1
|
Xenakis A, Ruiz-Soler A, Keshmiri A. Multi-Objective Optimisation of a Novel Bypass Graft with a Spiral Ridge. Bioengineering (Basel) 2023; 10:489. [PMID: 37106676 PMCID: PMC10136357 DOI: 10.3390/bioengineering10040489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 04/04/2023] [Accepted: 04/18/2023] [Indexed: 04/29/2023] Open
Abstract
The low long-term patency of bypass grafts is a major concern for cardiovascular treatments. Unfavourable haemodynamic conditions in the proximity of distal anastomosis are closely related to thrombus creation and lumen lesions. Modern graft designs address this unfavourable haemodynamic environment with the introduction of a helical component in the flow field, either by means of out-of-plane helicity graft geometry or a spiral ridge. While the latter has been found to lack in performance when compared to the out-of-plane helicity designs, recent findings support the idea that the existing spiral ridge grafts can be further improved in performance through optimising relevant design parameters. In the current study, robust multi-objective optimisation techniques are implemented, covering a wide range of possible designs coupled with proven and well validated computational fluid dynamics (CFD) algorithms. It is shown that the final set of suggested design parameters could significantly improve haemodynamic performance and therefore could be used to enhance the design of spiral ridge bypass grafts.
Collapse
Affiliation(s)
- Antonios Xenakis
- School of Engineering, The University of Manchester, Manchester M13 9PL, UK
| | - Andres Ruiz-Soler
- School of Engineering, The University of Manchester, Manchester M13 9PL, UK
| | - Amir Keshmiri
- School of Engineering, The University of Manchester, Manchester M13 9PL, UK
- Department of Cardiothoracic Surgery, Manchester University NHS Foundation Trust, Manchester M13 9WL, UK
| |
Collapse
|
2
|
Cunnane CV, Houston JG, Moran DT, Broderick SP, Ross RA, Walsh MT. Spiral Laminar Flow is Associated with a Reduction in Disturbed Shear in Patient-Specific Models of an Arteriovenous Fistula. Cardiovasc Eng Technol 2023; 14:152-165. [PMID: 36151366 DOI: 10.1007/s13239-022-00644-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 09/03/2022] [Indexed: 11/02/2022]
Abstract
PURPOSE Areas of disturbed shear that arise following arteriovenous fistula (AVF) creation are believed to contribute to the development of intimal hyperplasia (IH). The presence of helical flow can suppress areas of disturbed shear, which may protect the vasculature from IH. Therefore, the aim of this study is to determine if helical flow, specifically spiral laminar flow (SLF), is present in patient-specific AVF models and is associated with a reduction in exposure to disturbed shear. METHODS Four AVF were imaged using MRI within the first two weeks following fistula creation. Patient-specific boundary conditions were obtained using phase-contrast MRI and applied at the inlet and outlets of each model. Computational fluid dynamics was used to analyse the hemodynamics in each model and compare the helical content of the flow to the distribution of disturbed shear. RESULTS BC-1 and RC-2 are characterised by the presence of SLF, which coincides with the lowest distribution of disturbed shear. Contrastingly, SLF is absent from BC-2 and RC-1 and experience the largest amount of disturbed shear. Interestingly, BC-2 and RC-1 developed an anastomosis stenosis, while BC-1 and RC-2 remained stenosis free. CONCLUSION These findings are in agreement with previous clinical studies and further highlight the clinical potential of SLF as a prognostic marker for a healthy AVF, as its presence correlates with an overall reduction in exposure to disturbed shear and a decrease in the incidence of AVF dysfunction, albeit in a small sample size.
Collapse
Affiliation(s)
- Connor V Cunnane
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland
- School of Engineering, Faculty of Science and Engineering, University of Limerick, Limerick, Ireland
| | - J Graeme Houston
- Cardiovascular and Diabetes Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - Daniel T Moran
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland
- School of Engineering, Faculty of Science and Engineering, University of Limerick, Limerick, Ireland
| | - Stephen P Broderick
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland
- School of Engineering, Faculty of Science and Engineering, University of Limerick, Limerick, Ireland
| | - Rose A Ross
- NHS Tayside Vascular Department, Ninewells Hospital, Dundee, UK
| | - Michael T Walsh
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland.
- School of Engineering, Faculty of Science and Engineering, University of Limerick, Limerick, Ireland.
- Health Research Institute, University of Limerick, Limerick, Ireland.
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Kingsmore D, Jackson A, Stevenson K. A critical review of surgical strategies to minimise venous stenosis in arteriovenous grafts. J Vasc Access 2021; 24:11297298211060944. [PMID: 34847754 DOI: 10.1177/11297298211060944] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
It is inevitable that complications arising from surgical procedures are ascribed to surgical technique, and this applies to venous stenosis (VS) in arteriovenous grafts. However, despite a wide range of cellular studies, computer modelling, observational series and clinical trials, there remains uncertainty on whether surgical technique contributes to VS. This article reviews evidence from basic science, fluid dynamics and clinical data to try and rationalise the main surgical options to modify the occurrence of venous stenosis. There is sufficient data from diverse sources to make recommendations on clinical practice (size of target vein, shape of anastomosis, angle of approach, distance from venous needling, trauma to the target vein) whilst at the same time this emphasises the need to carefully report the practical aspects of surgical technique in future clinical trials.
Collapse
Affiliation(s)
- David Kingsmore
- Department of Vascular Surgery, Queen Elizabeth University Hospital Trust, Glasgow, UK
- Department of Renal Transplantation, Queen Elizabeth University Hospital Trust, Glasgow, UK
| | - Andrew Jackson
- Department of Renal Transplantation, Queen Elizabeth University Hospital Trust, Glasgow, UK
| | - Karen Stevenson
- Department of Renal Transplantation, Queen Elizabeth University Hospital Trust, Glasgow, UK
| |
Collapse
|
5
|
Ashraf F, Ambreen T, Park CW, Kim DI. Comparative evaluation of ballet-type and conventional stent graft configurations for endovascular aneurysm repair: A CFD analysis. Clin Hemorheol Microcirc 2021; 78:1-27. [PMID: 33459700 PMCID: PMC8293652 DOI: 10.3233/ch-200996] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE: Cross limb stent graft (SG) configuration technique for endovascular aneurysm repair (EVAR) is employed for splayed aortic bifurcations to avoid device kinking and smoothen cannulation. The present study investigates three types of stent graft (SG) configurations for endovascular aneurysm repair (EVAR) in abdominal aortic aneurysm. A computational fluid dynamic analysis was performed on the pulsatile non-Newtonian flow characteristics in three ideally modeled geometries of abdominal aortic (AA) SG configurations. METHODS: The three planar and crosslimb SG configurations were ideally modeled, namely, top-down nonballet-type, top-down ballet-type, and bottom-up nonballet-type configurations. In top-down SG configuration, most of the device is deployed in the main body in the vicinity of renal artery and the limbs are extended to the iliac artery. While in the bottom-up configuration, some of the SG device is deployed in the main body, the limbs are deployed in aortic bifurcation, and the extra stent graft of the main body is extended to the proximal aorta until the below of the renal artery. The effects of non-Newtonian pulsatile flow on the wall stresses and flow patterns of the three models were investigated and compared. Moreover, the average wall shear stress (AWSS), oscillatory shear stress index (OSI), absolute helicity, pressure distribution, graft displacement and flow visualization plots were analyzed. RESULTS: The top-down ballet-type showed less branch blockage effect than the top-down nonballet-type models. Furthermore, the top-down ballet-type configuration showed an increased tendency to sustain high WSS and higher helicity characteristics than that of the bottom-up and top-down non-ballet type configurations. However, displacement forces of the top-down ballet-type configuration were 40% and 9.6% higher than those of the bottom-up and top-down nonballet-type configurations, respectively. CONCLUSIONS: Some complications such as graft tearing, thrombus formation, limb disconnection during long term follow up periods might be relevant to hemodynamic characteristics according to the configurations of EVAR. Hence, the reported data required to be validated with the clinical results.
