scholarly journals Towards a multi-physics modelling framework for thrombolysis under the influence of blood flow

2015 ◽  
Vol 12 (113) ◽  
pp. 20150949 ◽  
Author(s):  
Andris Piebalgs ◽  
X. Yun Xu
Keyword(s):  
Blood Flow ◽  
Thrombolytic Therapy ◽  
Effective Means ◽  
Reaction Diffusion ◽  
Clot Lysis ◽  
Local Flow ◽  
Pressure Drops ◽  
Modelling Framework ◽  
Internal Bleeding ◽  
Diffusion Convection

Thrombolytic therapy is an effective means of treating thromboembolic diseases but can also give rise to life-threatening side effects. The infusion of a high drug concentration can provoke internal bleeding while an insufficient dose can lead to artery reocclusion. It is hoped that mathematical modelling of the process of clot lysis can lead to a better understanding and improvement of thrombolytic therapy. To this end, a multi-physics continuum model has been developed to simulate the dissolution of clot over time upon the addition of tissue plasminogen activator (tPA). The transport of tPA and other lytic proteins is modelled by a set of reaction–diffusion–convection equations, while blood flow is described by volume-averaged continuity and momentum equations. The clot is modelled as a fibrous porous medium with its properties being determined as a function of the fibrin fibre radius and voidage of the clot. A unique feature of the model is that it is capable of simulating the entire lytic process from the initial phase of lysis of an occlusive thrombus (diffusion-limited transport), the process of recanalization, to post-canalization thrombolysis under the influence of convective blood flow. The model has been used to examine the dissolution of a fully occluding clot in a simplified artery at different pressure drops. Our predicted lytic front velocities during the initial stage of lysis agree well with experimental and computational results reported by others. Following canalization, clot lysis patterns are strongly influenced by local flow patterns, which are symmetric at low pressure drops, but asymmetric at higher pressure drops, which give rise to larger recirculation regions and extended areas of intense drug accumulation.

Autoradiographic Evidence for Flow-Metabolism Uncoupling During Stimulation of the Nucleus Basalis of Meynert in the Conscious Rat

1997 ◽  
Vol 17 (6) ◽  
pp. 686-694 ◽  
Author(s):  
Elvire Vaucher ◽  
Josiane Borredon ◽  
Gilles Bonvento ◽  
Jacques Seylaz ◽  
Pierre Lacombe
Keyword(s):  
Blood Flow ◽  
Electrical Stimulation ◽  
Metabolic Activity ◽  
Nucleus Basalis ◽  
Nucleus Basalis Of Meynert ◽  
Conscious Rat ◽  
Local Flow ◽  
Cortical Blood Flow ◽  
Subcortical Regions ◽  
Stimulation Of

We earlier reported that electrical stimulation of the rat nucleus basalis of Meynert (NBM) induces large cerebral blood flow increases, particularly in frontal cortical areas but also in some subcortical regions. The present study was designed to address the issue of blood flow control exerted by NBM projections. To this aim, we have determined whether these flow increases were associated with proportionate changes in metabolic activity as evaluated by cerebral glucose utilization (CGU) strictly under the same experimental conditions in the conscious rat. An electrode was chronically implanted in a reactive site of the NBM as determined by laser-Doppler flowmetry (LDF) of the cortical circulation. One to two weeks later, while the cortical blood flow was monitored by LDF, we measured CGU using the [14C]2-deoxyglucose autoradiographic technique during unilateral electrical stimulation of the NBM, and analyzed the local flow-metabolism relationship. The large increases in cortical blood flow induced by NBM stimulation, exceeding 300% in various frontal areas, were associated with at most 24% increases in CGU (as compared with the control group) in one frontal area. By contrast, strong increases in CGU exceeding 150% were observed in subcortical regions ipsilateral to the stimulation, especially in extrapyramidal structures, associated with proportionate CBF changes. Thus, none of the blood flow changes observed in the cortex can be ascribed to an increased metabolic activity, whereas CBF and CGU were coupled in many subcortical areas. This result indicates that different mechanisms, which do not necessarily involve any metabolic factor, contribute to the regulation of the cerebral circulation at the cortical and subcortical level. Because the distribution of the uncoupling is coincident with that of cholinergic NBM projections directly reaching cortical microvessels, these data strongly support the hypothesis that NBM neurons are capable of exerting a neurogenic control of the cortical microcirculation.

