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Baltazar S, Northrup H, Chang J, Somarathna M, Isayeva Waldrop T, Lee T, Shiu YT. Effects of endothelial nitric oxide synthase on mouse arteriovenous fistula hemodynamics. Sci Rep 2023; 13:22786. [PMID: 38123618 PMCID: PMC10733286 DOI: 10.1038/s41598-023-49573-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 12/09/2023] [Indexed: 12/23/2023] Open
Abstract
Newly created arteriovenous fistulas (AVFs) often fail to mature for dialysis use due to disturbed blood flow at and near the AVF anastomosis. The disturbed flow inhibits the endothelial nitric oxide synthase (NOS3) pathway, thus decreasing the production of nitric oxide, a vasodilator. Previously, our group reported that NOS3 expression levels affect AVF lumen size in a mouse model. In this study, we performed MRI-based computational fluid dynamics simulations to investigate the hemodynamical parameters (velocity, wall shear stress (WSS), and vorticity) in a mouse AVF model at day 7 and day 21 post-AVF creation using three NOS3 strains: overexpression (OE), knockout (KO), and wild-type (WT) control. This study is the first to reveal hemodynamics over time in mouse AVFs, consider spatial heterogeneity along the vein, and reveal the effect of NOS3 on the natural history of mouse AVF hemodynamics. From day 7 to day 21, OE has smoother streamlines and had significantly lower vorticity and WSS than WT and KO, suggesting that WSS was attempting to return to pre-surgery baseline, respectively. Our results conclude that the overexpression of NOS3 leads to desired optimal hemodynamics during AVF remodeling. Future studies can investigate enhancing the NOS3 pathway to improve AVF development.
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Affiliation(s)
- Shelly Baltazar
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Utah, 30 N Mario Capecchi Drive, 3rd Floor South, Salt Lake City, UT, 84112, USA
| | - Hannah Northrup
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Utah, 30 N Mario Capecchi Drive, 3rd Floor South, Salt Lake City, UT, 84112, USA
| | - Joshua Chang
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Utah, 30 N Mario Capecchi Drive, 3rd Floor South, Salt Lake City, UT, 84112, USA
| | - Maheshika Somarathna
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Tatyana Isayeva Waldrop
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Timmy Lee
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
- Veterans Affairs Medical Center, Birmingham, AL, USA
| | - Yan-Ting Shiu
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Utah, 30 N Mario Capecchi Drive, 3rd Floor South, Salt Lake City, UT, 84112, USA.
- Veterans Affairs Medical Center, Salt Lake City, UT, USA.
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Hülsmann J, Fraune T, Dodawatta B, Reuter F, Beutner M, Beck V, Hackert-Oschätzchen M, Ohl CD, Bettenbrock K, Janiga G, Wippermann J, Wacker M. Integrated biophysical matching of bacterial nanocellulose coronary artery bypass grafts towards bioinspired artery typical functions. Sci Rep 2023; 13:18274. [PMID: 37880281 PMCID: PMC10600183 DOI: 10.1038/s41598-023-45451-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 10/19/2023] [Indexed: 10/27/2023] Open
Abstract
Revascularization via coronary artery bypass grafting (CABG) to treat cardiovascular disease is established as one of the most important lifesaving surgical techniques worldwide. But the shortage in functionally self-adaptive autologous arteries leads to circumstances where the clinical reality must deal with fighting pathologies coming from the mismatching biophysical functionality of more available venous grafts. Synthetic biomaterial-based CABG grafts did not make it to the market yet, what is mostly due to technical hurdles in matching biophysical properties to the complex demands of the CABG niche. But bacterial Nanocellulose (BNC) Hydrogels derived by growing biofilms hold a naturally integrative character in function-giving properties by its freedom in designing form and intrinsic fiber architecture. In this study we use this integral to combine impacts on the luminal fiber matrix, biomechanical properties and the reciprocal stimulation of microtopography and induced flow patterns, to investigate biomimetic and artificial designs on their bio-functional effects. Therefore, we produced tubular BNC-hydrogels at distinctive designs, characterized the structural and biomechanical properties and subjected them to in vitro endothelial colonization in bioreactor assisted perfusion cultivation. Results showed clearly improved functional properties and gave an indication of successfully realized stimulation by artery-typical helical flow patterns.
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Affiliation(s)
- Jörn Hülsmann
- Department for Cardiac Surgery, Medical Faculty, Otto von Guericke University, Magdeburg, Germany.
| | - Theresa Fraune
- Department for Cardiac Surgery, Medical Faculty, Otto von Guericke University, Magdeburg, Germany
| | - Baratha Dodawatta
- Laboratory of Fluid Dynamics and Technical Flows, Otto von Guericke University, Magdeburg, Germany
| | - Fabian Reuter
- Department Soft Matter, Otto von Guericke University, Magdeburg, Germany
| | - Martin Beutner
- Chair of Manufacturing Technology with Focus Machining, Institute of Manufacturing Technology and Quality Management, Otto von Guericke University, Magdeburg, Germany
| | - Viktoria Beck
- Department for Cardiac Surgery, Medical Faculty, Otto von Guericke University, Magdeburg, Germany
| | - Matthias Hackert-Oschätzchen
- Chair of Manufacturing Technology with Focus Machining, Institute of Manufacturing Technology and Quality Management, Otto von Guericke University, Magdeburg, Germany
| | - Claus Dieter Ohl
- Department Soft Matter, Otto von Guericke University, Magdeburg, Germany
| | - Katja Bettenbrock
- Max Plank Institute for Dynamics of Complex Technical Systems, Magdeburg, Germany
| | - Gabor Janiga
- Laboratory of Fluid Dynamics and Technical Flows, Otto von Guericke University, Magdeburg, Germany
| | - Jens Wippermann
- Department for Cardiac Surgery, Medical Faculty, Otto von Guericke University, Magdeburg, Germany
| | - Max Wacker
- Department for Cardiac Surgery, Medical Faculty, Otto von Guericke University, Magdeburg, Germany
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Wen J, Liu X, Lei J, Wang J, Chen X, Zheng T, Yuan D. Hemodynamics in renal arteries with partial coverage after endovascular aneurysm repair affected by renal orientations. MEDICINE IN NOVEL TECHNOLOGY AND DEVICES 2023. [DOI: 10.1016/j.medntd.2023.100224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023] Open
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A realistic arteriovenous dialysis graft model for hemodynamic simulations. PLoS One 2022; 17:e0269825. [PMID: 35862379 PMCID: PMC9302782 DOI: 10.1371/journal.pone.0269825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 05/30/2022] [Indexed: 11/19/2022] Open
Abstract
Objective The hemodynamic benefit of novel arteriovenous graft (AVG) designs is typically assessed using computational models that assume highly idealized graft configurations and/or simplified boundary conditions representing the peripheral vasculature. The objective of this study is to evaluate whether idealized AVG models are suitable for hemodynamic evaluation of new graft designs, or whether more realistic models are required. Methods An idealized and a realistic, clinical imaging based, parametrized AVG geometry were created. Furthermore, two physiological boundary condition models were developed to represent the peripheral vasculature. We assessed how graft geometry (idealized or realistic) and applied boundary condition models of the peripheral vasculature (physiological or distal zero-flow) impacted hemodynamic metrics related to AVG dysfunction. Results Anastomotic regions exposed to high WSS (>7, ≤40 Pa), very high WSS (>40 Pa) and highly oscillatory WSS were larger in the simulations using the realistic AVG geometry. The magnitude of velocity perturbations in the venous segment was up to 1.7 times larger in the realistic AVG geometry compared to the idealized one. When applying a (non-physiological zero-flow) boundary condition that neglected blood flow to and from the peripheral vasculature, we observed large regions exposed to highly oscillatory WSS. These regions could not be observed when using either of the newly developed distal boundary condition models. Conclusion Hemodynamic metrics related to AVG dysfunction are highly dependent on the geometry and the distal boundary condition model used. Consequently, the hemodynamic benefit of a novel graft design can be misrepresented when using idealized AVG modelling setups.