Collapse
Affiliation(s)
- Fahmida Ashraf
- School of Mechanical Engineering, Kyungpook National University, Daegu, South Korea
| | - Tehmina Ambreen
- School of Mechanical Engineering, Kyungpook National University, Daegu, South Korea
| | - Cheol Woo Park
- School of Mechanical Engineering, Kyungpook National University, Daegu, South Korea
| | - Dong-Ik Kim
- Division of Vascular Surgery, Samsung Medical Center, School of Medicine, Sungkyunkwan University, Seoul, South Korea
| |
Collapse
|
6
|
Wasson EM, Dubbin K, Moya ML. Go with the flow: modeling unique biological flows in engineered in vitro platforms. LAB ON A CHIP 2021; 21:2095-2120. [PMID: 34008661 DOI: 10.1039/d1lc00014d] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Interest in recapitulating in vivo phenomena in vitro using organ-on-a-chip technology has grown rapidly and with it, attention to the types of fluid flow experienced in the body has followed suit. These platforms offer distinct advantages over in vivo models with regards to human relevance, cost, and control of inputs (e.g., controlled manipulation of biomechanical cues from fluid perfusion). Given the critical role biophysical forces play in several tissues and organs, it is therefore imperative that engineered in vitro platforms capture the complex, unique flow profiles experienced in the body that are intimately tied with organ function. In this review, we outline the complex and unique flow regimes experienced by three different organ systems: blood vasculature, lymphatic vasculature, and the intestinal system. We highlight current state-of-the-art platforms that strive to replicate physiological flows within engineered tissues while introducing potential limitations in current approaches.
Collapse
Affiliation(s)
- Elisa M Wasson
- Material Engineering Division, Lawrence Livermore National Laboratory, 7000 East Ave L-222, Livermore, CA 94551, USA.
| | - Karen Dubbin
- Material Engineering Division, Lawrence Livermore National Laboratory, 7000 East Ave L-222, Livermore, CA 94551, USA.
| | - Monica L Moya
- Material Engineering Division, Lawrence Livermore National Laboratory, 7000 East Ave L-222, Livermore, CA 94551, USA.
| |
Collapse
|
7
|
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.
Collapse
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
| |
Collapse
|
8
|
Conti M, Ferrarini A, Finotello A, Salsano G, Auricchio F, Palombo D, Spinella G, Pane B. Patient-specific computational fluid dynamics of femoro-popliteal stent-graft thrombosis. Med Eng Phys 2020; 86:57-64. [PMID: 33261734 DOI: 10.1016/j.medengphy.2020.10.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 06/18/2020] [Accepted: 10/14/2020] [Indexed: 01/07/2023]
Abstract
Intra-stent thrombosis is one of the major failure modes of popliteal aneurysm endovascular repair, especially when the diseased arterial segment is long and requires overlapping stent-grafts having different nominal diameters in order to accommodate the native arterial tapering. However, the interplay between stent sizing, post-operative arterial tortuosity, luminal diameter, local hemodynamics, and thrombosis onset is not elucidated, yet. In the present study, a popliteal aneurysm was treated with endovascular deployment of two overlapped stent-grafts, showing intra-stent thrombosis at one-year follow-up examination. Patient-specific computational fluid-dynamics analyses including straight- and bent-leg position were performed. The computational fluid-dynamics analysis showed that the overlapping of the stent-grafts induces a severe discontinuity of lumen, dividing the stented artery in two regions: the proximal part, affected by thrombosis, is characterized by larger diameter, low tortuosity, low flow velocity, low helicity, and low wall shear stress; the distal part presents higher tortuosity and smaller lumen diameter promoting higher flow velocity, higher helicity, and higher wall shear stress. Moreover, leg bending induces an overall increase of arterial tortuosity and reduces flow velocity promoting furtherly the luminal area exposed to low wall shear stress.
Collapse
Affiliation(s)
- Michele Conti
- Department of Civil Engineering and Architecture, University of Pavia, Via Ferrata 3, 27100 Pavia, Italy.
| | - Anna Ferrarini
- Department of Civil Engineering and Architecture, University of Pavia, Via Ferrata 3, 27100 Pavia, Italy
| | - Alice Finotello
- Department of Surgical and Integrated Diagnostic Sciences, University of Genoa, Italy
| | - Giancarlo Salsano
- Department of Radiology, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Ferdinando Auricchio
- Department of Civil Engineering and Architecture, University of Pavia, Via Ferrata 3, 27100 Pavia, Italy
| | - Domenico Palombo
- Vascular and Endovascular Surgery Unit, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Giovanni Spinella
- Vascular and Endovascular Surgery Unit, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Bianca Pane
- Vascular and Endovascular Surgery Unit, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| |
Collapse
|
9
|
Wen J, Tang J, Ran S, Ho H. Computational modelling for the spiral flow in umbilical arteries with different systole/diastole flow velocity ratios. Med Eng Phys 2020; 84:96-102. [PMID: 32977927 DOI: 10.1016/j.medengphy.2020.08.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 05/16/2020] [Accepted: 08/06/2020] [Indexed: 10/23/2022]
Abstract
The systole/diastole (S/D) flow velocity ratios in umbilical arteries (UAs) have been used to assess the health status of the feto-placental circulation, yet its connection to the morphology of UAs, specifically its coiling pattern remains unclear. Spiral flow induces unbalanced wall shear stress (WSS) distribution in UAs, and may contribute to the uneven arterial wall thickness, and the chirality. In this paper, we use a 3D computational fluid dynamics (CFD) technique to quantify the wall shear stress (WSS) in UA models of two configurations, i.e. at 0.17 and 0.50 spirals per centimeter, to represent normo- and hyper-coiling, respectively. For CFD simulations we use two different S/D ratios (3.02 and 5.70) revealed from the ultrasonography waveforms of a normal and an intrauterine growth restriction (IUGR) case. We found that more coils in the UA model enhanced WSS throughout a cardiac cycle (up to 24%) with the same inflow condition. In addition, time-averaged WSS are generally increased and more uneven in the hyper-coiling model. We suggest that the large WSS difference between the peak systole and end diastole (62% higher in the IURG case than the normal case) may induce uneven stenosis distribution at UAs, and contribute to UA chirality.
Collapse
Affiliation(s)
- J Wen
- Institute of Civil Engineering and Architecture, Southwest University of Science and Technology, Mianyang, Sichuan, China
| | - J Tang
- Ultrasound Department, Chongqing Health Center for Women and Children, Chongqing, China
| | - S Ran
- Ultrasound Department, Chongqing Health Center for Women and Children, Chongqing, China.
| | - H Ho
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
| |
Collapse
|
10
|
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.
Collapse
|
11
|
Helical flow: A means to identify unstable plaques and a new direction for the design of vascular grafts and stents. Atherosclerosis 2020; 300:34-36. [PMID: 32216972 DOI: 10.1016/j.atherosclerosis.2020.03.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 03/02/2020] [Accepted: 03/05/2020] [Indexed: 12/25/2022]
|
12
|
Kirsanov RI, Kulikov VP. Helical Blood Flow in Hemodynamically Significant Carotid Stenosis. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2020; 39:543-550. [PMID: 31502308 DOI: 10.1002/jum.15131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 08/14/2019] [Accepted: 08/21/2019] [Indexed: 06/10/2023]
Abstract
OBJECTIVES To define helical blood flow (HBF) characteristics in hemodynamically significant atherosclerotic stenosis of the internal carotid artery (ICA) by means of duplex scanning. METHODS Twenty-five hemodynamically significant (65.0% [range, 63.0%-69.0%]) carotid stenoses were examined in 23 patients. The severity of the stenosis was calculated by the European Carotid Surgery Trial grading method by transverse section scanning in the B-mode. Rotational components were estimated in color flow mapping by transverse-section scanning of a vessel at the most narrowed site, as well as in the prestenotic and poststenotic segments. A quantitative evaluation of HBF was performed on the basis of pulsed wave Doppler imaging of longitudinal and transverse sections of the arterial lumen. RESULTS Helical blood flow was most often (68%) registered in the poststenotic segment of the ICA as a single vortex (52%) or double vortices (16%). At the most narrowed site, HBF was registered in 48% of the cases (44% single vortex and 4% double vortices), whereas in the prestenotic segment of the blood vessel, it was registered in only 16% of the cases (8% single vortex and 8% double vortices). The time-averaged maximum blood flow velocities at the most narrowed site were 88.5 cm/s (25th-75th percentiles, 73.8-127.8 cm/s) for the axial component and 33.1 cm/s (22.7-40.9 cm/s) for the rotational component. The calculated summary velocity of motion of the blood particles in helical paths was 92.2 cm/s (75.7-144.2 cm/s). CONCLUSIONS It has been shown that HBF can be registered by Doppler ultrasound in atherosclerotic stenosis, and its registration rate increases while passing through the narrowed segment of the ICA.
Collapse
Affiliation(s)
- Roman Ivanovich Kirsanov
- Department of Pathological Physiology, Altai State Medical University, Barnaul, Russia
- Department of Functional Diagnostics, Regional Clinical Hospital, Barnaul, Russia
| | - Vladimir Pavlovich Kulikov
- Department of Clinical Pathophysiology and Functional Diagnostics, Altai Medical Institute of Postgraduate Education, Barnaul, Russia
| |
Collapse
|
13
|
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.
