Computational Fluid Dynamics Analysis of Blood Flow Through Stented Arteries

2013 ◽  
Author(s):  
Shafiullah Mohammad ◽  
Pradip Majumdar
Keyword(s):  
Blood Flow ◽  
Femoral Artery ◽  
Cardiac Cycle ◽  
Stokes Equations ◽  
Interventional Procedure ◽  
Wall Thickening ◽  
Velocity Waveform ◽  
Arterial Lumen ◽  
Computational Fluid Dynamics Analysis ◽  
Intravascular Stents

Atherosclerosis is a vascular disease that reduces arterial lumen size through plaque deposition and arterial wall thickening. The pathological complications of atherosclerosis, namely heart disease and stroke, remain the leading cause of mortality in the world. The most common interventional procedure against atherosclerosis involves the placement of an intravascular stent. Intravascular stents are small tube like structures placed into Stenotic arteries to restore the blood flow. In this study CFD analysis is performed on the femoral artery by considering blood flow as a pulsating, incompressible and Newtonian flow over a realistic velocity waveform of the femoral artery. The artery is considered as a rigid and straight with a branch. The governing transient Navier-Stokes equations are solved using commercial software code Star-CCM+. Simulations are performed on healthy, atherosclerosis affected and Stented femoral arteries. Velocity and wall shear stress fields over the cardiac cycle are analyzed to predict the outcome of the interventions in terms of recirculation and stagnation regions and identify improved stent designs. The flow patterns in the arteries are highly modulating along with the cardiac cycle and a strong function of the waveform created by the heartbeat. The complex blood flow pattern with slow moving regions, flow separation and recirculatory form near the wall during cardiac cycle is the major contributing factor to the formation of the atherosclerotic plaque at that location. It was demonstrated that adverse flow field created upstream and downstream of the blockage may cause enhanced growth in size of the blockage. The stent design also plays significant role in the possibility of restenosis.

scholarly journals Requirement of β1 integrin for endothelium-dependent vasodilation and collateral formation in hindlimb ischemia

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Carina Henning ◽  
Anna Branopolski ◽  
Dominik Schuler ◽  
Dimitrios Dimitroulis ◽  
Patrik Huelsemann ◽  
...  
Keyword(s):  
Blood Flow ◽  
Endothelial Cell ◽  
Femoral Artery ◽  
Β1 Integrin ◽  
Hindlimb Ischemia ◽  
High Frequency Ultrasound ◽  
Blocking Antibody ◽  
Arterial Lumen ◽  
Collateral Arteries ◽  
Acute Increase

AbstractAn acute increase in blood flow triggers flow-mediated dilation (FMD), which is mainly mediated by endothelial nitric oxide synthase (eNOS). A long-term increase in blood flow chronically enlarges the arterial lumen, a process called arteriogenesis. In several common human diseases, these processes are disrupted for as yet unknown reasons. Here, we asked whether β1 integrin, a mechanosensory protein in endothelial cells, is required for FMD and arteriogenesis in the ischemic hindlimb. Permanent ligation of the femoral artery in C57BL/6 J mice enlarged pre-existing collateral arteries and increased numbers of arterioles in the thigh. In the lower leg, the numbers of capillaries increased. Notably, injection of β1 integrin-blocking antibody or tamoxifen-induced endothelial cell-specific deletion of the gene for β1 integrin (Itgb1) inhibited both arteriogenesis and angiogenesis. Using high frequency ultrasound, we demonstrated that β1 integrin-blocking antibody or endothelial cell-specific depletion of β1 integrin attenuated FMD of the femoral artery, and blocking of β1 integrin function did not further decrease FMD in eNOS-deficient mice. Our data suggest that endothelial β1 integrin is required for both acute and chronic widening of the arterial lumen in response to hindlimb ischemia, potentially via functional interaction with eNOS.