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Wen J, Wu W, Peng L. 'Heart-like' cross-sectional shape can better improve the hemodynamics in spiral laminar flow graft for small-caliber bypass application: a numerical study. Comput Methods Biomech Biomed Engin 2021; 25:1487-1498. [PMID: 34937461 DOI: 10.1080/10255842.2021.2017905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Small-caliber grafts remain disappointed in the long-term bypass surgeries of coronary and peripheral arterial diseases. In order to improve the hemodynamics in small-caliber artery bypass grafts (ABGs), an improved spiral laminar flow (improved-SLF) graft with a 'heart-like' cross-sectional shape was proposed and verified by computational fluid dynamics simulation in this study. The results show that such graft can indeed induce a spiral flow and enhance the WSS distribution on the graft section. Furthermore, the helically distributed ribbon of unfavorable WSS observed in the original SLF graft was eliminated in the improved-SLF graft due to its smoothed and gentle helical ridge. On the other hand, improved-SLF ABG improved the WSS distribution in the distal anastomosis as well, because it maintained the strength of spiral flow when entering the anastomosis region. Finally, the improved-SLF ABG slightly increased the pressure drop along the bypass due to its small change of the general graft structure. As a proof-of-concept study, it can be concluded that improved-SLF graft can not only evenly enhance the WSS distribution in the graft section, but also improve the hemodynamic environment in the distal anastomosis without significantly increasing the pressure drop along the bypass, indicating such new helical-type graft may be more suitable to be used in the small-caliber graft bypass surgeries.
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Affiliation(s)
- Jun Wen
- Department of Mechanics, Institute of Civil Engineering and Architecture, Southwest University of Science and Technology, Mianyang, China
| | - Wenqing Wu
- Department of Mathematics, School of Science, Southwest University of Science and Technology, Mianyang, China
| | - Liqing Peng
- Department of Radiology, West China Hospital, Sichuan University, Chengdu, China
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Williams D, Leuthardt EC, Genin GM, Zayed M. Tailoring of arteriovenous graft-to-vein anastomosis angle to attenuate pathological flow fields. Sci Rep 2021; 11:12153. [PMID: 34108499 PMCID: PMC8190231 DOI: 10.1038/s41598-021-90813-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 05/04/2021] [Indexed: 02/05/2023] Open
Abstract
Arteriovenous grafts are routinely placed to facilitate hemodialysis in patients with end stage renal disease. These grafts are conduits between higher pressure arteries and lower pressure veins. The connection on the vein end of the graft, known as the graft-to-vein anastomosis, fails frequently and chronically due to high rates of stenosis and thrombosis. These failures are widely believed to be associated with pathologically high and low flow shear strain rates at the graft-to-vein anastomosis. We hypothesized that consistent with pipe flow dynamics and prior work exploring vein-to-artery anastomosis angles in arteriovenous fistulas, altering the graft-to-vein anastomosis angle can reduce the incidence of pathological shear rate fields. We tested this via computational fluid dynamic simulations of idealized arteriovenous grafts, using the Bird-Carreau constitutive law for blood. We observed that low graft-to-vein anastomosis angles ([Formula: see text]) led to increased incidence of pathologically low shear rates, and that high graft-to-vein anastomosis angles ([Formula: see text]) led to increased incidence of pathologically high shear rates. Optimizations predicted that an intermediate ([Formula: see text]) graft-to-anastomosis angle was optimal. Our study demonstrates that graft-to-vein anastomosis angles can significantly impact pathological flow fields, and can be optimized to substantially improve arteriovenous graft patency rates.
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Affiliation(s)
- Dillon Williams
- Vascular Surgery Biomedical Research Laboratory, Washington University School of Medicine, Saint Louis, MO, 60613, USA
- Center for Innovation in Neuroscience and Technology, Department of Neurological Surgery, Washington University School of Medicine, Saint Louis, MO, 60613, USA
| | - Eric C Leuthardt
- Center for Innovation in Neuroscience and Technology, Department of Neurological Surgery, Washington University School of Medicine, Saint Louis, MO, 60613, USA
- Department of Biomedical Engineering, Washington University, Saint Louis, MO, 63130, USA
| | - Guy M Genin
- Center for Innovation in Neuroscience and Technology, Department of Neurological Surgery, Washington University School of Medicine, Saint Louis, MO, 60613, USA.
- Department of Biomedical Engineering, Washington University, Saint Louis, MO, 63130, USA.
- NSF Science and Technology Center for Engineering MechanoBiology, Washington University in St. Louis, Saint Louis, USA.
| | - Mohamed Zayed
- Vascular Surgery Biomedical Research Laboratory, Washington University School of Medicine, Saint Louis, MO, 60613, USA.
