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Chlupac J, Frank J, Sedmera D, Fabian O, Simunkova Z, Mrazova I, Novak T, Vanourková Z, Benada O, Pulda Z, Adla T, Kveton M, Lodererova A, Voska L, Pirk J, Fronek J. External Support of Autologous Internal Jugular Vein Grafts with FRAME Mesh in a Porcine Carotid Artery Model. Biomedicines 2024; 12:1335. [PMID: 38927542 PMCID: PMC11201386 DOI: 10.3390/biomedicines12061335] [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: 05/01/2024] [Revised: 05/28/2024] [Accepted: 06/12/2024] [Indexed: 06/28/2024] Open
Abstract
BACKGROUND Autologous vein grafts are widely used for bypass procedures in cardiovascular surgery. However, these grafts are susceptible to failure due to vein graft disease. Our study aimed to evaluate the impact of the latest-generation FRAME external support on vein graft remodeling in a preclinical model. METHODS We performed autologous internal jugular vein interposition grafting in porcine carotid arteries for one month. Four grafts were supported with a FRAME mesh, while seven unsupported grafts served as controls. The conduits were examined through flowmetry, angiography, macroscopy, and microscopy. RESULTS The one-month patency rate of FRAME-supported grafts was 100% (4/4), whereas that of unsupported controls was 43% (3/7, Log-rank p = 0.071). On explant angiography, FRAME grafts exhibited significantly more areas with no or mild stenosis (9/12) compared to control grafts (3/21, p = 0.0009). Blood flow at explantation was higher in the FRAME grafts (145 ± 51 mL/min) than in the controls (46 ± 85 mL/min, p = 0.066). Area and thickness of neo-intimal hyperplasia (NIH) at proximal anastomoses were similar for the FRAME and the control groups: 5.79 ± 1.38 versus 6.94 ± 1.10 mm2, respectively (p = 0.558) and 480 ± 95 vs. 587 ± 52 μm2/μm, respectively (p = 0.401). However, in the midgraft portions, the NIH area and thickness were significantly lower in the FRAME group than in the control group: 3.73 ± 0.64 vs. 6.27 ± 0.64 mm2, respectively (p = 0.022) and 258 ± 49 vs. 518 ± 36 μm2/μm, respectively (p = 0.0002). CONCLUSIONS In our porcine model, the external mesh FRAME improved the patency of vein-to-carotid artery grafts and protected them from stenosis, particularly in the mid regions. The midgraft neo-intimal hyperplasia was two-fold thinner in the meshed grafts than in the controls.
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Affiliation(s)
- Jaroslav Chlupac
- Transplantation Surgery Department, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (J.F.); (T.N.); (J.F.)
- Department of Anatomy, Second Faculty of Medicine, Charles University, V Uvalu 84, 150 06 Prague, Czech Republic
| | - Jan Frank
- Transplantation Surgery Department, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (J.F.); (T.N.); (J.F.)
| | - David Sedmera
- Institute of Anatomy, First Faculty of Medicine, Charles University, U Nemocnice 3, Praha 2, 128 00 Prague, Czech Republic;
| | - Ondrej Fabian
- Clinical and Transplant Pathology Centre, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (O.F.); (M.K.); (A.L.); (L.V.)
- Department of Pathology and Molecular Medicine, Third Faculty of Medicine, Charles University, and Thomayer University Hospital, Ruska 87, 100 00 Prague, Czech Republic
| | - Zuzana Simunkova
- Experimental Medicine Centre, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (Z.S.); (I.M.); (Z.V.)
| | - Iveta Mrazova
- Experimental Medicine Centre, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (Z.S.); (I.M.); (Z.V.)
| | - Tomas Novak
- Transplantation Surgery Department, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (J.F.); (T.N.); (J.F.)
| | - Zdenka Vanourková
- Experimental Medicine Centre, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (Z.S.); (I.M.); (Z.V.)
| | - Oldrich Benada
- Laboratory of Molecular Structure Characterization, Institute of Microbiology of the Czech Academy of Sciences, Vídeňská 1083, 142 00 Prague, Czech Republic;
| | - Zdenek Pulda
- Department of Imaging Methods, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (Z.P.); (T.A.)
| | - Theodor Adla
- Department of Imaging Methods, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (Z.P.); (T.A.)
| | - Martin Kveton
- Clinical and Transplant Pathology Centre, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (O.F.); (M.K.); (A.L.); (L.V.)
- Third Faculty of Medicine, Charles University, Ruska 87, 100 00 Prague, Czech Republic
| | - Alena Lodererova
- Clinical and Transplant Pathology Centre, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (O.F.); (M.K.); (A.L.); (L.V.)
| | - Ludek Voska
- Clinical and Transplant Pathology Centre, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (O.F.); (M.K.); (A.L.); (L.V.)
| | - Jan Pirk
- Cardiovascular Surgery Department, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic;
| | - Jiri Fronek
- Transplantation Surgery Department, Institute for Clinical and Experimental Medicine (IKEM), Videnska 1958/9, 140 21 Prague, Czech Republic; (J.F.); (T.N.); (J.F.)
- Department of Anatomy, Second Faculty of Medicine, Charles University, V Uvalu 84, 150 06 Prague, Czech Republic
- First Surgical Clinic, First Faculty of Medicine, Charles University, U Nemocnice 499/2, 128 08 Prague, Czech Republic
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2
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Szafron JM, Heng EE, Boyd J, Humphrey JD, Marsden AL. Hemodynamics and Wall Mechanics of Vascular Graft Failure. Arterioscler Thromb Vasc Biol 2024; 44:1065-1085. [PMID: 38572650 PMCID: PMC11043008 DOI: 10.1161/atvbaha.123.318239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 03/12/2024] [Indexed: 04/05/2024]
Abstract
Blood vessels are subjected to complex biomechanical loads, primarily from pressure-driven blood flow. Abnormal loading associated with vascular grafts, arising from altered hemodynamics or wall mechanics, can cause acute and progressive vascular failure and end-organ dysfunction. Perturbations to mechanobiological stimuli experienced by vascular cells contribute to remodeling of the vascular wall via activation of mechanosensitive signaling pathways and subsequent changes in gene expression and associated turnover of cells and extracellular matrix. In this review, we outline experimental and computational tools used to quantify metrics of biomechanical loading in vascular grafts and highlight those that show potential in predicting graft failure for diverse disease contexts. We include metrics derived from both fluid and solid mechanics that drive feedback loops between mechanobiological processes and changes in the biomechanical state that govern the natural history of vascular grafts. As illustrative examples, we consider application-specific coronary artery bypass grafts, peripheral vascular grafts, and tissue-engineered vascular grafts for congenital heart surgery as each of these involves unique circulatory environments, loading magnitudes, and graft materials.
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Affiliation(s)
- Jason M Szafron
- Departments of Pediatrics (J.M.S., A.L.M.), Stanford University, CA
| | - Elbert E Heng
- Cardiothoracic Surgery (E.E.H., J.B.), Stanford University, CA
| | - Jack Boyd
- Cardiothoracic Surgery (E.E.H., J.B.), Stanford University, CA
| | - Jay D Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT (J.D.H.)
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3
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Fashina O, Abbasciano RG, McQueen LW, Ladak S, George SJ, Suleiman S, Punjabi PP, Angelini GD, Zakkar M. Large animal model of vein grafts intimal hyperplasia: A systematic review. Perfusion 2022:2676591221091200. [PMID: 35624557 DOI: 10.1177/02676591221091200] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Coronary artery bypass grafting remains the treatment of choice for a large cohort of patients with significant coronary disease. Despite the increased use of arterial grafts, the long saphenous vein remains the most commonly used conduit. Long-term graft patency continues to be the Achilles heel of saphenous vein grafts. This is due to the development of intimal hyperplasia, a chronic inflammatory disease that results in the narrowing and occlusion of a significant number of vein grafts. Research models for intimal hyperplasia are essential for a better understanding of pathophysiological processes of this condition. Large animal models resemble human anatomical structures and have been used as a surrogate to study disease development and prevention over the years. In this paper, we systematically review all published studies that utilized large animal models of vein graft disease with a focus on the type of model and any therapeutic intervention, specifically the use of external stents/mesh.
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Affiliation(s)
- Oluwatomini Fashina
- Department of Cardiovascular Sciences, University of Leicester, Glenfield Hospital, Leicester, UK
| | - Riccardo G Abbasciano
- Department of Cardiovascular Sciences, University of Leicester, Glenfield Hospital, Leicester, UK
| | - Liam W McQueen
- Department of Cardiovascular Sciences, University of Leicester, Glenfield Hospital, Leicester, UK
| | - Shameem Ladak
- Department of Cardiovascular Sciences, University of Leicester, Glenfield Hospital, Leicester, UK
| | - Sarah J George
- Bristol Heart Institute and Translational Biomedical Research Centre, Bristol Medical School, University of Bristol, Bristol Royal Infirmary, Bristol, UK
| | - Sadeeh Suleiman
- Bristol Heart Institute and Translational Biomedical Research Centre, Bristol Medical School, University of Bristol, Bristol Royal Infirmary, Bristol, UK
| | - Prakash P Punjabi
- Department of Cardiovascular Sciences, Imperial College, Hammersmith Hospital, London, UK
| | - Gianni D Angelini
- Bristol Heart Institute and Translational Biomedical Research Centre, Bristol Medical School, University of Bristol, Bristol Royal Infirmary, Bristol, UK
| | - Mustafa Zakkar
- Department of Cardiovascular Sciences, University of Leicester, Glenfield Hospital, Leicester, UK
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Wang Y, Tao M, Wei H, Arslan Ahmad M, Ma Y, Mao X, Hao L, Ao Q. PLCL vascular external sheath carrying prednisone for improving patency rate of the vein graft. Tissue Eng Part A 2021; 28:394-404. [PMID: 34605672 DOI: 10.1089/ten.tea.2021.0118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Coronary artery bypass graft surgery (CABG) is an impactful treatment for coronary heart disease. Intimal hyperplasia is the central reason for the restenosis of vein grafts after CABG. The introduction of external vascular sheaths around VGs (VGs) can effectively inhibit intimal hyperplasia and ensure the patency of VGs. In this study, the well-known biodegradable copolymer poly (ε-caprolactone-co-L, L-lactide) (PLCL) was electrospun into high porosity external sheaths. The prednisone loaded in the PLCL sheath was slowly released during the degradation process of PLCL. Under the combined effects of sheath and prednisone, intimal hyperplasia was inhibited. For the cell experiments, all sheaths show low cytotoxicity to L929 cells at different concentrations at different time intervals. The ultrasonography and histological results showed prominent dilation and intimal hyperplasia of VG without sheath after two months of surgery. But there was no dilation in PLCL and PLCLPrednisone groups. Notably, the prednisone-loaded sheath group exhibited efficacy in inhibiting intimal hyperplasia and ensured graft patency.