Collapse
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.
| |
Collapse
|
14
|
Amghizar I, Dedeyne JN, Brown DJ, Marin GB, Van Geem KM. Sustainable innovations in steam cracking: CO2 neutral olefin production. REACT CHEM ENG 2020. [DOI: 10.1039/c9re00398c] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Steam cracking of hydrocarbons is and will be the main process to produce light olefins but emits large quantities of CO2. Enhancing heat transfer in the radiation section, using green energy and novel furnace designs will be key to substantially reducing CO2 emissions.
Collapse
Affiliation(s)
- Ismaël Amghizar
- Ghent University
- Laboratory for Chemical Technology
- 9052 Gent
- Belgium
| | - Jens N. Dedeyne
- Ghent University
- Laboratory for Chemical Technology
- 9052 Gent
- Belgium
| | | | - Guy B. Marin
- Ghent University
- Laboratory for Chemical Technology
- 9052 Gent
- Belgium
| | | |
Collapse
|
15
|
Cunnane CV, Cunnane EM, Moran DT, Walsh MT. The presence of helical flow can suppress areas of disturbed shear in parameterised models of an arteriovenous fistula. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2019; 35:e3259. [PMID: 31483945 DOI: 10.1002/cnm.3259] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 07/17/2019] [Accepted: 09/01/2019] [Indexed: 06/10/2023]
Abstract
Areas of disturbed shear that develop following arteriovenous fistula (AVF) creation are believed to trigger the onset of intimal hyperplasia (IH), leading to AVF dysfunction. The presence of helical flow can suppress the flow disturbances that lead to disturbed shear in other areas of the vasculature. However, the relationship between helical flow and disturbed shear remains unevaluated in AVF. In this study, computational fluid dynamics (CFD) is used to evaluate the relationship between geometry, helical flow, and disturbed shear in parameterised models of an AVF characterised by four different anastomosis angles. The AVF models with a small anastomosis angle demonstrate the lowest distribution of low/oscillating shear and are characterised by a high helical intensity coupled with a strong balance between helical structures. Contrastingly, the models with a large anastomosis angle experience the least amount of high shear, multidirectional shear, as well as spatial and temporal gradients of shear. Furthermore, the intensity of helical flow correlates strongly with curvature (r = 0.73, P < .001), whereas it is strongly and inversely associated with taper (r = -0.87, P < .001). In summary, a flow field dominated by a high helical intensity coupled with a strong balance between helical structures can suppress exposure to low/oscillating shear but is ineffective when it comes to other types of shear. This highlights the clinical potential of helical flow as a diagnostic marker of exposure to low/oscillating shear, as helical flow can be identified in vivo with the use of ultrasound imaging.
Collapse
Affiliation(s)
- Connor V Cunnane
- Bio Materials Research Centre, Bernal Institute, School of Engineering, Health Research Institute (HRI), University of Limerick, Limerick, Ireland
| | - Eoghan M Cunnane
- Bio Materials Research Centre, Bernal Institute, School of Engineering, Health Research Institute (HRI), University of Limerick, Limerick, Ireland
| | - Daniel T Moran
- Bio Materials Research Centre, Bernal Institute, School of Engineering, Health Research Institute (HRI), University of Limerick, Limerick, Ireland
| | - Michael T Walsh
- Bio Materials Research Centre, Bernal Institute, School of Engineering, Health Research Institute (HRI), University of Limerick, Limerick, Ireland
| |
Collapse
|
16
|
Gage SM, Lawson M, Nichols C, Sycks D, Manson RJ, Knight JA. An immediate access dialysis graft designed to prevent needle-related complications: Results from the initial pre-clinical studies. J Vasc Access 2019; 21:328-335. [PMID: 31526086 DOI: 10.1177/1129729819874987] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
INTRODUCTION No technology has been specifically developed with the intent to reduce needle-related vascular access injuries; a significant source of complications and abandonment. We present the initial pre-clinical study results of a novel, self-sealing, immediate cannulation dialysis graft that aims to prevent needle-related complications; to promote safe, reliable needle access; to reduce catheter use; and could facilitate home hemodialyisis. METHODS The innovative graft design consists of two cannulation chambers with self-sealing properties and materials that prevent side and back wall needle puncture. Study and control grafts (expanded polytetrafluoroethylene) were implanted in one pig and 10 sheep in two studies over the course of 1 year. First cannulation occurred immediately post implant for all study grafts. Post-cannulation time to hemostasis, hematoma and seroma formation, infection, and patency were recorded. RESULTS The two studies account for nearly 60 weeks (average 6.4 weeks/graft) of study graft follow-up. In the ovine study, average study graft time to hemostasis was 27.3 s (standard deviation = 26.3, range = 0-120), and the control averaged 177.2 s (standard deviation = 113.4, range = 60-600), p < 0.0001. Secondary patency was 75% and 67% for the study and control grafts, respectively. Neither study nor control groups experienced seroma, graft infections, or deaths. DISCUSSION All novel grafts in the studies were implanted successfully and functioned as intended. There were no complications related to tunneling of the study graft and the chamber prevented back/side wall needle injury. This novel technology may help to mitigate these needle-related complications, while allowing for early/immediate cannulation which could also reduce catheter contact time.
Collapse
Affiliation(s)
- Shawn M Gage
- InnAVasc Medical, Inc., Durham, NC, USA.,Duke University, Durham, NC, USA
| | | | | | | | | | - Joseph A Knight
- InnAVasc Medical, Inc., Durham, NC, USA.,Duke University, Durham, NC, USA
| |
Collapse
|
17
|
Genkel VV, Kuznetcova AS, Shaposhnik II. Biomechanical Forces and Atherosclerosis: From Mechanism to Diagnosis and Treatment. Curr Cardiol Rev 2019; 16:187-197. [PMID: 31362692 PMCID: PMC7536809 DOI: 10.2174/1573403x15666190730095153] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 07/16/2019] [Accepted: 07/17/2019] [Indexed: 11/22/2022] Open
Abstract
The article provides an overview of current views on the role of biomechanical forces in the pathogenesis of atherosclerosis. The importance of biomechanical forces in maintaining vascular homeostasis is considered. We provide descriptions of mechanosensing and mechanotransduction. The roles of wall shear stress and circumferential wall stress in the initiation, progression and destabilization of atherosclerotic plaque are described. The data on the possibilities of assessing biomechanical factors in clinical practice and the clinical significance of this approach are presented. The article concludes with a discussion on current therapeutic approaches based on the modulation of biomechanical forces.
Collapse
Affiliation(s)
- Vadim V Genkel
- Department of Internal Medicine, Federal State Budgetary Educational Institution of Higher Education "South-Ural State Medical University" of the Ministry of Healthcare of the Russian Federation, Chelyabinsk, Russian Federation
| | - Alla S Kuznetcova
- Department of Hospital Therapy Federal State Budgetary Educational Institution of Higher Education "South-Ural State Medical University" of the Ministry of Healthcare of the Russian Federation, Chelyabinsk, Russian Federation
| | - Igor I Shaposhnik
- Department of Internal Medicine, Federal State Budgetary Educational Institution of Higher Education "South-Ural State Medical University" of the Ministry of Healthcare of the Russian Federation, Chelyabinsk, Russian Federation
| |
Collapse
|
18
|
Liu J, Tian L, Wang S, Luo Z. Study of Hepatic Vascular Dynamics Based on Symmetrical Pulsating Perfusion. Ann Transplant 2019; 24:214-222. [PMID: 31000689 PMCID: PMC6486798 DOI: 10.12659/aot.913008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Background The traditionally used perfusion method is constant flow. This study proposes a novel method called Symmetric Pulsating Flow (SPF) and verified that this method is applicable. Material/Methods The fluid dynamic behavior of perfusate in the vessel, the shear stress, and the vascular deformation were simulated based on the bi-directional fluid-structure interaction. The differences of the fluid dynamic behaviors and the mechanical characteristics of vascular wall were studied and compared between the 2 methods during the process of hepatic perfusion. The simulations and comparisons were carried out on 3 different vascular models. Results Utilizing the constant flow perfusion, a double vortex clearly appeared at the rear end of the foreign matter and reflux retention can be caused by the double vortex. The reflux retention caused lower shear stress against the vascular wall and thus brought new accumulation of foreign matter. The SPF perfusion, however, prevented the double vortex, and avoided such reflux retention during the vascular perfusion. In addition, the SPF can clean the vascular wall better with a slower speed, which causes less injury to the vessel, and the pulsating effect can reduce the accumulation of new foreign matter. Conclusions The SPF perfusion can clean the vascular wall more thoroughly with less injury.
