Effects of Stenosis Asymmetry on Blood Flow in Stenotic Arteries and Wall Compression

1999 ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Zhongdan Huan ◽  
David N. Ku
Keyword(s):  
Thrombus Formation ◽  
Flow Characteristics ◽  
Wall Stress ◽  
Critical Flow ◽  
Factors Affecting ◽  
Wall Deformation ◽  
Stenosis Severity ◽  
Wall Compliance ◽  
Stenotic Arteries ◽  
Considerable Work

Abstract Severe stenoses in arteries cause critical flow conditions which may be related to thrombus formation, artery compression and plaque cap rupture. The exact mechanism of these events and the conditions causing them are not well understood. Considerable work for flow in stenotic tubes have been reported in last twenty years and many interesting phenomena such as flow limitation, choking, flutter and wall collapse have been observed [3]. Stenosis severity, wall compliance and pressure conditions have been identified as dominating factors affecting wall deformation and flow and pressure fields. However, real arteries are rarely axisymmetric. Stenosis asymmetry may have considerable effects on wall stress and the critical flow characteristics.

Influence of Plaque Stiffness on Change of Blood Vessel Geometry Leading Hemodynamical Changes in PVA-H Stenosis Models

2012 ◽  
Author(s):  
Yasutomo Shimizu ◽  
Shuya Shida ◽  
Kenichi Funamoto ◽  
Toshiyuki Hayase ◽  
Makoto Ohta
Keyword(s):  
Mechanical Properties ◽  
Blood Flow ◽  
Internal Pressure ◽  
Flow Pattern ◽  
Flow Patterns ◽  
Parent Artery ◽  
Steady Flows ◽  
Factors Affecting ◽  
Stenosis Severity ◽  
Stenotic Arteries

One of the main factors affecting blood flow conditions in stenotic arteries is plaque geometry. Plaques can be deformed by the internal pressure, and hence plaque behavior varies depending on its stiffness. Blood flow pattern around a plaque is complicated by plaque behavior, and these complications may lead to growth of the plaque itself. Thus, we can say that geometry and mechanical properties of a plaque, and blood flow will affect each other. To understand the relationship between plaque stiffness and flow pattern, flow measurement using elastic models, which mimic the mechanical properties of blood vessels, is required. Flow patterns with steady flows and a range of hydrostatic pressures were observed by particle image velocimetry. The results show that the model is deformed by hydrostatic pressures. Furthermore, flow patterns are also changed as the results of model deformation, especially at reattachment points. Simultaneously, we performed a numerical simulation for finding a critical parameter of the flow patterns. These results show that the reattachment length increases in the model with high stenosis severity and in a vertically oriented parent artery. In conclusion, a parent artery and plaque can deform because of internal pressure, and these deformation will affect blood flow patterns.

3-D Simulation for Blood Flow and Artery Compression in Asymmetric Stenotic Arteries With Axial Stretch

2001 ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Shunnichi Kobayashi
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Shear Stress ◽  
Wall Stress ◽  
Small Strain ◽  
Rigid Wall ◽  
Severe Stenosis ◽  
Physiological Conditions ◽  
Oscillating Shear Stress ◽  
Stenotic Arteries

Abstract There has been increasing evidence that severe stenosis may cause artery compression and plaque cap rupture leading to heart attack and stroke. The physiological conditions under which that may occur and mechanisms involved are not well understood. It has been known that severe stenosis causes critical flow and wall mechanical conditions such as flow limitation, flow separation, low and oscillating shear stress distal to the stenosis, high shear stress and low or even negative flow pressure at the throat of stenosis, artery compression or even collapse. Those conditions are related to limitation of blood supply, intimal thickening and thrombosis formation, endothelism damage, platelet activation and aggregation, plaque cap rupture (for review, see [1,2]). Due to the complexity of the problem and lack of experimental data for mechanical properties of arteries under both expansion and compression, previous models were limited primarily to flow behaviors and with various limitations (axisymmetry, rigid wall, small strain, small pressure gradient). In this paper, experimental data for artery mechanical properties under physiological conditions were measured and a 3-d computational model is introduced to investigate flow behaviors and wall stress and strain distributions with fluid-structure interactions to better understand the mechanism involved in artery compression and plaque cap rupture.

scholarly journals Fluid-Structure Interaction Simulation of an Intra-Atrial Fontan Connection

Biology ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 412
Author(s):  
Elaine Tang ◽  
Zhenglun (Alan) Wei ◽  
Mark A. Fogel ◽  
Alessandro Veneziani ◽  
Ajit P. Yoganathan
Keyword(s):  
Magnetic Resonance ◽  
Power Loss ◽  
Phase Contrast ◽  
Fluid Structure Interaction ◽  
Rigid Wall ◽  
Patient Specific ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Wall Deformation ◽  
Wall Compliance

