Lavon Karin, Halevi Rotem, Marom Gil, Ben Zekry Sagit, Hamdan Ashraf, Joachim Schäfers Hans, Raanani Ehud, Haj-Ali Rami
Faculty of Engineering, School of Mechanical Engineering, Tel Aviv University, Tel Aviv 6997801, Israel.
Biomedical Engineering Department, Stony Brook University, Stony Brook, NY 11794.
J Biomech Eng. 2018 Mar 1;140(3). doi: 10.1115/1.4038329.
Bicuspid aortic valve (BAV) is the most common type of congenital heart disease, occurring in 0.5-2% of the population, where the valve has only two rather than the three normal cusps. Valvular pathologies, such as aortic regurgitation and aortic stenosis, are associated with BAVs, thereby increasing the need for a better understanding of BAV kinematics and geometrical characteristics. The aim of this study is to investigate the influence of the nonfused cusp (NFC) angle in BAV type-1 configuration on the valve's structural and hemodynamic performance. Toward that goal, a parametric fluid-structure interaction (FSI) modeling approach of BAVs is presented. Four FSI models were generated with varying NFC angles between 120 deg and 180 deg. The FSI simulations were based on fully coupled structural and fluid dynamic solvers and corresponded to physiologic values, including the anisotropic hyper-elastic behavior of the tissue. The simulated angles led to different mechanical behavior, such as eccentric jet flow direction with a wider opening shape that was found for the smaller NFC angles, while a narrower opening orifice followed by increased jet flow velocity was observed for the larger NFC angles. Smaller NFC angles led to higher concentrated flow shear stress (FSS) on the NFC during peak systole, while higher maximal principal stresses were found in the raphe region during diastole. The proposed biomechanical models could explain the early failure of BAVs with decreased NFC angles, and suggests that a larger NFC angle is preferable in suture annuloplasty BAV repair surgery.
二叶式主动脉瓣（BAV）是最常见的先天性心脏病类型，在0.5%-2%的人群中出现，其瓣膜只有两个而非正常的三个瓣叶。瓣膜病变，如主动脉反流和主动脉狭窄，与二叶式主动脉瓣相关，因此更需要深入了解二叶式主动脉瓣的运动学和几何特征。本研究的目的是探讨1型二叶式主动脉瓣构型中非融合瓣叶（NFC）角度对瓣膜结构和血流动力学性能的影响。为实现该目标，提出了一种二叶式主动脉瓣的参数化流固耦合（FSI）建模方法。生成了四个FSI模型，其NFC角度在120°至180°之间变化。FSI模拟基于完全耦合的结构和流体动力学求解器，并对应于生理值，包括组织的各向异性超弹性行为。模拟角度导致不同的力学行为，例如较小的NFC角度会出现偏心射流方向且开口形状更宽，而较大的NFC角度则观察到开口孔变窄且射流速度增加。较小的NFC角度在收缩期峰值时导致NFC上的血流剪切应力（FSS）更高，而在舒张期在嵴部区域发现更大的最大主应力。所提出的生物力学模型可以解释NFC角度减小的二叶式主动脉瓣的早期失效，并表明在缝线瓣环成形术二叶式主动脉瓣修复手术中，较大的NFC角度更可取。