- Center for Innovation in Neuroscience and Technology, Department of Neurological Surgery, Washington University School of Medicine, Saint Louis, MO, 60613, USA.
- Department of Biomedical Engineering, Washington University, Saint Louis, MO, 63130, USA.
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Quicken S, Delhaas T, Mees BME, Huberts W. Haemodynamic optimisation of a dialysis graft design using a global optimisation approach. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2021; 37:e3423. [PMID: 33249781 PMCID: PMC7900962 DOI: 10.1002/cnm.3423] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 10/14/2020] [Accepted: 11/18/2020] [Indexed: 06/12/2023]
Abstract
Disturbed flow and the resulting non-physiological wall shear stress (WSS) at the graft-vein anastomosis play an important role in arteriovenous graft (AVG) patency loss. Modifying graft geometry with helical features is a popular approach to minimise the occurrence of detrimental haemodynamics and to potentially increase graft longevity. Haemodynamic optimisation of AVGs typically requires many computationally expensive computational fluid dynamics (CFD) simulations to evaluate haemodynamic performance of different graft designs. In this study, we aimed to develop a haemodynamically optimised AVG by using an efficient meta-modelling approach. A training dataset containing CFD evaluations of 103 graft designs with helical features was used to develop computationally low-cost meta-models for haemodynamic metrics related to graft dysfunction. During optimisation, the meta-models replaced CFD simulations that were otherwise needed to evaluate the haemodynamic performance of possible graft designs. After optimisation, haemodynamic performance of the optimised graft design was verified using a CFD simulation. The obtained optimised graft design contained both a helical graft centreline and helical ridge. Using the optimised design, the magnitude of flow disturbances and the size of the anastomotic areas exposed to non-physiological WSS was successfully reduced compared to a regular straight graft. Our meta-modelling approach allowed to reduce the total number of CFD model evaluations required for our design optimisation by approximately a factor 2000. The applied efficient meta-modelling technique was successful in identifying an optimal, helical graft design at relatively low computational costs. Future studies should evaluate the in vivo benefits of the developed graft design.
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Affiliation(s)
- Sjeng Quicken
- Department of Biomedical EngineeringCARIM School for Cardiovascular Diseases, Maastricht UniversityMaastrichtThe Netherlands
- Eindhoven University of TechnologyDepartment of Biomedical EngineeringEindhovenNetherlands
| | - Tammo Delhaas
- Department of Biomedical EngineeringCARIM School for Cardiovascular Diseases, Maastricht UniversityMaastrichtThe Netherlands
| | - Barend M. E. Mees
- Department of Vascular SurgeryMaastricht University Medical CentreMaastrichtthe Netherlands
| | - Wouter Huberts
- Department of Biomedical EngineeringCARIM School for Cardiovascular Diseases, Maastricht UniversityMaastrichtThe Netherlands
- Eindhoven University of TechnologyDepartment of Biomedical EngineeringEindhovenNetherlands
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The Effect of Geometric Graft Modification on Arteriovenous Graft Patency in Haemodialysis Patients: A Systematic Review and Meta-Analysis. Eur J Vasc Endovasc Surg 2020; 60:568-577. [PMID: 32807670 DOI: 10.1016/j.ejvs.2020.06.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 05/30/2020] [Accepted: 06/16/2020] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Arteriovenous grafts (AVGs) are the second best option for haemodialysis access when native arteriovenous fistulae placement is not possible, because they have a lower patency owing to neointimal hyperplasia at the venous anastomosis. This review aimed to evaluate the effect of geometric graft modification to the graft-vein interface on AVG patency. DATA SOURCES The MEDLINE and Embase (OvidSP) databases were systematically searched for relevant studies analysing the effect of geometrically modified AVGs on graft patency and stenosis formation (last search July 2019). REVIEW METHODS Data regarding AVG type, patency, and graft outlet stenosis was extracted for further evaluation. Data were pooled in a random effects model to estimate the relative risk of graft occlusion within one year. Follow up, number of patients, and relevant patient characteristics were extracted for the quality assessment of the included studies using Newcastle-Ottawa Scale and Cochrane Risk of Bias Tool. The quality of the evidence was determined according to the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) system. RESULTS Search strategies produced 2772 hits, of which eight articles met predetermined inclusion criteria. Overall, the included articles had low to moderate risk of bias. In total, 414 expanded polytetrafluoroethylene AVGs (232 geometrically modified and 182 standard) were analysed, comprising two modified AVG types: a prosthetic cuff design (Venaflo®) and grafts with a Tyrell vein patch. Overall, modified grafts did not show a statistically significantly higher one year primary (relative risk [RR] 0.86, 95% confidence interval [CI] 95% 0.64-1.16; GRADE: "low to very low") or secondary patency (RR 0.57, 95% CI 0.32-1.02; GRADE: "low to very low") when compared with standard AVGs. Analysis of prosthetic cuffed grafts (112 patients) separately demonstrated a statistically significantly higher one year primary (RR 0.75, 95% CI 0.61-0.91) and one year secondary patency (RR 0.47, 95% CI 0.30-0.75) compared with standard grafts (92 patients). The results on stenosis formation were inconclusive and inadmissible to quantitative analyses. CONCLUSION The meta-analysis showed that a prosthetic cuff design significantly improves AVG patency, while a venous cuff does not. Although the heterogeneity and low number of available studies limit the strength of the results, this review shows the potential of grafts with geometric modification to the graft-vein anastomosis and should stimulate further clinical and fundamental research on improving graft geometry to improve graft patency.
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De Nisco G, Gallo D, Siciliano K, Tasso P, Lodi Rizzini M, Mazzi V, Calò K, Antonucci M, Morbiducci U. Hemodialysis arterio-venous graft design reducing the hemodynamic risk of vascular access dysfunction. J Biomech 2020; 100:109591. [PMID: 31902610 DOI: 10.1016/j.jbiomech.2019.109591] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/04/2019] [Accepted: 12/18/2019] [Indexed: 11/18/2022]
Abstract
Although arterio-venous grafts (AVGs) represent the second choice as permanent vascular access for hemodialysis, this solution is still affected by a relevant failure rate due to graft thrombosis, and development of neointimal hyperplasia (IH) at the distal vein. As a key role in these processes has been attributed to the abnormal hemodynamics establishing in the distal vein, the optimization of AVGs design aimed at minimizing flow disturbances would reduce AVG hemodynamic-related risks. In this study we used computational fluid dynamics to investigate the impact of alternative AVG designs on the reduction of IH and thrombosis risk at the distal venous anastomosis. The performance of the newly designed AVGs was compared to that of commercially available devices. In detail, a total of eight AVG models in closed-loop configuration were constructed: two models resemble the commercially available straight conventional and helical-shaped AVGs; six models are characterized by the insertion of a flow divider (FD), straight or helical shaped, differently positioned inside the graft. Unfavorable hemodynamic conditions were analyzed by assessing the exposure to disturbed shear at the distal vein. Bulk flow was investigated in terms of helical blood flow features, potential thrombosis risk, and pressure drop over the graft. Findings from this study clearly show that using a helically-shaped FD located at the venous side of the graft could induce beneficial helical flow patterns that, minimizing flow disturbances, reduce the IH-related risk of failure at the distal vein, with a clinically irrelevant increase in thrombosis risk and pressure drop over the graft.