A NONLINEAR UNSTEADY RESPONSE OF NON-NEWTONIAN BLOOD FLOW PAST AN OVERLAPPING ARTERIAL CONSTRICTION

2007 ◽  
Vol 07 (04) ◽  
pp. 463-489
Author(s):  
S. SEN ◽  
S. CHAKRAVARTY
Keyword(s):  
Blood Flow ◽  
Flow Field ◽  
Arterial Wall ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Physiological Flow ◽  
Arterial Lumen ◽  
Shear Dependent Viscosity

The present study deals with an appropriate mathematical model describing blood flow through a constricted artery that is used to analyze the physiological flow field. The time-variant geometry of the arterial segment having an overlapping type of constriction in the arterial lumen — which frequently occurs in diseased arteries, causing flow disorder and leading to malfunction of the cardiovascular system — is framed mathematically. Blood flow contained in the stenosed artery is treated as non-Newtonian (having shear-dependent viscosity) and is considered to be two-dimensional. The motion of the arterial wall and its effect on local fluid mechanics are not ruled out from the present pursuit. The flow analysis applies the time-dependent, two-dimensional incompressible nonlinear Navier–Stokes equations for non-Newtonian fluids. The flow field can be obtained by first transforming radial coordinates with the use of appropriate boundary conditions, and then adopting a suitable finite difference scheme numerically. The unsteady response of the system and the influence of the arterial wall distensibility, the non-Newtonian rheology of blood, and the presence of stenosis on the important aspects of the physiological flow phenomena are quantified in order to indicate the susceptibility to atherosclerotic lesions and thereby validate the applicability of the present theoretical model.

scholarly journals Computational Fluid Dynamics Analysis of Pulsatile Blood Flow Behavior in Modelled Stenosed Vessels with Different Severities

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Mohsen Mehrabi ◽  
Saeed Setayeshi
Keyword(s):  
Fluid Dynamics ◽  
Blood Flow ◽  
Stokes Equations ◽  
Numerical Technique ◽  
Flow Behavior ◽  
Blood Flow Rate ◽  
Pulsatile Blood Flow ◽  
Cross Sectional ◽  
Medical Practitioners ◽  
Computational Fluid Dynamics Analysis

This study focuses on the behavior of blood flow in the stenosed vessels. Blood is modelled as an incompressible non-Newtonian fluid which is based on the power law viscosity model. A numerical technique based on the finite difference method is developed to simulate the blood flow taking into account the transient periodic behaviour of the blood flow in cardiac cycles. Also, pulsatile blood flow in the stenosed vessel is based on the Womersley model, and fluid flow in the lumen region is governed by the continuity equation and the Navier-Stokes equations. In this study, the stenosis shape is cosine by using Tu and Devil model. Comparing the results obtained from three stenosed vessels with 30%, 50%, and 75% area severity, we find that higher percent-area severity of stenosis leads to higher extrapressure jumps and higher blood speeds around the stenosis site. Also, we observe that the size of the stenosis in stenosed vessels does influence the blood flow. A little change on the cross-sectional value makes vast change on the blood flow rate. This simulation helps the people working in the field of physiological fluid dynamics as well as the medical practitioners.

Assessment of Myocardial Viability in Persistent Defects on Thallium-201 SPECT after Reinjection Using Gradient-Echo MRI

1996 ◽  
Vol 35 (05) ◽  
pp. 146-152 ◽  
Author(s):  
A. Kögler ◽  
H.-A. Schmitt ◽  
D. Emrich ◽  
H. Kreuzer ◽  
D. L. Munz ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Myocardial Viability ◽  
Cardiac Cycle ◽  
Single Photon ◽  
Contractile Function ◽  
Left Ventricular ◽  
Wall Thickening ◽  
Gradient Echo ◽  
Systolic Wall Thickening

SummaryThis prospective study assessed myocardial viability in 30 patients with coronary heart disease and persistent defects despite reinjection on TI-201 single-photon computed tomography (SPECT). In each patient, three observers graded TI-201 uptake in 7 left ventricular wall segments. Gradient-echo magnetic resonance imaging in the region of the persistent defect generated 12 to 16 short axis views representing a cardiac cycle. A total of 120 segments were analyzed. Mean end-diastolic wall thickness and systolic wall thickening (± SD) was 11.5 ± 2.7 mm and 5.8 ± 3.9 mm in 48 segments with normal TI-201 uptake, 10.1 ± 3.4 mm and 3.7 ± 3.1 mm in 31 with reversible lesions, 11.3 ± 2.8 mm and 3.3 ± 1.9 mm in 10 with mild persistent defects, 9.2 ± 2.9 mm and 3.2 ±2.2 mm in 15 with moderate persistent defects, 5.8 ± 1.7 mm and 1.3 ± 1.4 mm in 16 with severe persistent defects, respectively. Significant differences in mean end-diastolic wall thickness (p <0.0005) and systolic wall thickening (p <0.005) were found only between segments with severe persistent defects and all other groups, but not among the other groups. On follow-up in 11 patients after revascularization, 6 segments with mild-to-moderate persistent defects showed improvement in mean systolic wall thickening that was not seen in 6 other segments with severe persistent defects. These data indicate that most myocardial segments with mild and moderate persistent TI-201 defects after reinjection still contain viable tissue. Segments with severe persistent defects, however, represent predominantly nonviable myocardium without contractile function.

