1,721,158 research outputs found
Editorial: Image-based computational approaches for personalized cardiovascular medicine: improving clinical applicability and reliability through medical imaging and experimental data
Full text linkMedical Instruments & Bio-Inspired Technolog
Fluid-dynamics and biological features of unstable plaques: different shear stress for different plaques
Full text linkModelling 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
Investigating the effect of drug release on in-stent restenosis: A hybrid continuum – agent-based modelling approach
Full text linkBackground 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
Haemodynamic assessment of surgical aortic valves: a fluid-structure interaction perspective
No full text
Virtual bench testing to study coronary bifurcation stenting
Full text linkVirtual bench testing is a numerical methodology which has been applied to the study of coronary interventions. It exploits the amazing growth of computer performance for scientific calculation and makes it possible to simulate very different and complex multiphysics environments and processes, including coronary bifurcation stenting. The quality of prediction from any computer model is very sensitive to the quality of the input data and assumptions. This also holds true in stent virtual bench testing. This paper reviews the state of the art in the field of bifurcation stenting modelling and identifies the current advantages and limitations of this methodology
Investigating the effect of drug release on in-stent restenosis: a hybrid continuum – agent-based modelling approach
Full text linkBackground 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
Coronary stenting: from optical coherence tomography to fluid dynamic simulations
No full textThe presence of stents within coronary arteries
alters the hemodynamic condition. Computational fluid dynamics (CFD) simulations offer the possibility to study local
hemodynamics of a stented artery to identify the stimuli of instent
restenosis, i.e. the local reduction of lumen size after stent
deployment. The results of CFD simulations are more accurate when the analyses are performed with a model reproducing real
in vivo conditions. For this purpose, optical coherence tomography (OCT) is a promising tool to reconstruct 3D
geometries of stented coronary arteries, due to its higher resolution compared to the other imaging techniques.
In the present work a reconstruction method of stented coronary bifurcation geometrical models starting from OCT
images was developed. An OCT exam performed in a stented coronary bifurcation silicone sample was considered. The vessel
and the stent were reconstructed separately, and then they were merged together. Vessel reconstruction was performed with a semi-automatic process: the main branch was reconstructed by fitting the lumen boundary with ellipses and subsequently by creating a mesh of the vessel; the side branch was created like an ideal cylinder. Stent struts were identified with an automatic
algorithm; then, the stent was reconstructed in a manual way. After the creation of the 3D geometry of the bifurcation, a transient fluid dynamic simulation was carried out. CFD results
showed that the highest risk of restenosis is located in the region near the bifurcation
An agent-based model of cardiac allograft vasculopathy: toward a better understanding of chronic rejection dynamics
Full text linkCardiac allograft vasculopathy (CAV) is a coronary artery disease affecting 50% of heart transplant (HTx) recipients, and it is the major cause of graft loss. CAV is driven by the interplay of immunological and non-immunological factors, setting off a cascade of events promoting endothelial damage and vascular dysfunction. The etiology and evolution of tissue pathology are largely unknown, making disease management challenging. So far, in vivo models, mostly mouse-based, have been widely used to study CAV, but they are resource-consuming, pose many ethical issues, and allow limited investigation of time points and important biomechanical measurements. Recently, agent-based models (ABMs) proved to be valid computational tools for deciphering mechanobiological mechanisms driving vascular adaptation processes at the cell/tissue level, augmenting cost-effective in vivo lab-based experiments, at the same time guaranteeing richness in observation time points and low consumption of resources. We hypothesize that integrating ABMs with lab-based experiments can aid in vivo research by overcoming those limitations. Accordingly, this work proposes a bidimensional ABM of CAV in a mouse coronary artery cross-section, simulating the arterial wall response to two distinct stimuli: inflammation and hemodynamic disturbances, the latter considered in terms of low wall shear stress (WSS). These stimuli trigger i) inflammatory cell activation and ii) exacerbated vascular cell activities. Moreover, an extensive analysis was performed to investigate the ABM sensitivity to the driving parameters and inputs and gain insights into the ABM working mechanisms. The ABM was able to effectively replicate a 4-week CAV initiation and progression, characterized by lumen area decrease due to progressive intimal thickening in regions exposed to high inflammation and low WSS. Moreover, the parameter and input sensitivity analysis highlighted that the inflammatory-related events rather than the WSS predominantly drive CAV, corroborating the inflammatory nature of the vasculopathy. The proof-of-concept model proposed herein demonstrated its potential in deepening the pathology knowledge and supporting the in vivo analysis of CAV
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