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Spatial patterns of elevated wall shear stress and pressure due to blood flowpast aortic stenosis (AS) are studied using GPU-accelerated patient-specificcomputational fluid dynamics. Three cases of moderate AS, one with a dilatedascending aorta and two within the normal range (root diameter less than 4cm)are simulated for physiological beat cycle waveforms obtained fromechocardiography data. The computational framework is built based onsharp-interface Immersed Boundary Method, where aortic geometries segmentedfrom CT angiograms are integrated into a high-order incompressibleNavier-Stokes solver. We show that even though the wall shear stress iselevated and oscillatory due to turbulence in the ascending aorta for all thecases, its spatial distribution is significantly more focused for the case withdilation than those without dilation. This focal area is linked to aortic valvejet impingement on the outer curvature of the ascending aorta, and has beenshown in vivo using 4D flow MRI of aortic stenosis patients with aorticdilation (van Ooij et al., J. Am. Heart Assoc., 6(9), 2017). We show that thisfocal area also accommodates a persistent pocket of high pressure, which islikely to have contributed to the dilation process through an increasedwall-normal forcing. The cases without dilation, on the contrary, showed arather oscillatory pressure behaviour, with no persistent pressure buildupeffect. We further argue that a more proximal branching of the aortic archcould explain the lack of a focal area of elevated wall shear stress andpressure, because it interferes with the impingement process due to fluidsuction effects. These phenomena are further illustrated using an idealizedaortic geometry. We finally show that a restored inflow condition eliminatesthe focal area of elevated wall shear stress and pressure zone from theascending aorta.

Wall shear stress and pressure patterns in aortic stenosis patients with  and without aortic dilation captured by high-performance image-based  computational fluid dynamics