Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, GA, USA.
Ann Biomed Eng. 2012 Aug;40(8):1760-75. doi: 10.1007/s10439-012-0527-2. Epub 2012 Feb 9.
The congenital bicuspid aortic valve (BAV) is associated with increased leaflet calcification, ascending aortic dilatation, aortic stenosis (AS) and regurgitation (AR). Although underlying genetic factors have been primarily implicated for these complications, the altered mechanical environment of BAVs could potentially accelerate these pathologies. The objective of the current study is to characterize BAV hemodynamics in an in vitro system. Two BAV models of varying stenosis and jet eccentricity and a trileaflet AV (TAV) were constructed from excised porcine AVs. Particle Image Velocimetry (PIV) experiments were conducted at physiological flow and pressure conditions to characterize fluid velocity fields in the aorta and sinus regions, and ensemble averaged Reynolds shear stress and 2D turbulent kinetic energy were calculated for all models. The dynamics of the BAV and TAV models matched the characteristics of these valves which are observed clinically. The eccentric and stenotic BAV showed the strongest systolic jet (V = 4.2 m/s), which impinged on the aortic wall on the non-fused leaflet side, causing a strong vortex in the non-fused leaflet sinus. The magnitudes of TKE and Reynolds stresses in both BAV models were almost twice as large as comparable values for TAV, and these maximum values were primarily concentrated around the central jet through the valve orifice. The in vitro model described here enables detailed characterization of BAV flow characteristics, which is currently challenging in clinical practice. This model can prove to be useful in studying the effects of altered BAV geometry on fluid dynamics in the valve and ascending aorta. These altered flows can be potentially linked to increased calcific responses from the valve endothelium in stenotic and eccentric BAVs, independent of concomitant genetic factors.
先天性二叶式主动脉瓣（BAV）与瓣叶钙化、升主动脉扩张、主动脉瓣狭窄（AS）和反流（AR）的发生率增加相关。尽管这些并发症主要与潜在的遗传因素有关，但 BAV 的力学环境改变可能会加速这些病理变化。本研究的目的是在体外系统中描述 BAV 的血流动力学。从切除的猪主动脉瓣构建了两个具有不同狭窄程度和射流偏心程度的 BAV 模型和一个三叶式主动脉瓣（TAV）模型。在生理流动和压力条件下进行了粒子图像速度测量（PIV）实验，以描述主动脉和窦区的流体速度场，并计算了所有模型的平均雷诺剪切应力和二维湍流动能。BAV 和 TAV 模型的动力学与临床观察到的这些瓣膜的特征相匹配。偏心和狭窄的 BAV 显示出最强的收缩射流（V = 4.2 m/s），该射流撞击在非融合瓣叶侧的主动脉壁上，在非融合瓣窦中引起强烈的涡旋。两个 BAV 模型中的 TKE 和雷诺应力的幅度几乎是可比 TAV 值的两倍，这些最大值主要集中在通过瓣膜孔的中央射流周围。这里描述的体外模型能够详细描述 BAV 的流动特征，这在临床实践中目前具有挑战性。该模型可用于研究 BAV 几何形状改变对瓣膜和升主动脉内流动动力学的影响。这些改变的流动可能与狭窄和偏心 BAV 中瓣膜内皮的钙化反应增加有关，而与伴随的遗传因素无关。
