This study aims to quantitatively and qualitatively assess energy dissipation in the aortic valve as a function of systolic aortic flow waveform representing pathologies where flow time-to-peak is delayed. A bioprosthetic valve was tested in the aortic position of a left-heart simulator under physiological pressure and flow conditions. The flow loop piston pump was programmed to generate three different flow waveforms each with a different peak time annotated as early peak (EP) with a rapid acceleration, mid peak (MP) and late peak (LP) with a rapid deceleration. Energy dissipation was calculated from flow and pressure measurements while sinus vorticity dynamics were evaluated using time-resolved planar particle image velocimetry. Average pressure gradients during systole are found 30.2 ± 0.19, 30.7 ± 0.25 and 32.9 ± 0.29 mmHg and average dissipation over systole is found 0.95 ± 0.026, 1.05 ± 0.034 and 1.25 ± 0.043 W for EP, MP and LP respectively. As systole's acceleration phase is slower, sinus vortices are more likely to form, necessitating more energy exchange from shear layers inducing more viscous dissipation. EP found in healthy individuals is superior in terms of reducing energy dissipation and increasing aortic valve efficiency. In the context of possible left ventricular dysfunction and aortic stenosis, this means that delayed time-to-peak in the aortic flow waveform seen is not compensatory.

中文翻译：

---

脉动流波形对主动脉瓣能量损失的意义。

这项研究的目的是定量和定性地评估主动脉瓣的能量消散，作为收缩期主动脉血流波形的函数，该波形代表了血流至峰值时间延迟的病理状况。在生理压力和血流条件下，在左心模拟器的主动脉位置测试了生物人工瓣膜。对流量环流活塞泵进行了编程，以生成三个不同的流量波形，每个波形具有不同的峰值时间，分别表示为快速加速的早期峰值（EP），快速减速的中期峰值（MP）和后期峰值（LP）。根据流量和压力测量结果计算能量耗散，同时使用时间分辨平面粒子图像测速仪评估窦性涡旋动力学。发现收缩期的平均压力梯度为30.2±0.19、30.7±0.25和32.9±0。对于EP，MP和LP，发现29 mmHg和整个收缩期的平均耗散分别为0.95±0.026、1.05±0.034和1.25±0.043 W. 由于收缩期的加速阶段较慢，因此更容易形成窦性涡流，从而需要从剪切层进行更多的能量交换，从而导致更多的粘性耗散。在健康个体中发现的EP在减少能量耗散和增加主动脉瓣效率方面具有优势。在可能出现的左心室功能不全和主动脉瓣狭窄的情况下，这意味着所观察到的主动脉血流波形延迟至峰值时间是无补偿的。必须从剪切层进行更多的能量交换，从而导致更多的粘性耗散。在健康个体中发现的EP在减少能量耗散和增加主动脉瓣效率方面具有优势。在可能出现的左心室功能不全和主动脉瓣狭窄的情况下，这意味着所观察到的主动脉血流波形延迟至峰值时间是无补偿的。必须从剪切层进行更多的能量交换，从而导致更多的粘性耗散。在健康个体中发现的EP在减少能量耗散和增加主动脉瓣效率方面具有优势。在可能出现的左心室功能不全和主动脉瓣狭窄的情况下，这意味着所观察到的主动脉血流波形延迟至峰值时间是无补偿的。