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Affiliation(s)
- Yang Wang
- China Medical University, 38019, School of Forensic Medicine, Shenyang, China.,China Medical University, School of Intelligent Medicine, Shenyang, China;
| | - Meihan Tao
- China Medical University, 38019, School of Intelligent Medicine, Shenyang, China;
| | - Huan Wei
- The First Affiliated Hospital of China Medical University, 159407, Shenyang, Liaoning, China;
| | | | - Yizhan Ma
- China Medical University, 38019, School of Intelligent Medicine, Shenyang, China;
| | - Xiaoyan Mao
- China Medical University, 38019, School of Intelligent Medicine, Shenyang, China;
| | - Liang Hao
- China Medical University, School of Forensic Medicine, Shenyang, China;
| | - Qiang Ao
- China Medical University, 38019, School of Intelligent Medicine, Shenyang, China.,Sichuan University, 12530, Chengdu, Sichuan, China;
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5
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Goldstein DJ. Device Profile of the VEST for External Support of SVG Coronary Artery Bypass Grafting: Historical Development, Current Status and Future Directions. Expert Rev Med Devices 2021; 18:921-931. [PMID: 34311644 DOI: 10.1080/17434440.2021.1960504] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
A search for strategies to address saphenous vein graft (SVG) failure - the main factor limiting the long-term success of coronary bypass grafting - has led to trialing of external stenting technologies. AREAS COVERED The manuscript covers historical development and current status of external scaffolding for the treatment of SVG intimal hyperplasia. Comprehensive literature review and personal communication with VGS leadership, the developer of the VEST device, served as the sources. EXPERT OPINION If the external scaffolding concept proves to be successful in mitigating the intimal hyperplasia inherent to arterialized saphenous vein conduits, it could have a dramatic impact on the recurrence of anginal symptoms, the need for repeat revascularization, and the incidence of myocardial infarction following CABG surgery. These laudable sequelae could ultimately convey significant public health repercussions by reducing healthcare resource use and improving the long-term survival and quality of life of CABG recipients.
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Affiliation(s)
- Daniel J Goldstein
- Montefiore Medical Center - Cardiothoracic Surgery, Bainbridge Ave MAP Building, 5th Fl Bronx, New York, USA
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Boire TC, Himmel LE, Yu F, Guth CM, Dollinger BR, Werfel TA, Balikov DA, Duvall CL. Effect of pore size and spacing on neovascularization of a biodegradble shape memory polymer perivascular wrap. J Biomed Mater Res A 2021; 109:272-288. [PMID: 32490564 PMCID: PMC8270373 DOI: 10.1002/jbm.a.37021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 04/11/2020] [Accepted: 04/19/2020] [Indexed: 12/13/2022]
Abstract
Neointimal hyperplasia (NH) is a main source of failures in arteriovenous fistulas and vascular grafts. Several studies have demonstrated the promise of perivascular wraps to reduce NH via promotion of adventitial neovascularization and providing mechanical support. Limited clinical success thus far may be due to inappropriate material selection (e.g., nondegradable, too stiff) and geometric design (e.g., pore size and spacing, diameter). The influence of pore size and spacing on implant neovascularization is investigated here for a new biodegradable, thermoresponsive shape memory polymer (SMP) perivascular wrap. Following an initial pilot, 21 mice were each implanted with six scaffolds: four candidate SMP macroporous designs (a-d), a nonporous SMP control (e), and microporous GORETEX (f). Mice were sacrificed after 4 (N = 5), 14 (N = 8), and 28 (N = 8) days. There was a statistically significant increase in neovascularization score between all macroporous groups compared to nonporous SMP (p < .023) and microporous GORETEX (p < .007) controls at Day 28. Wider-spaced, smaller-sized pore designs (223 μm-spaced, 640 μm-diameter Design c) induced the most robust angiogenic response, with greater microvessel number (p < .0114) and area (p < .0055) than nonporous SMPs and GORETEX at Day 28. This design also produced significantly greater microvessel density than nonporous SMPs (p = 0.0028) and a smaller-spaced, larger-sized pore (155 μm-spaced, 1,180 μm-sized Design b) design (p = .0013). Strong neovascularization is expected to reduce NH, motivating further investigation of this SMP wrap with controlled pore spacing and size in more advanced arteriovenous models.
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Affiliation(s)
- Timothy C Boire
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Lauren E Himmel
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Fang Yu
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Christy M Guth
- Department of Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Bryan R Dollinger
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Thomas A Werfel
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Biomedical Engineering Program, University of Mississippi, Oxford, Mississippi, USA
| | - Daniel A Balikov
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Craig L Duvall
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
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7
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Hernandez DR, Applewhite B, Martinez L, Laurito T, Tabbara M, Rojas MG, Wei Y, Selman G, Knysheva M, Velazquez OC, Salman LH, Andreopoulos FM, Shiu YT, Vazquez-Padron RI. Inhibition of Lysyl Oxidase with β-aminopropionitrile Improves Venous Adaptation after Arteriovenous Fistula Creation. KIDNEY360 2020; 2:270-278. [PMID: 34322674 PMCID: PMC8315119 DOI: 10.34067/kid.0005012020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND The arteriovenous fistula (AVF) is the preferred hemodialysis access for end-stage renal disease (ESRD) patients. Yet, establishment of a functional AVF presents a challenge, even for the most experienced surgeons, since postoperative stenosis frequently occludes the AVF. Stenosis results from the loss of compliance in fibrotic areas of the fistula which turns intimal hyperplasia into an occlusive feature. Fibrotic remodeling depends on deposition and crosslinking of collagen by lysyl oxidase (LOX), an enzyme that catalyzes the deamination of lysine and hydroxylysine residues, facilitating intra/intermolecular covalent bonds. We postulate that pharmacological inhibition of lysyl oxidase (LOX) increases postoperative venous compliance and prevents stenosis in a rat AVF model. METHODS LOX gene expression and vascular localization were assayed in rat AVFs and human pre-access veins, respectively. Collagen crosslinking was measured in humans AVFs that matured or failed, and in rat AVFs treated with β-aminopropionitrile (BAPN), an irreversible LOX inhibitor. BAPN was either injected systemically or delivered locally around rat AVFs using nanofiber scaffolds. The major endpoints were AVF blood flow, wall fibrosis, collagen crosslinking, and vascular distensibility. RESULTS Non-maturation of human AVFs was associated with higher LOX deposition in pre-access veins (N=20, P=0.029), and increased trivalent crosslinks (N=18, P=0.027) in human AVF tissues. Systemic and local inhibition of LOX increased AVF distensibility, while reducing wall fibrosis and collagen crosslinking in rat fistulas. CONCLUSIONS Our results demonstrate that BAPN-mediated inhibition of LOX significantly improves vascular remodeling in experimental fistulas.
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Affiliation(s)
- Diana R. Hernandez
- DeWitt Daughtry Family Department of Surgery, Division of Vascular Surgery, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida
| | - Brandon Applewhite
- DeWitt Daughtry Family Department of Surgery, Division of Vascular Surgery, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida,Department of Biomedical Engineering, College of Engineering, University of Miami, Coral Gables, Florida
| | - Laisel Martinez
- DeWitt Daughtry Family Department of Surgery, Division of Vascular Surgery, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida
| | - Tyler Laurito
- Department of Biomedical Engineering, College of Engineering, University of Miami, Coral Gables, Florida
| | - Marwan Tabbara
- DeWitt Daughtry Family Department of Surgery, Division of Vascular Surgery, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida
| | - Miguel G. Rojas
- DeWitt Daughtry Family Department of Surgery, Division of Vascular Surgery, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida
| | - Yuntao Wei
- DeWitt Daughtry Family Department of Surgery, Division of Vascular Surgery, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida
| | - Guillermo Selman
- Division of Nephrology and Hypertension, Albany Medical College, Albany, New York
| | - Marina Knysheva
- Division of Nephrology and Hypertension, University of Utah, Salt Lake City, Utah
| | - Omaida C. Velazquez
- DeWitt Daughtry Family Department of Surgery, Division of Vascular Surgery, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida
| | - Loay H. Salman
- Division of Nephrology and Hypertension, Albany Medical College, Albany, New York
| | - Fotios M. Andreopoulos
- Department of Biomedical Engineering, College of Engineering, University of Miami, Coral Gables, Florida
| | - Yan-Ting Shiu
- Division of Nephrology and Hypertension, University of Utah, Salt Lake City, Utah
| | - Roberto I. Vazquez-Padron
- DeWitt Daughtry Family Department of Surgery, Division of Vascular Surgery, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida
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Samano N, Souza D, Dashwood MR. Saphenous veins in coronary artery bypass grafting need external support. Asian Cardiovasc Thorac Ann 2020; 29:457-467. [PMID: 33307718 PMCID: PMC8167919 DOI: 10.1177/0218492320980936] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The saphenous vein is the most commonly used conduit for coronary artery bypass grafting. Arterial grafts are harvested with the outer pedicle intact whereas saphenous veins are harvested with the pedicle removed in the conventional graft harvesting technique. This conventional procedure causes considerable vascular damage. One strategy to improve vein graft patency has been to provide external support. Ongoing studies show that fitting a metal external support improves conventionally harvested saphenous vein graft patency. On the other hand, the no-touch technique of harvesting the saphenous vein provides an improved graft with long-term patency comparable to that of the internal mammary artery. This improvement is suggested to be due to preservation of vessel structures. Interestingly, many of the mechanisms proposed to be associated with the beneficial actions of an artificial external support on saphenous vein graft patency are similar to those underlying the beneficial effect of no-touch saphenous vein grafts where the intact outer layer acts as a natural support. Additional actions of external supports have been advocated, including promotion of angiogenesis, increased production of vascular-protective factors, and protection of endothelial cells. Using no-touch harvesting, normal vascular architecture is maintained, tissue and cell damage is minimized, and factors beneficial for graft patency are preserved. In this review, the significance of external support of saphenous vein grafts in coronary artery bypass grafting is discussed.
