1,720,958 research outputs found
Numerical Analysis of the Bicaval Transcatheter System for the Treatment of Severe Tricuspid Regurgitation
No full textTricuspid regurgitation (TR), also called tricuspid insufficiency, is a relatively common valvular diseases that can result from structural abnormalities of any anatomic part of the tricuspid valve apparatus. While trivial and moderate TR are compensated by the right atrial compliance, severe regurgitation conditions can result in congestive heart failure and hemodynamic impairment. We aim to model the non-invasive caval implantation treatment of TR seen in one patient using the novel bicaval transcatheter system (TricValve). Geometric models of TricValve devices were obtained from manufacturing guidelines and photography of devices. Then, the TricValve was simulated in a patient-specific model to assess the device structural performance. Computational fluid dynamics was also used to evaluate the pre- and post-TricValve haemodynamic. Ultimately, this study has the potential to better understanding the biomechanical performance of the novel TricValve system and may improve the way we design the next-generation of transcatheter therapies for severe TR
Evaluating the accuracy of 3D printing and finite element analysis in transcatheter aortic valveimplantation: a comparative study against post-TAVI CT imaging
No full textTranscatheter aortic valve implantation (TAVI) is now the standard treatment for aortic stenosis, offering a less invasive alternative to surgery. While 3D printing and finite element analysis (FEA) show promise for pre-procedural planning, their accuracy in predicting post-TAVI device geometry remains unclear. This study evaluates the agreement between patient-specific FEA models, 3D-printed phantoms, and post-TAVI CT imaging in replicating implanted device geometry. Ten patients treated with the SAPIEN 3 Ultra (S3) device were analysed using pre- and post-TAVI CT scans. Both FEA simulations and 3D-printed models were assessed for stent deformation and anatomical fit. Agreement was quantified using statistical tools including concordance correlation coefficient (CCC), intraclass correlation coefficient (ICC), and Bland-Altman plots. FEA showed stronger agreement with post-TAVI CT (ICC = 0.614, CCC = 0.479) than 3D printing (ICC = 0.363, CCC = 0.165), which had higher variability. While FEA closely approximated device expansion at the annular level, both methods had limitations due to material and computational assumptions. The study supports the greater reliability of FEA in pre-procedural planning, highlighting the need for further validation and standardisation
Biomechanical performance of the Bicaval Transcatheter System for the treatment of severe tricuspid regurgitation
Full text linkIntroduction: Tricuspid regurgitation (TR) is a relatively common valvular disease, which can result from structural abnormalities of any anatomic part of the tricuspid valve. Severe TR is linked to congestive heart failure and hemodynamic impairment, resulting in high mortality when repaired by elective surgery. This study was undertaken to quantify the structural and hemodynamic performance of the novel Transcatheter Bicaval Valves System (TricValve) percutaneously implanted in the superior vena cava (SVC) and inferior vena cava (IVC) of two patients with severe TR and venous congestion. Methods: After developing the SVC and IVC device models, the contact pressure exerted on the vena cava wall was obtained by computational analysis. Both smoothed-particle hydrodynamics (SPH) and computational fluid dynamics were carried out to quantify caval reflux in the right atrium and the pressure field of pre- and post-TricValve scenarios, respectively. Results: Analysis of contact pressure highlighted the main anchoring area of the SVC device occurring near the SVC device belly, while the IVC device exerted pronounced forces in the device’s proximal and distal parts. SPH-related flow velocities revealed the absence of caval reflux, and a decrease in time-averaged pressure was observed near the SVC and IVC after TricValve implantation. Discussion: Findings demonstrated the potential of computational tools for enhancing our understanding of the biomechanical performance of structural tricuspid valve interventions and improving the way we design next-generation transcatheter therapies to treat the tricuspid valve with heterotopic caval valve implantation
A custom-built planar biaxial system for soft tissue material testing