Collapse
Affiliation(s)
- Jun Liu
- Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, National Demonstration Center for Experimental Mechanical and Electrical Engineering Education, Tianjin University of Technology, Tianjin, China (mainland)
| | - Lanlan Tian
- Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, National Demonstration Center for Experimental Mechanical and Electrical Engineering Education, Tianjin University of Technology, Tianjin, China (mainland)
| | - Songli Wang
- Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, National Demonstration Center for Experimental Mechanical and Electrical Engineering Education, Tianjin University of Technology, Tianjin, China (mainland)
| | - Zhiwei Luo
- Organization of Advanced Science and Technology, Kobe University, Kobe, Hyogo, Japan
| |
Collapse
|
19
|
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.
Collapse
|
20
|
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
| |
Collapse
|
21
|
Li Y, Shi G, Du J, Wang J, Bian P. Analysis and preparation of rotational flow mechanism of artificial blood vessel with spiral folds on inner wall. Biomech Model Mechanobiol 2018; 18:411-423. [DOI: 10.1007/s10237-018-1092-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 10/29/2018] [Indexed: 10/27/2022]
|
22
|
Corbett RW, Grechy L, Iori F, Crane JS, Herbert PE, Di Cocco P, Gedroyc W, Vincent PE, Caro CG, Duncan ND. Heterogeneity in the nonplanarity and arterial curvature of arteriovenous fistulas in vivo. J Vasc Surg 2018; 68:152S-163S. [PMID: 30064838 DOI: 10.1016/j.jvs.2018.04.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 04/02/2018] [Indexed: 11/19/2022]
Abstract
OBJECTIVE Native arteriovenous fistulas (AVFs) for hemodialysis are susceptible to nonmaturation. Adverse features of local blood flow have been implicated in the formation of perianastomotic neointimal hyperplasia that may underpin nonmaturation. Whereas computational fluid dynamic simulations of idealized models highlight the importance of geometry on fluid and vessel wall interactions, little is known in vivo about AVF geometry and its role in adverse clinical outcomes. This study set out to examine the three-dimensional geometry of native AVFs and the geometric correlates of AVF failure. METHODS As part of an observational study between 2013 and 2016, patients underwent creation of an upper limb AVF according to current surgical best practice. Phase-contrast magnetic resonance imaging was performed on the day of surgery to obtain luminal geometry along with ultrasound measurements of flow. Magnetic resonance imaging data sets were segmented and reconstructed for quantitative and qualitative analysis of local geometry. Clinical maturation was evaluated at 6 weeks. RESULTS There were 60 patients who were successfully imaged on the day of surgery. Radiocephalic (n = 17), brachiocephalic (n = 40), and brachiobasilic (n = 3) fistulas were included in the study. Centerlines extracted from segmented vessel lumen exhibited significant heterogeneity in arterial nonplanarity and curvature. Furthermore, these features are more marked in brachiocephalic than in radiocephalic fistulas. Across the cohort, the projected bifurcation angle was 73 ± 16 degrees (mean ± standard deviation). Geometry was preserved at 2 weeks in 20 patients who underwent repeated imaging. A greater degree of arterial nonplanarity (log odds ratio [logOR], 0.95 per 0.1/vessel diameter; 95% confidence interval [CI], 0.22-1.90; P = .03) and a larger bifurcation angle (logOR, 0.05 per degree; 95% CI, 0.01-0.09; P = .02) are associated with a greater rate of maturation, as is fistula location (upper vs lower arm; logOR, -1.9; 95% CI, -3.2 to 0.7; P = .002). CONCLUSIONS There is significant heterogeneity in the three-dimensional geometry of AVFs, in particular, arterial nonplanarity and curvature. In this largest cohort of AVF geometry to date, the effect of individual geometric correlates on maturation is uncertain but supports the premise that future modeling studies will need to acknowledge the complex geometry of AVFs.
Collapse
Affiliation(s)
- Richard W Corbett
- Department of Renal Medicine, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom.
| | - Lorenza Grechy
- Department of Aeronautics, Imperial College London, London, United Kingdom
| | - Francesco Iori
- Department of Aeronautics, Imperial College London, London, United Kingdom
| | - Jeremy S Crane
- Department of Renal Medicine, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - Paul E Herbert
- Department of Renal Medicine, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - Pierpaolo Di Cocco
- Department of Renal Medicine, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - Wady Gedroyc
- Department of Radiology, St Mary's Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - Peter E Vincent
- Department of Aeronautics, Imperial College London, London, United Kingdom
| | - Colin G Caro
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Neill D Duncan
- Department of Renal Medicine, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| |
Collapse
|
23
|
Schleimer K, Jalaie H, Afify M, Woitok A, Barbati ME, Hoeft K, Jacobs M, Tolba RH, Steitz J. Sheep models for evaluation of novel patch and prosthesis material in vascular surgery: tips and tricks to avoid possible pitfalls. Acta Vet Scand 2018; 60:42. [PMID: 29976210 PMCID: PMC6034312 DOI: 10.1186/s13028-018-0397-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 06/27/2018] [Indexed: 11/25/2022] Open
Abstract
Background In vascular surgery, novel synthetic prosthesis materials for patch-angioplasties, interpositions, bypasses and shunts are continuously under development and optimization. The characteristics of an ideal vascular prosthesis would display long-term patency, biocompatibility, durability, low porosity, lack of stich hole bleeding, ease of handling, kink resistance, infection resistance and reasonable costs. The aim of this study was to establish and report a reliable sheep model including potential pitfalls where those parameters could be analyzed. Before surgery, sheep were acclimatized for 4–8 weeks, during which parasite infections were treated and blood and serum parameters monitored. Twenty-four sheep underwent surgery, and carotid patch-angioplasties (n = 12), graft interpositions (n = 6) or arteriovenous prosthetic shunts (n = 6) were implanted. Half of the animals in each group were sacrificed after 2 weeks and the other half after 8 weeks. The implants were analyzed for patency, endothelialization, thrombogenicity and biocompatibility by clinical observation, blood flow measurement and pathological and histopathological (H&E, EvG) as well as immunohistochemical (Ki67, CD31) evaluations. Results Health monitoring of the sheep revealed a parasitic burden with endoparasites in all animals. Some animals showed thereby infestations in the bile duct causing fibrotic cholangitis with calcifications in the liver. In addition, sarcosporidia were detected in histopathological specimen of the heart in all animals. Parasitic burden correlated with blood counts and serum bilirubin levels. Both were significantly reduced by albendazole treatment within the acclimatization time. Patches, interposition grafts, and straight shunts were successfully implanted bilaterally in all animals. The total average operation time was 136 ± 21 min. Most animals (23/24) showed good patency rates and general condition after implantation. Pathological and histopathological/immunohistochemical analyses were suitable to determine thrombogenicity, endothelialization, cellular/fibroblastic proliferation, biocompatibility, inflammatory cell infiltration, and thickness of neointima in the prosthesis material. Conclusions We have developed a suitable experimental protocol with standardized and successful anesthesia- and surgical-procedures for patch-angioplasty, graft interposition, and arteriovenous prosthetic shunts. This sheep model allows testing of new prosthetic materials for biocompatibility, thrombogenicity, and endothelialization.
Collapse
|
24
|
Ghaffari M, Alaraj A, Du X, Zhou XJ, Charbel FT, Linninger AA. Quantification of near-wall hemodynamic risk factors in large-scale cerebral arterial trees. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2018; 34:e2987. [PMID: 29601146 PMCID: PMC6043404 DOI: 10.1002/cnm.2987] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 03/21/2018] [Accepted: 03/23/2018] [Indexed: 05/18/2023]
Abstract
Detailed hemodynamic analysis of blood flow in pathological segments close to aneurysm and stenosis has provided physicians with invaluable information about the local flow patterns leading to vascular disease. However, these diseases have both local and global effects on the circulation of the blood within the cerebral tree. The aim of this paper is to demonstrate the importance of extending subject-specific hemodynamic simulations to the entire cerebral arterial tree with hundreds of bifurcations and vessels, as well as evaluate hemodynamic risk factors and waveform shape characteristics throughout the cerebral arterial trees. Angioarchitecture and in vivo blood flow measurement were acquired from healthy subjects and in cases with symptomatic intracranial aneurysm and stenosis. A global map of cerebral arterial blood flow distribution revealed regions of low to high hemodynamic risk that may significantly contribute to the development of intracranial aneurysms or atherosclerosis. Comparison of pre-intervention and post-intervention of pathological cases further shows large angular phase shift (~33.8°), and an augmentation of the peak-diastolic velocity. Hemodynamic indexes of waveform analysis revealed on average a 16.35% reduction in the pulsatility index after treatment from lesion site to downstream distal vessels. The lesion regions not only affect blood flow streamlines of the proximal sites but also generate pulse wave shift and disturbed flow in downstream vessels. This network effect necessitates the use of large-scale simulation to visualize both local and global effects of pathological lesions.