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Affiliation(s)
- Ninos Samano
- Department of Cardiothoracic and Vascular Surgery and University Health Care Research Center, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
| | - Domingos Souza
- Department of Cardiothoracic and Vascular Surgery and University Health Care Research Center, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
| | - Michael R Dashwood
- Surgical and Interventional Sciences, Royal Free Hospital Campus, University College Medical School, London, UK
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Magnan L, Labrunie G, Fénelon M, Dusserre N, Foulc MP, Lafourcade M, Svahn I, Gontier E, Vélez V. J, McAllister TN, L'Heureux N. Human textiles: A cell-synthesized yarn as a truly "bio" material for tissue engineering applications. Acta Biomater 2020; 105:111-120. [PMID: 31996332 DOI: 10.1016/j.actbio.2020.01.037] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 01/22/2020] [Accepted: 01/22/2020] [Indexed: 01/06/2023]
Abstract
In the field of tissue engineering, many groups have come to rely on the extracellular matrix produced by cells as the scaffold that provides structure and strength to the engineered tissue. We have previously shown that sheets of Cell-Assembled extracellular Matrix (CAM), which are entirely biological yet robust, can be mass-produced for clinical applications using normal, adult, human fibroblasts. In this article, we demonstrate that CAM yarns can be generated with a range of physical and mechanical properties. We show that this material can be used as a simple suture to close a wound or can be assembled into fully biological, human, tissue-engineered vascular grafts (TEVGs) that have high mechanical strength and are implantable. By combining this truly "bio" material with a textile-based assembly, this original tissue engineering approach is highly versatile and can produce a variety of strong human textiles that can be readily integrated in the body. STATEMENT OF SIGNIFICANCE: Yarn of synthetic biomaterials have been turned into textiles for decades because braiding, knitting and weaving machines can mass-produce medical devices with a wide range of shapes and mechanical properties. Here, we show that robust, completely biological, and human yarn can be produced by normal cells in vitro. This yarn can be used as a simple suture material or to produce the first human textiles. For example, we produced a woven tissue-engineered vascular grafts with burst pressure, suture retention strength and transmural permeability that surpassed clinical requirements. This novel strategy holds the promise of a next generation of medical textiles that will be mechanically strong without any foreign scaffolding, and will have the ability to truly integrate into the host's body.
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Yasuda S, Goda M, Shibuya T, Uchida K, Suzuki S, Noishiki Y, Yokoyama U, Ishikawa Y, Masuda M. An appropriately sized soft polyester external stent prevents enlargement and neointimal hyperplasia of a saphenous vein graft in a canine model. Artif Organs 2019; 43:577-583. [DOI: 10.1111/aor.13399] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 11/06/2018] [Accepted: 11/20/2018] [Indexed: 12/21/2022]
Affiliation(s)
- Shota Yasuda
- Department of Surgery Yokohama City University Yokohama Japan
| | - Motohiko Goda
- Department of Surgery Yokohama City University Yokohama Japan
| | - Taisuke Shibuya
- Department of Surgery Yokohama City University Yokohama Japan
| | - Keiji Uchida
- Cardiovascular Center Yokohama City University Medical Center Yokohama Japan
| | - Shinichi Suzuki
- Department of Surgery Yokohama City University Yokohama Japan
| | - Yasuharu Noishiki
- Department of Neurological Anatomy Yokohama City University Yokohama Japan
| | - Utako Yokoyama
- Cardiovascular Research Institute Yokohama City University Yokohama Japan
| | - Yoshihiro Ishikawa
- Cardiovascular Research Institute Yokohama City University Yokohama Japan
| | - Munetaka Masuda
- Department of Surgery Yokohama City University Yokohama Japan
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11
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Zhang Y, Fang Q, Niu K, Gan Z, Yu Q, Gu T. Time-dependently slow-released multiple-drug eluting external sheath for efficient long-term inhibition of saphenous vein graft failure. J Control Release 2019; 293:172-182. [DOI: 10.1016/j.jconrel.2018.12.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2018] [Revised: 11/19/2018] [Accepted: 12/01/2018] [Indexed: 12/22/2022]
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12
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Tianshu-Chu, Congrong-Gao, Zhiwei-Zhao, Fei-Ling, Ayu-Sun, Yuanbiao-Zheng, Jing-Cao, Ge J. Rapamycin Combined with α-Cyanoacrylate Contributes to Inhibiting Intimal Hyperplasia in Rat Models. Arq Bras Cardiol 2018; 112:3-10. [PMID: 30570064 PMCID: PMC6317635 DOI: 10.5935/abc.20180247] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 07/23/2018] [Indexed: 11/30/2022] Open
Abstract
Background Vein graft restenosis has an adverse impact on bridge vessel circulation and
patient prognosis after coronary artery bypass grafting. Objectives We used the extravascular supporter α-cyanoacrylate (α-CA), the
local application rapamycin/sirolimus (RPM), and a combination of the two
(α-CA-RPM) in rat models of autogenous vein graft to stimulate vein
graft change. The aim of our study was to observe the effect of α-CA,
RPM, and α-CA-RPM on vein hyperplasia. Methods Fifty healthy Sprague Dawley (SD) rats were randomized into the following 5
groups: sham, control, α-CA, RPM, and α-CA-RPM. Operating
procedure as subsequently described was used to build models of grafted rat
jugular vein on carotid artery on one side. The level of endothelin-1 (ET-1)
was determined by enzyme-linked immunosorbent assay (ELISA). Grafted veins
were observed via naked eye 4 weeks later; fresh veins were observed via
microscope and image-processing software in hematoxylin-eosin (HE) staining
and immunohistochemistry after having been fixed and stored” (i.e. First
they were fixed and stored, and second they were observed); α-Smooth
Muscle Actin (αSMA) and von Willebrand factor (vWF) were measured
with reverse transcription-polymerase chain reaction (RT-PCR). Comparisons
were made with single-factor analysis of variance and Fisher’s least
significant difference test, with p < 0.05 considered significant. Results We found that intimal thickness of the α-CA, RPM, and α-CA-RPM
groups was lower than that of the control group (p < 0.01), and the
thickness of the α-CA-RPM group was notably lower than that of the
α-CA and RPM groups (p < 0.05). Conclusion RPM combined with α-CA contributes to inhibiting intimal hyperplasia
in rat models and is more effective for vascular patency than individual use
of either α-CA or RPM.
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Affiliation(s)
| | | | | | - Fei-Ling
- Anhui Medical University, Hefei - China
| | - Ayu-Sun
- Anhui Medical University, Hefei - China
| | | | - Jing-Cao
- Anhui Medical University, Hefei - China
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13
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Taggart DP, Webb CM, Desouza A, Yadav R, Channon KM, De Robertis F, Di Mario C. Long-term performance of an external stent for saphenous vein grafts: the VEST IV trial. J Cardiothorac Surg 2018; 13:117. [PMID: 30453984 PMCID: PMC6245530 DOI: 10.1186/s13019-018-0803-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 11/05/2018] [Indexed: 01/04/2023] Open
Abstract
Background Externally stenting saphenous vein grafts reduces intimal hyperplasia, improves lumen uniformity and reduces oscillatory shear stress 1 year following surgery. The present study is the first to present the longer-term (4.5 years) performance and biomechanical effects of externally stented saphenous vein grafts. Methods Thirty patients previously implanted with the VEST external stent in the randomized, within-patient-controlled VEST I study were followed up for adverse events; 21 of these were available to undergo coronary angiography and intravascular ultrasound. Results Twenty-one stented and 29 nonstented saphenous vein grafts were evaluated by angiography and ultrasound at 4.5 ± 0.3 years. Vein graft failure rates were comparable between stented and nonstented grafts (30 and 23% respectively; p = 0.42). All failures were apparent at 1 year except for one additional nonstented failure at 4.5 years. In patent vein grafts, Fitzgibbon perfect patency remained significantly higher in the stented versus nonstented vein grafts (81 and 48% respectively, p = 0.002), while intimal hyperplasia area (4.27 mm2 ± 1.27 mm2 and 5.23 mm2 ± 1.83 mm2 respectively, p < 0.001) and thickness (0.36 mm ± 0.09 mm and 0.42 mm ± 0.11 mm respectively, p < 0.001) were significantly reduced. Intimal hyperplasia proliferation correlated with lumen uniformity and with the distance between the stent and the lumen (p = 0.04 and p < 0.001 respectively). Conclusions External stenting mitigates saphenous vein graft remodeling and significantly reduces diffuse intimal hyperplasia and the development of lumen irregularities 4.5 years after coronary artery bypass surgery. Close conformity of the stent to the vessel wall appears to be an important factor. Trial registration NCT01415245. Registered 11 August 2011.
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Affiliation(s)
- David P Taggart
- Nuffield Department of Surgery, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Carolyn M Webb
- National Heart & Lung Institute, Imperial College London, London, UK. .,Department of Cardiology, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.
| | - Anthony Desouza
- Department of Cardiothoracic Surgery, Royal Brompton Hospital, Sydney Street, London, UK
| | - Rashmi Yadav
- Department of Cardiothoracic Surgery, Royal Brompton Hospital, Sydney Street, London, UK
| | - Keith M Channon
- Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Fabio De Robertis
- Department of Cardiothoracic Surgery, Harefield Hospital, Middlesex, London, UK
| | - Carlo Di Mario
- Department of Cardiology, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK
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14
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Samano N, Dashwood M, Souza D. No-touch vein grafts and the destiny of venous revascularization in coronary artery bypass grafting-a 25 th anniversary perspective. Ann Cardiothorac Surg 2018; 7:681-685. [PMID: 30505753 DOI: 10.21037/acs.2018.05.15] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Ischemic heart disease is currently the leading cause of death globally, with coronary artery bypass grafting among the most common operations performed worldwide. More extensive use of arterial grafts has been advocated because of their high long-term patency, long-term survival benefit, and freedom from reinterventions. Despite this, the saphenous vein is the most frequently used conduit in patients undergoing coronary artery bypass surgery since its introduction over 50 years ago. Consequently, the saphenous vein remains an indispensable conduit in coronary artery bypass grafting and maintaining its long-term patency is one of the most crucial challenges in cardiovascular surgery. This situation led to the development of the no-touch saphenous vein harvesting technique, where the vein is harvested completely with its pedicle of surrounding tissue. Several studies report a superior long-term patency rate, slower progression of atherosclerosis, and better clinical outcomes whilst employing no-touch harvesting technique. The success of the technique is multifactorial, including the decreased risk for graft spasm-and the need for manual distension-preservation of the vaso vasorum and an intact endothelium, reducing neointimal hyperplasia and subsequent atherosclerosis. Furthermore, the intact perivascular tissue, including the surrounding cushion of fat, may act as a "natural external stent", providing mechanical support preventing the graft from kinking. We are convinced that the use of arterial grafts, in combination with the no-touch saphenous vein graft, will significantly improve the results of coronary artery bypass grafting. This is important for achieving a comprehensive and evidence-based balance between the major treatment strategies of ischemic heart disease, explicitly coronary artery bypass grafting and percutaneous coronary intervention. The no-touch technique is becoming increasingly popular among surgeons, with further studies to be initiated worldwide.
