• Fibers and Polymers
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• v.6 no.1
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• pp.49-54
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• 2005

The purpose of this study has been to investigate the effect of dilation on the some mechanical properties of several types of warp-knitted vascular grafts. The structures of warp knit vascular grafts used in the experiments were reverse locknit, locknit, and Tricot. Various mechanical properties of these grafts were determined using devices developed for the purpose. Clinical data obtained were compared with experimental results of warp knit vascular grafts. The most important mechanical properties are found to be creep extension, bursting strengths, and compliance. Preliminary results indicate that vascular grafts are non-compliant and exhibit creep which is predictive of the long term dilation that has been noted in the clinical results. It is found that there is a positive correlation between experimental data and clinical results for at least the grafts tested.

• Journal of Chest Surgery
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• v.28 no.6
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• pp.557-564
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• 1995

Microvel knitted double velour vascular grafts coated with biodegradable algin were evaluated in the canine experimental model as a new biologically coated Dacron graft. Three series of implantations were conducted involving the insertion of 6 mm diameter grafts in the abdominal aortae of mongrel dogs. The first series used the regular Microvel vascular grafts coated with algin,whereas the second and third series used Hemashield [collagen-coated grafts and the regular Microvel grafts with preclotting,respectively as control groups. Each series involved the implantation of one prosthesis for each of 2 preselected periods,namely 3 months and 6 months. In addition,algin-impregnated grafts were implanted for 4 hours,72 hours,2 weeks,and 4 weeks. All grafts were patent when the animals were sacrificed at intervals ranging from 4 hours to 6 months. Histological examinations revealed no obvious or significant differences in the healing characteristics of the algin-coated grafts and the control grafts after 3 months and 6 months of implantation. Endothelial cell-like cells were present on the midsegments of all grafts explanted from animals sacrificed after 3 months and 6 months,except a suspicious finding in the 3 month-implantation animal of a preclotted graft. With special stains,the algin became invisible between the polyester filaments during the first 3 months of implantation. This study has demonstrated that the use of a biodegradable algin coating is a feasible approach as biological sealants for textile arterial prostheses.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.45-47
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• 2002

Although Dacron and ePTFE have most widely been used for artificial vascular grafts, these materials cannot be used for small-diameter grafts (l.D.<6mm) due to thrombotic occlusion. To overcome this limitation, a small-diameter vascular graft was developed with stem cell and tissue engineering method. Autologous bone marrow stem cells were cultured and seeded onto small-diameter (4mm) collagen tubular matrices. The matrices were anastomosed to carotid arteries in canine models. Prior to implantation, histological and electron microscopical examination revealed stem cell adhesion and growth on the matrices. Angiography indicated that the vascular grafts maintained patent for 8 weeks. Histological examination showed the regeneration of endothelium, media and adventitia in the grafts. This study may allow us to step forward to the development of tissue-engineered small-diameter vascular graft appropriate for clinical applications.

• Journal of Chest Surgery
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• v.51 no.6
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• pp.423-426
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• 2018

This study determined the feasibility of the cuff technique for small-caliber vascular grafts in a rat model. A graft was implanted with the cuff technique or suture technique in a 1-cm segment of the abdominal aorta in 12 rats. The mean aortic clamp time was 29 minutes with the cuff technique and 44 minutes with the suture technique; the cuff technique was significantly shorter. Abdominal angiography at 1 week after implantation showed no significant stenosis in 9 rats, focal stenosis of the mid-portion of the graft in 1 rat with each technique, and total occlusion of the graft in 1 rat with the suture technique. We have successfully used the cuff technique for anastomosis for small-caliber vascular grafts in an animal model.

• Journal of Chest Surgery
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• v.19 no.3
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• pp.412-420
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• 1986

From 1968 through September 1986, the authors have experienced 34 cases of peripheral arterial surgery using various vascular grafts. Almost all patients [32] were men, and age distribution was variable according to the disease entities. There were twenty eight cases of chronic occlusive peripheral vascular disease including ASO [21], Buerger`s disease [6], Aortoenteric fistula complicating infrarenal abdominal aortic aneurysm [1], four cases of vascular trauma, one case of acute arterial embolism [1] and one case of unknown etiology. The indications of operations for chronic vascular disease was intermittent claudication in 48%, rest pain in 45%, ischemic pregangrene or gangrene in 28%, and sensory change in 10% of patients. Types of operation used were arterial bypass in 28 cases [Aortobifemoral in 5, Aortoiliac in 3, Aortofemoral in 4, Aortoiliac with Aortofemoral in 1, Femorofemoral in 1, Femoropopliteal in 8, Femoroperoneal in 2, Axillofemoral in 3 cases of patients], graft interposition in four and patch angioplasty in three cases. Thirty four prosthetic vascular grafts including Dacron, Gore-Tex, Nylon and two autogenous saphenous vein graft and patch were used for vascular reconstruction in thirty four patients. Unfortunately recently performed one vein bypass was failed immediate postoperatively due to severity of disease and poor case selection. The authors experienced five post operative complications: wound infection [1], graft infection [1], bleeding [1], great saphenous neuralgia [1], pseudoaneurysm [1]. Twenty two of thirty four patients were followed up for more than one month and their cumulative patency rate was 81% [17/22] at 1 month and, 31% [7/22] at 5 month.

