2,349 research outputs found
Reconstruction of stented coronary arteries from optical coherence tomography images: feasibility, validation, and repeatability of a segmentation method
No full textData of the paper "Chiastra et al. PLOS ONE 2017
Editorial: Image-based computational approaches for personalized cardiovascular medicine: improving clinical applicability and reliability through medical imaging and experimental data
No full textMedical Instruments & Bio-Inspired Technolog
Modelling of blood flow in coronary stented arteries.
No full textAtherosclerosis is the underlying cause of the majority of clinical cardiovascular events in the developed societies. Atherosclerotic lesions in coronary arteries are usually treated with percutaneous procedures which consist of placing wire mesh tubular structures, known as stents, into the diseased vessel. The main clinical complication is the in-stent restenosis (ISR) which is the local reduction in lumen size as a result of neointimal hyperplasia.
Mechanisms and causes of ISR are not fully understood; in addition to stent design, vascular injury caused by device implantation, hemodynamic alterations induced by its presence can be associated with neointimal hyperplasia. Therefore, the study of the fluid dynamics of stented coronary arteries is of extreme importance for a better comprehension of the mechanisms involved in ISR.
In the present chapter a review of the works on the hemodynamics of stented coronary arteries is given, focusing in particular on the computational fluid dynamics (CFD) models. Indeed, CFD allows the investigation of local hemodynamics at a level of detail not always accessible with experimental techniques, calculating fluid flow variables (e.g. wall shear stress) that can be used as indicators to predict sites where neointimal hyperplasia is excessive.
Application of CFD to idealized, population-specific and patient-specific coronary stented models is outlined as wel
Fluid-dynamics and biological features of unstable plaques: different shear stress for different plaques
No full textOn the necessity of modelling fluid–structure interaction for stented coronary arteries
No full textAlthough stenting is the most commonly performed procedure for the treatment of coronary atherosclerotic lesions, in-stent restenosis (ISR) remains one of the most serious clinical complications.
An important stimulus to ISR is the altered hemodynamics with abnormal shear stresses on endothelial cells generated by the stent presence.
Computational fluid dynamics is a valid tool for studying the local emodynamics of stented vessels, allowing the calculation of the wall shear stress (WSS), which is otherwise not directly possible to be measured in vivo. However, in these numerical simulations the arterial wall and the stent are assumed to be rigid and fixed, and then influencing the WSS and flow patterns. Therefore, the aim of this work is to perform fluid-structure interaction (FSI) analyses of a stented coronary artery in order to
understand the effects of the wall compliance on the hemodynamic quantities. Two different standard stents are considered: cobalt-chromium (CoCr) and polymeric (poly-L-lactide - PLLA). The results of the FSI and the corresponding rigid-wall models are compared, especially focusing on the analysis of the WSS distribution.
Results showed similar trends in terms of instantaneous and time-averaged WSS between compliant and rigid-wall cases. In particular, the difference between the percentage area exposed to time-averaged WSS lower than 0.4 Pa in the stented region was small for the CoCr (about 1.5%) and PLLA
(about 1.0%) cases.
The results indicate that, for idealized models of stented coronary artery, rigid-wall assumption for fluid dynamic simulations is adequate when the aim of the study is the analysis of near-wall quantities like WSS
Investigating the effect of drug release on in-stent restenosis: a hybrid continuum – agent-based modelling approach
No full textBackground and objective:
In-stent restenosis (ISR) following percutaneous coronary intervention with drug-eluting stent (DES) implantation remains an unresolved issue, with ISR rates up to 10%. The use of antiproliferative drugs on DESs has significantly reduced ISR. However, a complete knowledge of the mechanobiological processes underlying ISR is still lacking. Multiscale agent-based modelling frameworks, integrating continuum- and agent-based approaches, have recently emerged as promising tools to decipher the mechanobiological events driving ISR at different spatiotemporal scales. However, the integration of sophisticated drug models with an agent-based model (ABM) of ISR has been under-investigated. The aim of the present study was to develop a novel multiscale agent-based modelling framework of ISR following DES implantation.
Methods:
The framework consisted of two bi-directionally coupled modules, namely (i) a drug transport module, simulating drug transport through a continuum-based approach, and (ii) a tissue remodelling module, simulating cellular dynamics through an ABM. Receptor saturation (RS), defined as the fraction of target receptors saturated with drug, is used to mediate cellular activities in the ABM, since RS is widely regarded as a measure of drug efficacy. Three studies were performed to investigate different scenarios in terms of drug mass (DM), drug release profiles (RP), coupling schemes and idealized vs. patient-specific artery geometries.
Results:
The studies demonstrated the versatility of the framework and enabled exploration of the sensitivity to different settings, coupling modalities and geometries. As expected, changes in the DM, RP and coupling schemes illustrated a variation in RS over time, in turn affecting the ABM response. For example, combined small DM – fast RP led to similar ISR degrees as high DM – moderate RP (lumen area reduction of ∼13/17% vs. ∼30% without drug). The use of a patient-specific geometry with non-equally distributed struts resulted in a heterogeneous RS map, but did not remarkably impact the ABM response.