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Affiliation(s)
- Ninos Samano
- Department of Cardiothoracic and Vascular Surgery, University Health Care Research Center, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
| | - Michael Dashwood
- Surgical and Interventional Sciences, Royal Free Hospital Campus, University College London Medical School, London, UK
| | - Domingos Souza
- Department of Cardiothoracic and Vascular Surgery, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
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15
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Ruiter MS, Pesce M. Mechanotransduction in Coronary Vein Graft Disease. Front Cardiovasc Med 2018; 5:20. [PMID: 29594150 PMCID: PMC5861212 DOI: 10.3389/fcvm.2018.00020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 02/22/2018] [Indexed: 12/19/2022] Open
Abstract
Autologous saphenous veins are the most commonly used conduits in revascularization of the ischemic heart by coronary artery bypass graft surgery, but are subject to vein graft failure. The current mini review aims to provide an overview of the role of mechanotransduction signalling underlying vein graft failure to further our understanding of the disease progression and to improve future clinical treatment. Firstly, limitation of damage during vein harvest and engraftment can improve outcome. In addition, cell cycle inhibition, stimulation of Nur77 and external grafting could form interesting therapeutic options. Moreover, the Hippo pathway, with the YAP/TAZ complex as the main effector, is emerging as an important node controlling conversion of mechanical signals into cellular responses. This includes endothelial cell inflammation, smooth muscle cell proliferation/migration, and monocyte attachment/infiltration. The combined effects of expression levels and nuclear/cytoplasmic translocation make YAP/TAZ interesting novel targets in the prevention and treatment of vein graft disease. Pharmacological, molecular and/or mechanical conditioning of saphenous vein segments between harvest and grafting may potentiate targeted and specific treatment to improve long-term outcome.
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Affiliation(s)
- Matthijs Steven Ruiter
- Cardiovascular Tissue Engineering Unit, Centro Cardiologico Monzino (IRCCS), Milan, Italy
| | - Maurizio Pesce
- Cardiovascular Tissue Engineering Unit, Centro Cardiologico Monzino (IRCCS), Milan, Italy
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16
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Huang AH, Balestrini JL, Udelsman BV, Zhou KC, Zhao L, Ferruzzi J, Starcher BC, Levene MJ, Humphrey JD, Niklason LE. Biaxial Stretch Improves Elastic Fiber Maturation, Collagen Arrangement, and Mechanical Properties in Engineered Arteries. Tissue Eng Part C Methods 2017; 22:524-33. [PMID: 27108525 DOI: 10.1089/ten.tec.2015.0309] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Tissue-engineered blood vessels (TEVs) are typically produced using the pulsatile, uniaxial circumferential stretch to mechanically condition and strengthen the arterial grafts. Despite improvements in the mechanical integrity of TEVs after uniaxial conditioning, these tissues fail to achieve critical properties of native arteries such as matrix content, collagen fiber orientation, and mechanical strength. As a result, uniaxially loaded TEVs can result in mechanical failure, thrombus, or stenosis on implantation. In planar tissue equivalents such as artificial skin, biaxial loading has been shown to improve matrix production and mechanical properties. To date however, multiaxial loading has not been examined as a means to improve mechanical and biochemical properties of TEVs during culture. Therefore, we developed a novel bioreactor that utilizes both circumferential and axial stretch that more closely simulates loading conditions in native arteries, and we examined the suture strength, matrix production, fiber orientation, and cell proliferation. After 3 months of biaxial loading, TEVs developed a formation of mature elastic fibers that consisted of elastin cores and microfibril sheaths. Furthermore, the distinctive features of collagen undulation and crimp in the biaxial TEVs were absent in both uniaxial and static TEVs. Relative to the uniaxially loaded TEVs, tissues that underwent biaxial loading remodeled and realigned collagen fibers toward a more physiologic, native-like organization. The biaxial TEVs also showed increased mechanical strength (suture retention load of 303 ± 14.53 g, with a wall thickness of 0.76 ± 0.028 mm) and increased compliance. The increase in compliance was due to combinatorial effects of mature elastic fibers, undulated collagen fibers, and collagen matrix orientation. In conclusion, biaxial stretching is a potential means to regenerate TEVs with improved matrix production, collagen organization, and mechanical properties.
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Affiliation(s)
- Angela H Huang
- 1 Department of Biomedical Engineering, School of Engineering and Applied Science, Yale University , New Haven, Connecticut
| | - Jenna L Balestrini
- 1 Department of Biomedical Engineering, School of Engineering and Applied Science, Yale University , New Haven, Connecticut
| | | | - Kevin C Zhou
- 1 Department of Biomedical Engineering, School of Engineering and Applied Science, Yale University , New Haven, Connecticut
| | - Liping Zhao
- 2 School of Medicine, Yale University , New Haven, Connecticut
| | - Jacopo Ferruzzi
- 1 Department of Biomedical Engineering, School of Engineering and Applied Science, Yale University , New Haven, Connecticut
| | - Barry C Starcher
- 3 Department of Biochemistry, The University of Texas Health Science Center at Tyler , Tyler, Texas
| | - Michael J Levene
- 1 Department of Biomedical Engineering, School of Engineering and Applied Science, Yale University , New Haven, Connecticut
| | - Jay D Humphrey
- 1 Department of Biomedical Engineering, School of Engineering and Applied Science, Yale University , New Haven, Connecticut
| | - Laura E Niklason
- 1 Department of Biomedical Engineering, School of Engineering and Applied Science, Yale University , New Haven, Connecticut.,2 School of Medicine, Yale University , New Haven, Connecticut
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17
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Mylonaki I, Allémann É, Saucy F, Haefliger JA, Delie F, Jordan O. Perivascular medical devices and drug delivery systems: Making the right choices. Biomaterials 2017; 128:56-68. [PMID: 28288349 DOI: 10.1016/j.biomaterials.2017.02.028] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 02/13/2017] [Accepted: 02/26/2017] [Indexed: 12/31/2022]
Abstract
Perivascular medical devices and perivascular drug delivery systems are conceived for local application around a blood vessel during open vascular surgery. These systems provide mechanical support and/or pharmacological activity for the prevention of intimal hyperplasia following vessel injury. Despite abundant reports in the literature and numerous clinical trials, no efficient perivascular treatment is available. In this review, the existing perivascular medical devices and perivascular drug delivery systems, such as polymeric gels, meshes, sheaths, wraps, matrices, and metal meshes, are jointly evaluated. The key criteria for the design of an ideal perivascular system are identified. Perivascular treatments should have mechanical specifications that ensure system localization, prolonged retention and adequate vascular constriction. From the data gathered, it appears that a drug is necessary to increase the efficacy of these systems. As such, the release kinetics of pharmacological agents should match the development of the pathology. A successful perivascular system must combine these optimized pharmacological and mechanical properties to be efficient.
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Affiliation(s)
- Ioanna Mylonaki
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, rue Michel Servet 1, CH-1211 Geneva 4, Switzerland
| | - Éric Allémann
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, rue Michel Servet 1, CH-1211 Geneva 4, Switzerland
| | - François Saucy
- Department of Vascular Surgery, Lausanne University Hospital, rue du Bugnon 46, CH-1011 Lausanne, Switzerland
| | - Jacques-Antoine Haefliger
- Department of Vascular Surgery, Lausanne University Hospital, rue du Bugnon 46, CH-1011 Lausanne, Switzerland
| | - Florence Delie
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, rue Michel Servet 1, CH-1211 Geneva 4, Switzerland
| | - Olivier Jordan
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, rue Michel Servet 1, CH-1211 Geneva 4, Switzerland.
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18
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Salinas HM, Khan SI, McCormack MC, Fernandes JR, Gfrerer L, Watkins MT, Redmond RW, Austen WG. Prevention of vein graft intimal hyperplasia with photochemical tissue passivation. J Vasc Surg 2017; 65:190-196. [DOI: 10.1016/j.jvs.2015.11.049] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 11/15/2015] [Indexed: 10/22/2022]
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19
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Neointima development in externally stented saphenous vein grafts. ADVANCES IN INTERVENTIONAL CARDIOLOGY 2016; 12:334-339. [PMID: 27980547 PMCID: PMC5133322 DOI: 10.5114/aic.2016.63634] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 03/30/2016] [Indexed: 11/23/2022] Open
Abstract
Introduction The main limitation of coronary artery bypass grafting (CABG) is rapid neointimal hyperplasia leading to graft failure. Aim To assess plaque formation in saphenous vein grafts (SVG) covered by an external Dacron stent in comparison with the classical technique. Material and methods In the study group vein grafts covered by external stent mesh made of Dacron were implanted. An intravascular ultrasonography (IVUS) study was performed in 35 aorto-coronary SVG covered by an external Dacron stent and in 64 normal SVG during the first year after CABG. In each SVG 25 mm of good quality IVUS image, volumes of lumen, plaque (neointima), outer border of the vein graft (external SVG) and adventitia were calculated in three time periods: 0–130 days, 130–260 days and 260–390 days. Results Between the first and second time period, lumen volume (mm3) was reduced from 10.33 ±4.4, to 6.80 ±2.23 in the second period and 5.69 ±1.26 in the third one. This effect was much less marked in normal grafts. The corresponding lumen volume (mm3) was: 10.90 ±3.9, 9.15 ±2.94 and 8.92 ±2.93 in consecutive time periods. Plaque volume (mm3) did not change in control grafts during the course of the study, but it increased very significantly in stented grafts from 0.86 ±1.24 in the first period to 2.70 ±1.58 in the second and 3.29 ±2.66 in the third one. Conclusions The experimental technique of implanting SVG covered with an external elastic Dacron stent seems to be inferior to traditional ones. This is probably due to the more complicated process of vein implantation and higher micro-injury occurrence during the surgery.
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20
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Boire TC, Balikov DA, Lee Y, Guth CM, Cheung-Flynn J, Sung HJ. Biomaterial-Based Approaches to Address Vein Graft and Hemodialysis Access Failures. Macromol Rapid Commun 2016; 37:1860-1880. [PMID: 27673474 PMCID: PMC5156561 DOI: 10.1002/marc.201600412] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 08/15/2016] [Indexed: 12/19/2022]
Abstract
Veins used as grafts in heart bypass or as access points in hemodialysis exhibit high failure rates, thereby causing significant morbidity and mortality for patients. Interventional or revisional surgeries required to correct these failures have been met with limited success and exorbitant costs, particularly for the US Centers for Medicare & Medicaid Services. Vein stenosis or occlusion leading to failure is primarily the result of neointimal hyperplasia. Systemic therapies have achieved little long-term success, indicating the need for more localized, sustained, biomaterial-based solutions. Numerous studies have demonstrated the ability of external stents to reduce neointimal hyperplasia. However, successful results from animal models have failed to translate to the clinic thus far, and no external stent is currently approved for use in the US to prevent vein graft or hemodialysis access failures. This review discusses current progress in the field, design considerations, and future perspectives for biomaterial-based external stents. More comparative studies iteratively modulating biomaterial and biomaterial-drug approaches are critical in addressing mechanistic knowledge gaps associated with external stent application to the arteriovenous environment. Addressing these gaps will ultimately lead to more viable solutions that prevent vein graft and hemodialysis access failures.
