Reconstruction of blood flow patterns in human arteries

Xu, Xiao Yun; Long, Quan; Collins, M. W.; Bourne, Michael W.; Griffith, T. M.

doi:10.1243/0954411991535022

Cited by 30 publications

(19 citation statements)

References 12 publications

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“…6 Sudden contrasting differences in endothelial shear stress levels can be observed in vivo near bifurcations, particularly those of the aorta. 1,30,31 Thus, from the preselected specimens described in the previous paragraph, the following selection was made: the abdominal aorta bifurcation, the common iliac artery, and the branch of the common carotid artery from the aortic arch. In the aortic arch of a 13-year-old donor, at the geometrically regular sites where laminar Table 1), sectioned, and used for in situ hybridization.…”

Section: Differential Expression Of Lklf Near Vessel Bifurcationsmentioning

confidence: 99%

“…It has been demonstrated in various model systems and by in vivo measurements, that the endothelium at the inner walls of the common iliac arteries, immediately after the aorta bifurcation, is generally exposed to laminar flow and thus higher levels of shear stress ( Figure 3A). 1,30,31 Using in situ hybridization, high endothelial LKLF signals were observed at the inner walls of the common iliac arteries obtained from a 34-year-old female donor ( Figure 3, B and C). At the outer wall, an early lesion was present and the hybridization signal of LKLF was substantially lower in the endothelium covering this neointima area ( Figure 3D).…”

Section: Differential Expression Of Lklf Near Vessel Bifurcationsmentioning

confidence: 99%

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Endothelial KLF2 Links Local Arterial Shear Stress Levels to the Expression of Vascular Tone-Regulating Genes

Dekker

Thienen

Rohlena

et al. 2005

The American Journal of Pathology

329

299

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Lung Krüppel-like factor (LKLF/KLF2) is an endothelial transcription factor that is crucially involved in murine vasculogenesis and is specifically regulated by flow in vitro. We now show a relation to local flow variations in the adult human vasculature: decreased LKLF expression was noted at the aorta bifurcations to the iliac and carotid arteries, coinciding with neointima formation. The direct involvement of shear stress in the in vivo expression of LKLF was determined independently by in situ hybridization and laser microbeam microdissection/reverse transcriptase-polymerase chain reaction in a murine carotid artery collar model, in which a 4-to 30-fold induction of LKLF occurred at the high-shear sites. Dissection of the biomechanics of LKLF regulation in vitro demonstrated that steady flow and pulsatile flow induced basal LKLF expression 15-and 36-fold at shear stresses greater than ϳ5 dyne/cm 2 , whereas cyclic stretch had no effect. The focal development of atherosclerosis has been linked to the local variations in blood flow that are observed near the irregular blood vessel geometries of bifurcations and bends. 1,2 Continuous exposure of endothelial cells to flow in vivo generates a tangential force, shear stress, across their apical surfaces. A large number of studies support the hypothesized antiatherosclerotic effect of shear stress on the endothelium, and are mainly based on the ability of shear stress to modulate endothelial gene expression. 3 Throughout the recent years, a collection of shear stress-responsive endothelial genes has been established. 4 -8 Usually no clear distinction is made between genes induced by prolonged shear and those induced by short-term shear (Ͻ24 hours), although the latter class typically represents a general stress response also observed with turbulent flow types and seems more related to endothelial dysfunction. Based on the rationale that only genes induced by prolonged shear would represent the healthy transcriptome, we previously identified a limited number of genes that are still highly induced after exposing human umbilical vein endothelial cells (HUVECs) to flow for 7 days, but which are not induced by various other (inflammatory) stimuli. 6 The expression of one of those genes, the transcription factor lung Krü ppel-like factor (LKLF/

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Section: Differential Expression Of Lklf Near Vessel Bifurcationsmentioning

confidence: 99%

Section: Differential Expression Of Lklf Near Vessel Bifurcationsmentioning

confidence: 99%

Endothelial KLF2 Links Local Arterial Shear Stress Levels to the Expression of Vascular Tone-Regulating Genes

Dekker

Thienen

Rohlena

et al. 2005

The American Journal of Pathology

329

299

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“…Doppler ultrasound [8]and MRI phase-contrast [9, 10, 11]techniques potentially provide a direct measurement of vascular geometry and blood flow velocities. Numerical simulations [12, 13]and analytical models [14, 15, 16, 17]have also been used in order to elucidate the fundamental physical properties of pulsatile flow.…”