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Affiliation(s)
- Giuseppe De Nisco
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Diego Gallo
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Katia Siciliano
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Paola Tasso
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Maurizio Lodi Rizzini
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Valentina Mazzi
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Karol Calò
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | | | - Umberto Morbiducci
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.
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Tasso P, Lodi Rizzini M, Raptis A, Matsagkas M, De Nisco G, Gallo D, Xenos M, Morbiducci U. In-stent graft helical flow intensity reduces the risk of migration after endovascular aortic repair. J Biomech 2019; 94:170-179. [PMID: 31421805 DOI: 10.1016/j.jbiomech.2019.07.034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 07/25/2019] [Accepted: 07/27/2019] [Indexed: 10/26/2022]
Abstract
During the last years endovascular aneurysm repair (EVAR) became the elective treatment for abdominal aortic aneurysms (AAAs) thanks to lower mortality and morbidity rates than open surgery. In face of these advantages, stent-graft performances are still clinically suboptimal. In particular, post-surgical complications derive from device migration as a consequence of the hemodynamic forces acting on the endograft. In this regard, while the importance of hemodynamic surface forces is well recognized, the role of the in-stent flow is still unclear. Here we hypothesize that in-stent helical blood flow patterns might influence the distribution of the displacement forces (DFs) acting on the stent-graft and, ultimately, the risk of stent migration. To test this hypothesis, the hemodynamics of 20 post-EVAR models of patients treated with two different commercial endografts was analyzed using computational hemodynamics. The main findings of the study indicate that: (1) helical flow intensity decreases the risk of endograft migration, as given by an inverse correlation between helicity intensity (h2) and time-averaged displacement forces (TADFs) (p < 0.05); (2) unbalanced counter-rotating helical structures in the legs of the device contribute, in particular along the systole, to significantly suppress TADFs (p < 0.01); (3) as expected, helical flow intensity is positively correlated with pressure drop and resistance to flow (p < 0.001). The findings of this study suggest that a design strategy promoting in-stent helical flow structures could contribute to minimize the risk of migration of implanted EVAR devices.
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Affiliation(s)
- Paola Tasso
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino, Italy
| | - Maurizio Lodi Rizzini
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino, Italy
| | - Anastasios Raptis
- Laboratory for Vascular Simulations, Institute of Vascular Diseases, Larissa, Greece
| | - Mitialdis Matsagkas
- Department of Vascular Surgery, Faculty of Medicine, University of Thessaly, Larissa, Greece
| | - Giuseppe De Nisco
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino, Italy
| | - Diego Gallo
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino, Italy
| | - Michalis Xenos
- Department of Mathematics University of Ioannina, Ioannina, Greece
| | - Umberto Morbiducci
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino, Italy.
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Shiu YT, Rotmans JI, Geelhoed WJ, Pike DB, Lee T. Arteriovenous conduits for hemodialysis: how to better modulate the pathophysiological vascular response to optimize vascular access durability. Am J Physiol Renal Physiol 2019; 316:F794-F806. [PMID: 30785348 PMCID: PMC6580244 DOI: 10.1152/ajprenal.00440.2018] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 02/04/2019] [Accepted: 02/17/2019] [Indexed: 12/11/2022] Open
Abstract
Vascular access is the lifeline for patients on hemodialysis. Arteriovenous fistulas (AVFs) are the preferred vascular access, but AVF maturation failure remains a significant clinical problem. Currently, there are no effective therapies available to prevent or treat AVF maturation failure. AVF maturation failure frequently results from venous stenosis at the AVF anastomosis, which is secondary to poor outward vascular remodeling and excessive venous intimal hyperplasia that narrows the AVF lumen. Arteriovenous grafts (AVGs) are the next preferred vascular access when an AVF creation is not possible. AVG failure is primarily the result of venous stenosis at the vein-graft anastomosis, which originates from intimal hyperplasia development. Although there has been advancement in our knowledge of the pathophysiology of AVF maturation and AVG failure, this has not translated into effective therapies for these two important clinical problems. Further work will be required to dissect out the mechanisms of AVF maturation failure and AVG failure to develop more specific therapies. This review highlights the major recent advancements in AVF and AVG biology, reviews major clinical trials, and discusses new areas for future research.
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Affiliation(s)
- Yan-Ting Shiu
- Division of Nephrology, University of Utah , Salt Lake City, Utah
| | - Joris I Rotmans
- Department of Internal Medicine, Leiden University Medical Center , Leiden , The Netherlands
| | - Wouter Jan Geelhoed
- Department of Internal Medicine, Leiden University Medical Center , Leiden , The Netherlands
| | - Daniel B Pike
- Division of Nephrology, University of Utah , Salt Lake City, Utah
| | - Timmy Lee
- Department of Medicine and Division of Nephrology, University of Alabama at Birmingham , Birmingham, Alabama
- Veterans Affairs Medical Center , Birmingham, Alabama
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12
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Efficiently Generating Mixing by Combining Differing Small Amplitude Helical Geometries. FLUIDS 2019. [DOI: 10.3390/fluids4020059] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Helical geometries have been used in recent years to form cardiovascular prostheses such as stents and shunts. The helical geometry has been found to induce swirling flow, promoting in-plane mixing. This is hypothesised to reduce the formation of thrombosis and neo-intimal hyperplasia, in turn improving device patency and reducing re-implantation rates. In this paper we investigate whether joining together two helical geometries, of differing helical radii, in a repeating sequence, can produce significant gains in mixing effectiveness, by embodying a ‘streamline crossing’ flow environment. Since the computational cost of calculating particle trajectories over extended domains is high, in this work we devised a procedure for efficiently exploring the large parameter space of possible geometry combinations. Velocity fields for the single geometries were first obtained using the spectral/hp element method. These were then discontinuously concatenated, in series, for the particle tracking based mixing analysis of the combined geometry. Full computations of the most promising combined geometries were then performed. Mixing efficiency was evaluated quantitatively using Poincaré sections, particle residence time data, and information entropy. Excellent agreement was found between the idealised (concatenated flow field) and the full simulations of mixing performance, revealing that a strict discontinuity between velocity fields is not required for mixing enhancement, via streamline crossing, to occur. Optimal mixing was found to occur for the combination R = 0.2 D and R = 0.5 D , producing a 70 % increase in mixing, compared with standard single helical designs. The findings of this work point to the benefits of swirl disruption and suggest concatenation as an efficient means to determine optimal configurations of repeating geometries for future designs of vascular prostheses.