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Affiliation(s)
- Timothy C Boire
- Department of Biomedical Engineering, Vanderbilt University, 37235, Nashville, TN, USA
| | - Daniel A Balikov
- Department of Biomedical Engineering, Vanderbilt University, 37235, Nashville, TN, USA
| | - Yunki Lee
- Department of Biomedical Engineering, Vanderbilt University, 37235, Nashville, TN, USA
| | - Christy M Guth
- Division of Vascular Surgery, Department of Surgery, Vanderbilt University Medical Center, Nashville, TN, 37235, USA
| | - Joyce Cheung-Flynn
- Division of Vascular Surgery, Department of Surgery, Vanderbilt University Medical Center, Nashville, TN, 37235, USA
| | - Hak-Joon Sung
- Department of Biomedical Engineering, Vanderbilt University, 37235, Nashville, TN, USA
- Severance Biomedical Science Institute, College of Medicine, Yonsei University, Seoul, 120-752, Republic of Korea
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21
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Papakonstantinou NA, Baikoussis NG, Goudevenos J, Papadopoulos G, Apostolakis E. Novel no touch technique of saphenous vein harvesting: Is great graft patency rate provided? Ann Card Anaesth 2016; 19:481-8. [PMID: 27397453 PMCID: PMC4971977 DOI: 10.4103/0971-9784.185537] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 05/25/2016] [Indexed: 11/09/2022] Open
Abstract
Coronary artery bypass grafting surgery effectively relieves signs and symptoms of myocardial ischemia. The left internal thoracic artery (LITA) graft is the gold standard having 90-95% patency rate at 10 years, whereas only 50% of saphenous vein (SV) grafts are patent at 10 years. However, there is a novel "no touch" technique in order to harvest an SV complete with its cushion of surrounding tissue, thus maintaining its endothelium-intact. Significantly superior short- and long-term graft patency rates comparable to LITA grafts can be achieved. Consequently, the SV may be revived as an important conduit in coronary artery bypass surgery.
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Affiliation(s)
- Nikolaos A. Papakonstantinou
- Department of Cardiothoracic Surgery, University Hospital of Ioannina, School of Medicine, 45500 Ioannina, Greece
- Department of Cardiothoracic Surgery, General Hospital of Athens “Evangelismos”, Athens, Greece
| | - Nikolaos G. Baikoussis
- Department of Cardiothoracic Surgery, General Hospital of Athens “Evangelismos”, Athens, Greece
| | - John Goudevenos
- Department of Cardiology, University Hospital of Ioannina, School of Medicine, 45500 Ioannina, Greece
| | - George Papadopoulos
- Department of Anesthesiology, University Hospital of Ioannina, School of Medicine, 45500 Ioannina, Greece
| | - Efstratios Apostolakis
- Department of Cardiothoracic Surgery, University Hospital of Ioannina, School of Medicine, 45500 Ioannina, Greece
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22
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Kahraman N, Yumun G, Gücü A, Özsin KK, Taner T, Şener E, Göncü MT. Administration of perivascular cyanoacrylate for the prevention of cellular damage in saphenous vein grafts: an experimental model. Cardiovasc J Afr 2015; 27:159-163. [PMID: 26506883 PMCID: PMC5101453 DOI: 10.5830/cvja-2015-078] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 10/04/2015] [Indexed: 11/20/2022] Open
Abstract
Objective: The saphenous vein is the most commonly used graft in coronary artery bypass surgery, since no suitable arterial graft is available. However, the frequency of late graft failure is a cause for research into graft protection. The objective of this study was to investigate the effect of synthetic adhesive cyanoacrylate administration on the saphenous vein graft for preventing vascular damage due to internal pressure on the graft. Methods: In this study we enrolled 20 volunteer subjects who had undergone coronary artery bypass surgery and who had excess saphenous vein grafts. Perivascular cyanoacrylate was administered to one of two saphenous vein grafts explanted from each patient. The other saphenous vein graft from each patient was not treated and was used as the control. A model of the arterial system was created using a saphenous vein cardiopulmonary bypass system. Circulation was maintained at 120 mmHg for 45 minutes. Afterwards, the grafts were subjected to histopathological examination. Results: The cyanoacrylate group of grafts did not develop severe vascular damage compared with many instances of moderate and severe damage due to compression in the control group of grafts (p = 0.003). Conclusion Perivascular administration of cyanoacrylate appeared to be successful in the prevention of early saphenous vein graft injury. No in vivo study has been performed to date to assess endothelial damage in the saphenous vein, in order to demonstrate the long-term effect of cyanoacrylate. Further investigations are needed in this regard.
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Affiliation(s)
- Nail Kahraman
- Bursa Yuksek Ihtisas Education and Research Hospital, Bursa, Turkey
| | | | - Arif Gücü
- Department of Cardiovascular Surgery, Bursa Yuksek Ihtisas Education and Research Hospital, Bursa, Turkey
| | - Kadir K Özsin
- Department of Cardiovascular Surgery, Bursa Yuksek Ihtisas Education and Research Hospital, Bursa, Turkey
| | - Temmuz Taner
- Department of Cardiovascular Surgery, Bursa Yuksek Ihtisas Education and Research Hospital, Bursa, Turkey
| | - Ebru Şener
- Department of Pathology, Erzurum Education and Research Hospital, Erzurum, Turkey
| | - Mehmet T Göncü
- Department of Cardiovascular Surgery, Bursa Yuksek Ihtisas Education and Research Hospital, Bursa, Turkey
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23
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Samano N, Geijer H, Liden M, Fremes S, Bodin L, Souza D. The no-touch saphenous vein for coronary artery bypass grafting maintains a patency, after 16 years, comparable to the left internal thoracic artery: A randomized trial. J Thorac Cardiovasc Surg 2015; 150:880-8. [DOI: 10.1016/j.jtcvs.2015.07.027] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 06/23/2015] [Accepted: 07/08/2015] [Indexed: 10/23/2022]
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24
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A novel biodegradable external mesh stent improved long-term patency of vein grafts by inhibiting intimal–medial hyperplasia in an experimental canine model. Gen Thorac Cardiovasc Surg 2015; 64:1-9. [DOI: 10.1007/s11748-015-0591-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 09/17/2015] [Indexed: 10/23/2022]
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25
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Singh C, Wang X. A new design concept for knitted external vein-graft support mesh. J Mech Behav Biomed Mater 2015; 48:125-133. [PMID: 25916819 DOI: 10.1016/j.jmbbm.2015.04.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 03/31/2015] [Accepted: 04/01/2015] [Indexed: 11/24/2022]
Abstract
Autologous vein-graft failure significantly limits the long-term efficacy of coronary artery bypass procedures. The major cause behind this complication is biomechanical mismatch between the vein and coronary artery. The implanted vein experiences a sudden increase (10-12 fold) in luminal pressures. The resulting vein over-distension or 'ballooning' initiates wall thickening phenomenon and ultimate occlusion. Therefore, a primary goal in improving the longevity of a coronary bypass procedure is to inhibit vein over-distension using mechanical constriction. The idea of using an external vein-graft support mesh has demonstrated sustained benefits and wide acceptance in experimental studies. Nitinol based knitted structures have offered more promising mechanical features than other mesh designs owing to their unique loosely looped construction. However, the conventional plain knit construction still exhibits limitations (radial compliance, deployment ease, flexibility, and bending stresses) which limit this design from proving its real clinical advantage. The new knitted mesh design presented in this study is based on the concept of composite knitting utilising high modulus (nitinol and polyester) and low modulus (polyurethane) material components. The experimental comparison of the new design with a plain knit design demonstrated significant improvement in biomechanical (compliance, flexibility, extensibility, viscoelasticity) and procedural (deployment limit) parameters. The results are indicative of the promising role of new mesh in restoring the lost compliance and pulsatility of vein-graft at high arterial pressures. This way it can assist in controlled vein-graft remodelling and stepwise restoration of vein mechanical homoeostasis. Also, improvement in deployment limit parameter offers more flexibility for a surgeon to use a wide range of vein diameters, which may otherwise be rendered unusable for a plain knit mesh.
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Affiliation(s)
- Charanpreet Singh
- Australian Future Fibres Research and Innovation Centre, Institute for Frontier Materials, Deakin University, Geelong, Victoria 3216, Australia
| | - Xungai Wang
- Australian Future Fibres Research and Innovation Centre, Institute for Frontier Materials, Deakin University, Geelong, Victoria 3216, Australia; School of Textile Science and Engineering, Wuhan Textile University, Wuhan 430073, China.
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26
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Dai L, Gao M, Gu C, Zhang F, Yu Y. Perivenous application of cyanoacrylate tissue sealants reduces intimal and medial thickening of the vein graft and inflammatory responses in a rabbit model of carotid artery bypass grafting. Eur J Cardiothorac Surg 2015; 49:675-81. [PMID: 25838460 DOI: 10.1093/ejcts/ezv111] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 02/17/2015] [Indexed: 01/03/2023] Open
Abstract
OBJECTIVES Effective therapies to prevent vein graft failure after coronary artery bypass grafting (CABG) are still lacking. α-Cyanoacrylate (α-CA, 99% n-octyl-α-cyanoacrylate + n-butyl-α-cyanoacrylate) has been increasingly used as a tissue sealant for wound closure because of its bacteriostatic, biodegradable and haemostatic properties. As a strong tissue adhesive, α-CA might prevent an arterial circulation-induced mechanical stretch on vein graft to attenuate intimal hyperplasia. Here, we investigated the effects of perivenous application of α-CA on the vein graft in a rabbit model of carotid artery bypass grafting. METHODS Healthy New Zealand white rabbits were randomized into no graft, graft or graft + α-CA group (n = 10 per group). Rabbit carotid artery was bypassed with the jugular vein. α-CA sealants were sprayed on the entire jugular graft including both anastomotic sites after completion of anastomoses. Blood flow parameters and histological characteristics of the vein grafts including vessel wall thickness, number of medial elastic lamina and proliferation index were evaluated 4 weeks after the surgery. The mRNA or protein levels of proinflammatory factors, chemokine (C-C motif) ligand-2 (CCL-2) and tumour necrosis factor-α (TNF-α) were measured 4 weeks after the operation by quantitative reverse transcription polymerase chain reaction or enzyme-linked immunosorbent assay. RESULTS Compared with the untreated vein grafts at Week 4 after the operation, the α-CA spray significantly improved graft flow (39.4 ± 1.5 vs 27.8 ± 2.9 ml/min, P < 0.01), attenuated intimal and medial thickening (116.3 ± 1.0 vs 159.7 ± 0.9 μm, P < 0.01), reduced anti-proliferating cell nuclear antigen proliferation index of the vein grafts (15.0 ± 0.4 vs 23.6 ± 0.4%, P < 0.01), decreased the mRNA levels of plasminogen activator inhibitor-1 and CCL-2, and reduced the serum levels of TNF-α (92.9 ± 1.7 vs 102.7 ± 1.8 pg/ml, P < 0.01). CONCLUSION Perivenous application of α-CA sealants exerts short-term beneficial effects on the vein graft and reduces inflammatory responses in a rabbit model of carotid artery bypass grafting. Long-term effects of α-CA on vein graft remodelling and the clinical significance of α-CA in CABG remain to be determined in future studies.
