Abstract 16209: Commissure Orientation Influences Aortic Aneurysm Morphology in Normally Functioning Bicuspid Aortic Valves: A Parametric, Computational Fluid Dynamic Study
Objective. Role of hemodynamics in pathogenesis of ascending aortic aneurysm (AAA) associated with normally functioning bicuspid aortic valve (BAV) remains controversial. A finite element analysis model was built to define influence of BAV orientation on aortic flow dynamics and propensity for specific AAA formation.
Methods. Surface model of aortic root and ascending aorta were obtained from MRI of healthy subjects with normal BAV using segmentation capabilities of Vascular Modeling Toolkit. Non-stenotic bicuspid (area=1.9 cm2) orifices were mathematically defined representing the entire spectrum of antero-posterior (AP) (0°, 30°, 150°) and latero-lateral (LL)(60°, 90°, 120°) commissure orientation. Models were turned into volumetric mesh of linear tetrahedra for computational fluid dynamics simulations performed with Finite Element Code LifeV (MOX-Milan, INRIA-Paris, EPFL-Lausanne). Physiological inflow boundary conditions at inlet were imposed by introduction of a Lagrange multiplier. Wall shear stress (WSS) and flow velocity fields were assessed for each configuration at four levels: annulus, sinus of Valsalva, sinotubular junction, ascending aorta.
Results. WSS was maximal (from blue to red, from 0.01 to 3 Pa) at mid-ascending aorta regardless of commissure orientation (Figure: from right-left, upper row: 0°, 30°, 60°; lower row: 90°, 120°, 150°). Contrary to AP, LL commissure configurations (60°, 90°) exhibited maximal WSS even at sinus of Valsalva and sinotubular junction. Flow velocity fields confirmed highest velocity and greatest asymmetry index starting at sinus and sinotubular junction in LL commissure configurations.
Conclusions. Non-stenotic BAV causes pathological WSS, maximal at mid-aortic level, supporting hemodynamic hypothesis for aneurysm formation. AP BAV configurations are associated with divergent aneurysm (maximum diameter at mid-aorta) morphology, while LL with tubular (uniform dilatation).
- © 2011 by American Heart Association, Inc.