Fluid dynamics of venous valve closure

Qui, Yuchen; Quijano, Rodolfo C.; Wang, S. K.; Hwang, Ned H. C.

doi:10.1007/bf02584474

Cited by 23 publications

(19 citation statements)

References 7 publications

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“…Valve closure occurs when the pressure caused by the recirculation eddy exceeds the pressure on the luminal side of the valvular leaflets as a result of the proximally directed jet. Thus venous valves are operated by pressure rather than driven by flow so that little or no reflux occurs in bringing about complete closure of the valve (36, 475). …”

Section: Occurrence Of Disturbed Flow In Pathophysiological Condmentioning

confidence: 99%

Effects of Disturbed Flow on Vascular Endothelium: Pathophysiological Basis and Clinical Perspectives

Chiu

Chien

2011

Physiological Reviews

1,757

1,694

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Vascular endothelial cells (ECs) are exposed to hemodynamic forces, which modulate EC functions and vascular biology/pathobiology in health and disease. The flow patterns and hemodynamic forces are not uniform in the vascular system. In straight parts of the arterial tree, blood flow is generally laminar and wall shear stress is high and directed; in branches and curvatures, blood flow is disturbed with nonuniform and irregular distribution of low wall shear stress. Sustained laminar flow with high shear stress upregulates expressions of EC genes and proteins that are protective against atherosclerosis, whereas disturbed flow with associated reciprocating, low shear stress generally upregulates the EC genes and proteins that promote atherogenesis. These findings have led to the concept that the disturbed flow pattern in branch points and curvatures causes the preferential localization of atherosclerotic lesions. Disturbed flow also results in postsurgical neointimal hyperplasia and contributes to pathophysiology of clinical conditions such as in-stent restenosis, vein bypass graft failure, and transplant vasculopathy, as well as aortic valve calcification. In the venous system, disturbed flow resulting from reflux, outflow obstruction, and/or stasis leads to venous inflammation and thrombosis, and hence the development of chronic venous diseases. Understanding of the effects of disturbed flow on ECs can provide mechanistic insights into the role of complex flow patterns in pathogenesis of vascular diseases and can help to elucidate the phenotypic and functional differences between quiescent (nonatherogenic/nonthrombogenic) and activated (atherogenic/thrombogenic) ECs. This review summarizes the current knowledge on the role of disturbed flow in EC physiology and pathophysiology, as well as its clinical implications. Such information can contribute to our understanding of the etiology of lesion development in vascular niches with disturbed flow and help to generate new approaches for therapeutic interventions.

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Section: Occurrence Of Disturbed Flow In Pathophysiological Condmentioning

confidence: 99%

Effects of Disturbed Flow on Vascular Endothelium: Pathophysiological Basis and Clinical Perspectives

Chiu

Chien

2011

Physiological Reviews

1,757

1,694

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“…The collapsed behavior can be seen in the flow in veins when an external pressure is applied to the fluid flow in veins. [32] The knowledge of the flow physics involved can play a key role to improve clinical treatment and for future designing and developing artificial valves. [33] Geometry and boundary conditions The modeling of the described problem and the related equations have been discussed, which are used to solve the flow in the model.…”

Section: Computational Approachmentioning

confidence: 99%

Numerical simulations of thrombosis

Ramunigari¹,

Roy²

2013

Chron Young Sci

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Background: Mathematical approaches for biological events have gained significant importance in development of biomedical research. Deep vein thrombosis (DVT) is caused by blood clot in veins deeply rooted in the body, resulting in loss of blood, pain, and numbness of the body part associated with that vein. This situation can get complicated and can be fatal, when the blood clot travels to other parts of the body which may result in pulmonary embolism (PE). PE causes approximately 300,000 deaths annually in the United States alone. Materials and Methods: We are trying to propose a computational approach for understanding venous thrombosis using the theory of fluid mechanics. In our study, we are trying to establish a computational model that mimics the venous blood flow containing unidirectional venous valves and will be depicting the blood flow in the veins. We analyzed the flow patterns in veins, which are included with lump like substances. This lump like substances can be clots, tissue debris, collagen or even cholesterol. Our study will facilitate better understanding of the biophysical process in case of thrombosis. Results: The predicted model analyzes the consequences that occur due to the clot formations in veins. Knowledge of Navier-Stokes equations in fluid dynamics along with the computational model of a complex biological system would help in diagnosis of the problem at much faster rate of time. Valves of the deep veins are damaged as a result of DVT, with no valves to prevent deep system reflux, the hydrostatic venous pressure in the lower extremity increases dramatically. Conclusion: Our model is used to determine the effects of an interrupted blood flow as a result of thrombin formation, which might result in disturbed systemic circulation. Our results indicated a positive inverse correlation exists between clots and the flow velocity. This would support medical practitioners to recommend faster curing measures.

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“…The frame rate is low as several pulse transmissions are necessary along each line to achieve a usable image. 2-D duplex mode (B-mode image combined with CFM) in commercial scanners are performed at frame rates down to [8][9][10] Hz. This is unsuitable for visualizing rapid temporal changes in the blood flow.…”

Section: Introductionmentioning

confidence: 99%

Fast Blood Vector Velocity Imaging using ultrasound: In-vivo examples of complex blood flow in the vascular system

Hansen

Udesen

Gran

et al. 2008

2008 IEEE Ultrasonics Symposium

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Conventional ultrasound methods for acquiring color flow images of the blood motion are restricted by a relatively low frame rate and angle dependent velocity estimates. The Plane Wave Excitation (PWE) method has been proposed to solve these limitations. The frame rate can be increased, and the 2-D vector velocity of the blood motion can be estimated. The transmitted pulse is not focused, and a full speckle image of the blood can be acquired for each emission. A 13 bit Barker code is transmitted simultaneously from each transducer element. The 2-D vector velocity of the blood is found using 2-D speckle tracking between segments in consecutive speckle images. The flow patterns of six bifurcations and two veins were investigated invivo. It was shown: 1) that a stable vortex in the carotid bulb was present opposed to other examined bifurcations, 2) that retrograde flow was present in the superficial branch of the femoral artery during diastole, 3) that retrograde flow was present in the subclavian artery and antegrade in the common carotid artery during diastole, 4) that vortices were formed in the buckets behind the venous valves in both antegrade and retrograde flow, and 5) that secondary flow was present in various vessels. The in-vivo results have revealed complex flow patterns not previously visualized with ultrasound imaging and indicate a flow complexity in both simple and complex vessel geometries.

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Fluid dynamics of venous valve closure

Cited by 23 publications

References 7 publications

Effects of Disturbed Flow on Vascular Endothelium: Pathophysiological Basis and Clinical Perspectives

Effects of Disturbed Flow on Vascular Endothelium: Pathophysiological Basis and Clinical Perspectives

Numerical simulations of thrombosis

Fast Blood Vector Velocity Imaging using ultrasound: In-vivo examples of complex blood flow in the vascular system

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