• Archives of Plastic Surgery
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• v.36 no.4
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• pp.380-384
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• 2009

Purpose: Autologous vessels remain the gold standard for vascular grafts in microanastomoses. However, they are sometimes unavailable and have a limited long - term patency. Synthetic vessels have high success rates in large - diameter reconstructions but failed when used as small - diameter grafts due to graft occlusion. It has been proved that endothelial cell seeding improves prosthesis performance and long - term patency. Among polyurethane, PET and ePTFE, polyurethane has the best affinity to endothelial cells and mechanical properties closest to human vessels. We examined the ability of endothelial cells to attach to a polyurethane graft manufactured by the electrospinning method. Methods: Endothelial cells, which were cultured from porcine internal jugular veins, were attached to polyurethane grafts with an internal diameter of 3 mm. The same cells were attached to allogeneic decellularized porcine internal carotid artery grafts as controls. Both of the 10 mm - long grafts were exposed to endothelial cells in a well for 1 hour. Each well contained $2{\times}10^5$ endothelial cells. The graft materials were rotated through 90 degrees every 15 minutes in order to minimize the effect of gravity. The extent of cell attachment was examined with the MTT assay. Results: The MTT assay showed good incorporation of endothelial cells into both grafts. For the evaluation of affinity, the number of attached cells was counted at 10 fields of microscopic examination with ${\times}40$ magnification. Endothelial cells adhered more to polyurethane grafts (mean, $127.4{\pm}6.2cells$) compared to porcine artery grafts (mean $45.8{\pm}5.1cells$)(p<0.05,Mann - Whitney test). Conclusion: In this study, we attached porcine endothelial cells to polyurethane grafts, manufactured by electrospinning. The grafts exhibited a better affinity to endothelial cells than allogeneic decellularized porcine internal carotid artery grafts. It is suggested that the time required for endothelial cells to attach to decellulized artery grafts may be longer than that which is required for attachment to polyurethane grafts.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.281-285
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• 2010

Hemodialysis vascular access dysfunction (HVAD) due to the aggressive development of venous neointimal hyperplasia remains a major complication for patients with synthetic arteriovenous grafts. Paclitaxel-coated expanded polytetrafluoroethylene (ePTFE) grafts effectively prevent neointimal hyperplasia and stenosis. However, perigraft inflammation or edema can be another complication of ePTFE grafts, preventing early cannulation. Three different types of ePTFE grafts, including grafts without paclitaxel coating (control group, n = 12), grafts with paclitaxel coating at a dose density of $0.61ug/mm^2$ (low concentration group, n = 12), and grafts with paclitaxel coating at a dose density of $1.15ug/mm^2$ (high concentration group, n = 12) were placed in the backs of 12 rabbits, simultaneously. Six rabbits were euthanized after one week and the remaining six were euthanized two weeks after implantation. Perigraft inflammation, graft wall inflammation, stromal cell proliferation, blood vessel formation, tissue necrosis and edema were analyzed for the grafts in each animal. Inflammation surrounding the paclitaxel-coated grafts was significantly reduced compared to the control group. Stromal cell layers were detected at the interface between the graft and the surrounding tissue in the control group, infiltrated into the graft interstices, and differentiated into myofibroblasts for graft healing. Paclitaxel-coated grafts inhibited stromal cell proliferation and infiltration into the graft wall. Tissue necrosis and edema were not detected in either of the paclitaxel-coated graft groups.

