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An understanding of aortic root biomechanics is pivotal for the optimisation of surgical procedures aimed at restoring normal root function in pathological subjects. For this purpose, computational models can provide important information, as long as they realistically capture the main anatomical and functional features of the aortic root. Here we present a novel and realistic finite element (FE) model of the physiological aortic root, which simulates its function during the entire cardiac cycle. Its geometry is based on magnetic resonance imaging (MRI) data obtained from 10 healthy subjects and accounts for the geometrical differences between the leaflet-sinus units. Morphological realism is combined with the modelling of the leaflets' non-linear and anisotropic mechanical response, in conjunction with dynamic boundary conditions. The results show that anatomical differences between leaflet-sinus units cause differences in stress and strain patterns. These are notably higher for the leaflets and smaller for the sinuses. For the maximum transvalvular pressure value, maximum principal stresses on the leaflets are equal to 759, 613 and 603 kPa on the non-coronary, right and left leaflet, respectively. For the maximum aortic pressure, average maximum principal stresses values are equal to 118, 112 and 111 kPa on the right, non-coronary and left sinus, respectively. Although liable of further improvements, the model seems to reliably reproduce the behaviour of the real aortic root: the model's leaflet stretches, leaflet coaptation lengths and commissure motions, as well as the timings of aortic leaflet closures and openings, all matched with the experimental findings reported in the literature.

OBJECTIVE: Bicuspid aortic valve disease is heterogeneous with respect to valve morphology and aortopathy risk. This study searched for early imaging predictors of aortopathy in patients with a bicuspid aortic valve with right-left coronary cusp fusion, the most common morphotype. METHODS: Time-resolved magnetic resonance imaging was performed in 36 subjects with nonstenotic, nonregurgitant bicuspid aortic valves and nondilated aortas and in 10 healthy controls with tricuspid aortic valves. Sinus dimensions (diameter, width, and height), ascending tract diameters, and wall strain were measured for each sinus/leaflet unit and corresponding ascending tract area to account for asymmetries. A novel parameter, "cusp opening angle," measured the degree of valve leaflet alignment to outflow axis in systole, quantifying cusp motility. Phase-contrast magnetic resonance imaging and computational fluid dynamic models assessed flow patterns. Aortic growth rate was estimated over a follow-up period ranging from 9 to 84 months. RESULTS: The expected restriction of bicuspid aortic valve opening (conjoint cusp opening angle, 62° ± 5° vs 76° ± 3° for nonfused leaflet and 75° ± 3° for tricuspid aortic valve cusps; P < .001) was confirmed, and the introduced parameter reproducibly quantified this phenomenon. Phase-contrast magnetic resonance imaging demonstrated systolic flow deflection toward the right, affecting the right anterolateral ascending wall. Computational models confirmed that restricted cusp motion alone is sufficient to cause the observed flow pattern. Ascending tract wall strain was not circumferentially homogeneous in bicuspid aortic valves. In multivariable analyses, the conjoint cusp opening angle independently predicted ascending aorta diameters and growth rate (P < .001). CONCLUSIONS: In the bicuspid aortic valve commonly defined as normofunctional by echocardiographic criteria, restricted systolic conjoint cusp motion causes flow deflection. The novel measurement introduced can quantify restricted cusp opening, possibly assuming prognostic importance.

Objective Congenital bicuspid aortic valves frequently cause aortic stenosis or regurgitation. Improved understanding of valve and root biomechanics is needed to achieve advancements in surgical repair techniques. By using imaging-derived data, finite element models were developed to quantify aortic valve and root biomechanical alterations associated with bicuspid geometry. Methods A dynamic 3-dimensional finite element model of the aortic root with a bicuspid aortic valve (type 1 right/left) was developed. The model's geometry was based on measurements from 2-dimensional magnetic resonance images acquired in 8 normotensive and otherwise healthy subjects with echocardiographically normal function of their bicuspid aortic valves. Numeric results were compared with those obtained from our previous model representing the normal root with a tricuspid aortic valve. The effects of raphe thickening on valve kinematics and stresses were also evaluated. Results During systole, the bicuspid valve opened asymmetrically compared with the normal valve, resulting in an elliptic shape of its orifice. During diastole, the conjoint cusp occluded a larger proportion of the valve orifice and leaflet bending was altered, although competence was preserved. The bicuspid model presented higher stresses compared with the tricuspid model, particularly in the central basal region of the conjoint cusp (+800%). The presence of a raphe partially reduced stress in this region but increased stress in the other cusp. Conclusions Aortic valve function is altered in clinically normally functioning bicuspid aortic valves. Bicuspid geometry per se entails abnormal leaflet stress. The stress location suggests that leaflet stress may play a role in tissue remodeling at the raphe region and in early leaflet degeneration.