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Affiliation(s)
- Longsheng Dai
- Department of Cardiac Surgery, Beijing An Zhen Hospital, Capital Medical University, Beijing, China Beijing Institute of Heart Lung and Blood Vessel Diseases, Beijing, China
| | - Mingxin Gao
- Department of Cardiac Surgery, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Chengxiong Gu
- Department of Cardiac Surgery, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Fan Zhang
- Department of Cardiac Surgery, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Yang Yu
- Department of Cardiac Surgery, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
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Xie P, Shi E, Gu T, Zhang Y, Mao N. Inhibition of intimal hyperplasia of the vein graft with degradable poly lactic-co-glycolic acid vascular external sheaths carrying slow-release bosentan. Eur J Cardiothorac Surg 2015; 48:842-9; discussion 849. [DOI: 10.1093/ejcts/ezv025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2014] [Accepted: 12/11/2014] [Indexed: 11/14/2022] Open
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Longchamp A, Allagnat F, Berard X, Alonso F, Haefliger JA, Deglise S, Corpataux JM. Procedure for human saphenous veins ex vivo perfusion and external reinforcement. J Vis Exp 2014:e52079. [PMID: 25350681 DOI: 10.3791/52079] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The mainstay of contemporary therapies for extensive occlusive arterial disease is venous bypass graft. However, its durability is threatened by intimal hyperplasia (IH) that eventually leads to vessel occlusion and graft failure. Mechanical forces, particularly low shear stress and high wall tension, are thought to initiate and to sustain these cellular and molecular changes, but their exact contribution remains to be unraveled. To selectively evaluate the role of pressure and shear stress on the biology of IH, an ex vivo perfusion system (EVPS) was created to perfuse segments of human saphenous veins under arterial regimen (high shear stress and high pressure). Further technical innovations allowed the simultaneous perfusion of two segments from the same vein, one reinforced with an external mesh. Veins were harvested using a no-touch technique and immediately transferred to the laboratory for assembly in the EVPS. One segment of the freshly isolated vein was not perfused (control, day 0). The two others segments were perfused for up to 7 days, one being completely sheltered with a 4 mm (diameter) external mesh. The pressure, flow velocity, and pulse rate were continuously monitored and adjusted to mimic the hemodynamic conditions prevailing in the femoral artery. Upon completion of the perfusion, veins were dismounted and used for histological and molecular analysis. Under ex vivo conditions, high pressure perfusion (arterial, mean = 100 mm Hg) is sufficient to generate IH and remodeling of human veins. These alterations are reduced in the presence of an external polyester mesh.
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Affiliation(s)
- Alban Longchamp
- Department of Surgery, Brigham and Women's Hospital/Harvard Medical School;
| | - Florent Allagnat
- Laboratory of Experimental Medicine, Department of Medicine, CHUV University Hospital
| | - Xavier Berard
- Department of Vascular Surgery, Pellegrin Hospital, University of Bordeaux
| | - Florian Alonso
- Laboratory of Experimental Medicine, Department of Medicine, CHUV University Hospital
| | | | - Sébastien Deglise
- Department of Thoracic and Vascular Surgery, CHUV University Hospital
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The use of external mesh reinforcement to reduce intimal hyperplasia and preserve the structure of human saphenous veins. Biomaterials 2014; 35:2588-99. [DOI: 10.1016/j.biomaterials.2013.12.041] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 12/18/2013] [Indexed: 01/14/2023]
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Ghista DN, Kabinejadian F. Coronary artery bypass grafting hemodynamics and anastomosis design: a biomedical engineering review. Biomed Eng Online 2013; 12:129. [PMID: 24330653 PMCID: PMC3867628 DOI: 10.1186/1475-925x-12-129] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 12/10/2013] [Indexed: 12/24/2022] Open
Abstract
In this paper, coronary arterial bypass grafting hemodynamics and anastomosis designs are reviewed. The paper specifically addresses the biomechanical factors for enhancement of the patency of coronary artery bypass grafts (CABGs). Stenosis of distal anastomosis, caused by thrombosis and intimal hyperplasia (IH), is the major cause of failure of CABGs. Strong correlations have been established between the hemodynamics and vessel wall biomechanical factors and the initiation and development of IH and thrombus formation. Accordingly, several investigations have been conducted and numerous anastomotic geometries and devices have been designed to better regulate the blood flow fields and distribution of hemodynamic parameters and biomechanical factors at the distal anastomosis, in order to enhance the patency of CABGs. Enhancement of longevity and patency rate of CABGs can eliminate the need for re-operation and can significantly lower morbidity, and thereby reduces medical costs for patients suffering from coronary stenosis. This invited review focuses on various endeavors made thus far to design a patency-enhancing optimized anastomotic configuration for the distal junction of CABGs.
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Affiliation(s)
| | - Foad Kabinejadian
- Department of Biomedical Engineering, National University of Singapore, 9 Engineering Drive 1, Block EA #03-12, Singapore 117576, Singapore.
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31
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Harskamp RE, Lopes RD, Baisden CE, de Winter RJ, Alexander JH. Saphenous vein graft failure after coronary artery bypass surgery: pathophysiology, management, and future directions. Ann Surg 2013; 257:824-33. [PMID: 23574989 DOI: 10.1097/sla.0b013e318288c38d] [Citation(s) in RCA: 237] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
OBJECTIVE To review our current understanding of the epidemiology and pathogenesis of vein graft failure (VGF), give an overview of current preventive and interventional measures, and explore strategies that may improve vein graft patency. BACKGROUND VGF and progression of native coronary artery disease limit the long-term efficacy of coronary artery bypass graft surgery. METHODS We reviewed the published literature on the pathophysiology, prevention, and/or treatment of VGF by searching the MEDLINE (January 1, 1966-January 1, 2012), EMBASE (January 1, 1980-January 1, 2012), and Cochrane (January 1, 1995-January 1, 2012) databases. In addition, we reviewed references from the selected articles for studies not identified in the initial search. Basic science and clinical studies were included; non-English language publications were excluded. RESULTS Acute thrombosis, neointimal hyperplasia, and accelerated atherosclerosis are the 3 mechanisms that lead to VGF. Preventive measures include matching and quality assessment of conduit and target vessel, lipid-lowering drugs, antithrombotic therapy, and cessation of smoking. Treatment of VGF includes medical therapy, percutaneous intervention, and redo coronary artery bypass graft surgery. In patients undergoing graft intervention, the use of drug-eluting stents, antiplatelet agents, and embolic protection devices may improve clinical outcomes. CONCLUSIONS Despite advances in management, VGF remains one of the leading causes of poor in-hospital and long-term outcomes after coronary artery bypass graft surgery. New developments in VGF prevention such as gene therapy, external graft support, fully tissue-engineered grafts, hybrid grafts, and synthetic conduits are promising but unproven. Future efforts to reduce VGF require a multidisciplinary approach with a primary focus on prevention.
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Affiliation(s)
- Ralf E Harskamp
- Duke Clinical Research Institute, Duke University Medical Center, Durham, NC 27705, USA
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Expandable external support device to improve Saphenous Vein Graft Patency after CABG. J Cardiothorac Surg 2013; 8:122. [PMID: 23641948 PMCID: PMC3661403 DOI: 10.1186/1749-8090-8-122] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2012] [Accepted: 04/29/2013] [Indexed: 11/20/2022] Open
Abstract
Objectives Low patency rates of saphenous vein grafts remain a major predicament in surgical revascularization. We examined a novel expandable external support device designed to mitigate causative factors for early and late graft failure. Methods For this study, fourteen adult sheep underwent cardiac revascularization using two vein grafts for each; one to the LAD and the other to the obtuse marginal artery. One graft was supported with the device while the other served as a control. Target vessel was alternated between consecutive cases. The animals underwent immediate and late angiography and were then sacrificed for histopathologic evaluation. Results Of the fourteen animals studied, three died peri-operatively (unrelated to device implanted), and ten survived the follow-up period. Among surviving animals, three grafts were thrombosed and one was occluded, all in the control group (p = 0.043). Quantitative angiographic evaluation revealed no difference between groups in immediate level of graft uniformity, with a coefficient-of-variance (CV%) of 7.39 in control versus 5.07 in the supported grafts, p = 0.082. At 12 weeks, there was a significant non-uniformity in the control grafts versus the supported grafts (CV = 22.12 versus 3.01, p < 0.002). In histopathologic evaluation, mean intimal area of the supported grafts was significantly lower than in the control grafts (11.2 mm^2 versus 23.1 mm^2 p < 0.02). Conclusions The expandable SVG external support system was found to be efficacious in reducing SVG’s non-uniform dilatation and neointimal formation in an animal model early after CABG. This novel technology may have the potential to improve SVG patency rates after surgical myocardial revascularization.
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Abstract
Saphenous vein remains a widely used conduit in coronary surgery. However, the long-term success of surgical myocardial revascularization is largely limited by the development of neointimal hyperplasia and superimposed atherosclerosis in vein grafts. Although strategies for preventing vein graft failure have been constantly explored, few therapeutic interventions to date have shown sustained benefits in the clinical setting. The application of external support has emerged as a promising strategy for modulating the overall biomechanical responses in venous wall. Nonetheless, clinical translation of this intervention has been formerly challenged, primarily due to several technique limitations. The purpose of the current review is to summarize the possible mechanisms involved in the external support strategy for preventing vein graft failure. Furthermore, several previously tested biomaterials and delivery techniques are also highlighted.
