Biomech Model Mechanobiol DOI 10.1007/s10237-012-0375-x ORIGINAL PAPER Computational assessment of bicuspid aortic valve wall-shear stress: implications for calcific aortic valve disease Santanu Chandra · Nalini M. Rajamannan · Philippe Sucosky Received: 12 September 2011 / Accepted: 14 January 2012 © Springer-Verlag 2012 Abstract The bicuspid aortic valve (BAV) is associated with a high prevalence of calcific aortic valve disease (CAVD). Although abnormal hemodynamics has been pro- posed as a potential pathogenic contributor, the native BAV hemodynamic stresses remain largely unknown. Fluid- structure interaction models were designed to quantify the regional BAV leaflet wall-shear stress over the course of CAVD. Systolic flow and leaflet dynamics were computed in two-dimensional tricuspid aortic valve (TAV) and type- 1 BAV geometries with different degree of asymmetry (10 and 16% eccentricity) using an arbitrary Lagrangian–Euleri- an approach. Valvular performance and regional leaflet wall- shear stress were quantified in terms of valve effective orifice area (EOA), oscillatory shear index (OSI) and temporal shear magnitude (TSM). The dependence of those characteristics on the degree of leaflet calcification was also investigated. The models predicted an average reduction of 49% in BAV peak-systolic EOA relative to the TAV. Regardless of the anatomy, the leaflet wall-shear stress was side-specific and characterized by high magnitude and pulsatility on the ven- tricularis and low magnitude and oscillations on the fibrosa. While the TAV and non-coronary BAV leaflets shared sim- ilar shear stress characteristics, the base of the fused BAV Electronic supplementary material The online version of this article (doi:10.1007/s10237-012-0375-x) contains supplementary material, which is available to authorized users. S. Chandra · P. Sucosky (B ) Department of Aerospace and Mechanical Engineering, University of Notre Dame, 143 Multidisciplinary Research Building, Notre Dame, IN 46556-5637, USA e-mail: philippe.sucosky@nd.edu N. M. Rajamannan Division of Cardiology and Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA leaflet fibrosa exhibited strong abnormalities, which were modulated by the degree of calcification (6-fold, 10-fold and 16-fold TSM increase in the normal, mildly and severely calcified BAV, respectively, relative to the normal TAV). This study reveals the existence of major differences in wall-shear stress pulsatility and magnitude on TAV and BAV leaflets. Given the ability of abnormal fluid shear stress to trigger valvular inflammation, the results support the existence of a mechano-etiology of CAVD in the BAV. Keywords Bicuspid aortic valve · Calcification · Fluid-structure interaction modeling · Shear stress · Blood flow · Arbitrary Lagrangian–Eulerian method 1 Introduction The bicuspid aortic valve (BAV) is the most common con- genital cardiac anomaly and is present in 2–3% of the general population (Roberts 1970). While a normal tricuspid aortic valve (TAV) consists of three leaflets, a BAV is formed with only two. The most common type-1 anatomy consists of one small non-coronary leaflet, one larger leaflet resulting from the fusion of the right and left coronary leaflets, and a cen- tral fibrous raphe at the site of leaflet fusion (Sievers and Schmidtke 2007). Despite its limited prevalence, the BAV malformation has emerged as the first indication for surgi- cal valve replacement and as a major risk factor for calcific aortic valve disease (CAVD) (Lewin and Otto 2005; Roberts and Ko 2005; Ward 2000). This condition, which consists of the formation of calcific lesions on the leaflets, contributes to the obstruction of the left ventricular outflow and progressive heart failure (O’Brien 2006; Otto 1999). While CAVD has been historically linked to genetic and atherogenic origins, hemodynamics has emerged as 123