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Prashantha B, Anish S. Computational investigations on the hemodynamic performance of a new swirl generator in bifurcated arteries. Comput Methods Biomech Biomed Engin 2019; 22:364-375. [DOI: 10.1080/10255842.2018.1556974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- B. Prashantha
- Department of Mechanical Engineering, M S Ramaiah Institute of Technology, Bengaluru, Karnataka, India
| | - S. Anish
- Advanced Fluid Mechanics Laboratory, Department of Mechanical Engineering, National Institute of Technology, Surathkal, Karnataka, India
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14
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McNally A, Akingba AG, Sucosky P. Effect of arteriovenous graft flow rate on vascular access hemodynamics in a novel modular anastomotic valve device. J Vasc Access 2018; 19:446-454. [PMID: 30192183 DOI: 10.1177/1129729818758229] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
PURPOSE Perturbed vascular access hemodynamics is considered a potential driver of intimal hyperplasia, the leading cause of vascular access failure. To improve vascular access patency, a modular anastomotic valve device has been designed to normalize venous flow between hemodialysis periods while providing normal vascular access during hemodialysis. The objective of this study was to quantify the effects of arteriovenous graft flow rate on modular anastomotic valve device vascular access hemodynamics under realistic hemodialysis conditions. METHODS Modular anastomotic valve device inlet and outlet flow conditions and velocity profiles were measured by ultrasound Doppler in a vascular access flow loop replicating arteriovenous graft flow rates of 800, 1000, and 1500 mL/min. Fluid-structure interaction simulations were performed to identify low wall shear stress regions on the vein wall and to characterize them in terms of temporal shear magnitude, oscillatory shear index, and relative residence time. The model was validated with respect to the Doppler measurements. RESULTS The low wall shear stress region generated downstream of the anastomosis under low and moderate arteriovenous graft flow rates was eliminated under the highest arteriovenous graft flow rate. Increase in arteriovenous graft flow rate from 800 to 1500 mL/min resulted in a substantial increase in wall shear stress magnitude (27-fold increase in temporal shear magnitude), the elimination of wall shear stress bidirectionality (0.20-point reduction in oscillatory shear index), and a reduction in flow stagnation (98% decrease in relative residence time). While the results suggest the ability of high arteriovenous graft flow rates to protect the venous wall from intimal hyperplasia-prone hemodynamics, they indicate their adverse impact on the degree of venous hemodynamic abnormality.
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Affiliation(s)
- Andrew McNally
- 1 Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN, USA
| | - A George Akingba
- 2 Department of Vascular and Endovascular Surgery, Detroit Medical Center, Detroit, MI, USA
| | - Philippe Sucosky
- 3 Department of Mechanical and Materials Engineering, Wright State University, Dayton, OH, USA
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15
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Ene-Iordache B, Remuzzi A. Blood Flow in Idealized Vascular Access for Hemodialysis: A Review of Computational Studies. Cardiovasc Eng Technol 2017; 8:295-312. [PMID: 28664239 DOI: 10.1007/s13239-017-0318-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 06/26/2017] [Indexed: 10/19/2022]
Abstract
Although our understanding of the failure mechanism of vascular access for hemodialysis has increased substantially, this knowledge has not translated into successful therapies. Despite advances in technology, it is recognized that vascular access is difficult to maintain, due to complications such as intimal hyperplasia. Computational studies have been used to estimate hemodynamic changes induced by vascular access creation. Due to the heterogeneity of patient-specific geometries, and difficulties with obtaining reliable models of access vessels, idealized models were often employed. In this review we analyze the knowledge gained with the use of computational such simplified models. A review of the literature was conducted, considering studies employing a computational fluid dynamics approach to gain insights into the flow field phenotype that develops in idealized models of vascular access. Several important discoveries have originated from idealized model studies, including the detrimental role of disturbed flow and turbulent flow, and the beneficial role of spiral flow in intimal hyperplasia. The general flow phenotype was consistent among studies, but findings were not treated homogeneously since they paralleled achievements in cardiovascular biomechanics which spanned over the last two decades. Computational studies in idealized models are important for studying local blood flow features and evaluating new concepts that may improve the patency of vascular access for hemodialysis. For future studies we strongly recommend numerical modelling targeted at accurately characterizing turbulent flows and multidirectional wall shear disturbances.
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Affiliation(s)
- Bogdan Ene-Iordache
- Laboratory of Biomedical Technologies, Clinical Research Center for Rare Diseases Aldo e Cele Daccò, IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri", Via G.B. Camozzi 3, 24020, Ranica, BG, Italy.