Section: Introductionmentioning

confidence: 99%

Flow in Elliptical Vessels Calculated for a Physiological Waveform

Robertson

Köhler²,

Hoskins³

et al. 2001

J Vasc Res

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Understanding the nature of pulsatile flow is an important issue in haemodynamics, especially the initiation and progression of vascular disease. The geometry of a non-circular vessel was idealised to an elliptical cross-section, and the dynamic properties of the flow were calculated for a physiological waveform. The Fourier harmonics for a common carotid waveform were determined, and the velocity profile and wall shear stress were calculated from the superposition of the individual contributions from each harmonic. The effects of ellipticity on the flow pattern were found to be significant. The velocity profile along the major axis of the elliptical cross-section developed a flattened peak, which widened as the vessel became more elliptical. Wall shear stress demonstrated an angular dependence in elliptical vessels, where the point of minimum shear stress was located at the end of the major axis. Comparison with a cylindrical vessel demonstrated a 3% decrease in peak wall shear stress (τ = 2.96, N·m^–2) at the end of the major axis, and 10% in the mean wall shear stress (τ = 0.44 N· m^–2), for an elliptical vessel (Ε = 0.8). The temporal average wall shear stress, which has been associated with atherogenic sites, also displayed a minimum at the end of the major axis that decreased with more elliptical cross-sections.

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“…These assumptions will influence the estimates of hemodynamic parameters presented here: the velocity profile in the common carotid artery may not conform precisely to that predicted by the Womersley solution, although previous studies suggest this is reasonably realistic assumption (20,25). Nonplanar features of bifurcations have been reported to influence secondary flow patterns (3,16,27,29,30). Previous modeling studies suggest that the assumption of noncompliant walls has only modest effects on flow patterns (18,30) but may reduce average shear stress by ϳ20-30% (1) and instantaneous maximum and minimum shear stress to a greater degree (1,30).…”

Section: Discussionmentioning

confidence: 94%

Measurement of hemodynamics in human carotid artery using ultrasound and computational fluid dynamics

Starmans-Kool

Stanton

Zhao

et al. 2002

Journal of Applied Physiology

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Measurement of hemodynamics in human carotid artery using ultrasound and computational fluid dynamics. J Appl Physiol 92: 957-961, 2002; 10.1152/japplphysiol.00171.2001.-The objective of the study was to investigate the feasibility of using computational fluid dynamic modeling (CFD) with noninvasive ultrasound measurements to determine time-variant three-dimensional (3D) carotid arterial hemodynamics in humans in vivo. The effects of hyperoxia and hypoxic hypercapnia on carotid artery local hemodynamics were examined by use of this approach. Six normotensive volunteers followed a double-blind randomized crossover design. Blood pressure, heart rate, and carotid blood flow were measured while subjects breathed normal air, a mixture of 5% CO2 and 15% O2 (hypoxic hypercapnia), and 100% O2 (hyperoxia). Carotid artery geometry was reconstructed on the basis of B-mode ultrasound images by using purpose-built image processing software. Time-variant 3D carotid hemodynamics were estimated by using finite volume-based CFD. Systemic blood pressure was not significantly affected by hyperoxia or hypoxic hypercapnia, but heart rate decreased significantly with hyperoxia. There was an increase in diastolic flow velocity in the external carotid artery after hypoxic hypercapnia, but otherwise carotid blood flow velocities did not change significantly. Compared with normal air, hyperoxic conditions were associated with a decrease in the width of the region of flow separation in the external carotid artery. During hyperoxia, there was also an increase in the minimum and a decrease in maximum shear stress in the bifurcation and hence a reduction in cyclic variation in shear stress. Hypoxic hypercapnia was associated with a reduced duration of flow separation in the external carotid artery and an increase in the minimum shear stress without affecting the cyclic variation in shear stress. This study demonstrates the feasibility of using noninvasive ultrasound techniques in conjunction with CFD to describe time-variant 3D hemodynamics in the human carotid arterial bifurcation in vivo. blood flow; hyperoxia; hypoxic hypercapnia; shear stress ATHEROSCLEROSIS IS A MAJOR cause of cardiovascular mortality and morbidity. An important feature of atherosclerosis is the focal nature of lesions and their characteristic location at particular sites in the vasculature, such as regions of marked curvature and branch points (24, 28). It has been proposed that this is a consequence of local hemodynamics in such regions (4) and that shear stress gradients adversely affect endothelial function at such sites (8, 9) and, hence, increase the risk of atheroma formation (11, 23). However, the measurement of flow and shear stress in the regions relevant to atheroma formation (e.g., arterial bifurcations) is difficult because of the complex nature of flows at such sites. Computational flow dynamic modeling (CFD) is widely used in engineering to calculate flows in complex geometries, and recently this approach has been successfully applied to modeling flow in ...

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Reconstruction of blood flow patterns in human arteries

Cited by 30 publications

References 12 publications

Endothelial KLF2 Links Local Arterial Shear Stress Levels to the Expression of Vascular Tone-Regulating Genes

Endothelial KLF2 Links Local Arterial Shear Stress Levels to the Expression of Vascular Tone-Regulating Genes

Flow in Elliptical Vessels Calculated for a Physiological Waveform

Measurement of hemodynamics in human carotid artery using ultrasound and computational fluid dynamics

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