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Calcific aortic valve disease (CAVD) is characterized by calcification accumulation and thickening of the aortic valve cusps, leading to stenosis. The importance of fluid flow shear stress in the initiation and regulation of CAVD progression is well known and has been studied recently using fluid-structure interaction (FSI) models. While cusp calcifications are three-dimensional (3D) masses, previously published FSI models have represented them as either stiffened or thickened two-dimensional (2D) cusps. This study investigates the hemodynamic effect of these calcifications employing FSI models using 3D patient-specific calcification masses. A new reverse calcification technique (RCT) is used for modeling different stages of calcification growth based on the spatial distribution of calcification density. The RCT is applied to generate the 3D calcification deposits reconstructed from a patient-specific CT scans. Our results showed that consideration of 3D calcification deposits led to both higher fluid shear stresses and unique fluid shear stress distribution on the aortic side of the cusps that may have an impact on the calcification growth rate. However, the flow did not seem to affect the geometry of the calcification during the growth phase.

Bicuspid aortic valve (BAV) is the most common type of congenital heart disease, occurring in 0.5-2% of the population, where the valve has only two rather than the three normal cusps. Valvular pathologies, such as aortic regurgitation and aortic stenosis, are associated with BAVs, thereby increasing the need for a better understanding of BAV kinematics and geometrical characteristics. The aim of this study is to investigate the influence of the nonfused cusp (NFC) angle in BAV type-1 configuration on the valve's structural and hemodynamic performance. Toward that goal, a parametric fluid-structure interaction (FSI) modeling approach of BAVs is presented. Four FSI models were generated with varying NFC angles between 120 deg and 180 deg. The FSI simulations were based on fully coupled structural and fluid dynamic solvers and corresponded to physiologic values, including the anisotropic hyper-elastic behavior of the tissue. The simulated angles led to different mechanical behavior, such as eccentric jet flow direction with a wider opening shape that was found for the smaller NFC angles, while a narrower opening orifice followed by increased jet flow velocity was observed for the larger NFC angles. Smaller NFC angles led to higher concentrated flow shear stress (FSS) on the NFC during peak systole, while higher maximal principal stresses were found in the raphe region during diastole. The proposed biomechanical models could explain the early failure of BAVs with decreased NFC angles, and suggests that a larger NFC angle is preferable in suture annuloplasty BAV repair surgery.

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