Collapse
Affiliation(s)
- Mahsa Ghaffari
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Ali Alaraj
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA
- Department of Neurosurgery, University of Illinois at Chicago, Chicago, IL, USA
| | - Xinjian Du
- Department of Neurosurgery, University of Illinois at Chicago, Chicago, IL, USA
| | - Xiaohong Joe Zhou
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA
- Department of Neurosurgery, University of Illinois at Chicago, Chicago, IL, USA
- Department of Radiology, University of Illinois at Chicago, Chicago, IL, USA
- Center for MR Research, University of Illinois at Chicago, Chicago, IL, USA
| | - Fady T. Charbel
- Department of Neurosurgery, University of Illinois at Chicago, Chicago, IL, USA
| | - Andreas A. Linninger
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA
- Department of Neurosurgery, University of Illinois at Chicago, Chicago, IL, USA
| |
Collapse
|
25
|
Zhu Y, Chen R, Juan YH, Li H, Wang J, Yu Z, Liu H. Clinical validation and assessment of aortic hemodynamics using computational fluid dynamics simulations from computed tomography angiography. Biomed Eng Online 2018; 17:53. [PMID: 29720173 PMCID: PMC5932836 DOI: 10.1186/s12938-018-0485-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 04/23/2018] [Indexed: 02/02/2023] Open
Abstract
Background Hemodynamic information including peak systolic pressure (PSP) and peak systolic velocity (PSV) carry an important role in evaluation and diagnosis of congenital heart disease (CHD). Since MDCTA cannot evaluate hemodynamic information directly, the aim of this study is to provide a noninvasive method based on a computational fluid dynamics (CFD) model, derived from multi-detector computed tomography angiography (MDCTA) raw data, to analyze the aortic hemodynamics in infants with CHD, and validate these results against echocardiography and cardiac catheter measurements. Methods This study included 25 patients (17 males, and 8 females; a median age of 2 years, range: 4 months–4 years) with CHD. All patients underwent both transthoracic echocardiography (TTE) and MDCTA within 2 weeks prior to cardiac catheterization. CFD models were created from MDCTA raw data. Boundary conditions were confirmed by lumped parameter model and transthoracic echocardiography (TTE). Peak systolic velocity derived from CFD models (PSVCFD) was compared to TTE measurements (PSVTTE), while the peak systolic pressure derived from CFD (PSPCFD) was compared to catheterization (PSPCC). Regions with low and high peak systolic wall shear stress (PSWSS) were also evaluated. Results PSVCFD and PSPCFD showed good agreements between PSVTTE (r = 0.968, p < 0.001; mean bias = − 7.68 cm/s) and PSPCC (r = 0.918, p < 0.001; mean bias = 1.405 mmHg). Regions with low and high PSWSS) can also be visualized. Skewing of velocity or helical blood flow was also observed at aortic arch in patients. Conclusions Our result demonstrated that CFD scheme based on MDCTA raw data is an accurate and convenient method in obtaining the velocity and pressure from aorta and displaying the distribution of PSWSS and flow pattern of aorta. The preliminary results from our study demonstrate the capability in combining clinical imaging data and novel CFD tools in infants with CHD and provide a noninvasive approach for diagnose of CHD such as coarctation of aorta in future.
Collapse
Affiliation(s)
- Yulei Zhu
- Department of Radiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, No. 106, Zhong Shan Er Lu, Guangzhou, 510080, Guangdong, China.,School of Medicine, South China University of Technology, Guangzhou, 510006, Guangdong, China
| | - Rui Chen
- Department of Radiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, No. 106, Zhong Shan Er Lu, Guangzhou, 510080, Guangdong, China.,School of Medicine, South China University of Technology, Guangzhou, 510006, Guangdong, China
| | - Yu-Hsiang Juan
- Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Linkou Chang Gung University, Taoyuan, Taiwan
| | - He Li
- Department of Cardiac Surgery, Guangdong Cardiovascular Institute, Guangdong Provincial Key Laboratory of South China Structural Heart Disease, Guangdong General Hospital, Guangdong Academy of Medical Sciences, No. 106, Zhong Shan Er Lu, Guangzhou, 510080, Guangdong, China
| | - Jingjing Wang
- Department of Radiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, No. 106, Zhong Shan Er Lu, Guangzhou, 510080, Guangdong, China.,School of Medicine, South China University of Technology, Guangzhou, 510006, Guangdong, China
| | - Zhuliang Yu
- School of Medicine, South China University of Technology, Guangzhou, 510006, Guangdong, China. .,College of Automation Science and Technology, South China University of Technology, 381 Wushan Road, Guangzhou, 510080, Guangdong, China.
| | - Hui Liu
- Department of Radiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, No. 106, Zhong Shan Er Lu, Guangzhou, 510080, Guangdong, China. .,School of Medicine, South China University of Technology, Guangzhou, 510006, Guangdong, China.
| |
Collapse
|
26
|
Chen Y, Deng X, Shan X, Xing Y. Study of helical flow inducers with different thread pitches and diameters in vena cava. PLoS One 2018; 13:e0190609. [PMID: 29298357 PMCID: PMC5752007 DOI: 10.1371/journal.pone.0190609] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 12/18/2017] [Indexed: 11/25/2022] Open
Abstract
Pulmonary embolism is a severe, potentially life-threatening condition. Inferior vena cava filters have been used to prevent recurrent pulmonary embolisms. However, the build-up of thrombosis in vena cava filters after deployment presents a severe problem to patients. Previous studies proposed that filters with helical flow are beneficial and capable of alleviating this problem. In this study, the hemodynamic performances of four typical helical flow inducers in the vena cava are determined using computational fluid dynamics simulations (steady-state and pulsatile flow) and compared. Pilot in vitro experiments were also conducted. The simulation results demonstrate that large-diameter inducers produce helical flow. Among inducers with identical diameter, those with a smaller thread pitch are more likely to induce increased helical flow. We also observed that the small thread pitch inducers can yield higher shear rates. Furthermore, a large diameter, small thread pitch helical flow inducer increases the time-averaged wall shear stress and reduces the oscillating shear index and relative residence time on the vessel wall in the vicinity of the helical flow inducer. In vitro experiments also verify that large diameter inducers generate a helical flow. A notable observation of this study is that the diameter is the key parameter that affects the induction of a helical flow. This study will likely provide important guidance for the design of interventional treatments and the deployment of filters associated with helical flow in the vena cava.
Collapse
Affiliation(s)
- Ying Chen
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
- Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, China
| | - Xiaoyan Deng
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
- Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, China
- * E-mail:
| | - Xinying Shan
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
- Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, China
| | - Yubin Xing
- Department of Infection Management and Disease Control, The General Hospital of People’s Liberation Army, Beijing, China
| |
Collapse
|
27
|
Design and Comparison of Large Vessel Stents: Balloon Expandable and Self-Expanding Peripheral Arterial Stents. Interv Cardiol Clin 2017; 5:365-380. [PMID: 28582034 DOI: 10.1016/j.iccl.2016.03.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Endovascular stenting has evolved over the last 50 years since its inception into the framework of management of vascular atherosclerotic disease. Stent design has evolved as lesion complexity has increased. Nevertheless, certain first principles regarding stent design have been recapitulated time and again with every iteration of endovascular stents. This article reviews principles of endovascular stent design and compares and contrasts key aspects of balloon expandable and self-expanding stents.
