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Patient-specific finite element (FE) models can assess the impact of mitral valve (MV) repair on the complex MV anatomy and function. However, FE excessive time requirements hamper their use for surgical planning; mass-spring models (MSMs) represent a more approximate approach but can provide almost real-time simulations. On this basis, we implemented MSMs of three healthy MVs from cardiac magnetic resonance (cMR) imaging to simulate the systolic MV closure, including the in vivo papillary muscles and annular kinematics, and the anisotropic and non-linear mechanical response of MV tissues. To test MSM reliability we compared the systolic peak configurations computed by MSMs and FE: mismatches by less than twice the in-plane cMR image resolution were detected over 75% of the leaflets' surface, independently of the MSM mesh refinement and of the specific MV anatomy. Data on MSMs time-efficiency and data from the comparison of MSMs vs. FE models suggest that MSM could represent a suitable trade-off between almost real-time simulations and reliability when computing MV systolic configuration, with the potential to be used in a clinical setting either as a support to the decisional process or as a virtual training tool., (Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.)

Numerical modeling can provide detailed and quantitative information on aortic root (AR) biomechanics, improving the understanding of AR complex pathophysiology and supporting the development of more effective clinical treatments. From this standpoint, fluid-structure interaction (FSI) models are currently the most exhaustive and potentially realistic computational tools. However, AR FSI modeling is extremely challenging and computationally expensive, due to the explicit simulation of coupled AR fluid dynamics and structural response, while accounting for complex morphological and mechanical features. We developed a novel FSI model of the physiological AR simulating its function throughout the entire cardiac cycle. The model includes an asymmetric MRI-based geometry, the description of aortic valve (AV) non-linear and anisotropic mechanical properties, and time-dependent blood pressures. By comparison to an equivalent finite element structural model, we quantified the balance between the extra information and the extra computational cost associated with the FSI approach. Tissue strains and stresses computed through the two approaches did not differ significantly. The FSI approach better captured the fast AV opening and closure, and its interplay with blood fluid dynamics within the Valsalva sinuses. It also reproduced the main features of in vivo AR fluid dynamics. However, the FSI simulation was ten times more computationally demanding than its structural counterpart. Hence, the FSI approach may be worth the extra computational cost when the tackled scenarios are strongly dependent on AV transient dynamics, Valsalva sinuses fluid dynamics in relation to coronary perfusion (e.g. sparing techniques), or AR fluid dynamic alterations (e.g. bicuspid AV)., (Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.)

The incomplete efficacy of current surgical repair procedures of the tricuspid valve (TV) demands a deeper comprehension of the physiological TV biomechanics. To this purpose, computational models can provide quantitative insight into TV biomechanical response and allow analysing the role of each TV substructure. We present here a three-dimensional finite element model of the tricuspid valve that takes into account most of its peculiar features. Experimental measurements were performed on human and porcine valves to obtain a more detailed TV anatomical framework. To overcome the complete lack of information on leaflets mechanical properties, we performed a sensitivity analysis on the parameters of the adopted non-linear hyperelastic constitutive model, hypothesizing three different parameter sets for three significant collagen fibre distributions. Results showed that leaflets' motion and maximum principal stress distribution were almost insensitive to the different material parameters considered. Highest stresses (about 100kPa) were located near the annulus of the anterior and septal leaflets, while the posterior leaflet experienced lower stresses (about 55kPa); stresses at the commissures were nearly zero. Conversely, changes in constitutive parameters deeply affected leaflets' strains magnitude, but not their overall pattern. Strains computed assuming that TV leaflets tissue are reinforced by a sparse and loosely arranged network of collagen fibres fitted best experimental data, thus suggesting that this may be the actual microstructure of TV leaflets. In a long-term perspective, this preliminary study aims at providing a starting point for the development of a predictive tool to quantitatively evaluate TV diseases and surgical repair procedures., (Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.)

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., ((c) 2009 IPEM. Published by Elsevier Ltd. All rights reserved.)

David and Yacoub sparing techniques are the most common procedures adopted for the surgical correction of aortic root aneurysms. These surgical procedures entail the replacement of the sinuses of Valsalva with a synthetic graft, inside which the cusps are re-suspended. Root replacement by a synthetic graft may result in altered valve behaviour both in terms of coaptation and stress distribution, thus leading to the failure of the correction. A finite element approach was used to investigate this phenomenon; four 3D models of the aortic root were developed to simulate the root in physiological, pathological and post-operative conditions after the two different surgical procedures. The physiological 3D geometrical model was developed on the basis of anatomical data obtained from echocardiographic images; it was then modified to obtain the pathological and post-operative models. The effectiveness of both techniques was assessed by comparison with the first two simulated conditions, in terms of stresses acting on the root, leaflet coaptation and interaction between leaflets and the graft during valve opening. Results show that both sparing techniques are able to restore aortic valve coaptation and to reduce stresses induced by the initial root dilation. Nonetheless, both techniques lead to altered leaflet kinematics, with more evident alterations after David repair.