Total cavopulmonary connection (TCPC) hemodynamics has been hypothesized to be associated with long-term complications in single ventricle heart defect patients. Rigid wall assumption has been commonly used when evaluating TCPC hemodynamics using computational fluid dynamics (CFD) simulation. Previous study has evaluated impact of wall compliance on extra-cardiac TCPC hemodynamics using fluid-structure interaction (FSI) simulation. However, the impact of ignoring wall compliance on the presumably more compliant intra-atrial TCPC hemodynamics is not fully understood. To narrow this knowledge gap, this study aims to investigate impact of wall compliance on an intra-atrial TCPC hemodynamics. A patient-specific model of an intra-atrial TCPC is simulated with an FSI model. Patient-specific 3D TCPC anatomies were reconstructed from transverse cardiovascular magnetic resonance images. Patient-specific vessel flow rate from phase-contrast magnetic resonance imaging (MRI) at the Fontan pathway and the superior vena cava under resting condition were prescribed at the inlets. From the FSI simulation, the degree of wall deformation was compared with in vivo wall deformation from phase-contrast MRI data as validation of the FSI model. Then, TCPC flow structure, power loss and hepatic flow distribution (HFD) were compared between rigid wall and FSI simulation. There were differences in instantaneous pressure drop, power loss and HFD between rigid wall and FSI simulations, but no difference in the time-averaged quantities. The findings of this study support the use of a rigid wall assumption on evaluation of time-averaged intra-atrial TCPC hemodynamic metric under resting breath-held condition.

Misinterpretation of the Functional Severity of Coronary Stenosis Due To Variability in Arterial Wall Compliance

2010 ◽  
Author(s):  
Bhaskar Chandra Konala ◽  
Ashish Das ◽  
Mohamed Effat ◽  
Arif Imran ◽  
Rupak K. Banerjee
Keyword(s):  
Arterial Wall ◽  
Coronary Intervention ◽  
Diagnostic Parameter ◽  
Carreau Model ◽  
Newtonian Viscosity ◽  
Coronary Stenoses ◽  
Wall Compliance ◽  
Wall Interaction ◽  
Stenotic Arteries ◽  
Parameter Values

Effect of arterial wall compliance on the invasive coronary diagnostic parameters for various severities of coronary stenoses was assessed. The Mooney-Rivlin model was used to define the non-linear properties of the arterial wall and the plaque regions. The non-Newtonian viscosity of blood was modeled using the Carreau model. A finite element method was employed to solve the pulsatile fluid (blood)-structure (arterial wall) interaction (FSI) equations. Variability in the diagnostic parameter values can occur near the cut-off value due to change in compliance of stenotic arteries between the range of 84% and 89% area stenosis. This may lead to misdiagnosis and might wrongly lead to postponement of coronary intervention.

Computed tomography angiography as an adjunct to computational fluid dynamics for prediction of oxygenator thrombus formation

Perfusion ◽  
2020 ◽  
pp. 026765912094410
Author(s):  
Robert G Conway ◽  
Jiafeng Zhang ◽  
Jean Jeudy ◽  
Charles Evans ◽  
Tieluo Li ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computed Tomography ◽  
Computational Fluid Dynamics ◽  
Computed Tomography Angiography ◽  
Thrombus Formation ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Region Of Interest ◽  
Computational Fluid Dynamics Analysis ◽  
Clot Burden

Introduction: Extracorporeal membrane oxygenation circuit performance can be compromised by oxygenator thrombosis. Stagnant blood flow in the oxygenator can increase the risk of thrombus formation. To minimize thrombogenic potential, computational fluid dynamics is frequently applied for identification of stagnant flow conditions. We investigate the use of computed tomography angiography to identify flow patterns associated with thrombus formation. Methods: A computed tomography angiography was performed on a Quadrox D oxygenator, and video densitometric parameters associated with flow stagnation were measured from the acquired videos. Computational fluid dynamics analysis of the same oxygenator was performed to establish computational fluid dynamics–based flow characteristics. Forty-one Quadrox D oxygenators were sectioned following completion of clinical use. Section images were analyzed with software to determine oxygenator clot burden. Linear regression was used to correlate clot burden to computed tomography angiography and computational fluid dynamics–based flow characteristics. Results: Clot burden from the explanted oxygenators demonstrated a well-defined pattern, with the largest clot burden at the corner opposite the blood inlet and outlet. The regression model predicted clot burden by region of interest as a function of time to first opacification on computed tomography angiography (R2 = 0.55). The explanted oxygenator clot burden map agreed well with the computed tomography angiography predicted clot burden map. The computational fluid dynamics parameter of residence time, when summed in the Z-direction, was partially predictive of clot burden (R2 = 0.35). Conclusion: In the studied oxygenator, clot burden follows a pattern consistent with clinical observations. Computed tomography angiography–based flow analysis provides a useful adjunct to computational fluid dynamics–based flow analysis in understanding oxygenator thrombus formation.