Collapse
|
28
|
Ruiz-Soler A, Kabinejadian F, Slevin MA, Bartolo PJ, Keshmiri A. Optimisation of a Novel Spiral-Inducing Bypass Graft Using Computational Fluid Dynamics. Sci Rep 2017; 7:1865. [PMID: 28500311 PMCID: PMC5431846 DOI: 10.1038/s41598-017-01930-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 04/06/2017] [Indexed: 11/09/2022] Open
Abstract
Graft failure is currently a major concern for medical practitioners in treating Peripheral Vascular Disease (PVD) and Coronary Artery Disease (CAD). It is now widely accepted that unfavourable haemodynamic conditions play an essential role in the formation and development of intimal hyperplasia, which is the main cause of graft failure. This paper uses Computational Fluid Dynamics (CFD) to conduct a parametric study to enhance the design and performance of a novel prosthetic graft, which utilises internal ridge(s) to induce spiral flow. This design is primarily based on the identification of the blood flow as spiral in the whole arterial system and is believed to improve the graft longevity and patency rates at distal graft anastomoses. Four different design parameters were assessed in this work and the trailing edge orientation of the ridge was identified as the most important parameter to induce physiological swirling flow, while the height of the ridge also significantly contributed to the enhanced performance of this type of graft. Building on these conclusions, an enhanced configuration of spiral graft is proposed and compared against conventional and spiral grafts to reaffirm its potential benefits.
Collapse
Affiliation(s)
- Andres Ruiz-Soler
- Engineering and Materials Research Centre, Manchester Metropolitan University, Manchester, M1 5GD, UK.,School of Mechanical, Aerospace and Civil Engineering (MACE), The University of Manchester, Manchester, M13 9PL, UK
| | - Foad Kabinejadian
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, 48109-2110, USA
| | - Mark A Slevin
- Healthcare Science Research Centre, Manchester Metropolitan University, Manchester, M1 5GD, UK
| | - Paulo J Bartolo
- School of Mechanical, Aerospace and Civil Engineering (MACE), The University of Manchester, Manchester, M13 9PL, UK
| | - Amir Keshmiri
- School of Mechanical, Aerospace and Civil Engineering (MACE), The University of Manchester, Manchester, M13 9PL, UK.
| |
Collapse
|
29
|
Impact of Using Conventional Inlet/Outlet Boundary Conditions on Haemodynamic Metrics in a Subject-Specific Rabbit Aorta. Proc Inst Mech Eng H 2017; 232:103-113. [DOI: 10.1177/0954411917699237] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Computational fluid dynamics is a tool capable of accurately measuring metrics currently used to predict the behaviour of cardiovascular diseases. This study quantifies the impact various commonly used inlet and outlet boundary conditions have on various shear rate–based haemodynamic metrics currently used for predicting the localisation of cardiovascular diseases. Simulations are conducted on an accurately represented rabbit aorta configuration and comparison has been made against available in vivo data. The boundary conditions studied include two different inlet profiles, three outlet boundary conditions, and steady-state versus pulsatile flow cases. Large variations were found in the results, particularly when using different outlet boundary conditions, and the discrepancies were evaluated both quantitatively and qualitatively. The results clearly highlight the importance of the type of boundary condition used when simulating complex cardiovascular models. By restricting the attention to the flow within the aorta and the intercostal branches, the results suggest that prescribing transient simulation and fully developed flow at the inlet are not required. Furthermore, assuming the widely accepted low wall shear stress theory of Caro, it was found that Murray’s law–based outlet boundary condition returns the most physiologically accurate results when compared to in vivo data.
Collapse
|
30
|
Zhang Q, Gao B, Chang Y. The study on hemodynamic effect of series type LVAD on aortic blood flow pattern: a primary numerical study. Biomed Eng Online 2016; 15:163. [PMID: 28155672 PMCID: PMC5260100 DOI: 10.1186/s12938-016-0252-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Background Left ventricular assist device (LVAD) has become an alternative treatment for end-stage heart failure patients. Series type of LVAD, as a novel LVAD, has attracted more and more attention. The hemodynamic effects of series type LVAD on aortic blood pattern are considered as its important characteristics; however, the precise mechanism of it is still unclear. Methods To clarify the hemodynamic effects of series type LVAD on aortic blood flow pattern, a comparative study on the aortic blood flow pattern and hemodynamic states were carried out numerically for two cases, including series type LVAD support and normal condition. The steady-state computational fluid dynamic (CFD) approach was employed. The blood flow streamline, blood velocity vector and distribution of wall shear stress (WSS) were calculated to evaluate the differences of hemodynamic effects between both conditions. Results The results demonstrated that the aortic flow pattern under series type LVAD showed significant different from that of normal condition. The strength of aortic swirling flow was significantly enhanced by the series type LVAD support. Meanwhile, the rotating direction of swirling flow under LVAD support was also dominated by the rotating direction of series type LVAD. Moreover, the blood velocity and WSS under LVAD support were also significantly enhanced, compared with that under normal condition. Conclusion The hemodynamic states, including the aortic swirling flow characteristic, was significantly dominated by LVAD support. Present investigation could provide not only a useful information on the vascular complications caused by LVAD support, but also provide a useful guide for optimal the structure of the series type LVAD.
Collapse
Affiliation(s)
- Qi Zhang
- School of Life Science and BioEngineering, Beijing University of Technology, Beijing, 100124, People's Republic of China
| | - Bin Gao
- School of Life Science and BioEngineering, Beijing University of Technology, Beijing, 100124, People's Republic of China
| | - Yu Chang
- School of Life Science and BioEngineering, Beijing University of Technology, Beijing, 100124, People's Republic of China.
| |
Collapse
|
31
|
Numerical Assessment of Novel Helical/Spiral Grafts with Improved Hemodynamics for Distal Graft Anastomoses. PLoS One 2016; 11:e0165892. [PMID: 27861485 PMCID: PMC5115668 DOI: 10.1371/journal.pone.0165892] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 10/19/2016] [Indexed: 11/19/2022] Open
Abstract
In the present work, numerical simulations were conducted for a typical end-to-side distal graft anastomosis to assess the effects of inducing secondary flow, which is believed to remove unfavourable flow environment. Simulations were carried out for four models, generated based on two main features of 'out-of-plane helicity' and 'spiral ridge' in the grafts as well as their combination. Following a qualitative comparison against in vitro data, various mean flow and hemodynamic parameters were compared and the results showed that helicity is significantly more effective in inducing swirling flow in comparison to a spiral ridge, while their combination could be even more effective. In addition, the induced swirling flow was generally found to be increasing the wall shear stress and reducing the flow stagnation and particle residence time within the anastomotic region and the host artery, which may be beneficial to the graft longevity and patency rates. Finally, a parametric study on the spiral ridge geometrical features was conducted, which showed that the ridge height and the number of spiral ridges have significant effects on inducing swirling flow, and revealed the potential of improving the efficiency of such designs.
Collapse
|
32
|
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]
|
33
|
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.
Collapse
|
34
|
Microarterial anastomoses: A parameterised computational study examining the effect of suture position on intravascular blood flow. Microvasc Res 2016; 105:141-8. [DOI: 10.1016/j.mvr.2016.02.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 02/04/2016] [Accepted: 02/04/2016] [Indexed: 11/19/2022]
|
35
|
BERNAD ELENAS, BERNAD SANDORI, SARGAN IZABELLA, CRAINA MARIUSL. SAPHENOUS VEIN GRAFT PATENCY AFTER GEOMETRY REMODELING. J MECH MED BIOL 2015. [DOI: 10.1142/s0219519415400515] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Tortuous saphenous vein graft (SVG) hemodynamics was investigated using computational fluid dynamics (CFD) techniques. Computed tomography (CT) technology is used for noninvasive bypass graft assessment seven days after surgery. CT investigation shows two regions with severe shape remodeling, one is an angle type contortion and the other one is a sharp curvature with tortuous area reduction. The numerical analysis carefully examines the effect of an SVG geometry remodeling through flow separation, particle deposition, and wall shear stress (WSS). During the cardiac cycle, overall pressure drop increases from 2.6[Formula: see text]mmHg to 4.4[Formula: see text]mmHg. In the accelerating part of the systolic phase, particles released in the inlet section move downstream toward the first narrowed part (elbow type contortion) with a helical motion. WSS range along the cardiac cycle varies from 2[Formula: see text]Pa to 42[Formula: see text]Pa, enough to damage the endothelial cells. Vessel torsion induced helical flow can reduce the flow disturbance and separation. Additionally, in the distal end of the graft, the high particle concentrations can promote the inflammatory processes in the vessels.