| | - Andrea Remuzzi
- Laboratory of Biomedical Technologies, Clinical Research Center for Rare Diseases Aldo e Cele Daccò, IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri", Via G.B. Camozzi 3, 24020, Ranica, BG, Italy.,Department of Management, Information and Production and Engineering, University of Bergamo, Dalmine, BG, Italy
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16
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Cunnane CV, Cunnane EM, Walsh MT. A Review of the Hemodynamic Factors Believed to Contribute to Vascular Access Dysfunction. Cardiovasc Eng Technol 2017; 8:280-294. [DOI: 10.1007/s13239-017-0307-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 05/09/2017] [Indexed: 11/29/2022]
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17
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Donadoni F, Pichardo-Almarza C, Bartlett M, Dardik A, Homer-Vanniasinkam S, Díaz-Zuccarini V. Patient-Specific, Multi-Scale Modeling of Neointimal Hyperplasia in Vein Grafts. Front Physiol 2017; 8:226. [PMID: 28458640 PMCID: PMC5394124 DOI: 10.3389/fphys.2017.00226] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 03/30/2017] [Indexed: 11/16/2022] Open
Abstract
Neointimal hyperplasia is amongst the major causes of failure of bypass grafts. The disease progression varies from patient to patient due to a range of different factors. In this paper, a mathematical model will be used to understand neointimal hyperplasia in individual patients, combining information from biological experiments and patient-specific data to analyze some aspects of the disease, particularly with regard to mechanical stimuli due to shear stresses on the vessel wall. By combining a biochemical model of cell growth and a patient-specific computational fluid dynamics analysis of blood flow in the lumen, remodeling of the blood vessel is studied by means of a novel computational framework. The framework was used to analyze two vein graft bypasses from one patient: a femoro-popliteal and a femoro-distal bypass. The remodeling of the vessel wall and analysis of the flow for each case was then compared to clinical data and discussed as a potential tool for a better understanding of the disease. Simulation results from this first computational approach showed an overall agreement on the locations of hyperplasia in these patients and demonstrated the potential of using new integrative modeling tools to understand disease progression.
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Affiliation(s)
| | | | | | - Alan Dardik
- The Department of Surgery, Yale University School of MedicineNew Haven, CT, USA.,Veteran Affairs Connecticut Healthcare SystemWest Haven, CT, USA
| | - Shervanthi Homer-Vanniasinkam
- Mechanical Engineering, University College LondonLondon, UK.,Leeds Vascular Institute, Leeds General InfirmaryLeeds, UK.,Division of Surgery, University of WarwickWarwick, UK
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18
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Bioinspired helical graft with taper to enhance helical flow. J Biomech 2016; 49:3643-3650. [DOI: 10.1016/j.jbiomech.2016.09.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Revised: 09/09/2016] [Accepted: 09/19/2016] [Indexed: 11/23/2022]
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19
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Chiastra C, Iannaccone F, Grundeken MJ, Gijsen FJH, Segers P, De Beule M, Serruys PW, Wykrzykowska JJ, van der Steen AFW, Wentzel JJ. Coronary fractional flow reserve measurements of a stenosed side branch: a computational study investigating the influence of the bifurcation angle. Biomed Eng Online 2016; 15:91. [PMID: 27495804 PMCID: PMC4974683 DOI: 10.1186/s12938-016-0211-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 07/20/2016] [Indexed: 12/31/2022] Open
Abstract
Background Coronary hemodynamics and physiology specific for bifurcation lesions was not well understood. To investigate the influence of the bifurcation angle on the intracoronary hemodynamics of side branch (SB) lesions computational fluid dynamics simulations were performed. Methods A parametric model representing a left anterior descending—first diagonal coronary bifurcation lesion was created according to the literature. Diameters obeyed fractal branching laws. Proximal and distal main branch (DMB) stenoses were both set at 60 %. We varied the distal bifurcation angles (40°, 55°, and 70°), the flow splits to the DMB and SB (55 %:45 %, 65 %:35 %, and 75 %:25 %), and the SB stenoses (40, 60, and 80 %), resulting in 27 simulations. Fractional flow reserve, defined as the ratio between the mean distal stenosis and mean aortic pressure during maximal hyperemia, was calculated for the DMB and SB (FFRSB) for all simulations. Results The largest differences in FFRSB comparing the largest and smallest bifurcation angles were 0.02 (in cases with 40 % SB stenosis, irrespective of the assumed flow split) and 0.05 (in cases with 60 % SB stenosis, flow split 55 %:45 %). When the SB stenosis was 80 %, the difference in FFRSB between the largest and smallest bifurcation angle was 0.33 (flow split 55 %:45 %). By describing the ΔPSB−QSB relationship using a quadratic curve for cases with 80 % SB stenosis, we found that the curve was steeper (i.e. higher flow resistance) when bifurcation angle increases (ΔP = 0.451*Q + 0.010*Q2 and ΔP = 0.687*Q + 0.017*Q2 for 40° and 70° bifurcation angle, respectively). Our analyses revealed complex hemodynamics in all cases with evident counter-rotating helical flow structures. Larger bifurcation angles resulted in more pronounced helical flow structures (i.e. higher helicity intensity), when 60 or 80 % SB stenoses were present. A good correlation (R2 = 0.80) between the SB pressure drop and helicity intensity was also found. Conclusions Our analyses showed that, in bifurcation lesions with 60 % MB stenosis and 80 % SB stenosis, SB pressure drop is higher for larger bifurcation angles suggesting higher flow resistance (i.e. curves describing the ΔPSB−QSB relationship being steeper). When the SB stenosis is mild (40 %) or moderate (60 %), SB resistance is minimally influenced by the bifurcation angle, with differences not being clinically meaningful. Our findings also highlighted the complex interplay between anatomy, pressure drops, and blood flow helicity in bifurcations.
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Affiliation(s)
- Claudio Chiastra
- Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.,Laboratory of Biological Structure Mechanics (LaBS), Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Milan, Italy
| | - Francesco Iannaccone
- Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.,IbiTech-bioMMeda, Department of Electronics and Information Systems iMinds Medical IT, Ghent University, Ghent, Belgium
| | - Maik J Grundeken
- The Heart Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Frank J H Gijsen
- Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands
| | - Patrick Segers
- IbiTech-bioMMeda, Department of Electronics and Information Systems iMinds Medical IT, Ghent University, Ghent, Belgium
| | - Matthieu De Beule
- IbiTech-bioMMeda, Department of Electronics and Information Systems iMinds Medical IT, Ghent University, Ghent, Belgium.,FEops bvba, Ghent, Belgium
| | - Patrick W Serruys
- International Centre for Circulatory Health, NHLI, Imperial College London, London, UK
| | - Joanna J Wykrzykowska
- The Heart Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | | | - Jolanda J Wentzel
- Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.