• Archives of Reconstructive Microsurgery
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• v.5 no.1
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• pp.46-55
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• 1996

The purpose of this study is to investigate if there is a higher rate of free flap failure in cases of vein grafts compared to non-vein graft, and to analyze the clinical usefulness and necessity in elective free flap surgery. We have used 24 vein grafts in 208 free flaps from May, 1986 until August, 1995. Vein grafts were from 2cm to 50cm in length between the recipient and donor vessels. Reconstructed sites were 10 lower extremities, 8 head and neck, 4 hand, and 2 trunk. Vein grafts were used 14 for arterial, 6 venous, 4 in both arterial and venous anastomoses. We intentionally used long vein grafts longer than 5cm for improved blood flow in cases of peripheral vascular disease, radionecrotic wounds, lower leg trauma. Short vein grafts of about 3cm in length were used to overcome the shortage of vascular length in cases of unexpected vessel anomaly, short donor vessel, and difficult access to recipient vessels after radical neck dissection. All veins were carefully handled with ligation of very small branches and were transferred to the recipient site without irrigation. 8 flaps were failed out of a total of 208 free flaps, however there was no failure among the 24 cases that needed vein grafts between the donor and recipient vessels. Success rates between non-vein grafts free flaps and vein graft free flaps were 95.6%(8/184) and 100%(0/24). Even though the vein grafts increase the operation time and the number of anastomoses, they do not result in any increased failure rate of free flap surgery(4.4% versus 0%). In addition to the reducing tension between recipient and donor vessels, the surgeon can select better recipient vessels with excellent blood flow so that vein grfats in microsurgery can provide a high success rate of free flaps.

• Journal of Biomedical Engineering Research
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• v.12 no.3
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• pp.157-164
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• 1991

Microvel $^{\textregistered}$ double velour graft impregnated with a biodegradable algin was studied as a new vatscular graft. It is impervious to blood but still retains high porosity. This graft does not require preclotting during implantation and has good tissue ingrowth and biological healing properties. Two vascular grafts impregnated with algin (6mm in diameter) were implanted in the aorta of mongrel dogs without preclotting. Two identical grafts were preclctted and served as controls. The grafts were harvested 2 and 4 months postoperatively, and the healing pattern was examined by a light microscope after hemRtoxylineosin staining. It was observed that endothelial cells were incompletely covered on both algin-impregnated and control grafts after 2 month Implantation, while they were fully covered on both grafts after 4 month. There were no significant differences in subendothelial granulation tissue organization and fibrinoid material absorption between the algin-impregnated and control grafts. The algin-impregnated graft did not show any harmful effect on the healing and thus can be a new promising graft which is not necessary preclotting during the implantation.

• Journal of Chest Surgery
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• v.36 no.2
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• pp.63-72
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• 2003

Although a variety of synthetic vascular grafts are available in modern vascular surgery, no ideal prosthesis ha,4 yet been developed. Small-caliber vascular grafts with low flow, as used in the lower extremity, continue to become thrombosed at unacceptable rates. We have developed and evaluated the new antithrombogenic blood contacting surfaces in canine model. Material and Method: Two now antithrombogenic blood contacting surfaces(Polyvinylalcohol -Polyurethane(PVA-PU) blend and natural Graphite-polyurethane(G-PU) blend) have been developed and evaluated in canine model, using vascular grafts and patches. The luminal surfaces of the test vascular grafts(5 mm ID) were fabricated by dipping a glass rod in PVA-PU blend solution(50 % PVA) using phase separation method. Mongrel dogs of either sex weighing 18-22 kg were anesthetized by endotracheal intubation using halothane and their lungs were ventilated with a volume-cycled ventilator, Maintenance anesthesia with 0.5-1.0% halothane and supplemental oxygen was used. Two pairs were used for comparison in the bilateral femoral arteries for both vascular grafts(PVA-PU vs. PU) and vascular patches(G-PU vs. PU). Bilateral groin incisions were made and the arteries were exposed and clamped. After an excision of 1 cm of the artery between clamps, a grail of 2.5 cm in length was implanted end-to-end using 6-0 polypropylene suture. The vascular patch was implanted as a form of on-lay patch. Animals were sacrificed at 1, 2, 4, 6, 8 and 16 weeks for vascular grafts and 1, 2. 4 and 6 weeks for vascular patches. Result The vascular grafts of PVA-PU blends showed patent lumina in the 2 and 16 weeks animals, while those of PU showed a patent lumen in 2 weeks animal. PVA-PU graft of 16 weeks showed a fairly clean luminal surface. A light microscopic finding of this graft demonstrated good tissue infiltration through porosity, The animals with vascular patches showed patent arteries in both groups except 2 weeks animal. Scanning electron microscopy of the luminal surfaces of G-PU patches in 4 and 6 weeks animals showed endothelial cell covering with microvilli. PU patches showed qualitatively less endothelial cell covering. Conclusion: In conclusion, PVA-PU and G-PU blends can be a promising blood contacting surfaces for application in a synthetic vascualr graft. However, further animal study is needed to determine the real long-term effects of these methods of surface modifications.