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Affiliation(s)
- Jia Hu
- Division of Cardiothoracic Surgery, Department of Surgery, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, People's Republic of China
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Huang C, Wang S, Qiu L, Ke Q, Zhai W, Mo X. Heparin loading and pre-endothelialization in enhancing the patency rate of electrospun small-diameter vascular grafts in a canine model. ACS APPLIED MATERIALS & INTERFACES 2013; 5:2220-2226. [PMID: 23465348 DOI: 10.1021/am400099p] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We herein proved that the two commonly used antithrombotic methods, heparin loading and pre-endothelialization could both greatly enhance the patency rate of a small-diameter graft in a canine model. Tubular grafts having an inner diameter of 4 mm were prepared by electrospinning poly(l-lactide-co-ε-caprolactone) (P(LLA-CL)) and heparin through a coaxial electrospinning technique. Seventy-two percent of heparin was found to be released sustainably from the graft within 14 days. To prepare the pre-endothelialized grafts, we seeded endothelial cells isolated from the femoral artery and cultured then dynamically on the lumen until a cell monolayer was formed. Digital subtraction angiography (DSA) and color Doppler flow imaging (CDFI) were used to monitor the patency without sacrificing the animals. Histological analyses revealed that following the direction of blood flow, a cell monolayer was formed at the proximal end of the heparin-loaded grafts, but such a monolayer could be found in the middle or distal region of the grafts. In contrast, the whole luminal surface of the pre-endothelialized graft was covered by a cell monolayer, suggesting the in vivo survival of the preseeded cells. This demonstrated that heparin was a comparatively simple method to achieve good patency, but the pre-endothelialization had better mechanical properties and cellular compatibility.
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Affiliation(s)
- Chen Huang
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, China
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35
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Dashwood MR, Tsui JC. 'No-touch' saphenous vein harvesting improves graft performance in patients undergoing coronary artery bypass surgery: a journey from bedside to bench. Vascul Pharmacol 2012; 58:240-50. [PMID: 22967905 DOI: 10.1016/j.vph.2012.07.008] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 07/14/2012] [Accepted: 07/31/2012] [Indexed: 11/19/2022]
Abstract
The saphenous vein is the most commonly used conduit in patients undergoing coronary artery bypass surgery yet its patency is inferior to the internal thoracic artery. Vascular damage inflicted to the vein when using conventional harvesting techniques affects its structure. Endothelial denudation is associated with early vein graft failure while damage of the outermost vessel layers has adverse long-term effects on graft performance. While many in vitro and in vivo experimental studies aimed at improving vein graft patency have been performed to date no significant 'bench to bedside' advances have been made. Among experimental strategies employed is the use of pharmacological agents, gene targeting and external stents. A 'no-touch' technique, where the saphenous vein is removed with minimal trauma and normal architecture preserved, produces a superior graft with long term patency comparable to the internal thoracic artery. Interestingly, many experimental studies are aimed at repairing or replacing those regions of the saphenous vein damaged when harvesting conventionally. 'No-touch' harvesting is superior in coronary artery bypass patients with long-term data published 5years ago. Here we describe a 'bedside to bench' situation where the mechanisms underlying the improved performance of 'no touch' saphenous vein grafts in patients have been studied in the laboratory.
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Affiliation(s)
- Michael R Dashwood
- Department of Clinical Biochemistry, Royal Free and University College Medical School, Pond Street, London NW3 2QG, United Kingdom.
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36
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Shukla N, Jeremy JY. Pathophysiology of saphenous vein graft failure: a brief overview of interventions. Curr Opin Pharmacol 2012; 12:114-20. [PMID: 22321569 DOI: 10.1016/j.coph.2012.01.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Revised: 01/05/2012] [Accepted: 01/06/2012] [Indexed: 12/01/2022]
Abstract
Coronary artery bypass graft surgery (CABG) is widely used for the treatment of atheromatous stenosis of coronary arteries. However, as many as 50% of grafts fail within 10 years after CABG due to neointima (NI) formation, a process involving the proliferation of vascular smooth muscle cells (VSMCs) and superimposed atherogenesis. To date no therapeutic intervention has proved successful in treating late vein graft failure. However, several diverse approaches aimed at preventing neointimal formation have been devised which have yielded promising results. In this review, therefore, we will summarise the pathophysiology of vein graft disease and then briefly consider interventional approaches to prevent late vein graft failure which include surgical technique, conventional pharmacology, external sheaths, cytostatic drugs and gene transfer.
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Affiliation(s)
- Nilima Shukla
- Bristol Heart Institute, The University of Bristol, UK.
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37
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Zilla P, Moodley L, Wolf MF, Bezuidenhout D, Sirry MS, Rafiee N, Lichtenberg W, Black M, Franz T. Knitted nitinol represents a new generation of constrictive external vein graft meshes. J Vasc Surg 2011; 54:1439-50. [DOI: 10.1016/j.jvs.2011.05.023] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Revised: 05/12/2011] [Accepted: 05/12/2011] [Indexed: 11/16/2022]
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38
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Endothelin-1 (ET-1) and vein graft failure and the therapeutic potential of ET-1 receptor antagonists. Pharmacol Res 2011; 63:483-9. [DOI: 10.1016/j.phrs.2010.10.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 10/27/2010] [Accepted: 10/29/2010] [Indexed: 12/21/2022]
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39
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Gauvin R, Guillemette M, Galbraith T, Bourget JM, Larouche D, Marcoux H, Aubé D, Hayward C, Auger FA, Germain L. Mechanical properties of tissue-engineered vascular constructs produced using arterial or venous cells. Tissue Eng Part A 2011; 17:2049-59. [PMID: 21457095 DOI: 10.1089/ten.tea.2010.0613] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
There is a clinical need for better blood vessel substitutes, as current surgical procedures are limited by the availability of suitable autologous vessels and suboptimal behavior of synthetic grafts in small caliber arterial graft (<5 mm) applications. The aim of the present study was to compare the mechanical properties of arterial and venous tissue-engineered vascular constructs produced by the self-assembly approach using cells extracted from either the artery or vein harvested from the same human umbilical cord. The production of a vascular construct comprised of a media and an adventitia (TEVMA) was achieved by rolling a continuous tissue sheet containing both smooth muscle cells and adventitial fibroblasts grown contiguously in the same tissue culture plate. Histology and immunofluorescence staining were used to evaluate the structure and composition of the extracellular matrix of the vascular constructs. The mechanical strength was assessed by uniaxial tensile testing, whereas viscoelastic behavior was evaluated by stepwise stress-relaxation and by cyclic loading hysteresis analysis. Tensile testing showed that the use of arterial cells resulted in stronger and stiffer constructs when compared with those produced using venous cells. Moreover, cyclic loading demonstrated that constructs produced using arterial cells were able to bear higher loads for the same amount of strain when compared with venous constructs. These results indicate that cells isolated from umbilical cord can be used to produce vascular constructs. Arterial constructs possessed superior mechanical properties when compared with venous constructs produced using cells isolated from the same human donor. This study highlights the fact that smooth muscle cells and fibroblasts originating from different cell sources can potentially lead to distinct tissue properties when used in tissue engineering applications.
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Affiliation(s)
- Robert Gauvin
- Centre LOEX de l'Université Laval, Génie tissulaire et régénérationand Département de Chirurgie, Faculté de Médecine, Université Laval Québec, Québec, Canada
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40
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Abbasi K, Shalileh K, Anvari MS, Rabbani S, Mahdanian A, Ahmadi SH, Moshtaghi N, Movahedi N, Karimi A. Perivascular Nitric Oxide Delivery to Saphenous Vein Grafts Prevents Graft Stenosis after Coronary Artery Bypass Grafting: A Novel Sheep Model. Cardiology 2011; 118:8-15. [DOI: 10.1159/000324316] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 01/08/2011] [Indexed: 11/19/2022]
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41
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Short-term effects of double-layer autologous vein graft on restraint of excessive distension and alleviation of neointimal hyperplasia in a porcine saphenous vein graft model. Heart Vessels 2010; 26:190-5. [DOI: 10.1007/s00380-010-0034-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Accepted: 02/12/2010] [Indexed: 10/18/2022]
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42
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Franz T, Human P, Dobner S, Reddy BD, Black M, Ilsley H, Wolf MF, Bezuidenhout D, Moodley L, Zilla P. Tailored sizes of constrictive external vein meshes for coronary artery bypass surgery. Biomaterials 2010; 31:9301-9. [DOI: 10.1016/j.biomaterials.2010.08.054] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Accepted: 08/24/2010] [Indexed: 10/19/2022]
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43
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Characterization of the Inhibition of Vein Graft Intimal Hyperplasia by a Biodegradable Vascular Stent. Cell Biochem Biophys 2010; 59:99-107. [DOI: 10.1007/s12013-010-9118-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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44
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Desai M, Mirzay-Razzaz J, von Delft D, Sarkar S, Hamilton G, Seifalian AM. Inhibition of neointimal formation and hyperplasia in vein grafts by external stent/sheath. Vasc Med 2010; 15:287-97. [DOI: 10.1177/1358863x10366479] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Synthetic and to a lesser extent vein graft failure is still a major problem in the treatment of peripheral arterial disease, with neointimal hyperplasia being the main cause for graft occlusion in the medium and long term. This review aims to establish the current status of external stents or sheaths in the prevention of intimal hyperplasia in small diameter (< 6 mm) vein grafts.
