Comparative finite-element model analysis of ascending aortic flow in bicuspid and tricuspid aortic valve

Abstract. Purpose: In bicuspid aortic valve (BAV) disease role of genetic and haemodynamic factors influencing ascending aortic pathology is controversial. To test the effect of BAV geometry on ascending aortic flow, a Finite Element analysis was undertaken. Methods: A surface model of aortic root and ascending aorta was obtained from magnetic resonance images of patients with BAV and tricuspid aortic valve using segmentation facilities of the image processing code Vascular Modelling Toolkit (developed at Mario Negri Institute). Analytical models of bicuspid (antero-posterior, type 1, and laterolateral, type 2, commissures) and tricuspid orifices were mathematically defined and turned into a volumetric mesh of linear tetrahedra for computational fluid dynamics simulations. Numerical simulations were performed with the Finite Element code LifeV. Flow velocity fields were assessed for four levels: aortic annulus, sinus of Valsalva, sinotubular junction, ascending aorta.Results: Comparison of finite-element analysis of bicuspid and tricuspid aortic valve shows different blood flow velocity pattern. Flow in bicuspid configurations shows asymmetrical distribution of velocity field towards the convexity of mid-ascending aorta returning symmetrical in distal ascending aorta. On the contrary, tricuspid flow is symmetrical in each aortic segment. Comparing type 1 BAV with type 2 BAV, more pronounced recirculation zones have been noticed in the least. Finally, we found that in both BAV configurations maximum wall shear stress is highly localized at the convex portion of mid-ascending aorta level.Conclusions: Comparison between models shows asymmetrical and higher flow velocity in bicuspid models, in particular in AP configuration. Asymmetry is more pronounced at the aortic level known to be more exposed to aneurysm formation in bicuspid patients. This supports the hypothesis that haemodynamic factors may contribute to ascending aortic pathology in this subset of patients.