Collapse
Affiliation(s)
- ELENA S. BERNAD
- University of Medicine and Pharmacy “Victor Babes” Timisoara University Clinic “Bega” P-ta Eftimie Murgu 2, RO-300041, Timisoara, Romania
| | - SANDOR I. BERNAD
- Romanian Academy, Timisoara Branch Centre for Fundamental and Advanced Technical Research Bd. Mihai Viteazul 24, RO-300223, Timisoara, Romania
| | - IZABELLA SARGAN
- University of Medicine and Pharmacy “Victor Babes” Timisoara University Clinic “Bega” P-ta Eftimie Murgu 2, RO-300041, Timisoara, Romania
| | - MARIUS L. CRAINA
- University of Medicine and Pharmacy “Victor Babes” Timisoara University Clinic “Bega” P-ta Eftimie Murgu 2, RO-300041, Timisoara, Romania
| |
Collapse
|
36
|
Qiao A, Dai X, Niu J, Jiao L. Hemodynamics in stented vertebral artery ostial stenosis based on computational fluid dynamics simulations. Comput Methods Biomech Biomed Engin 2015; 19:1190-200. [PMID: 26691981 DOI: 10.1080/10255842.2015.1123253] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Hemodynamic factors may affect the potential occurrence of in-stent restenosis (ISR) after intervention procedure of vertebral artery ostial stenosis (VAOS). The purpose of the present study is to investigate the influence of stent protrusion length in implantation strategy on the local hemodynamics of the VAOS. CTA images of a 58-year-old female patient with posterior circulation transient ischemic attack were used to perform a 3D reconstruction of the vertebral artery. Five models of the vertebral artery before and after the stent implantation were established. Model 1 was without stent implantation, Model 2-5 was with stent protruding into the subclavian artery for 0, 1, 2, 3 mm, respectively. Computational fluid dynamics simulations based on finite element analysis were employed to mimic the blood flow in arteries and to assess hemodynamic conditions, particularly the blood flow velocity and wall shear stress (WSS). The WSS and the blood flow velocity at the vertebral artery ostium were reduced by 85.33 and 35.36% respectively after stents implantation. The phenomenon of helical flow disappeared. Hemodynamics comparison showed that stent struts that protruded 1 mm into the subclavian artery induced the least decrease in blood speed and WSS. The results suggest that stent implantation can improve the hemodynamics of VAOS, while stent struts that had protruded 1 mm into the subclavian artery would result in less thrombogenesis and neointimal hyperplasia and most likely decrease the risk of ISR.
Collapse
Affiliation(s)
- Aike Qiao
- a College of Life Science and Bioengineering , Beijing University of Technology , Beijing , P.R. China
| | - Xuan Dai
- b Beijing Xuanwu Hospital , Capital Medical University , Beijing , P.R. China.,c Zhongnan Hospital , Wuhan University , Hubei , P.R. China
| | - Jing Niu
- a College of Life Science and Bioengineering , Beijing University of Technology , Beijing , P.R. China
| | - Liqun Jiao
- b Beijing Xuanwu Hospital , Capital Medical University , Beijing , P.R. China
| |
Collapse
|
37
|
Leow CH, Iori F, Corbett R, Duncan N, Caro C, Vincent P, Tang MX. Microbubble Void Imaging: A Non-invasive Technique for Flow Visualisation and Quantification of Mixing in Large Vessels Using Plane Wave Ultrasound and Controlled Microbubble Contrast Agent Destruction. ULTRASOUND IN MEDICINE & BIOLOGY 2015; 41:2926-2937. [PMID: 26297515 DOI: 10.1016/j.ultrasmedbio.2015.06.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 06/16/2015] [Accepted: 06/30/2015] [Indexed: 06/04/2023]
Abstract
There is increasing recognition of the influence of the flow field on the physiology of blood vessels and their development of pathology. Preliminary work is reported on a novel non-invasive technique, microbubble void imaging, which is based on ultrasound and controlled destruction of microbubble contrast agents, permitting flow visualisation and quantification of flow-induced mixing in large vessels. The generation of microbubble voids can be controlled both spatially and temporally using ultrasound parameters within the safety limits. Three different model vessel geometries-straight, planar-curved and helical-with known effects on the flow field and mixing were chosen to evaluate the technique. A high-frame-rate ultrasound system with plane wave transmission was used to acquire the contrast-enhanced ultrasound images, and an entropy measure was calculated to quantify mixing. The experimental results were cross-compared between the different geometries and with computational fluid dynamics. The results indicated that the technique is able to quantify the degree of mixing within the different configurations, with a helical geometry generating the greatest mixing, and a straight geometry, the lowest. There is a high level of concordance between the computational fluid dynamics and experimental results. The technique could also serve as a flow visualisation tool.
Collapse
Affiliation(s)
- Chee Hau Leow
- Department of Bioengineering, Imperial College London, London, UK
| | - Francesco Iori
- Department of Aeronautics, Imperial College London, London, UK
| | - Richard Corbett
- Imperial College Renal and Transplant Centre, Imperial College Healthcare NHS Trust, London, UK
| | - Neill Duncan
- Imperial College Renal and Transplant Centre, Imperial College Healthcare NHS Trust, London, UK
| | - Colin Caro
- Department of Bioengineering, Imperial College London, London, UK
| | - Peter Vincent
- Department of Aeronautics, Imperial College London, London, UK
| | - Meng-Xing Tang
- Department of Bioengineering, Imperial College London, London, UK.
| |
Collapse
|
38
|
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.
Collapse
|
39
|
Kokkalis E, Aristokleous N, Houston JG. Haemodynamics and Flow Modification Stents for Peripheral Arterial Disease: A Review. Ann Biomed Eng 2015; 44:466-76. [PMID: 26467554 PMCID: PMC4764640 DOI: 10.1007/s10439-015-1483-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2015] [Accepted: 10/07/2015] [Indexed: 02/02/2023]
Abstract
Endovascular stents are widely used for the treatment of peripheral arterial disease (PAD). However, the development of in-stent restenosis and downstream PAD progression remain a challenge. Stent revascularisation of PAD causes arterial trauma and introduces abnormal haemodynamics, which initiate complicated biological processes detrimental to the arterial wall. The interaction between stent struts and arterial cells in contact, and the blood flow field created in a stented region, are highly affected by stent design. Spiral flow is known as a normal physiologic characteristic of arterial circulation and is believed to prevent the development of flow disturbances. This secondary flow motion is lost in atheromatous disease and its re-introduction after endovascular treatment of PAD has been suggested as a method to induce stabilised and coherent haemodynamics. Stent designs able to generate spiral flow may support endothelial function and therefore increase patency rates. This review is focused on secondary flow phenomena in arteries and the development of flow modification stent technologies for the treatment of PAD.
Collapse
Affiliation(s)
- Efstratios Kokkalis
- Division of Cardiovascular and Diabetes Medicine, Ninewells Hospital and Medical School, University of Dundee, Mail Box 1, Dundee, DD1 9SY, United Kingdom
| | - Nicolas Aristokleous
- Division of Cardiovascular and Diabetes Medicine, Ninewells Hospital and Medical School, University of Dundee, Mail Box 1, Dundee, DD1 9SY, United Kingdom.
| | - J Graeme Houston
- Division of Cardiovascular and Diabetes Medicine, Ninewells Hospital and Medical School, University of Dundee, Mail Box 1, Dundee, DD1 9SY, United Kingdom
| |
Collapse
|
40
|
Numerical simulation of compliant artery bypass grafts using fluid-structure interaction framework. ASAIO J 2015; 60:533-40. [PMID: 24814837 DOI: 10.1097/mat.0000000000000101] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Early researches on the artery bypass graft (ABG) generally took the assumption of rigid vessel wall that ignored the wall compliancy. To obtain more realistic and physiological hemodynamic parameters, a fluid structure interaction study on a complete ABG was carried out. It was concluded: (1) a compliant vessel is able to expand its vessel diameter and decrease its anastomosis angle to achieve a buffer for the blood, thereby helping to reduce endothelial cell injury. (2) The vessel walls experienced their maximum deformation at the time of peak pressure while the deformation could be ignored during diastole. However, the consideration of wall compliance did not quantitatively change the flow characters compared to those of rigid walls. (3) Generally, the hemodynamic priority of helical-type ABG over a conventional one was further strengthened by adopting compliant vessel wall. (4) The consideration of the wall deformation revealed a hidden fact by the rigid wall assumption: Helical ABG aggravated the risk of intimal hyperplasia at its toe region due to its geometry and flow asymmetry. The present study may be useful for surgeons and graft designers to optimize the current and future ABG configurations and selection of materials.
Collapse
|
41
|
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.
