Can knitting structure affect dilation of polyester bifurcated prostheses? A randomized study with the use of helical computed tomography scanning.
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PURPOSE: The aim of this study was to prospectively evaluate the postoperative dilation of two types of knitted polyester arterial prostheses with the use of helical computed tomographic scanning. METHODS: Thirty-four patients who underwent aortoiliac or aortofemoral bifurcation grafting were randomized to receive a collagen-sealed warp-knitted polyester graft (n = 16 patients) or a gelatin-sealed Koper-knitted polyester graft (n = 18 patients). Alterations in size of all parts of the grafts were evaluated by helical computed tomographic scanning at postoperative day 8, at 3 months, and at 6 months. RESULTS: On postoperative day 8, the mean dilation of the Koper-knitted grafts was 18% +/- 8% for the stem and 15% +/- 12% for the limbs. At the same time period, the mean dilation of warp-knitted grafts was 27% +/- 13% for the stem and 33% +/- 18% for the limbs. No increase in graft dilation was observed at 3 and 6 months. Despite the wide range of values among patients with the same graft type, at each time interval, the Koper-knitted grafts dilated significantly less than the warp-knitted grafts (P <. 05). CONCLUSION: In this randomized study, helical computed tomographic scanning was an accurate technique with which to assess graft dilation. For a 6-month follow-up interval, the Koper-knitted polyester structure dilated less than the warp-knitted structure. Longer-term serial scans should allow a better understanding of the clinical significance of graft dilation. (+info)
Mechanism of dacron-activated monocytic cell oxidation of low density lipoprotein.
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PURPOSE: Oxidized lipids are believed to contribute to atherogenesis and may play a role in the development of anastomotic intimal hyperplasia in prosthetic vascular grafts. This study examines the hypothesis that clinically relevant graft material activates monocytes to oxidize low density lipoprotein (LDL). METHODS: LDL and Dacron or expanded polytetrafluoroethylene (ePTFE) graft material were incubated in the presence of U937 cells, a monocytic cell line. LDL oxidation was measured by conjugated dienes, lipid peroxides, thiobarbituric acid-reacting substances, and electrophoretic mobility. Cell production of superoxide was measured by ferricytochrome c reduction. Metal ion requirement was assessed with the metal chelators, ethylenediaminetetra-acidic acid, deferoxamine, and bathocuproinedisulfonic acid. To determine whether human monocytes were capable of being activated by Dacron graft material to oxidize LDL, freshly isolated peripheral blood monocytes were also studied. RESULTS: Incubation of LDL with U937 cells and Dacron increased LDL oxidation by 5- to 20-fold. LDL incubated with ePTFE or U937 cells alone resulted in minimal oxidation. Dacron graft increased U937 cell production of superoxide by 4-fold, whereas ePTFE had no effect. Superoxide dismutase inhibited Dacron-activated U937 cell oxidation of LDL by greater than 50%, which indicates a role for superoxide. Ethylenediaminetetra-acidic acid, deferoxamine, and bathocuproinedisulfonic acid each inhibited Dacron-activated U937 cell oxidation of LDL. Human peripheral blood monocytes were activated by Dacron graft material to oxidize LDL; superoxide dismutase inhibited Dacron-activated human monocytic oxidation of LDL, which suggests a role for superoxide. CONCLUSION: These results suggest that Dacron graft material activates monocytes to oxidize LDL by a mechanism that involves superoxide and requires iron and copper ions. Our work suggests a mechanism by which lipids that have been deposited within implanted vascular grafts may become oxidized. Oxidized lipids may contribute to the cellular dysfunction that results in anastomotic intimal hyperplasia and graft failure. (+info)
Isolation of endothelial cells and their progenitor cells from human peripheral blood.
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PURPOSE: We have developed techniques to isolate endothelial cell (EC) progenitors from human peripheral and umbilical cord blood. METHODS: Human adult peripheral and umbilical cord blood monocytes were isolated by centrifugation, and progenitor cells were separated with the use of magnetic polystyrene beads that were coated with a monoclonal antibody specific for the CD34 cell-membrane antigen. Cells were propagated in selective media, and developing cultures were immunostained for CD31, CD34, factor VIII, and vascular endothelial growth factor cell receptors. ECs that developed were transfected with a gene for prourokinase and used to line ePTFE grafts, which were evaluated in vitro in a pulsatile flow system. RESULTS: Umbilical cord monocyte cultures demonstrated colonies that resembled ECs at approximately 2 weeks, with growth being best supported by EC growth media plus 20% calf serum with iron. Immunostaining of colonies was positive for CD31 and factor VIII. After 18 days in culture, CD34(+) cells from adult peripheral blood were noted, which had the typical cobblestone appearance of ECs and immunostained positively for CD31 and factor VIII-related antigens. Cultures of umbilical cord-derived cells and adult peripheral blood-derived cells developed complex line formations within 1 week in culture that stained positively for vascular endothelial growth factor receptor-2. Urokinase-transfected ECs were shown to overexpress urokinase. Prosthetic grafts lined with transfected cells showed 87.33% +/- 4.97% cell adherence after 2 hours in a pulsatile flow system at clinically relevant shear stress. CONCLUSION: We conclude that endothelial progenitor cells can be isolated from human adult peripheral and umbilical cord blood and developed into EC cultures as a source of cells for vascular graft seeding and gene therapy. (+info)
Determinants of type and timing of initial permanent hemodialysis vascular access.
