Entity

Time filter

Source Type


Auricchio F.,University of Pavia | Auricchio F.,CNR Institute for Applied Mathematics and Information Technologies | Auricchio F.,Centro Of Simulazione Numerica Avanzata Cesna Iuss | Conti M.,University of Pavia | And 2 more authors.
Computer Methods in Biomechanics and Biomedical Engineering | Year: 2011

Sinotubular junction dilation is one of the most frequent pathologies associated with aortic root incompetence. Hence, we create a finite element model considering the whole root geometry; then, starting from healthy valve models and referring to measures of pathological valves reported in the literature, we reproduce the pathology of the aortic root by imposing appropriate boundary conditions. After evaluating the virtual pathological process, we are able to correlate dimensions of non-functional valves with dimensions of competent valves. Such a relation could be helpful in recreating a competent aortic root and, in particular, it could provide useful information in advance in aortic valve sparing surgery. © 2011 Taylor & Francis. Source


Auricchio F.,University of Pavia | Auricchio F.,CNR Institute for Applied Mathematics and Information Technologies | Auricchio F.,Centro Of Simulazione Numerica Avanzata Cesna Iuss | Conti M.,University of Pavia | And 3 more authors.
Computer Methods in Biomechanics and Biomedical Engineering | Year: 2014

Until recently, heart valve failure has been treated adopting open-heart surgical techniques and cardiopulmonary bypass. However, over the last decade, minimally invasive procedures have been developed to avoid high risks associated with conventional open-chest valve replacement techniques. Such a recent and innovative procedure represents an optimal field for conducting investigations through virtual computer-based simulations: in fact, nowadays, computational engineering is widely used to unravel many problems in the biomedical field of cardiovascular mechanics and specifically, minimally invasive procedures. In this study, we investigate a balloon-expandable valve and we propose a novel simulation strategy to reproduce its implantation using computational tools. Focusing on the Edwards SAPIEN valve in particular, we simulate both stent crimping and deployment through balloon inflation. The developed procedure enabled us to obtain the entire prosthetic device virtually implanted in a patient-specific aortic root created by processing medical images; hence, it allows evaluation of postoperative prosthesis performance depending on different factors (e.g. device size and prosthesis placement site). Notably, prosthesis positioning in two different cases (distal and proximal) has been examined in terms of coaptation area, average stress on valve leaflets as well as impact on the aortic root wall. The coaptation area is significantly affected by the positioning strategy (- 24%, moving from the proximal to distal) as well as the stress distribution on both the leaflets (+13.5%, from proximal to distal) and the aortic wall (- 22%, from proximal to distal). No remarkable variations of the stress state on the stent struts have been obtained in the two investigated cases. © 2013 Taylor & Francis. Source


Auricchio F.,University of Pavia | Auricchio F.,CNR Institute for Applied Mathematics and Information Technologies | Auricchio F.,Centro Of Simulazione Numerica Avanzata Cesna Iuss | Conti M.,University of Pavia | And 4 more authors.
Computer Methods in Biomechanics and Biomedical Engineering | Year: 2014

In some cases of aortic valve leaflet disease, the implant of a stentless biological prosthesis represents an excellent option for aortic valve replacement (AVR). In particular, if compared with the implant of mechanical valves, it provides a more physiological haemodynamic performance and a reduced thrombogeneticity, avoiding the use of anticoagulants. The clinical outcomes of AVR are strongly dependent on an appropriate choice of both prosthesis size and replacement technique, which is, at present, strictly related to surgeon's experience and skill. This represents the motivation for patient-specific finite element analysis able to virtually reproduce stentless valve implantation. With the aim of performing reliable patient-specific simulations, we remark that, on the one hand, it is not well established in the literature whether bioprosthetic leaflet tissue is isotropic or anisotropic; on the other hand, it is of fundamental importance to incorporate an accurate material model to realistically predict post-operative performance. Within this framework, using a novel computational methodology to simulate stentless valve implantation, we test the impact of using different material models on both the stress pattern and post-operative coaptation parameters (i.e. coaptation area, length and height). As expected, the simulation results suggest that the material properties of the valve leaflets affect significantly the post-operative prosthesis performance. © 2014 © 2012 Taylor & Francis. Source


Auricchio F.,University of Pavia | Auricchio F.,CNR Institute for Applied Mathematics and Information Technologies | Brezzi F.,Centro Of Simulazione Numerica Avanzata Cesna Iuss | Brezzi F.,CNR Institute for Applied Mathematics and Information Technologies | And 5 more authors.
Computer Methods in Applied Mechanics and Engineering | Year: 2015

In the present paper we study a finite element method for the incompressible Stokes problem with a boundary immersed in the domain on which essential constraints are imposed. Such type of methods may be useful to tackle problems with complex geometries, interfaces such as multiphase flow and fluid-structure interaction. The method we study herein consists in locally refining elements crossed by the immersed boundary such that newly added elements, called subelements, fit the immersed boundary. In this sense, this approach is of a fitted type, but with an original mesh given independently of the location of the immersed boundary. We use such a subdivision technique to build a new finite element basis, which enables us to represent accurately the immersed boundary and to impose strongly Dirichlet boundary conditions on it. However, the subdivision process may imply the generation of anisotropic elements, which, for the incompressible Stokes problem, may result in the loss of inf-sup stability even for well-known stable element schemes. We therefore use a finite element approximation, which appears stable also on anisotropic elements. We perform numerical tests to check stability of the chosen finite elements. Several numerical experiments are finally presented to illustrate the capabilities of the method. The method is presented for two-dimensional problems. © 2014 Elsevier B.V.. Source


Auricchio F.,University of Pavia | Auricchio F.,CNR Institute for Applied Mathematics and Information Technologies | Boffi D.,Centro Of Simulazione Numerica Avanzata Cesna Iuss | Boffi D.,CNR Institute for Applied Mathematics and Information Technologies | And 8 more authors.
Computers and Mathematics with Applications | Year: 2014

In the present paper we consider a 1D Poisson model characterized by the presence of an interface, where a transmission condition arises due to jumps of the coefficients. We aim at studying finite element methods with meshes not fitting such an interface. It is well known that when the mesh does not fit the material discontinuities the resulting scheme provides in general lower order accurate solutions. We focus on so-called embedded approaches, frequently adopted to treat fluid-structure interaction problems, with the aim of recovering higher order of approximation also in presence of non fitting meshes; we implement several methods inspired by: the Immersed Boundary method, the Fictitious Domain method, and the Extended Finite Element method. In particular, we present four formulations in a comprehensive and unified format, proposing several numerical tests and discussing their performance. Moreover, we point out issues that may be encountered in the generalization to higher dimensions and we comment on possible solutions. © 2014 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations