FLUID-STRUCTURE INTERACTION PREDICTIONS OF ASCENDING AORTA HEMODYNAMICS UNDER TRICUSPID AND BICUSPID AORTIC VALVE FLOWS

摘要

The bicuspid aortic valve (BAV) is the most common congenital cardiac anomaly and is present in 2-3% of the general population. As compared to the normal tricuspid aortic valve (TAV) which consists of three leaflets, the most prevalent type-I BAV morphology forms with two as a result of left-/right-coronary cusp fusion. While the BAV anatomy may not intrinsically hamper valvular function, it is associated with a spectrum of secondary aortopathy such as aortic dilation and subsequent dissection. The dilation and thinning of the ascending aorta downstream of a BAV is marked by structural wall abnormalities including smooth muscle cell depletion, elastic fiber degeneration and abnormal extracellular matrix remodeling, which localize to the convexity of the aortic wall. While BAV aortopathy has been historically linked to the same congenital defect as that responsible for the BAV morphogenesis, the abnormal BAV hemodynamics has emerged as a potential alternate or coincident etiology. Specifically, given the particular sensitivity of the arterial wall to its surrounding hemodynamics, the fluid shear stress abnormalities observed on the disease-prone convexity of the BAV ascending aorta may trigger pathological remodeling processes that ultimately lead to dilation and dissection. In light of these observations we hypothesized that type-I BAVs generates fluid shear stress abnormalities in regions of the ascending aorta prone to aortic dilation. Therefore, the objective of this study was to compare the native hemodynamic stresses on the convexity (i.e., region prone to dilation) of an ascending aorta subjected to TAV and type-I BAV flows using three-dimensional (3D) fluid-structure interaction (FSI) modeling.