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BACKGROUND: We undertook a population-based study of hemodialysis (HD) patients to determine which factors are important in predicting the type of permanent access initially placed and if a functional permanent access is in place at the start of HD. METHODS: Selected characteristics were abstracted from the United States Renal Data System (USRDS) Dialysis Morbidity and Mortality Study (DMMS) Wave 2. Logistic regression was used to estimate the independent contribution of specific characteristics in predicting whether the initial permanent access placed was an arteriovenous (AV) fistula compared with a polytetrafluoroethylene (PTFE) graft, and in predicting whether permanent access (fistula or graft) was in place at the initiation of dialysis. RESULTS: Sixty-seven percent of the patients had an AV graft placed as their first permanent access. Characteristics important in predicting if a fistula was initially placed included age (per decade; aOR = 0.84, P < 0.001), female gender (aOR = 0.52, P < 0.001), body mass index (per standard deviation; aOR = 0.70, P = 0.09), avoiding blood draws (aOR = 1.96, P < 0.001), ability to ambulate (aOR = 2.24, P = 0.008), underlying renal disease (glomerular compared with diabetes, aOR = 2.19, P = 0.009), college education (aOR = 1.72, P = 0.002), and sharing in decision making (aOR = 1.50, P = 0.02). Thirty-four percent of patients (34.4%) had functional permanent access at the start of HD. Characteristics important in predicting which patients had functional permanent access included serum albumin (per 1 mg/dL increase, aOR =1.55, P = 0.003), erythropoietin prior to starting HD (aOR = 1.79, P = 0.002), fewer predialysis nephrologist visits (aOR = 0.21, P < 0.001), and when the patient was told they had renal disease (aOR = 0.33, P = 0.002). CONCLUSIONS: PTFE grafts were the most common initial permanent access. The majority of patients did not have permanent access at the start of dialysis. Factors that are thought to compromise identification of adequate veins were important predictors of PTFE graft placement. Permanent access at the start of HD was largely a function of early patient education and early referral to a nephrologist. (+info)
Prosthetic patch remnants to treat infected arterial grafts.
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PURPOSE: Our previous experience with the traditional management of infected prosthetic arterial grafts, which included graft excision and vein patch repair of the involved artery, was complicated by a high incidence of vein patch rupture. This study assessed the treatment of infected prosthetic grafts with subtotal graft excision and oversewing of small graft remnants. METHODS: During the last 20 years, we treated 53 wounds involving 45 infected prosthetic grafts in 42 patients by means of subtotal graft excision and oversewing of a residual 2- to 3-mm graft remnant (patch) at an intact arterial anastomosis. This technique was selectively used to maintain patency of small-diameter arteries (41 common femoral, five deep femoral, three axillary, two iliac, and two popliteal), which were critical for limb salvage or amputation healing. This strategy avoided difficult dissection of the underlying artery in scarred wounds and obviated the placement of a new patch in an infected field. Graft remnants were polytetrafluoroethylene in 51 cases and Dacron in two cases. Of the 45 grafts, 31 were occluded and 14 were patent. All infected tissue was widely debrided, wet-to-dry dressing changes were performed three times daily, and appropriate intravenous antibiotics were administered for at least 1 week. Secondary bypass grafting procedures were performed as needed to achieve limb salvage. The follow-up period in surviving patients averaged 32 months (range, 1 to 218 months). RESULTS: No complications were directly attributable to prosthetic patch remnants in 92% of cases (49 of 53 cases). Six of 42 patients (14%) died during hospitalization (three of cardiac complications and three of sepsis with multiple organ failure). Two infected pseudoaneurysms developed 8 and 34 months after surgery, and two wounds failed to heal. Sixteen secondary bypass grafting procedures were necessary to achieve limb salvage. Patch oversewing led to limb salvage without the need for secondary revascularization in 26 other cases and to the successful healing of 10 amputated limbs when secondary revascularization was not possible. CONCLUSION: Prosthetic patch remnants are a useful adjunct that simplify management of infected prosthetic grafts, are associated with a low incidence of wound complications, and help maintain patency of essential collaterals to achieve limb salvage or heal an amputation. (+info)
Local infusion of heparin reduces anastomotic neointimal hyperplasia in aortoiliac expanded polytetrafluoroethylene bypass grafts in baboons.