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20
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Kabinejadian F, Su B, Ghista DN, Ismail M, Kim S, Leo HL. Sequential venous anastomosis design to enhance patency of arterio-venous grafts for hemodialysis. Comput Methods Biomech Biomed Engin 2016; 20:85-93. [DOI: 10.1080/10255842.2016.1200564] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Foad Kabinejadian
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Boyang Su
- National Heart Centre Singapore, Singapore, Singapore
| | | | - Munirah Ismail
- Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore
| | - Sangho Kim
- Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore
| | - Hwa Liang Leo
- Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore
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21
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Graft Modification Strategies to Improve Patency of Prosthetic Arteriovenous Grafts for Hemodialysis. J Vasc Access 2016; 17 Suppl 1:S85-90. [DOI: 10.5301/jva.5000526] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/30/2015] [Indexed: 11/20/2022] Open
Abstract
Prosthetic arteriovenous grafts (AVGs) are indicated for vascular access for long-term hemodialysis in patients in whom creation or maintenance of an arteriovenous fistula (AVF) has failed or is contraindicated. AVGs have an inferior long-term patency as compared to AVFs. To ameliorate patency rates of prosthetic AVGs, different strategies have emerged to improve graft materials. This review aims to describe current strategies and future perspectives on graft modification, by graft geometry, drug coatings and graft surface technology, to improve AVG patency.
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22
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Pinto SIS, Campos JBLM. Numerical study of wall shear stress-based descriptors in the human left coronary artery. Comput Methods Biomech Biomed Engin 2016; 19:1443-55. [PMID: 26883291 DOI: 10.1080/10255842.2016.1149575] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The present work is about the application of wall shear stress descriptors - time averaged wall shear stress (TAWSS), oscillating shear index (OSI) and relative residence time (RRT) - to the study of blood flow in the left coronary artery (LCA). These descriptors aid the prediction of disturbed flow conditions in the vessels and play a significant role in the detection of potential zones of atherosclerosis development. Hemodynamic descriptors data were obtained, numerically, through ANSYS® software, for the LCA of a patient-specific geometry and for a 3D idealized model. Comparing both cases, the results are coherent, in terms of location and magnitude. Low TAWSS, high OSI and high RRT values are observed in the bifurcation - potential zone of atherosclerosis appearance. The dissimilarities observed in the TAWSS values, considering blood as a Newtonian or non-Newtonian fluid, releases the importance of the correct blood rheologic caracterization. Moreover, for a higher Reynolds number, the TAWSS values decrease in the bifurcation and along the LAD branch, increasing the probability of plaques deposition. Furthermore, for a stenotic LCA model, very low TAWSS and high RRT values in front and behind the stenosis are observed, indicating the probable extension, in the flow direction, of the lesion.
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Affiliation(s)
- S I S Pinto
- a Centro de Estudos de Fenómenos de Transporte, Departamento de Engenharia Química, Faculdade de Engenharia da Universidade do Porto , Porto , Portugal
| | - J B L M Campos
- a Centro de Estudos de Fenómenos de Transporte, Departamento de Engenharia Química, Faculdade de Engenharia da Universidade do Porto , Porto , Portugal
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23
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Bozzetto M, Ene-Iordache B, Remuzzi A. Transitional Flow in the Venous Side of Patient-Specific Arteriovenous Fistulae for Hemodialysis. Ann Biomed Eng 2015; 44:2388-2401. [PMID: 26698581 DOI: 10.1007/s10439-015-1525-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 11/29/2015] [Indexed: 01/28/2023]
Abstract
Arteriovenous fistula (AVF) is the first choice for providing vascular access for hemodialysis patients, but maintaining its patency is challenging. AVF failure is primarily due to development of neointimal hyperplasia (NH) and subsequent stenosis. Using idealized models of AVF we previously suggested that reciprocating hemodynamic wall shear is implicated in vessel stenosis. The aim of the present study was to investigate local hemodynamics in patient-specific side-to-end AVF. We reconstructed realistic geometrical models of four AVFs from magnetic resonance images acquired in a previous clinical study. High-resolution computational fluid dynamics simulations using patient-specific blood rheology and flow boundary conditions were performed. We then characterized the flow field and categorized disturbed flow areas by means of established hemodynamic wall parameters. In all AVF, either in upper or lower arm location, we consistently observed transitional laminar to turbulent-like flow developing in the juxta-anastomotic vein and damping towards the venous outflow, but not in the proximal artery. High-frequency fluctuations of the velocity vectors in these areas result in eddies that induce similar oscillations of wall shear stress vector. This condition may importantly impair the physiological response of endothelial cells to blood flow and be responsible for NH formation in newly created AVF.
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Affiliation(s)
- Michela Bozzetto
- Department of Biomedical Engineering, IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri", Via G.B. Camozzi, 3, 24020, Ranica, BG, Italy
| | - Bogdan Ene-Iordache
- Department of Biomedical Engineering, IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri", Via G.B. Camozzi, 3, 24020, Ranica, BG, Italy
| | - Andrea Remuzzi
- Department of Biomedical Engineering, IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri", Via G.B. Camozzi, 3, 24020, Ranica, BG, Italy. .,Department of Management, Information and Production and Engineering, University of Bergamo, Viale Marconi, 5, Dalmine, 24044, BG, Italy.
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24
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Effects of Vessel Tortuosity on Coronary Hemodynamics: An Idealized and Patient-Specific Computational Study. Ann Biomed Eng 2015; 44:2228-39. [PMID: 26498931 DOI: 10.1007/s10439-015-1492-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 10/16/2015] [Indexed: 01/09/2023]
Abstract
Although coronary tortuosity can influence the hemodynamics of coronary arteries, the relationship between tortuosity and flow has not been thoroughly investigated partly due to the absence of a widely accepted definition of tortuosity and the lack of patient-specific studies that analyze complete coronary trees. Using a computational approach we investigated the effects of tortuosity on coronary flow parameters including pressure drop, wall shear stress, and helical flow strength as measured by helicity intensity. Our analysis considered idealized and patient-specific geometries. Overall results indicate that perfusion pressure decreases with increased tortuosity, but the patient-specific results show that more tortuous vessels have higher physiological wall shear stress values. Differences between the idealized and patient-specific results reveal that an accurate representation of coronary tortuosity must account for all relevant geometric aspects, including curvature imposed by the heart shape. The patient-specific results exhibit a strong correlation between tortuosity and helicity intensity, and the corresponding helical flow contributes directly to the observed increase in wall shear stress. Therefore, helicity intensity may prove helpful in developing a universal parameter to describe tortuosity and assess its impact on patient health. Our data suggest that increased tortuosity could have a deleterious impact via a reduction in coronary perfusion pressure, but the attendant increase in wall shear stress could afford protection against atherosclerosis.