scholarly journals Diagnosis of Fibrotic Distal Ileum Stenosis after Ischemic Enteritis Using Transabdominal Ultrasonography

2021 ◽  
pp. 568-577
Author(s):  
Ryo Katsumata ◽  
Noriaki Manabe ◽  
Masaki Matsubara ◽  
Jun Nakamura ◽  
Kazuma Kawahito ◽  
...  
Keyword(s):  
Blood Flow ◽  
Case Reports ◽  
Blood Perfusion ◽  
Distal Ileum ◽  
Wall Thickening ◽  
Current Case ◽  
Abdominal Ultrasonography ◽  
Transabdominal Ultrasonography ◽  
Stenotic Lesion ◽  
Ischemic Enteritis

Ischemic enteritis (IE) is a rare disorder which is caused by inadequate blood flow to small intestine. The diagnostic procedure of this disease has not sufficiently established because of its rarity. Here, we report a case of IE in a hemodialysis-dependent 70-year-old man and summarize the diagnostic options for IE. The patient was admitted to our hospital because of acute abdominal distention and vomiting. He presented with mild tenderness in the lower abdomen and slightly elevated C-reactive protein level as revealed by blood tests. Radiographic imaging showed small bowel obstruction due to a stricture in the distal ileum. Contrast-enhanced abdominal ultrasonography revealed a 7-cm stenotic site with increased intestinal wall thickening, which preserved mucosal blood perfusion. Elastography revealed a highly elastic alteration of the stenotic lesion, indicating benign fibrotic changes resulting from chronic insufficient blood flow. Based on a clinical diagnosis of IE with fibrous stenosis, a partial ileostomy was performed. After surgical treatment, oral intake was initiated without recurrence of intestinal obstruction. Pathological findings revealed deep ulceration with inflammatory cell infiltration at the stenotic site. Occlusion and hyalinization of the venules in the submucosal layer indicated IE. In addition to current case, we reviewed past case reports of IE. Through this case presentation and literature review, we summarize the usefulness and safety of transabdominal ultrasonography for diagnosing IE.

COMPUTATIONS OF PULSATILE AORTIC BLOOD FLOW PROBLEMS ON PARALLEL COMPUTERS

2003 ◽  
Vol 15 (03) ◽  
pp. 109-114
Author(s):  
YANG-YAO NIU ◽  
SHOU-CHENG TCHENG
Keyword(s):  
Blood Flow ◽  
Stokes Equations ◽  
Computing Time ◽  
Time Integration ◽  
Parallel Computer ◽  
Aortic Blood Flow ◽  
Pc Cluster ◽  
Flow Problems ◽  
Aortic Blood ◽  
Speed Up

In this study, a parallel computing technology is applied on the simulation of aortic blood flow problems. A third-order upwind flux extrapolation with a dual-time integration method based on artificial compressibility solver is used to solve the Navier-Stokes equations. The original FORTRAN code is converted to the MPI code and tested on a 64-CPU IBM SP2 parallel computer and a 32-node PC Cluster. The test results show that a significant reduction of computing time in running the model and a super-linear speed up rate is achieved up to 32 CPUs at PC cluster. The speed up rate is as high as 49 for using IBM SP2 64 processors. The test shows very promising potential of parallel processing to provide prompt simulation of the current aortic flow problems.

