Biomechanical Assessment of Bicuspid Aortic Valve Phenotypes: A Fluid-Structure Interaction Modelling Approach.

Bicuspid aortic valve (BAV) is a congenital heart malformation with phenotypic heterogeneity. There is no prior computational study that assesses the haemodynamic and valve mechanics associated with BAV type 2 against a healthy tricuspid aortic valve (TAV) and other BAV categories. A proof-of-concept study incorporating three-dimensional fluid-structure interaction (FSI) models with idealised geometries (one TAV and six BAVs, namely type 0 with lateral and anterior-posterior orientations, type 1 with R-L, N-R and N-L leaflet fusion and type 2) has been developed. Transient physiological boundary conditions have been applied and simulations were run using an Arbitrary Lagrangian-Eulerian formulation. Our results showed the presence of abnormal haemodynamics in the aorta and abnormal valve mechanics: type 0 BAVs yielded the best haemodynamical and mechanical outcomes, but cusp stress distribution varied with valve orifice orientation, which can be linked to different cusp calcification location onset; type 1 BAVs gave rise to similar haemodynamics and valve mechanics, regardless of raphe position, but this position altered the location of abnormal haemodynamic features; finally, type 2 BAV constricted the majority of blood flow, exhibiting the most damaging haemodynamic and mechanical repercussions when compared to other BAV phenotypes. The findings of this proof-of-concept work suggest that there are specific differences across haemodynamics and valve mechanics associated with BAV phenotypes, which may be critical to subsequent processes associated with their pathophysiology processes.