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25
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Ha H, Choi W, Park H, Lee SJ. Effect of swirling blood flow on vortex formation at post-stenosis. Proc Inst Mech Eng H 2015; 229:175-83. [PMID: 25767153 DOI: 10.1177/0954411915573065] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Various clinical observations reported that swirling blood flow is a normal physiological flow pattern in various vasculatures. The swirling flow has beneficial effects on blood circulation through the blood vessels. It enhances oxygen transfer and reduces low-density lipoprotein concentration in the blood vessel by enhancing cross-plane mixing of the blood. However, the fluid-dynamic roles of the swirling flow are not yet fully understood. In this study, inhibition of material deposition at the post-stenosis region by the swirling flow was observed. To reveal the underlying fluid-dynamic characteristics, pathline flow visualization and time-resolved particle image velocimetry measurements were conducted. Results showed that the swirling inlet flow increased the development of vortices at near wall region of the post-stenosis, which can suppress further development of stenosis by enhancing transport and mixing of the blood flow. The fluid-dynamic characteristics obtained in this study would be useful for improving hemodynamic characteristics of vascular grafts and stents in which the stenosis frequently occurred. Moreover, the time-resolved particle image velocimetry measurement technique and vortex identification method employed in this study would be useful for investigating the fluid-dynamic effects of the swirling flow on various vascular environments.
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Affiliation(s)
- Hojin Ha
- Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Woorak Choi
- Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Hanwook Park
- Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Sang Joon Lee
- Center for Biofluid and Biomimic Research, Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang, Republic of Korea
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26
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Ha H, Choi W, Lee SJ. Beneficial fluid-dynamic features of pulsatile swirling flow in 45° end-to-side anastomosis. Med Eng Phys 2015; 37:272-9. [DOI: 10.1016/j.medengphy.2015.01.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Revised: 11/29/2014] [Accepted: 01/11/2015] [Indexed: 11/17/2022]
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27
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Malchesky PS. Dr. Sunny Eloot to Serve as a Co-Editor Representative of the European Society of Artificial Organs. Artif Organs 2015; 39:90-2. [DOI: 10.1111/aor.12479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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28
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Ha H, Hwang D, Choi WR, Baek J, Lee SJ. Fluid-dynamic optimal design of helical vascular graft for stenotic disturbed flow. PLoS One 2014; 9:e111047. [PMID: 25360705 PMCID: PMC4215892 DOI: 10.1371/journal.pone.0111047] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2014] [Accepted: 09/22/2014] [Indexed: 11/18/2022] Open
Abstract
Although a helical configuration of a prosthetic vascular graft appears to be clinically beneficial in suppressing thrombosis and intimal hyperplasia, an optimization of a helical design has yet to be achieved because of the lack of a detailed understanding on hemodynamic features in helical grafts and their fluid dynamic influences. In the present study, the swirling flow in a helical graft was hypothesized to have beneficial influences on a disturbed flow structure such as stenotic flow. The characteristics of swirling flows generated by helical tubes with various helical pitches and curvatures were investigated to prove the hypothesis. The fluid dynamic influences of these helical tubes on stenotic flow were quantitatively analysed by using a particle image velocimetry technique. Results showed that the swirling intensity and helicity of the swirling flow have a linear relation with a modified Germano number (Gn*) of the helical pipe. In addition, the swirling flow generated a beneficial flow structure at the stenosis by reducing the size of the recirculation flow under steady and pulsatile flow conditions. Therefore, the beneficial effects of a helical graft on the flow field can be estimated by using the magnitude of Gn*. Finally, an optimized helical design with a maximum Gn* was suggested for the future design of a vascular graft.
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Affiliation(s)
- Hojin Ha
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - Dongha Hwang
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - Woo-Rak Choi
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - Jehyun Baek
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - Sang Joon Lee
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
- Center for Biofluid and Biomimic Research, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
- * E-mail:
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29
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Physiological Significance of Helical Flow in the Arterial System and its Potential Clinical Applications. Ann Biomed Eng 2014; 43:3-15. [DOI: 10.1007/s10439-014-1097-2] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 08/16/2014] [Indexed: 01/12/2023]
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30
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Evaluation of the hemodynamics in straight 6-mm and tapered 6- to 8-mm grafts as upper arm hemodialysis vascular access. Med Biol Eng Comput 2014; 52:797-811. [DOI: 10.1007/s11517-014-1181-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 07/25/2014] [Indexed: 10/24/2022]
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31
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Guilak F, Butler DL, Goldstein SA, Baaijens FPT. Biomechanics and mechanobiology in functional tissue engineering. J Biomech 2014; 47:1933-40. [PMID: 24818797 DOI: 10.1016/j.jbiomech.2014.04.019] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Revised: 04/17/2014] [Accepted: 04/17/2014] [Indexed: 12/22/2022]
Abstract
The field of tissue engineering continues to expand and mature, and several products are now in clinical use, with numerous other preclinical and clinical studies underway. However, specific challenges still remain in the repair or regeneration of tissues that serve a predominantly biomechanical function. Furthermore, it is now clear that mechanobiological interactions between cells and scaffolds can critically influence cell behavior, even in tissues and organs that do not serve an overt biomechanical role. Over the past decade, the field of "functional tissue engineering" has grown as a subfield of tissue engineering to address the challenges and questions on the role of biomechanics and mechanobiology in tissue engineering. Originally posed as a set of principles and guidelines for engineering of load-bearing tissues, functional tissue engineering has grown to encompass several related areas that have proven to have important implications for tissue repair and regeneration. These topics include measurement and modeling of the in vivo biomechanical environment; quantitative analysis of the mechanical properties of native tissues, scaffolds, and repair tissues; development of rationale criteria for the design and assessment of engineered tissues; investigation of the effects biomechanical factors on native and repair tissues, in vivo and in vitro; and development and application of computational models of tissue growth and remodeling. Here we further expand this paradigm and provide examples of the numerous advances in the field over the past decade. Consideration of these principles in the design process will hopefully improve the safety, efficacy, and overall success of engineered tissue replacements.
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Affiliation(s)
- Farshid Guilak
- Departments of Orthopaedic Surgery and Biomedical Engineering, Duke University Medical Center, 375 MSRB, Box 3093, Durham, NC 27710, USA.
| | - David L Butler
- Department of Biomedical, Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH, USA
| | - Steven A Goldstein
- Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Frank P T Baaijens
- Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, The Netherlands
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