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PURPOSE: Recently, we designed and characterized a novel expanded polytetrafluoroethylene (ePTFE)-based local drug delivery approach that selectively concentrates infused pharmacologic agents specifically within those blood layers adjacent to the graft wall and at downstream anastomotic sites. In this study, we locally administrated standard heparin therapy and evaluated its effects on neointimal hyperplasia formation in a baboon model of aortoiliac bypass graft placement. METHODS: Six adult male baboons underwent bilateral aortoiliac bypass grafting with ringed ePTFE (4 mm internal diameter x 5 cm length). In each animal, the distal anastomosis of one graft was continuously infused with heparin (50 U/h) and the distal anastomosis of the contralateral graft was infused with saline solution at the same rate (2.5 microL/h), with osmotic pumps implanted for 4 weeks. Platelet counts and activated partial thromboplastin time measurements were performed weekly. The specimens were harvested at 4 weeks and were subjected to morphometric analysis. Cell proliferation was assessed with bromodeoxyuridine immunostaining. RESULTS: All the harvested grafts were patent except for one control graft. There were no significant differences in platelet counts or activated partial thromboplastin time measurements taken before and during heparin infusion. As expected, there were no significant differences in graft neointimal hyperplasia and cell proliferation at the proximal anastomoses between the heparin-infused and control grafts. In contrast, at the treated distal anastomoses, heparin infusion significantly reduced the graft neointimal area by 65% and the cell proliferation index by 47% as compared with the untreated control distal anastomoses. CONCLUSION: These results show that local infusion of heparin significantly reduces distal anastomotic neointimal hyperplasia and cell proliferation without measurable systemic anticoagulation or other side effects. Thus, this approach may represent an attractive strategy for prolonging ePTFE bypass graft patency. (+info)
Biocompatibility of phosphorylcholine coated stents in normal porcine coronary arteries.
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OBJECTIVE: To improve the biocompatibility of stents using a phosphorylcholine coated stent as a form of biomimicry. INTERVENTIONS: Implantation of phosphorylcholine coated (n = 20) and non-coated (n = 21) stents was performed in the coronary arteries of 25 pigs. The animals were killed after five days (n = 6), four weeks (n = 7), and 12 weeks (n = 8), and the vessels harvested for histology, scanning electron microscopy, and morphometry. MAIN OUTCOME MEASURES: Stent performance was assessed by studying early endothelialization, neointima formation, and vessel wall reaction to the synthetic coating. RESULTS: Stent thrombosis did not occur in either group. Morphometry showed no significant differences between the two study groups at any time point. At five days both the coated and non-coated stents were equally well endothelialised (91% v 92%, respectively). At four and 12 weeks there was no difference in intimal thickness between the coated and non-coated stents. Up to 12 weeks postimplant the phosphorylcholine coating was still discernible in the stent strut voids, and did not appear to elicit an adverse inflammatory response. CONCLUSION: In this animal model the phosphorylcholine coating showed excellent blood and tissue compatibility, unlike a number of other polymers tested in a similar setting. Given that the coating was present up to 12 weeks postimplant with no adverse tissue reaction, it may be a potential candidate polymer for local drug delivery. (+info)
Endovascular healing is inadequate for fixation of Dacron stent-grafts in human aortoiliac vessels.
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BACKGROUND: migration and kinking of stent-grafts can occur late after endovascular aneurysm repair. It is unknown if endovascular grafts incorporate enough to be permanently anchored. In this report, healing of aortic stent-grafts was assessed in humans. PATIENTS AND METHODS: we retrieved 23 Dacron stent-grafts from patients treated for an aortic aneurysm since 1993. Twelve stent-grafts were explanted at late conversion to open repair and 11 at autopsy. The deaths were unrelated to graft fixation. The median age of the patients was 74 years (IQR 55-84 years) and the grafts were explanted 9 months (1-31 months) after insertion. Microscopic slides were prepared by conventional techniques or by cutting and grinding arterial specimens embedded in plastic with the stent-grafts in situ. RESULTS: the stent-grafts detached readily from the native arteries at surgery or autopsy, except when the stents had hooks or barbs which engaged the vessel wall. A space filled with poorly organised blood components persisted between the graft and the aortic wall 2.5 years after implantation. No firm incorporation of the grafts was observed proximally in the aneurysm neck or distally in the iliac segment. A friable neo-intimal layer covered parts of the luminal aspect of the grafts. CONCLUSIONS: endovascular healing provides poor fixation of Dacron stent-grafts in humans. At present, fixation relies on the mechanical properties of the stent-grafts. (+info)