Polyglactin 910/polydioxanone bicomponent totally resorbable vascular prostheses

Previous studies from our laboratory have shown that bioresorbable vascular prostheses woven from lactide-glycolide copolymers and implanted into arteries of several animal models become replaced by cellular tissues; the rate of replacement parallels the kinetics of prosthetic resorption. This study evaluates the efficacy of bicomponent resorbable prostheses as a method of augmenting resistance to dilatation during the resorption period of the more rapidly resorbed component. Bicomponent prostheses (n = 37) were woven from compound yarns containing 74% polyglactin 910 (PG910) and 26% polydioxanone (PDS) and were interposed into adult white New Zealand rabbit infrarenal aortas. Resultant prosthesis-tissue complexes were harvested after 2 weeks to 12 months. Specimens were photographed and sectioned for light, scanning, and transmission electron microscopy. Randomly selected fresh explants at 1 and 3 months and control aortic segments from the same rabbits were simultaneously perfused with culture media (37 degrees C, 100/80 mm Hg, 60 ml/min) and perfusates assayed by means of tritiated radioimmunoassay techniques for the stable prostacyclin metabolite 6-keto-PGF1 alpha before and after the addition of sodium arachidonate (10 micrograms/ml) to the media. Results showed 100% patency, no aneurysms, and stenosis in 1 of 37 prostheses (3%). PG910 was totally resorbed by 2 months and PDS by 6 months. By 1 month inner capsule thickness was 303 +/- 30 microns. In contrast to previous reports this was significantly thicker than that within 100% PDS (230 +/- 40 microns) and significantly less thick than in 100% PG910 (530 +/- 62 microns). Inner capsules in all three groups stabilized at similar thicknesses (417 to 502 microns).(ABSTRACT TRUNCATED AT 250 WORDS)     

Prostacyclin production by blood-contacting surfaces of endothelialized vascular prostheses

This study examines prostacyclin production by blood-contacting surfaces within woven vascular prostheses of polydioxanone (PDS), polyglactin 910 (PG910), or Dacron interposed into rabbit infrarenal aortas. Grafts and normal aortic segments were explanted after 1, 3, and 6 months for pulsatile perfusion with Medium-199 for 60 minutes. Aliquots were removed serially for 6-keto-PGF1 alpha assay. After 30 minutes sodium arachidonate (10 micrograms/ml) was added. Specimens were studied by light microscopy, SEM and TEM. Patency in all three groups exceeded 90%. All three showed re-endothelialization at one month. Normal aorta produced low basal 6-keto-PGF1 alpha with a marked evanescent post arachidonate increase. Dacron did not differ from normal aorta. PG910 and PDS both produced significantly less 6-keto-PGF1 alpha post arachidonate at one month but both increased to normal by three months.     

Is the Preferential Use of ePTFE Grafts in Femorofemoral Bypass Justified?

The choice of prosthetic graft material for cross-femoral bypass has been evolving in the past two decades. Expanded polytetrafluoroethylene (ePTFE) has become our preferred graft material since 1995. However, few studies have looked into the optimal graft material in this procedure. Justification for the preferential use of ePTFE graft in lower limb revascularization remains unknown. The aim of the present study was to compare the long-term outcomes of Dacron and ePTFE grafts in femorofemoral bypass. The records of 61 consecutive patients who underwent femorofemoral bypass at the University of Hong Kong Medical Center from 1981 to 1998 were retrospectively reviewed. Dacron grafts were used in 27 patients and 34 patients had ePTFE grafts. The demographic features, patency, and limb salvage rates of the two groups of patients were compared. The 3-year primary patency rates of Dacron and ePTFE grafts were 85% (SE = 9.5%) and 66% (SE = 14.5%), respectively. The difference was not statistically significant. The limb salvage rates of Dacron and ePTFE grafts were 91% and 83% at 3 years, respectively (p = 0.27). The long-term outcomes of Dacron and ePTFE grafts in femorofemoral bypass were equivalent. The preferential use of ePTFE graft in femorofemoral bypass is not evidence based. Selection of an appropriate prosthetic graft for femorofemoral bypass should be based on the cost and its handling characteristics.     