scholarly journals COMPUTER MODELING OF STENT DEPLOYMENT AND PLAQUE PROGRESSION IN THE CORONARY ARTERIES

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Nenad Filipović ◽  
Velibor Isailović ◽  
Žarko Milosević ◽  
Dalibor Nikolić ◽  
Igor Saveljić ◽  
...  
Keyword(s):  
Blood Flow ◽  
Coronary Arteries ◽  
Mixed Finite Element ◽  
Flow Simulation ◽  
Reaction Diffusion ◽  
Navier Stokes ◽  
Stent Deployment ◽  
Specific Patient ◽  
Nonlinear Viscoelastic ◽  
Solute Dynamics

In this study stent deployment modeling with plaque formation and pro- gression for specific patient in the coronary arteries are described. State of the art method for the reported investigations of blood flow in the stented arteries is described. In the met- hod section, image segmentation method for arteries with stent is shortly described. Blood flow simulation is described with Navier-Stokes and continuity equation. Blood vessel tis- sue is modeled with nonlinear viscoelastic material properties. The coupling of fluid dynamics and solute dynamics at the endothelium was achieved by the Kedem-Katchalsky equations. The inflammatory process is modeled using three additional reaction-diffusion partial differential equations. Coupled method with mixed finite element and DPD (Dissi- pative Particle Dynamics) method is presented. In the results section, the examples with rigid and deformable arterial wall with stented and unstented arteries are presented. Effecti- ve stress analysis results for stent deployment have been shown. It can be seen that stent reduces wall shear stress significantly after deployment which is caused by opening the artery and reducing the narrowing. Some results for stent deployment model obtained with solver developed under PAK software package. These computer models can make better understanding and preparation of the surgeons for stent deployment in everyday clinical practice.

scholarly journals Existence of reaction-diffusion-convection waves in unbounded strips

2005 ◽  
Vol 2005 (2) ◽  
pp. 169-193 ◽  
Author(s):  
M. Belk ◽  
B. Kazmierczak ◽  
V. Volpert
Keyword(s):  
Implicit Function Theorem ◽  
Unbounded Domains ◽  
Reaction Diffusion ◽  
Fredholm Property ◽  
Implicit Function ◽  
Solvability Conditions ◽  
All Speeds ◽  
Diffusion Convection ◽  
Rayleigh Numbers ◽  
Property Index

Existence of reaction-diffusion-convection waves in unbounded strips is proved in the case of small Rayleigh numbers. In the bistable case the wave is unique, in the monostable case they exist for all speeds greater than the minimal one. The proof uses the implicit function theorem. Its application is based on the Fredholm property, index, and solvability conditions for elliptic problems in unbounded domains.

Abstract 566: Experimental Investigation of Blood Flow in the Femoral Bifurcated Artery

2015 ◽  
Vol 35 (suppl_1) ◽  
Author(s):  
Azadeh Lotfi ◽  
Zachary Lawler ◽  
Omar Jan ◽  
Tracie Barber ◽  
Anne Simmons
Keyword(s):  
Blood Flow ◽  
Additional Treatment ◽  
Arterial Stenosis ◽  
Patient Specific ◽  
Local Flow ◽  
Micro Piv ◽  
Stent Restenosis ◽  
Tibial Arteries ◽  
Hemodynamic Disturbance ◽  
Good Patency

Stent implantation is one of the most widely used interventional treatments for arterial stenosis which occurs predominantly due to atherosclerosis. Although stent placement can ensure very good patency of the lumen, stent-induced hemodynamic disturbance, which can lead to further stenosis, still remains a common clinical complication. This study investigates the degree of hemodynamic disturbance induced by stenting an idealized bifurcated popliteal artery, which branches into the anterior and posterior tibial arteries, and is known as a site prone to atherosclerosis. Both stent-free and stented bifurcated arteries were examined, and the local flow patterns analysed for the comparative disturbance through the use of Micro Particle Image Velocity (micro-PIV) system. A life-size model of the artery was reconstructed using dimensions obtained from a patient specific MRI scan. The experiments were conducted under steady flow conditions, and the flow rates across the bifurcation were visualized and measured using the micro-PIV system. It was shown that hemodynamic disturbances induced by the blood flow over the stent can further disrupt the arterial wall downstream of the stent causing further downstream vascular damage in addition to the in-stent restenosis. This downstream vascular disruption may require additional treatment depending on the type and severity of the damage. The results also support the hypothesis that links certain flow dynamic behaviour with the development of early intimal thickening, as the near wall low fluid momentum regions are found at locations where thickening was localized in bifurcated arteries in clinical studies.

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