Full text linkAccurate material characterization of soft tissues is crucial for understanding the physiopathology of cardiovascular diseases. However, commercial biaxial testing systems are expensive, prompting the need for affordable custom solutions. This study aimed to develop a low-cost custom biaxial system capable of accurately characterizing the mechanical behavior of soft tissues. The biaxial system was constructed using 3D printing technology and non-captive linear actuators for precise displacement control. A real-time marker tracking system was implemented to estimate dis-placements without the need for costly hardware. The system's performance was evaluated through tests on a calibration spring and frozen porcine aorta samples. The linear actuators demonstrated excellent response to user position input after motor tuning, showing no discrepancies between commands and actual positions. The experimental testing of the calibration spring showed good agreement with the analytical solution, validating the system's ability to accurately test materials. Testing on porcine aorta samples revealed stress–strain responses consistent with existing literature, accounting for potential variations due to tissue preservation and regional material property heterogeneity. Overall, this custom biaxial system demonstrates promising performance in accurately assessing the mechanical behavior of soft tissues, providing researchers with a valuable tool for cardiovascular disease research and tissue engineering applications
Improving Understanding of Cardiovascular Structures: A Workflow to Visualize Patient-Specific Simulations in Virtual Reality
No full textComputational simulations have contributed to improve the understanding of pathophysiology and treatment planning for cardiovascular diseases highlighting the possibilities of the Virtual Human Twin (VHT). Access to simulations’ results can, however, be a time- and resource-consuming process, which limits the access to modelling to experts only. Virtual Reality (VR) has been widely recognized for enriching the visualization process and lowering the barrier to access multi-source data. To date, there is not a comprehensive solution to integrate computational results into a VR platform for patient-specific simulations in the cardiovascular field. To overcome this challenge, we developed a semi-automated workflow designed to convert efficiently data of various sources into formats compatible with our in-house VR platform designed for patient-specific models (i.e. VheaRts). To demonstrate feasibility and effectiveness of our proposed methodology, we showcase the visualization of computational fluid dynamics (CFD) and fluid-structure interaction (FSI) simulations of three patient-specific simulations. Through our VR-based visualization approach, the immersive experience of an anatomical model was enriched with detailed information about the dynamic flow patterns, pressure distributions and stress maps. The presented project will contribute to lower the barriers of access to computational results and in turn enhance the translation of the VHT
Shape of the mitral annulus in normal individuals and dilated cardiomyopathies: computational modeling insights into leaflet stress distribution
Full text linkIntroduction: The mitral valve annulus naturally adopts a saddle shape in systole, likely concentrating systolic stress on the commissures where fibrous trigones are located. This study hypothesized that in patients with dilated cardiomyopathies, where the annulus is large and planar, the stress would be redirected. Methods: Computational modeling was employed to compare the stress distribution in saddle-shaped mitral valves (n.10 patients) with planar annuli seen in dilated cardiomyopathy (n.10 patients) using kinematics of the mitral valve annulus from systole to diastole extrapolated from computed tomography angiography. Results: Simulations revealed high stress near the anterolateral and posteromedial commissures in normal valves, in contrast to high leaflet stress in planar annuli. Significant differences in stress distribution were observed near the anterolateral (S = 0.427 ± 0.053 MPa in normal valves vs S = 0.211 ± 0.123 MPa in diseased valves, p < 0.001) and posterolateral commissures (S = 0.340 ± 0.008 MPa in normal valves vs S = 0.208 ± 0.060 MPa in diseased valves, p < 0.001). Additionally, mitral annulus disjunction was present in healthy patients but absent in those with annulus planarity due to dilated cardiomyopathy. Discussion: This study suggests that while the saddle-shaped annulus focuses leaflet stress on commissures, planar annuli distribute systolic stress over leaflet surfaces. This may trigger embryonic pathways and alter mitral leaflet collagen content, ultimately leading to valve remodeling. Identifying patients with early annular planarity prior to substantial leaflet remodeling may provide early treatments to prevent increasing mitral regurgitation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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