstream of the valve orifice and increased eccentricity of the jet flow. The maximum Reynolds shear stress in the severe stenosis case was found similar to the bileaflet mechanical valve reported by previous literature, which was below the risk threshold of blood cell damage but could potentially increase the risks of platelet activation and aggregation.

中文翻译：

---

人工主动脉瓣狭窄模型中脉动血流特性的实验分析。

生物人工瓣膜被广泛用于患有严重主动脉疾病的患者的主动脉瓣置换。然而，由于钙化，组织工程化的小叶通常会随着时间的流逝而恶化，导致危及生命的状况，需要重新手术。人工狭窄引起的血液动力学复杂，尚未完全了解。这项体外实验研究的重点是两种具有不同修复条件的主动脉瓣模型的流体动力学。利用体外心血管流动模拟器来提供脉动生理流动条件。锁相粒子图像测速（PIV）和高频压力传感器用于测量流场和压力波形。对代表中度和重度狭窄情况的两种模型的压力数据进行了评估，分别。严重的假体狭窄导致射血期延长和加速时间比率增加。PIV结果表明，与中度狭窄的情况相比，严重的假体狭窄导致峰值射流速度增加两倍，峰值湍流动能增加三倍。严重的狭窄还导致阀孔下游的射流快速膨胀，并增加了射流的偏心率。发现严重狭窄病例中的最大雷诺剪切应力与先前文献报道的双叶机械瓣相似，低于血细胞损害的风险阈值，但可能增加血小板活化和聚集的风险。PIV结果表明，与中度狭窄的情况相比，严重的假体狭窄导致峰值射流速度增加两倍，峰值湍流动能增加三倍。严重的狭窄还导致阀孔下游的射流快速膨胀，并增加了射流的偏心率。发现严重狭窄病例中的最大雷诺剪切应力与先前文献报道的双叶机械瓣相似，低于血细胞损伤的风险阈值，但可能增加血小板活化和聚集的风险。PIV结果表明，与中度狭窄的情况相比，严重的假体狭窄导致峰值射流速度增加两倍，峰值湍流动能增加三倍。严重的狭窄还导致阀孔下游的射流快速膨胀，并增加了射流的偏心率。发现严重狭窄病例中的最大雷诺剪切应力与先前文献报道的双叶机械瓣相似，低于血细胞损害的风险阈值，但可能增加血小板活化和聚集的风险。严重的狭窄还导致阀孔下游的射流快速膨胀，并增加了射流的偏心率。发现严重狭窄病例中的最大雷诺剪切应力与先前文献报道的双叶机械瓣相似，低于血细胞损害的风险阈值，但可能增加血小板活化和聚集的风险。严重的狭窄还导致阀孔下游的射流快速膨胀，并增加了射流的偏心率。发现严重狭窄病例中的最大雷诺剪切应力与先前文献报道的双叶机械瓣相似，低于血细胞损害的风险阈值，但可能增加血小板活化和聚集的风险。