Conclusion:
The application to a patient-specific geometry highlights the potential of the framework to address complex realistic scenarios and lays the foundations for future research, including calibration and validation on patient datasets and the investigation of the effects of different plaque composition on the arterial response to DES
In silico biomechanical design of the metal frame of transcatheter aortic valves: multi-objective shape and cross-sectional size optimization
No full textTranscatheter aortic valve (TAV) implantation has become an established alternative to open-hearth surgical valve replacement.
Current research aims to improve the treatment safety and extend the range of eligible patients. In this regard, computational
modeling is a valuable tool to address these challenges, supporting the design phase by evaluating and optimizing the mechanical
performance of the implanted device. In this study, a computational framework is presented for the shape and cross-sectional size
optimization of TAV frames. Finite element analyses of TAV implantation were performed in idealized aortic root models with
and without calcifications, implementing a mesh-morphing procedure to parametrize the TAV frame. The pullout force magnitude,
peak maximum principal stress within the aortic wall, and contact pressure in the left ventricular outflow tract were defined
as objectives of the optimization problem to evaluate the device mechanical performance. Design of experiment coupled with
surrogate modeling was used to define an approximate relationship between the objectives and the TAV frame parameters.
Surrogate models were interrogated within a fixed design space and multi-objective design optimization was conducted. The
investigation of the parameter combinations within the design space allowed the successful identification of optimized TAV
frame geometries, suited to either a single or groups of aortic root anatomies. The optimization framework was efficient, resulting
in TAV frame designs with improvedmechanical performance, ultimately leading to enhanced procedural outcomes and reduced
costs associated with the device iterative development cycle
Patient-Specific Modeling of Stented Coronary Arteries Reconstructed from Optical Coherence Tomography: Towards a Widespread Clinical Use of Fluid Dynamics Analyses
No full textThe recent widespread application of optical coherence tomography (OCT) in interventional cardiology has improved patient-specific modeling of stented coronary arteries for the investigation of local hemodynamics. In this review, the workflow for the creation of fluid dynamics models of stented coronary arteries from OCT images is presented. The algorithms for lumen contours and stent strut detection from OCT as well as the reconstruction methods of stented geometries are discussed. Furthermore, the state of the art of studies that investigate the hemodynamics of OCT-based stented coronary artery geometries is reported. Although those studies analyzed few patient-specific cases, the application of the current reconstruction methods of stented geometries to large populations is possible. However, the improvement of these methods and the reduction of the time needed for the entire modeling process are crucial for a widespread clinical use of the OCT-based models and future in silico clinical trials
Fluid-structure interaction simulation of mechanical aortic valves: a narrative review exploring its role in total product life cycle
No full textOver the last years computer modelling and simulation has emerged as an effective tool to support the total product life cycle of cardiovascular devices, particularly in the device preclinical evaluation and post-market assessment. Computational modelling is particularly relevant for heart valve prostheses, which require an extensive assessment of their hydrodynamic performance and of risks of hemolysis and thromboembolic complications associated with mechanically-induced blood damage. These biomechanical aspects are typically evaluated through a fluid-structure interaction (FSI) approach, which enables valve fluid dynamics evaluation accounting for leaflets movement. In this context, the present narrative review focuses on the computational modelling of bileaflet mechanical aortic valves through FSI approach, aiming to foster and guide the use of simulations in device total product life cycle. The state of the art of FSI simulation of heart valve prostheses is reviewed to highlight the variety of modelling strategies adopted in the literature. Furthermore, the integration of FSI simulations in the total product life cycle of bileaflet aortic valves is discussed, with particular emphasis on the role of simulations in complementing and potentially replacing the experimental tests suggested by international standards. Simulations credibility assessment is also discussed in the light of recently published guidelines, thus paving the way for a broader inclusion of in silico evidence in regulatory submissions. The present narrative review highlights that FSI simulations can be successfully framed within the total product life cycle of bileaflet mechanical aortic valves, emphasizing that credible in silico models evaluating the performance of implantable devices can (at least) partially replace preclinical in vitro experimentation and support post-market biomechanical evaluation, leading to a reduction in both time and cost required for device development
Modeling the stent deployment in coronary arteries and coronary bifurcations
No full textMathematical models are well recognized and widely adopted tools to study stenting procedures. Nowadays, the increased computational power allows satisfying clinical needs more easily. The simulations of complex patient-specific cases including the implantation of multiple stents in coronary bifurcations or curved vessels have become a reality. Thanks to image-based methods, the peculiar anatomical features prior and after a stent insertion are detectable. The stress state exerted within the arterial wall of a coronary artery can be estimated by means of structural simulations. This review chapter aims to describe the most recent advances in this area with particular focus on stent deployment simulations in coronary bifurcations
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