Hemodynamic characteristics of dilated ascending aorta in patients with bicuspid aortic valve.

Background: The 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).

Method: 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, three additional anatomical models were constructed with different AAo sizes of 4.0 cm, 5.0 cm and 5.5 cm 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.

Result: Hemodynamics environments in the AAo were simulated with different aortic sizes. As the aortic diameter increases, the blood flow becomes more disturbing; the wall pressure at AAo is higher; the wall shear stress at the AAo decreases; the oscillatory shear index of the outer part on the proximal AAo increases; 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.

Conclusion: The study revealed that the diameter of AAo can significantly affect the magnitude and distribution of the hemodynamics. There are altered flow patterns, pressure difference, WSS and OSI distribution features in bicuspid aortic valve patients with vascular dilatation. As the degree of aortic dilatation increases, particularly when exceeding 5.0 cm and progressing towards 5.5 cm, this study supports the recent guideline that aortic replacement should be considered for diameters ≥ 5.5 cm.