Influence of the aortic valve leaflets on the fluid-dynamics in aorta in presence of a normally functioning bicuspid valve

Abstract

In this work, we consider the blood fluid-dynamics in the ascending aorta in presence of a normally functioning bicuspid aortic valve (BAV). In particular, we perform an unsteady finite element study in real geometries with physiological velocity boundary conditions at the inlet to assess the effect of the inclusion of the leaflets on the fluid-dynamic abnormalities characterizing BAV cases. To this aim, we perform a comparison in two geometries (a dilated and a non-dilated ones) among three scenarios which are built up for each geometry: BAV without leaflets, BAV with leaflets, and tricuspid case with leaflets. For each case, we compute four indices quantifying flow asymmetry, reversal flows, helical patterns, and wall shear stresses. Our results show that the inclusion of the leaflets increases the fluid-dynamics abnormalities, especially for the non-dilated configuration, which presents a greater increment of the indices. In particular, we observe that the values of the time-averaged wall shear stress and of the systolic jet asymmetry increase by approximatively 100 and 40%, respectively, when considering the leaflets.

Bicuspid aortic valve aortopathies: An hemodynamics characterization in dilated aortas

“…Previous studies showed that the open systolic configuration of the BAV leaflets is sufficient to recreate the abnormal aortic hemodynamics associated (Bonomi et al 2015). Since the goal of this work was to study BAV related ascending hemodynamics at systole, BAV leaflets were reconstructed in a fixed peak systolic configuration.…”

“…Velocity vectors and vorticity fields were captured at sections A2 and A3. Aortic flow helicity was quantified using the positive helix fraction (PHF) index (Cao et al 2017;Bonomi et al 2015),…”

“…To quantify retrograde flows in the ascending aorta, the flow reversal ratio (FRR) index was used (Bonomi et al 2015),…”

“…According to this, research studies have tried to underline mechanisms associated with dilation onset and progression in the presence of a BAV. Computational works have provided further insight on the hemodynamic aspects of ascending aortic blood flow in this disease: flow eccentricity, skewness, helical patterns and abnormally elevated wall shear stress (WSS) have been reported by computational (Cao et al 2017;Bonomi et al 2015;Kimura et al 2017) and in vivo studies (Mahadevia et al 2014;Rodriguez-Palomares et al 2018). Nonetheless, further hemodynamics characterization of blood patterns in the ascending aorta in cases of dilation is necessary.…”

Aorta Ascending Aneurysm Analysis Using CFD Models towards Possible Anomalies

“…Based on these indices, it is possible to identify the type of aneurysm presented in each patient (Table 1). According to [1,[31][32][33][34][35], based on the TAA shape, different criteria for the TAA collapsibility can be applied: (i) if the TAA diameter is 45% higher than the non-deformed aorta diameter; (ii) if the asymmetry index factor is < 0.4; (iii) if the deformation diameter ratio > 3 × ; and (iv) if the saccular index < 0.6. However, the TAA dilation and potential rupture also depend on the hemodynamic loads.…”