Numerical and Experimental Analysis of 3D Micro-Corrugated Wing in Gliding Flight

2021 ◽  
Author(s):  
Nasim Chitsaz ◽  
Kamran Siddiqui ◽  
Romeo Marian ◽  
Javaan S. Chahl
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Aerodynamic Performance ◽  
Numerical Results ◽  
Three Dimensional Model ◽  
Wing Model ◽  
Computational Fluid Dynamics Analysis ◽  
Gliding Flight ◽  
Flat Profile

Abstract In this study, computational fluid dynamics analysis was performed on a three-dimensional model of a Libellulidae wing to determine aerodynamic performance in gliding flight. The wing is comprised of various corrugated features alongside the spanwise and chordwise directions, as well as twist. The detailed features of real 3D dragonfly wing models, including all the corrugations through both span and chord, have not been considered in the past for a detailed aerodynamic analysis. The simulations were conducted by solving the Navier-Stokes equations to demonstrate gliding performance over a range of angles of attack at low Reynolds numbers. The numerical model was validated against experimental data obtained from a fabricated corrugated wing model using particle image velocimetry. The numerical results demonstrate that bio-inspired wings with corrugations compared to flat profile wings generate more lift with lower drag, trapping the vortices in the valleys of wing corrugation leading to delayed flow separation and delayed stall. The experimental and numerical results demonstrate that the methodology presented in this study can be used to measure bio-inspired 3D wing flow characteristics, including the influence of complex corrugations on aerodynamic performance. These findings contribute to the advancement of knowledge required for designing an optimized bioinspired micro air vehicle.

Abstract 15312: Genetic Deletion of Toll-like Receptor 9 Accelerates Blood Flow Recovery after Hindlimb Ischemia

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Sachiko Nishimoto ◽  
Daiju Fukuda ◽  
Yasutomi Higashikuni ◽  
Kimie Tanaka ◽  
Yoichiro Hirata ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Blood Flow ◽  
Femoral Artery ◽  
Cpg Odn ◽  
Toll Like Receptor ◽  
Artery Ligation ◽  
Ischemic Limb ◽  
Tnf Α ◽  
Genetic Deletion ◽  
Inflammatory Molecules

Background: Peripheral artery disease causes significant functional disability and results in impaired quality of life. Toll-like receptor (TLR)-2, 3 and 4 are suggested to participate in blood flow recovery in ischemic limb by modulating inflammation and angiogenesis, however, the role of TLR9 remains unknown. TLR9 recognizes bacterial unmethylated DNA and plays a role in innate defense, although it can also provoke inflammation in response to fragmented DNA released from regenerated mammalian cells. This study tested the hypothesis that genetic deletion of TLR9 accelerates blood flow recovery after femoral artery ligation by inhibiting inflammation and improving endothelial cell function. Methods and Results: Unilateral femoral artery ligation was performed in TLR9-deficient (TLR9KO) mice and wild type (WT) mice. Femoral artery ligation significantly increased RNA expression of TLR9 (20-times) in WT mice and plasma levels of single-stranded DNA and double-stranded DNA, endogenous ligands for TLR9, in both strains of mice compared with each sham-operated group (P<0.05). Laser Doppler perfusion imaging demonstrated that TLR9KO mice significantly improved the ratio of the blood flow in the ischemic to non-ischemic limb compared with WT mice at 2 weeks after ligation (P<0.05). TLR9KO mice showed less accumulation of macrophages and less expression of inflammatory molecules (e.g., TNF-α, MCP-1 and IL-1β in ischemic muscle compared with WT mice (P<0.05, respectively). In vitro experiments using thioglycolate-stimulated peritoneal macrophages demonstrated that CpG ODN, agonistic oligonucleotide for TLR9, promoted the expression of pro-inflammatory molecules (e.g., MCP-1 and TNF-α) in WT macrophages (P<0.05, respectively) but not in TLR9 KO macrophages. Furthermore, activation of TLR9 by CpG ODN inhibited migration and proliferation of endothelial cells as determined by scratch-wound assay and MTS assay, respectively (P<0.05). Conclusion: Our results suggested that TLR9 enhances inflammation and affects migration and proliferation of endothelial cells, leading to impaired blood flow recovery in ischemic limb. TLR9 may serve as a potential therapeutic target for ischemic limb disease.

Sign in / Sign up

Export Citation Format

Share Document