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Affiliation(s)
- Mital Desai
- Centre for Nanotechnology and Regenerative Medicine, Division of Surgery & Interventional Science, University College London, London, UK, Cardiovascular Haemodynamic Group, University College London, London, UK
| | - Jalaledin Mirzay-Razzaz
- Centre for Nanotechnology and Regenerative Medicine, Division of Surgery & Interventional Science, University College London, London, UK, Cardiovascular Haemodynamic Group, University College London, London, UK
| | - Dirk von Delft
- Christiaan Barnard Division of Cardiothoracic Surgery, University of Cape Town, Cape Town, South Africa
| | - Sandip Sarkar
- Centre for Nanotechnology and Regenerative Medicine, Division of Surgery & Interventional Science, University College London, London, UK
| | - George Hamilton
- Vascular Unit, Royal Free Hampstead NHS Trust Hospital, London, UK
| | - Alexander M Seifalian
- Centre for Nanotechnology and Regenerative Medicine, Division of Surgery & Interventional Science, University College London, London, UK, Cardiovascular Haemodynamic Group, University College London, London, UK,
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45
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Bloor J, Shukla N, Smith FCT, Angelini GD, Jeremy JY. Folic acid administration reduces neointimal thickening, augments neo-vasa vasorum formation and reduces oxidative stress in saphenous vein grafts from pigs used as a model of diabetes. Diabetologia 2010; 53:980-8. [PMID: 20182861 PMCID: PMC3596781 DOI: 10.1007/s00125-010-1680-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Accepted: 12/14/2009] [Indexed: 01/13/2023]
Abstract
AIMS/HYPOTHESIS There is evidence that plasma homocysteine augments vein graft failure and that it augments both micro- and macro-angiopathy in patients with diabetes mellitus. It is therefore suggested that homocysteine may augment vein graft thickening, a major cause of vein graft failure, in diabetic patients, as well as impairing adaptive growth of a new vasa vasorum, possibly through overproduction of superoxide. In order to test these proposals, the effect of folic acid administration, which lowers plasma homocysteine, on vein graft thickening and microvessel density was studied in pigs used as a model of diabetes. METHODS Non-ketotic hyperglycaemia was induced in Landrace pigs by intravenous injection of streptozotocin, and folic acid was fed daily for 1 month. Vein grafts were excised and the thickness of the neointima and media and microvessel density were assessed by planimetry and superoxide formation. RESULTS Plasma total homocysteine was significantly reduced by folic acid in both control and diabetic pigs, whereas glucose was unchanged. Compared with controls, diabetic pigs showed increased neointimal thickness and superoxide formation and decreased adventitial microvessel density. Folic acid reduced neointimal thickness and superoxide formation and augmented microvessel density in diabetic but not in control pigs. CONCLUSIONS Folic acid administration reduces neointimal thickening, augments vasa vasorum neoformation and reduces oxidative stress in saphenous vein grafts from diabetic pigs. Folic acid may therefore be particularly effective in reducing vein graft failure in diabetic patients.
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Affiliation(s)
- J. Bloor
- Department of Vascular Surgery, University of Bristol, Bristol, UK
| | - N. Shukla
- Bristol Heart Institute, Bristol Royal Infirmary, Marlborough Street, Bristol BS2 8HW, UK
| | - F. C. T. Smith
- Department of Vascular Surgery, University of Bristol, Bristol, UK
| | - G. D. Angelini
- Bristol Heart Institute, Bristol Royal Infirmary, Marlborough Street, Bristol BS2 8HW, UK
| | - J. Y. Jeremy
- Bristol Heart Institute, Bristol Royal Infirmary, Marlborough Street, Bristol BS2 8HW, UK,
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46
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Zilla P, Wolf M, Rafiee N, Moodley L, Bezuidenhout D, Black M, Human P, Franz T. Utilization of shape memory in external vein-graft meshes allows extreme diameter constriction for suppressing intimal hyperplasia: A non-human primate study. J Vasc Surg 2009; 49:1532-42. [DOI: 10.1016/j.jvs.2009.01.068] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Revised: 01/22/2009] [Accepted: 01/31/2009] [Indexed: 11/25/2022]
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47
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Human P, Franz T, Scherman J, Moodley L, Zilla P. Dimensional analysis of human saphenous vein grafts: Implications for external mesh support. J Thorac Cardiovasc Surg 2009; 137:1101-8. [PMID: 19379974 DOI: 10.1016/j.jtcvs.2008.10.040] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 09/05/2008] [Accepted: 10/03/2008] [Indexed: 11/24/2022]
Abstract
OBJECTIVE Constrictive external mesh support of vein grafts was shown to mitigate intimal hyperplasia in animal experiments. To determine the degree of constriction required for the elimination of dimensional irregularities in clinically used vein grafts, a detailed anatomic study of human saphenous veins was conducted. METHODS In 200 consecutive patients having coronary artery bypass grafting, harvested saphenous veins (length 34.4 +/- 10.8 cm) were analyzed regarding diameter irregularities, side branch distribution, and microstructure. RESULTS The mean outer diameter of surgically distended saphenous veins was 4.2 +/- 0.6 mm (men, 4.3 +/- 0.6 mm vs women, 3.9 +/- 0.5 mm; P < .0001). Although the outer diameter significantly decreased over the initial 18 cm (-7.6%; P < .0001), the overall increase between malleolus and thigh was not significant (+11.2%). Smaller-diameter veins (<3.5 mm) had more pronounced diameter fluctuations than larger veins (31.8% +/- 11.0% vs 21.2% +/- 8.8%; P < .0001), with more than 71% of all veins showing caliber changes of more than 20%. There was 1 side branch every 5.4 +/- 4.3 cm, with a significantly higher incidence between 20 and 32 cm from the malleolus (P < .0001 to distal, P < .0004 to proximal). Generally, women had more side branches than men (0.30 +/- 0.15 cm(-1) vs 0.25 +/- 0.12 cm(-1); P = .0190). Thick-walled veins (565.7 +/- 138.4 mum) had a significantly higher number of large side branches (P < .0001), and thin-walled veins (398.7 +/- 123.2 mum) had significantly more small side branches (P < .0001). Pronounced intimal thickening ("cushions") was found in 28% of vessels (119.8 +/- 28.0 mum vs 40.1 +/- 18.2 mum; P < .0001). CONCLUSION Although the preferential location of side branches may be addressed by the deliberate discarding of infragenicular vein segments, a diameter constriction of 27% on average would eliminate diameter irregularities in 98% of vein grafts.
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Affiliation(s)
- Paul Human
- Christiaan Barnard Department of Cardiothoracic Surgery, University of Cape Town, Observatory, South Africa
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John LCH. Biomechanics of coronary artery and bypass graft disease: potential new approaches. Ann Thorac Surg 2009; 87:331-8. [PMID: 19101335 DOI: 10.1016/j.athoracsur.2008.07.023] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 07/08/2008] [Accepted: 07/09/2008] [Indexed: 12/01/2022]
Abstract
The contribution of biomechanical factors to the incidence and distribution of coronary artery and bypass graft disease is underrecognized. This review examined the literature to determine which factors were relevant and the evidence for their importance. It identified two primary biomechanical factors that predispose to disease: (1) low-wall shear stress and (2) high-wall mechanical stress or strain. A range of secondary biomechanical factors have also been identified and include: vessel geometry; vessel movement; vessel wall characteristics and the presence of reflection waves. Potential surgical approaches for minimizing these effects are discussed.
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Affiliation(s)
- Lindsay C H John
- Department of Cardiothoracic Surgery, Kings College Hospital, London, United Kingdom.
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Constrictive external nitinol meshes inhibit vein graft intimal hyperplasia in nonhuman primates. J Thorac Cardiovasc Surg 2008; 136:717-25. [PMID: 18805277 DOI: 10.1016/j.jtcvs.2008.02.068] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Revised: 01/23/2008] [Accepted: 02/15/2008] [Indexed: 11/21/2022]
Abstract
OBJECTIVE External mesh support of vein grafts has been shown to mitigate the formation of intimal hyperplasia. The aim of the present study was to address the issue of optimal mesh size in a nonhuman primate model that mimics the dimensional mismatch typically encountered between clinical vein grafts and their target arteries. METHODS The effect of mesh size on intimal hyperplasia and endothelial preservation was assessed in bilateral femoral interposition grafts in Chacma baboons (n(Sigma) = 32/n = 8 per mesh size). No mesh support (group I) was compared with external nitinol meshes at three different sizes: loose fitting (group II), 25% diameter constricting (group III), and 50% diameter constricting (group IV). Mesh sizes were seen not only in isolation but also against the background of anastomotic size mismatch at implantation, expressed as quotient of cross-sectional area of host artery to vein graft (Q(C)). RESULTS Significant amounts of intimal hyperplasia were found in group I (Q(C) median 0.20; intimal hyperplasia 6 weeks = 1.63 +/- 0.34 mm(2); intimal hyperplasia 12 weeks = 1.73 +/- 0.5 mm(2)) and group II (Q(C) median 0.25; intimal hyperplasia 6 weeks = 1.96 +/- 1.64 mm(2); intimal hyperplasia 12 weeks = 2.88 +/- 1.69 mm(2)). In contrast, group III (Q(C) median 0.45; intimal hyperplasia 6 weeks = 0.08 +/- 0.13 mm(2); intimal hyperplasia 12 weeks = 0.18 +/- 0.32 mm(2)) and IV (Q(C) median 1.16; intimal hyperplasia 6 weeks = 0.02 +/- 0.03 mm(2); intimal hyperplasia 12 weeks = 0.11 +/- 0.10 mm(2)) showed dramatically suppressed intimal hyperplasia (P < .01) at both time points. Endothelial integrity was only preserved in group IV (P < .05). There were no significant differences in vascularization and inflammation in either interlayer or intergroup comparisons. CONCLUSION By using an animal model that addressed the clinical phenomenon of diameter discrepancy between vein graft and bypassed artery, we could demonstrate that suppression of intimal hyperplasia required constrictive mesh sizes.
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El-Kurdi MS, Hong Y, Stankus JJ, Soletti L, Wagner WR, Vorp DA. Transient elastic support for vein grafts using a constricting microfibrillar polymer wrap. Biomaterials 2008; 29:3213-20. [PMID: 18455787 DOI: 10.1016/j.biomaterials.2008.04.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2008] [Accepted: 04/07/2008] [Indexed: 10/22/2022]
Abstract
Arterial vein grafts (AVGs) often fail due to intimal hyperplasia, thrombosis, or accelerated atherosclerosis. Various approaches have been proposed to address AVG failure, including delivery of temporary mechanical support, many of which could be facilitated by perivascular placement of a biodegradable polymer wrap. The purpose of this work was to demonstrate that a polymer wrap can be applied to vein segments without compromising viability/function, and to demonstrate one potential application, i.e., gradually imposing the mid-wall circumferential wall stress (CWS) in wrapped veins exposed to arterial levels of pressure. Poly(ester urethane)urea, collagen, and elastin were combined in solution, and then electrospun onto freshly-excised porcine internal jugular vein segments. Tissue viability was assessed via Live/Dead staining for necrosis, and vasomotor challenge with epinephrine and sodium nitroprusside for functionality. Wrapped vein segments were also perfused for 24h within an ex vivo vascular perfusion system under arterial conditions (pressure = 120/80 mmHg; flow = 100 mL/min), and CWS was calculated every hour. Our results showed that the electrospinning process had no deleterious effects on tissue viability, and that the mid-wall CWS vs. time profile could be dictated through the composition and degradation of the electrospun wrap. This may have important clinical applications by enabling the engineering of an improved AVG.
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Affiliation(s)
- Mohammed S El-Kurdi
- Department of Surgery, University of Pittsburgh, Pittsburgh, PA, 15219, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, 15219, United States
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