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Percentage of cell area with a paclitaxel concentration of at least 0.5 × 10 −3 mol m −3 for stents 1, 6 and 7 when considering the percentage area coverage of stent 7 as the maximum possible coverage at each time point. Measurements shown are the averaged values obtained from 20 to 50 % arterial wall thickness at time intervals of 1, 2 and 4.5 h
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The emergence of drug-eluting stents (DES) as a viable replacement for bare metal stenting has led to a significant decrease in the incidence of clinical restenosis. This is due to the transport of anti-restenotic drugs from within the polymer coating of a DES into the artery wall which arrests the cell cycle before restenosis can occur. The effica...
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Context 1
... 6 shows the performance of stents 1 and 7 normalised to performance of stent 7. Figure 7 describes the percentage of the maximum attain- able therapeutic concentration coverage for each of the stent designs at the early (1 h), middle (2 h) and late (4.5 h) time points. Figure 8 presents the results of the average area recieving a therapeutic level of drug concentration for the compressed stent 1, the most uncompressed stent 7 and the best perform- ing variable compression design, stent 6, at the early, middle and late time points. ...
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... stent 6 offers the most marked improvement in terms of drug coverage, it is compared individually to both bench- marks in Fig. 8. It is evident from this figure that compression of the artery wall affects the early delivery of drugs into the arterial tissue. However, the drug distributions converge at the later time points. It is important to state here that the results presented in Fig. 8 include a stent model with a uni- form radial compression equal to half ...
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... in terms of drug coverage, it is compared individually to both bench- marks in Fig. 8. It is evident from this figure that compression of the artery wall affects the early delivery of drugs into the arterial tissue. However, the drug distributions converge at the later time points. It is important to state here that the results presented in Fig. 8 include a stent model with a uni- form radial compression equal to half strut embedment of the artery wall thickness (stent 1), a stent with no compressive struts (stent 7) and a stent with a combination of both (stent 6). Literature suggests that compression values of the medial artery layers after stenting could be as high as 50-70 ...
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Coronary artery stenting is the treatment of choice for patients requiring coronary angioplasty. We describe the major advancements with this technology. There have been significant developments in the design of stents and adjunctive medical therapies. Newer-generation drug-eluting stents (DES) have almost negligible restenosis rates and, when comb...
Aims
The incidence and temporal change in coronary evagination (CE) after first-generation drug-eluting stent implantation is well established, whereas that after biodegradable polymer sirolimus-eluting stent (BP-SES) implantation has not yet been evaluated. The aim of this study is to assess the incidence and natural history of CE after BP-SES imp...
Citations
... Owing to the asymptomatic nature of the Atherosclerosis, it is not evident until myocardial infarction happens that the patient realizes he has CAD. As a matter of fact, the decrease in the coronary artery diameter and the subsequent oxygen shortage are the main reasons for a heart attack [1]. A myriad of invasive and non-invasive methods have been developed for the treatment of coronary artery stenosis, yet stent placement has been proven successful even for cases with more than 60% blockage [2]. ...
... Coagulant factors are activated by a wound which occurs during the stent inflation, consequently bringing about in-stent restenosis. Some researchers have suggested that the stent platform should be covered by an anti-restenotic drug which can entail anti-thrombogenic, immunosuppressive, anti-proliferative, antiinflammatory and anticoagulant effects [1,3,4]. The reason why DES is employed more than Bare Metal Stents (BMS) is the former's ability to reduce in-stent restenosis by approximately 12%. ...
... The reason why DES is employed more than Bare Metal Stents (BMS) is the former's ability to reduce in-stent restenosis by approximately 12%. The drug prevents Smooth Muscle Cells (SMC) migration by arresting the cell cycle [1,5,6]. Although several researchers give DES priority over BMS [6][7][8][9], others have questioned the long-term safety of DES [10][11][12]. ...
Article info: Abstract Arterial drug concentration distribution determines local toxicity. The safety issues dealing with Drug-Eluting Stents reveal the needs for investigation on the effective factors contributing to fluctuations in arterial drug uptake. The current study focuses on the importance of hypertension as an important and controversial risk factor among researchers on the efficacy of Heparin-Eluting Stents. For this purpose, the effect of blood pressure is systematically investigated in certain cardiac cycle modes. A comprehensive study is conducted on two classes, pulsatile (time-dependent), to have a more realistic simulation, and non-pulsatile (time-independent) blood flow, each one in four modes. The governing equations applied to drug release dynamics are obtained based on porous media theory. The equations are solved numerically using the Finite Volume Method. Results reveal that there is a significant difference when the plasma flow considered, and when it is neglected (regardless of time dependency). Moreover, the concentration level is more decreased in pulsatile blood flow rather than the non-pulsatile blood flow, although the penetration depth for pressure and concentration are nearly 20% and 5% of the wall thickness, respectively. In other words, the mass experienced by the arterial wall is lower in pulsatile blood flow in comparison to non-pulsatile blood flow. As a consequence, the risk of toxicity is declined as the blood pressure increases. Also, it can be seen that the polymer is diffusion-dominated so that no significant changes in the release characteristics are observed in the presence of the plasma filtration.