Collapse
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
| |
Collapse
|
42
|
Kokkalis E, Cookson AN, Stonebridge PA, Corner GA, Houston JG, Hoskins PR. Comparison of vortical structures induced by arteriovenous grafts using vector Doppler ultrasound. ULTRASOUND IN MEDICINE & BIOLOGY 2015; 41:760-774. [PMID: 25683221 DOI: 10.1016/j.ultrasmedbio.2014.10.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 08/18/2014] [Accepted: 10/18/2014] [Indexed: 06/04/2023]
Abstract
Arteriovenous prosthetic grafts are used in hemodialysis. Stenosis in the venous anastomosis is the main cause of occlusion and the role of local hemodynamics in this is considered significant. A new spiral graft design has been proposed to stabilize the flow phenomena in the host vein. Cross-flow vortical structures in the outflow of this graft were compared with those from a control device. Both grafts were integrated in identical in-house ultrasound-compatible flow phantoms with realistic surgical configurations. Constant flow rates were applied. In-plane 2-D velocity and vorticity mapping was developed using a vector Doppler technique. One or two vortices were detected for the spiral graft and two to four for the control, along with reduced stagnation points for the former. The in-plane peak velocity and circulation were calculated and found to be greater for the spiral device, implying increased in-plane mixing, which is believed to inhibit thrombosis and neo-intimal hyperplasia.
Collapse
Affiliation(s)
- Efstratios Kokkalis
- Institute for Medical Science and Technology, University of Dundee, Dundee, UK; Cardiovascular and Diabetes Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK.
| | - Andrew N Cookson
- Department of Biomedical Engineering, King's College London, London, UK
| | - Peter A Stonebridge
- Cardiovascular and Diabetes Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - George A Corner
- Medical Physics, Ninewells Hospital and Medical School, Dundee, UK
| | - J Graeme Houston
- Cardiovascular and Diabetes Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - Peter R Hoskins
- Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK
| |
Collapse
|
43
|
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]
|
44
|
Iori F, Grechy L, Corbett RW, Gedroyc W, Duncan N, Caro CG, Vincent PE. The effect of in-plane arterial curvature on blood flow and oxygen transport in arterio-venous fistulae. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2015; 27:031903. [PMID: 25829837 PMCID: PMC4368596 DOI: 10.1063/1.4913754] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 01/27/2015] [Indexed: 05/18/2023]
Abstract
Arterio-Venous Fistulae (AVF) are the preferred method of vascular access for patients with end stage renal disease who need hemodialysis. In this study, simulations of blood flow and oxygen transport were undertaken in various idealized AVF configurations. The objective of the study was to understand how arterial curvature affects blood flow and oxygen transport patterns within AVF, with a focus on how curvature alters metrics known to correlate with vascular pathology such as Intimal Hyperplasia (IH). If one subscribes to the hypothesis that unsteady flow causes IH within AVF, then the results suggest that in order to avoid IH, AVF should be formed via a vein graft onto the outer-curvature of a curved artery. However, if one subscribes to the hypothesis that low wall shear stress and/or low lumen-to-wall oxygen flux (leading to wall hypoxia) cause IH within AVF, then the results suggest that in order to avoid IH, AVF should be formed via a vein graft onto a straight artery, or the inner-curvature of a curved artery. We note that the recommendations are incompatible-highlighting the importance of ascertaining the exact mechanisms underlying development of IH in AVF. Nonetheless, the results clearly illustrate the important role played by arterial curvature in determining AVF hemodynamics, which to our knowledge has been overlooked in all previous studies.
Collapse
Affiliation(s)
- F Iori
- Department of Aeronautics, Imperial College London , South Kensington, London SW7 2AZ, United Kingdom
| | - L Grechy
- Department of Aeronautics, Imperial College London , South Kensington, London SW7 2AZ, United Kingdom
| | - R W Corbett
- Imperial College Renal and Transplant Centre, Hammersmith Hospital , London W12 0HS, United Kingdom
| | - W Gedroyc
- St. Mary's Hospital , Praed Street, London W2 1NY, United Kingdom
| | - N Duncan
- Imperial College Renal and Transplant Centre, Hammersmith Hospital , London W12 0HS, United Kingdom
| | - C G Caro
- Department of Bioengineering, Imperial College London , South Kensington, London SW7 2AZ, United Kingdom
| | - P E Vincent
- Department of Aeronautics, Imperial College London , South Kensington, London SW7 2AZ, United Kingdom
| |
Collapse
|
45
|
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.
Collapse
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:
| |
Collapse
|
46
|
Ha H, Lee SJ. Effect of pulsatile swirling flow on stenosed arterial blood flow. Med Eng Phys 2014; 36:1106-14. [DOI: 10.1016/j.medengphy.2014.06.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 04/18/2014] [Accepted: 06/07/2014] [Indexed: 10/25/2022]
|
47
|
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]
|
48
|
ZHAN FAN, CHEN ZENGSHENG, DENG XIAOYAN. SWIRLING FLOW CAN SUPPRESS MONOCYTES ADHESION IN END-TO-END ARTERIAL ANASTOMOSIS. J MECH MED BIOL 2014. [DOI: 10.1142/s0219519414500808] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
To test the hypothesis that the monocytes adhesion would be suppressed by intentionally inducing swirling flow in end-to-end arterial anastomosis to inhibit the flow disturbance, the comparing experimental and numerical investigation under both normal flow condition and swirling flow condition were executed, in which the sudden expanded tube and U-937 cells were used. The numerical results reveal that, comparing to normal flow, the swirling flow could reduce the size of flow disturbed zones and enhance the wall shear stress (WSS) in the closed downstream of sudden expanded tube. The experimental results show that there are disturbed flow zones in the sudden expanded tube, where the adhesion number of U-937 cells is larger than other zones. More importantly, comparing to the normal flow, the swirling flow could reduce the adhesion of U-937 cells, in which the adhesion number become smaller with the increasing of the swirling intensity. Therefore, the present study suggests that intentionally introducing swirling flow in end-to-end arterial anastomosis may be a solution to solve the problem of intimal hyperplasia (IH) by suppressing the flow disturbance and restraining the adhesion of monocytes to keep the favorably unimpeded flow.
Collapse
Affiliation(s)
- FAN ZHAN
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science & Medical Engineering, Beihang University, Beijing 100191, P. R. China
| | - ZENGSHENG CHEN
- Department of Engineering Mechanics, School of Aerospace, Tsinghua University, 100084 Beijing, P. R. China
| | - XIAOYAN DENG
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science & Medical Engineering, Beihang University, Beijing 100191, P. R. China
| |
Collapse
|
49
|
Wain RA, Whitty JP, Dalal MD, Holmes MC, Ahmed W. Blood flow through sutured and coupled microvascular anastomoses: A comparative computational study. J Plast Reconstr Aesthet Surg 2014; 67:951-9. [DOI: 10.1016/j.bjps.2014.03.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Revised: 01/09/2014] [Accepted: 03/15/2014] [Indexed: 10/25/2022]
|
50
|
Shek TLT, Tse LW, Nabovati A, Amon CH. Computational fluid dynamics evaluation of the cross-limb stent graft configuration for endovascular aneurysm repair. J Biomech Eng 2014; 134:121002. [PMID: 23363204 DOI: 10.1115/1.4007950] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The technique of crossing the limbs of bifurcated modular stent grafts for endovascular aneurysm repair (EVAR) is often employed in the face of splayed aortic bifurcations to facilitate cannulation and prevent device kinking. However, little has been reported about the implications of cross-limb EVAR, especially in comparison to conventional EVAR. Previous computational fluid dynamics studies of conventional EVAR grafts have mostly utilized simplified planar stent graft geometries. We herein examined the differences between conventional and cross-limb EVAR by comparing their hemodynamic flow fields (i.e., in the "direct" and "cross" configurations, respectively). We also added a "planar" configuration, which is commonly found in the literature, to identify how well this configuration compares to out-of-plane stent graft configurations from a hemodynamic perspective. A representative patient's cross-limb stent graft geometry was segmented using computed tomography imaging in Mimics software. The cross-limb graft geometry was used to build its direct and planar counterparts in SolidWorks. Physiologic velocity and mass flow boundary conditions and blood properties were implemented for steady-state and pulsatile transient simulations in ANSYS CFX. Displacement forces, wall shear stress (WSS), and oscillatory shear index (OSI) were all comparable between the direct and cross configurations, whereas the planar geometry yielded very different predictions of hemodynamics compared to the out-of-plane stent graft configurations, particularly for displacement forces. This single-patient study suggests that the short-term hemodynamics involved in crossing the limbs is as safe as conventional EVAR. Higher helicity and improved WSS distribution of the cross-limb configuration suggest improved flow-related thrombosis resistance in the short term. However, there may be long-term fatigue implications to stent graft use in the cross configuration when compared to the direct configuration.
Collapse
Affiliation(s)
- Tina L T Shek
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, M5S 3G8, Canada
| | | | | | | |
Collapse
|