Flow Analysis in Damaged Venous Valves Installed with an Artificial Venous Valve

Objectives The purpose of this study is to test venous valve performance and identify differences between native tissue and replacement devices developed with traditional tissue treatment methods using a new in vitro model with synchronized hemodynamic parameters and high-speed valve image acquisition. Methods An in vitro model mimicking the venous circulation to test valve performance was developed using hydrostatic pressure driven flow. Fresh and glutaraldehyde-treated vein segments were placed in the setup and opening/closing of the valves was captured by a high-speed camera. Hemodynamic data were obtained using synchronized hardware and virtual instrumentation. Results Geometric orifice area and opening/closing time of the valves was evaluated at the same hemodynamic conditions. A reduction in geometric orifice area of 27.2 ± 14.8% (p < 0.05) was observed following glutaraldehyde fixation. No significant difference in opening/closing time following chemical fixation was observed. Conclusions The developed in vitro model was shown to be an effective method for measuring the performance of venous valves. The observed decrease in geometric orifice area following glutaraldehyde treatment indicates a decrease in flow through the valve, demonstrating the consequences of traditional tissue treatment methods.

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Tissue Level Mechanical Properties and Extracellular Matrix Investigation of the Bovine Jugular Venous Valve Tissue

Bioengineering ◽

10.3390/bioengineering6020045 ◽

2019 ◽

Vol 6 (2) ◽

pp. 45 ◽

Cited By ~ 3

Author(s):

Adam A. Benson ◽

Hsiao-Ying Shadow Huang

Keyword(s):

Mechanical Properties ◽

Extracellular Matrix ◽

Radial Direction ◽

True Strain ◽

Transient Global Amnesia ◽

Tissue Level ◽

Mechanical Tests ◽

Circumferential Direction ◽

Venous Valve ◽

Venous Valves

Jugular venous valve incompetence has no long-term remedy and symptoms of transient global amnesia and/or intracranial hypertension continue to discomfort patients. During this study, we interrogate the synergy of the collagen and elastin microstructure that compose the bi-layer extracellular matrix (ECM) of the jugular venous valve. In this study, we investigate the jugular venous valve and relate it to tissue-level mechanical properties, fibril orientation and fibril composition to improve fundamental knowledge of the jugular venous valves toward the development of bioprosthetic venous valve replacements. Steps include: (1) multi loading biaxial mechanical tests; (2) isolation of the elastin microstructure; (3) imaging of the elastin microstructure; and (4) imaging of the collagen microstructure, including an experimental analysis of crimp. Results from this study show that, during a 3:1 loading ratio (circumferential direction: 900 mN and radial direction: 300 mN), elastin may have the ability to contribute to the circumferential mechanical properties at low strains, for example, shifting the inflection point toward lower strains in comparison to other loading ratios. After isolating the elastin microstructure, light microscopy revealed that the overall elastin orients in the radial direction while forming a crosslinked mesh. Collagen fibers were found undulated, aligning in parallel with neighboring fibers and orienting in the circumferential direction with an interquartile range of −10.38° to 7.58° from the circumferential axis (n = 20). Collagen crimp wavelength and amplitude was found to be 38.46 ± 8.06 µm and 4.51 ± 1.65 µm, respectively (n = 87). Analyzing collagen crimp shows that crimp permits about 12% true strain circumferentially, while straightening of the overall fibers accounts for more. To the best of the authors’ knowledge, this is the first study of the jugular venous valve linking the composition and orientation of the ECM to its mechanical properties and this study will aid in forming a structure-based constitutive model.

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Functional ultrasound imaging of the venous valve of the great saphenous vein in the area around the crosse using the novel vector flow technique

Clinical Hemorheology and Microcirculation ◽

10.3233/ch-209205 ◽

2020 ◽

Vol 76 (2) ◽

pp. 211-219

Author(s):

S. Kammerer ◽

C. Stroszczynski ◽

E.M. Jung

Keyword(s):