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Nowadays the use of Drug Eluting Stents (DESs) is considered as a successful method for the treatment of coronary artery blockage. In order to study the impact of the presence of topcoat on heparin-eluting stents efficacy, two designs (with and without drug free topcoat) have been compared. Moreover, here the importance of the plasma flow as a controversial topic among researchers has been studied. In order to have more realistic working heart, plasma flow is considered a pulsatile function. Also, the injury of the coronary artery penetrated to a depth of media layer during angioplasty. Volume-averaged porous media equations which describe the drug release dynamics are employed and solved numerically by Finite Volume Method (FVM). Results put the amount of strut penetration in the forefront of importance. Local drug pharmacokinetics experiences significant changes by strut passing through endothelium, intima and Internal Elastic Lamina (IEL) and being contiguous with media layer. Although the plasma flow decreases/increases the amount of concentration level and subsequently decreases/increases the amount of drug mass in media/adventitia layer, the results show that these effects are not significant. Among other findings, it is notable that the presence of topcoat has a negligible effect on the release characteristics.
... [2] . 700000 [3] . ...
Nowadays the use of Drug Eluting Stents (DESs) is considered as a successful method for the treatment of coronary artery blockage. In order to study the impact of the presence of topcoat on heparin-eluting stents efficacy, two designs (with and without drug free topcoat) have been compared. Moreover, here the importance of the plasma flow as a controversial topic among researchers has been studied. In order to have more realistic working heart, plasma flow is considered a pulsatile function. Also, the injury of the coronary artery penetrated to a depth of media layer during angioplasty. Volume-averaged porous media equations which describe the drug release dynamics are employed and solved numerically by Finite Volume Method (FVM). Results put the amount of strut penetration in the forefront of importance. Local drug pharmacokinetics experiences significant changes by strut passing through endothelium, intima and Internal Elastic Lamina (IEL) and being contiguous with media layer. Although the plasma flow decreases/increases the amount of concentration level and subsequently decreases/increases the amount of drug mass in media/adventitia layer, the results show that these effects are not significant. Among other findings, it is notable that the presence of topcoat has a negligible effect on the release characteristics.
We propose a Navier-Stokes-Biot fluid-structure interaction (FSI) model to study the in-4 teraction between an incompressible, viscous Newtonian fluid and a poroelastic medium with permeability 5 depending on the volumetric change of pore size. The FSI model is coupled to a set of advection-reaction-6 diffusion equations defined on moving domains, to study the interaction between the blood flow, a stented 7 coronary artery, and time-dependent pharmacokinetics of drug absorption in drug-eluting stents. A mono-8 lithic approach is used to implement the proposed problem numerically within the context of finite element 9 discretization. Nitsche's method is employed to enforce one of the coupling conditions at the moving fluid-10 poroelastic structure interface. Stability analysis is presented, providing conditions on the Nitsche's penalty 11 parameter under which the scheme is unconditionally stable. Using 3D simulations, five geometrically 12 different metallic stent platforms were considered with two different pharmacokinetics to show how stent 13 geometry and the type of coating impact the biomechanical environment, the local hemodynamics, and the 14 concentration of the pharmacological agents within the vascular wall and artery lumen. It is found that stent 15 implantation changes the permeability properties of the arterial wall, as well as local hemodynamics, which 16 may be responsible for the so-called edge effect, i.e., sub-optimal reduction in re-stenosis rates near the edges 17 of drug-eluting stents. To the best of our knowledge, this is the first study of drug-eluting stents that takes 18 into account fluid-poroelastic structure interaction with permeability depending on the volumetric change 19 of the pore size, coupled to an advection-reaction-diffusion model defined on moving domains. 20
In-stent restenosis is one of the important disadvantages of Drug Eluting Stents (DESs). Awareness of how polymer coated drug is distributed by these devices provides valuable information about its efficacy. Porous media theory has been employed in the modeling of drug polymer and the injured arterial wall is composed of media and adventitia. The established coupled PDEs describing local pharmacokinets of heparin have been solved numerically by finite volume method. Two approaches, single phase and two phases models have been chosen for coating and the effect of local mass non- equilibrium dynamics in the coating on drug distribution has been evaluated by allocating three magnitude for solid-liquid transfer time characteristic. Moreover, the effect of lost drug by vasavasorum and microcapilaries has been considered as well as cell metabolism. The results show a significant change in drug concentration distribution in the presence of phase change occurrence. Reducing in solid-liquid transfer time characteristic is associated with drastic reduction in both drug egression from polymer and washout from adventitia and has a pleasant effect. Also, consumption of drug decreases concentration level in the wall dramatically, especially in adventitia.
Cell alignment plays a critical role in various cell behaviors including cytoskeleton reorganization, membrane protein relocation, nucleus gene expression, and ECM remodeling. Cell alignment is also known to exert significant effects on tissue regeneration (e.g., neuron) and modulate mechanical properties of tissues including skeleton, cardiac muscle and tendon. Therefore, it is essential to engineer cell alignment in vitro for biomechanics, cell biology, tissue engineering and regenerative medicine applications. With advances in nano- and micro-scale technologies, a variety of approaches have been developed to engineer cell alignment in vitro, including mechanical loading, topographical patterning, and surface chemical treatment. In this review, we first present alignments of various cell types and their functionality in different tissues in vivo including muscle and nerve tissues. Then, we provide an overview of recent approaches for engineering cell alignment in vitro. Finally, concluding remarks and perspectives are addressed for future improvement of engineering cell alignment.
