Objective: Aim of this study is to investigate the influence of aortic diameter on hemodynamic environment characteristics in patient with the bicuspid aortic valve (BAV) and dilated ascending aorta (AAo) .
Methods: In this study, an MRI of one BAV patient with 4.5 cm AAo was collected and numerical model was constructed. Based on the images，the other three numerical models were constructed with different ascending aortic size with 4.0cm, 5.0cm and 5.5cm respectively while the size and the geometry of other parts were fixed. Then hemodynamics in these four models was simulated numerically and the flow patterns and loading distributions were investigated.
Results: Hemodynamics environments in the AAo were simulated with different aortic size. As the aortic diameter increases, we find: 1. the blood flow becomes more disturbing;2.the wall pressure at ascending aortic is higher; 3. the wall shear stress at the ascending aortic decreases; 4.oscillatory shear index of the outer part on the proximal AAo increases;5. all these hemodynamic parameters described above are asymmetrically distributed in dilated AAo and more parts of aorta would be affected as the AAo dilatation progresses.
Conclusions: The study revealed that the diameter of ascending aortic can significantly influence the magnitude and distribution of the dynamics. There are altered flow patterns, pressure difference, WSS and OSI distribution features in bicuspid aortic valve patients with vascular dilatation. As the extent of aortic dilatation increases especially exceed 5.5cm,this study support the recent guideline that aortic replacement should be considered .