Saphenous Vein ◽

Duplex Sonography ◽

Valve Closure ◽

Venous Valve ◽

Vein Thrombosis ◽

Venous Structure ◽

Venous Valves ◽

Valve Function ◽

And Gender ◽

Color Coded Duplex Sonography

PURPOSE: The aim of our pilot study is to consider if the new flow presentation of the vector flow (V-flow) allows an assessment of the valve morphology of the crosses with respect to an insufficiency. MATERIAL AND METHODS: We performed a total of 50 investigations in which we documented a complete valve closure at the so called “crosse” at the valve of the large saphenous vein, a delayed valve closure or an incomplete valve closure with consecutive insufficiency at the crosse. The valve function of the crosse is crucial for the development of varicosis. For our study we recorded age and gender of the patients. One patient in the study was suffering from Covid19. For the examinations we used a 3–9 MHz probe and a high-end ultrasound device. The examination was performed in a lying position and under quiet conditions. Before examination we practiced inhalation and exhalation as well as “pressing” or coughing with the patients, which resulted in a physiological closure of the venous valves. To rule out thrombosis, we carried out compression sonography on the legs. During the examination we documented the B-scan, the Color-Coded Duplex Sonography, the HR-flow and the V-flow for 3 seconds at the estuary of the crosses and incorporated these parameters into our measurements. Via V-flow, vectors can be imaged by representing the flow of erythrocytes and visually indicate a possible insufficiency due to delayed or incomplete valve closure. RESULTS: 31 of 50 patients (age 19–81years) showed a complete valve closure of the crosses, three of them suffered from thrombosis. In eight of the 50 study participants (age 45–79 years) a delayed valve closure could be diagnosed by V-flow within 1–2 seconds. None of them had a thrombosis, but six of them suffered from cancer. In eleven patients we derived an incomplete valve closure with insufficiency (age 51–88 years). With reflux it took >2 seconds to close the valve. The patient with Covid19 also showed an incomplete valve closure with insufficiency. At the same time this patient showed a Covid19-associated deep vein thrombosis. Eight additional patients also had a thrombosis. Six of them suffered from cancer. Overall, the results were best visualized by V-Flow. CONCLUSION: The crosse as a significant venous structure can be well investigated by V-flow with respect to hemodynamic changes and a resulted reflux. Also associated changes close to the valve can be visualized well.

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Fluid-structure interaction of blood flow around a vein valve

Bioimpacts ◽

10.34172/bi.2020.21 ◽

2020 ◽

Vol 10 (3) ◽

pp. 169-175 ◽

Cited By ~ 6

Author(s):

Zahra Hajati ◽

Farhad Sadegh Moghanlou ◽

Mohammad Vajdi ◽

Seyed Esmail Razavi ◽

Somaieh Matin

Keyword(s):

Blood Flow ◽

Fluid Flow ◽

Circulatory System ◽

Von Mises Stress ◽

Shear Stresses ◽

Venous Valve ◽

Vein Wall ◽

Venous Valves ◽

Sediment Formation ◽

Von Mises

Introduction: Venous valves are a type of one-way valves which conduct blood flow toward the heart and prevent its backflow. Any malfunction of these organs may cause serious problems in the circulatory system. Numerical simulation can give us detailed information and point to point data such as velocity, wall shear stress, and von Mises stress from veins with small diameters, as obtaining such data is almost impossible using current medical devices. Having detailed information about fluid flow and valves' function can help the treatment of the related diseases. Methods: In the present work, the blood flow through a venous valve considering the flexibility of the vein wall and valve leaflets is investigated numerically. The governing equations of fluid flow and solid domain are discretized and solved by the Galerkin finite element method. Results: The obtained results showed that the blood velocity increases from inlet to the leaflets and then decreases passing behind the valve. A pair of vortices and the trapped region was observed just behind the valves. These regions have low shear stresses and are capable of sediment formation. Conclusion: The von Mises stress which is a criterion for the breakdown of solid materials was obtained. It was also observed that a maximum value occurred at the bottom of the leaflets.

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Role of Panchvalkala Kwatha Dhawana Karma in the management of non-healing varicose ulcer – A case study

Ayurline: International Journal of Research in Indian Medicine ◽

10.52482/ayurline.v5i02.507 ◽

2021 ◽

Vol 5 (02) ◽

Author(s):

Umesh Mohite ◽

Mukund D. Magare

Keyword(s):

Lower Limb ◽

Venous Insufficiency ◽

Ulcer Formation ◽

Venous Valve ◽

Venous Valves ◽

Venous Ulcers ◽

Varicose Ulcer ◽

Healing Wounds

ABSTRACT Venous ulcers (varicose ulcers or stasis ulcers) are the wounds occurring due to inappropriate functioning of venous valves, commonly of legs. It is most common and serious chronic venous insufficiency complication. The overall incidence rate is 0.76% in men and 1.42% in women. When venous valve gets damaged, it prevents the backflow of blood, which causes pressure in the vein that leads to hypertension, which stretches the veins resulting in ulcer formation. If not treated properly, the ulcers may get infected leading to cellulitis or gangrene and eventually may need amputation of the part of limb. In Ayurvedic prospective, varicose ulcers can be correlated with ‘Siragata Dushta Vrana’. Acharya Sushruta has advocated the Shashthi upakrama 1 (60 procedures) for treating the dushta vrana, among which Dhawana/ Parishek2 become third upakrama/procedure that means parishek procedure is included in first top 3 procedures and is useful in infected and non-healing wounds. Patients with varicose ulcers was advised to take ‘Sukshma Triphala’ internally and ‘Panchavalkala Kwatha Dhawana’ over lower limb daily twice a day followed by cleaning and dressing of wound which proved very effective and the ulcer healed completely in 30 days.