Minimal effect of collateral flow on coronary microvascular resistance in the presence of intermediate and noncritical coronary stenoses

2012 ◽  
Vol 303 (4) ◽  
pp. H422-H428 ◽  
Author(s):  
Bart-Jan Verhoeff ◽  
Tim P. van de Hoef ◽  
Jos A. E. Spaan ◽  
Jan J. Piek ◽  
Maria Siebes
Keyword(s):  
Wall Stress ◽  
Coronary Intervention ◽  
Relative Difference ◽  
Collateral Flow ◽  
Fractional Flow ◽  
Flow Reserve ◽  
Before And After ◽  
Stenosis Severity ◽  
Microvascular Resistance ◽  
Relevant Range

Depending on stenosis severity, collateral flow can be a confounding factor in the determination of coronary hyperemic microvascular resistance (HMR). Under certain assumptions, the calculation of HMR can be corrected for collateral flow by incorporating the wedge pressure (Pw) in the calculation. However, although Pw > 25 mmHg is indicative of collateral flow, Pw does in part also reflect myocardial wall stress neglected in the assumptions. Therefore, the aim of this study was to establish whether adjusting HMR by Pw is pertinent for a diagnostically relevant range of stenosis severities as expressed by fractional flow reserve (FFR). Accordingly, intracoronary pressure and Doppler flow velocity were measured a total of 95 times in 29 patients distal to a coronary stenosis before and after stepwise percutaneous coronary intervention. HMR was calculated without (HMR) and with Pw-based adjustment for collateral flow (HMRC). FFR ranged from 0.3 to 1. HMR varied between 1 and 5 and HMRC between 0.5 and 4.2 mmHg·cm−1·s. HMR was about 37% higher than HMRC for stenoses with FFR < 0.6, but for FFR > 0.8, the relative difference was reduced to 4.4 ± 3.4%. In the diagnostically relevant range of FFR between 0.6 and 0.8, this difference was 16.5 ± 10.4%. In conclusion, Pw-based adjustment likely overestimates the effect of potential collateral flow and is not needed for the assessment of coronary HMR in the presence of a flow-limiting stenosis characterized by FFR between 0.6 and 0.8 or for nonsignificant lesions.

scholarly journals The Björk-Shiley aortic prosthesis: flow characteristics, thrombus formation and tissue overgrowth.

Circulation ◽  
1978 ◽  
Vol 58 (1) ◽  
pp. 70-76 ◽  
Author(s):  
A P Yoganathan ◽  
W H Corcoran ◽  
E C Harrison ◽  
J R Carl
Keyword(s):  
Thrombus Formation ◽  
Flow Characteristics ◽  
Aortic Prosthesis

scholarly journals Development of Coal Mine Filling Paste with Certain Early Strength and Its Flow Characteristics

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Feng Zhang ◽  
Jinxiao Liu ◽  
Haiming Ni ◽  
Wenxin Li ◽  
Yongle Liu
Keyword(s):  
Fly Ash ◽  
Coal Mine ◽  
Setting Time ◽  
Flow Characteristics ◽  
Coal Gangue ◽  
Practical Significance ◽  
Range Analysis ◽  
Factors Affecting ◽  
Early Strength ◽  
Backfill Strength

In coal mine paste filling technology, geomaterials like coal gangue and fly ash are used as the main component, and cement is applied as the cementing material. In the mining production, mining-and-filling is a cyclic work, where the filling immediately after mining and mining immediately after filling. Long solidification time after filling will affect mining; consequently, the paste should have early strength. In addition, the prepared paste will be conveyed to goaf through the pipeline. The paste flow characteristics will change to some extent in the conveying process, and there is uncertainty about whether the paste can meet the requirements of pumpability and strength. Therefore, the influence of pipeline conveying on flow characteristics of paste before filling the goaf should be taken into consideration. Based on the above two points, this paper studies the paste strength, backfill strength, and pumpability parameters in coal mine paste filling and determines the early and later strength of coal mine paste, as well as the pumpability parameters such as slump degree, segregation degree, setting time, and paste gradation. With the determined mass proportion of coal gangue, fly ash, and silicate cement, the orthogonal test was carried out with three factors including gypsum content, the content of early strength agent (Na2SO4), and the mass concentration, and at three levels. The factors affecting paste flow characteristics were determined by range analysis, and the factors affecting the paste’s early strength were determined by the XRD test and SEM test on its microstructure. With paste proportioning and pipeline conveying simulation system, taking slump, segregation degree, backfill strength, and other parameters as indicators, we obtain the influence law of pipeline conveying on the flow characteristics of paste. The research has great theoretical and practical significance for developing coal paste with early strength and its flow characteristics.

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