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Investigations on physico-chemical properties of TSPCU nonwoven for application as prosthetic venous valve

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2021-2156 ◽

2021 ◽

Vol 7 (2) ◽

pp. 613-616

Author(s):

Julia Schubert ◽

Daniela Arbeiter ◽

Andreas Götz ◽

Kerstin Lebahn ◽

Wolfram Schmidt ◽

...

Keyword(s):

Mechanical Properties ◽

Chemical Properties ◽

Storage Conditions ◽

Valve Leaflet ◽

Venous Valve ◽

Sem Images ◽

Venous Valves ◽

Prosthetic Valves ◽

Physico Chemical ◽

3D Printed

Abstract Electrospinning is used for producing nonwovens for medical polymer-based implants, such as prosthetic valves or covered scaffolds. In this study, nonwovens for prosthetic venous valves are investigated regarding their morphology and mechanics in physiological medium. Spinning molds were developed based on previous venous valve leaflet designs, 3D printed in different sizes and covered with electrospun nonwovens. Samples were stored in a physiological 0.9% saline at 37°C to investigate the influence of fiber rearrangement and swelling in medium for several weeks. Two different nonwovens of thermoplastic silicone-based polycarbonaturethane (TSPCU) were compared. Tensile test results show that storage in medium has a relevant influence on the mechanical properties. SEM images of TSPCU show substantially increased fiber diameters after 8 days stored in medium. After detaching the valve leaflet nonwovens from the molds, shrinkage of the material of approximately 12% was detected. A suitable valve size could be identified for joining with the stent structure into an interventional prosthetic venous valve. The results demonstrate the influence of storage conditions on the morphological and mechanical properties of electrospun TSPCU nonwovens. For development and dimensioning of venous valve leaflets, this change in mechanical behavior and possible shrinkage of the material has to be considered.

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Design and Modeling of a Prosthetic Venous Valve

Volume 4: 23rd Design for Manufacturing and the Life Cycle Conference; 12th International Conference on Micro- and Nanosystems ◽

10.1115/detc2018-86164 ◽

2018 ◽

Author(s):

Ryan Packer ◽

Brian D. Jensen ◽

Anton E. Bowden

Keyword(s):

Hydrostatic Pressure ◽

Shear Rate ◽

Femoral Vein ◽

The United States ◽

The Body ◽

Lower Limbs ◽

Venous Valve ◽

Venous Valves ◽

Prosthetic Valves ◽

Computational Fluid Dynamics Analysis

Chronic Venous Insufficiency (CVI) is a disease of the lower limbs that affects millions of people in the United States. CVI results from incompetent venous valves. The purpose of venous valves is to prevent retrograde blood flow to the lower limbs. Valve failure can lead to edema, pain, and ulcers. One solution that has great potential is to create an implantable venous valve that could restore function of the venous system. No prosthetic venous valves are clinically used currently because of problems with biocompatiblility and thrombogenicity caused by high shear rates. This paper presents a prosthetic venous valve that could overcome these difficulties by using carbon-infiltrated carbon nanotubes (CI-CNTs). This material has been proven to be thrombo-resistant, biocompatible due to its non-reactive properties, and durable. The valve was designed to be initially open and to close with physiological pressures. Finite element modeling showed that, with a hydrostatic pressure of 20 mmHg (the minimum hydrostatic pressure in the common femoral vein), it fully closed with a maximum stress of 117 MPa, which is below the ultimate strength of CI-CNTs. A computational fluid dynamics analysis demonstrated the valve would cause a maximum shear rate of 225.1 s−1, which is less than the maximum shear rate in the body. Hence, this valve would be less likely than previous prosthetic valves to develop blood clots. Currently, this is the lowest shear rate reported for a prosthetic venous valve. These results demonstrate that a CI-CNT prosthetic venous valve has the potential to be an effective treatment for CVI.

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Human venous valve disease caused by mutations in FOXC2 and GJC2

Journal of Experimental Medicine ◽

10.1084/jem.20160875 ◽

2017 ◽

Vol 214 (8) ◽

pp. 2437-2452 ◽

Cited By ~ 9

Author(s):

Oliver Lyons ◽

Prakash Saha ◽

Christopher Seet ◽

Adam Kuchta ◽

Andrew Arnold ◽

...

Keyword(s):

Endothelial Cells ◽

Blood Flow ◽

Transcription Factors ◽

Gap Junction ◽

Venous Hypertension ◽

Valve Disease ◽

Venous Valve ◽

Venous Valves ◽

Genetic Deletion ◽

Junction Proteins

Venous valves (VVs) prevent venous hypertension and ulceration. We report that FOXC2 and GJC2 mutations are associated with reduced VV number and length. In mice, early VV formation is marked by elongation and reorientation (“organization”) of Prox1hi endothelial cells by postnatal day 0. The expression of the transcription factors Foxc2 and Nfatc1 and the gap junction proteins Gjc2, Gja1, and Gja4 were temporospatially regulated during this process. Foxc2 and Nfatc1 were coexpressed at P0, and combined Foxc2 deletion with calcineurin-Nfat inhibition disrupted early Prox1hi endothelial organization, suggesting cooperative Foxc2–Nfatc1 patterning of these events. Genetic deletion of Gjc2, Gja4, or Gja1 also disrupted early VV Prox1hi endothelial organization at postnatal day 0, and this likely underlies the VV defects seen in patients with GJC2 mutations. Knockout of Gja4 or Gjc2 resulted in reduced proliferation of Prox1hi valve-forming cells. At later stages of blood flow, Foxc2 and calcineurin-Nfat signaling are each required for growth of the valve leaflets, whereas Foxc2 is not required for VV maintenance.

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Innovative Design of a Venous Valve Intended for PIV Measurements

ASME 2011 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2011-53515 ◽

2011 ◽

Author(s):

Benjamin Van Der Smissen ◽

Koen Van Canneyt ◽

Mathias Vermeulen ◽

Martin Bayley ◽

Andrew V. Narracott ◽

...

Keyword(s):

Vascular Access ◽

Artificial Kidney ◽

Venous Valve ◽

Innovative Design ◽

Piv Measurements ◽

Venous Valves ◽

Image Velocimetry ◽

Severe Chronic Kidney Disease ◽

High Flows ◽

Valve Model

Today, hemodialysis is a common therapy to treat people with severe chronic kidney disease. This therapy strongly relies upon the vascular access that connects the patient’s circulation to the artificial kidney and which is obtained by surgically creating an arteriovenous fistula in the arm. However, due to the high flows involved at the venous side and elevated venous pressures, the functioning of venous valves in the arm is significantly disturbed, which too often bring about serious dysfunctions or complications in the patient [1–2]. To this end, research is done to improve the outcome of vascular access in patients on hemodialysis therapy by means of computational modeling [3]. One crucial challenge, however, is experimental validation of these computer models, preferably by using Particle Image Velocimetry (PIV) for simulations of flow fields. Yet, the task of modeling the venous valve is daunting because this valve functions at very low physiological pressure differences. Moreover, PIV requires an experimental model to be fully transparent. In this study, we propose an innovative design of a PIV-compatible venous valve model which has the ability to function at minimal pressure differences and which is able to generate valuable PIV data.

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Diagnosis and Treatment of Postthrombotic Syndrome

Hämostaseologie ◽

10.1055/a-1145-0108 ◽

2020 ◽

Vol 40 (02) ◽

pp. 214-220

Author(s):

Guido Bruning ◽

Jasmin Woitalla-Bruning ◽

Anne-Caroline Queisser ◽

Johanna Katharina Buhr

Keyword(s):

Varicose Veins ◽

Compression Therapy ◽

Postthrombotic Syndrome ◽

Venous Reflux ◽

Venous Valve ◽

Vein Thrombosis ◽

Venous Valves ◽

Fast Progression ◽

Secondary Healing ◽

Deep Vein

AbstractAfter acute treatment of deep vein thrombosis, not only the risk but also associated side effects of postthrombotic syndrome (PTS) are often underestimated.There are essentially two main types of PTS.1. Obstructive type—no sufficient recanalization of the deep vein.2. Refluctive type—sufficient recanalization of the deep vein, but insufficient venous valves in conjunction with venous reflux.A statement regarding deep vein recanalization and venous valve function can be made at the earliest after 6 months.PTS is often diagnosed without appropriate medical history. However, the assessment of the degree of recanalization and venous reflux is paramount to the medical prognosis. In our opinion, beside proximal thrombosis, sufficient recanalization combined with a strong venous reflux, especially in the popliteal vein, works as a powerful predictor for an unfavorable and fast progression of PTS and chronic venous insufficiency. Thus, the obstructive type is prognostically more favorable. For PTS in general, consistent compression therapy represents the first-line treatment option.With concomitant varicosis, one should assess whether the varicose veins represent primary varicosis with reflux or secondary varicosis without reflux. Especially in the presence of venous ulcers, the elimination of concomitant primary varicosis leads to an improved prognosis. Moist wound treatment is considered to be the standard treatment for all wounds undergoing secondary healing. A standardized set of topical therapeutic agents also facilitates the treatment. In individual cases “ulcershaving” and mesh graft transplantation proved to be successful.

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