Compound polyglactin 910/polypropylene small vessel prostheses

This study evaluated morphologic and functional characteristics of tissue reactions to compound prostheses of 69% absorbable polyglactin 910 (PG910) and 31% nonabsorbable polypropylene in the rabbit. Forty-two woven PG910/polypropylene prostheses (24 X 4 mm internal diameter) implanted into rabbit infrarenal aortas were harvested after 2 weeks to 12 months. Each explant was photographed and sectioned for light microscopy and transmission and scanning electron microscopy. Randomly selected explants underwent either compliance and bursting strength measurements or assays of production of prostacyclin and thromboxane metabolites by luminal surfaces of both regenerated conduits and normal control aortas in response to administered sodium arachidonate. Results showed 100% patency with no aneurysms and 2% stenoses (1 of 42 prostheses). Confluent endothelial-like cellular luminal surfaces covering oriented smooth muscle-like myofibroblasts comprised the inner capsules whose thicknesses stabilized at 1 to 2 months. Only residual polypropylene remained in the prostheses after 2 months. Compliance studies reflected a 0.65 mm (14%) change over a pressure range of 0 to 160 mm Hg. All regenerated prosthesis-tissue complexes had bursting strengths greater than the proximal perianastomotic native aortas, which burst between 600 and 2000 mm Hg. At 1 month the rate of production of 6-keto-PGF1 alpha per square millimeter of surface area of experimental segments was normal. Production of 6-keto-PGF1 alpha by experimental segments at 3 months had increased fourfold whereas thromboxane B2 (TxB2) production remained unchanged. The 6-keto-PGF1 alpha/TxB2 ratio increased from 1 to 4 months. This study demonstrates clinically efficacious morphologic, mechanical, and biochemical characteristics of PG910/polypropylene-elicited vascular prosthesis-tissue complexes.     

Dacron versus polytetrafluoroethylene for Y-aortic bifurcation grafts: a six-year prospective, randomized trial.

BACKGROUND. A prospective, randomized trial was conducted to compare Dacron with expanded polytetrafluoroethylene (ePTFE) in reconstructive aortoiliac surgery. No comparable trial with a prospective, randomized design with a comparable number of patients or an equal long-term follow-up period can be found in the literature. METHODS. Between 1984 and 1989, 165 patients were randomized for either Dacron or ePTFE on the basis of age, sex, indication for surgery, diabetes, nicotine consumption, runoff, and operative approach. The two groups were well matched for randomization criteria, as well as the incidence of aneurysms. RESULTS. No statistically significant difference was found between the two graft materials in terms of patency rates (corrected 3-year patency rates: Dacron = 95% vs ePTFE = 95%; Breslow, p = 0.83; Mantel-Cox, p = 0.74). Subgroup analysis comparing long-term patency rates of the two graft materials and relating them to poor runoff, good runoff, aneurysms, and arterial occlusive disease also failed to show any significant differences between ePTFE and Dacron. Early graft failure (n = 6; 3.6% of the patient population; p = 0.045) and severe abdominal graft infection (n = 3; 1.8% of the total population) were seen only in ePTFE grafts. However, these did not affect the corrected long-term patency rate of ePTFE grafts. There were five late graft failures with PTFE (3.0%) and four with Dacron (2.4%). CONCLUSIONS. Graft materials currently available for aortoiliac repair were comparable in terms of corrected long-term patency rates. The alleged advantages of PTFE were not confirmed by our data. PTFE grafts were associated with a higher rate of complications, and more redo operations were required to duplicate the results obtained with Dacron.     

Endothelial cell seeding kinetics under chronic flow in prosthetic grafts

Improved patency of endothelial cell seeded grafts relies on good initial adherence and cell retention when the circulation is restored. In this study human adult endothelial cells (HAECs) were used to evaluate the suitability of commercially available prostheses for seeding. Acutely seeded indum-111 oxine labeled HAECs were used to measure cell adherence to plain and fibronectin (FN)-coated expanded polytetrafluoroethylene (ePTFE), gelatin-impregnated Dacron (Gelseal), and collagen-impregnated Dacron (Hemashield) grafts. Cell loss from FN-coated prostheses, when exposed to a simulated human arterial blood flow of 200 ml/min in an artificial pulsatile circulation, was quantified from the loss of gamma activity from the graft over 24 hours, pressure in the circulation being reduced to 15 mm Hg to reduce fluid loss. Initial HAEC adherence (mean [SD]) to plain grafts was 3(1)%, 47(9)%, and 53(9)% for ePTFE, Gelseal, and Hemashield, respectively. This improved significantly with FN coating (78[6]%, 60[8]%, and 76[4]%). Cell retention after 24 hours of flow to FN-coated grafts was 16(10)%, 25(5)%, and 65(4)% and was confirmed qualitatively by scanning electron microscopy and environmental scanning electron microscopy. FN significantly improved initial cell adherence with Dacron grafts showing the better adherence. Cell retention after 24 hours of flow was better with FN-coated Dacron than with ePTFE but was best with Hemashield grafts.     

An experimental study of the strength in arterial prosthetic anastomoses: relationship between anastomotic tensile strength and its organization]

Five types of 6-mm diameter arterial prostheses, i.e.m woven Teflon, woven Dacron, velour woven Dacron, velour knitted Dacron and expanded polytetrafluoroethylene (E-PTFE), were studied in the dog to assess anastomotic tensile strength and its organization. Five types of composite grafts, about 3.0cm in length, were implanted in the abdominal aorta of fifty-two adult mongrel dogs using absorbable polyglycolic acid suture. At 16 weeks after the implantation, if the composite graft was patent, tensile strength of the bilateral anastomoses were measured and its organizations were examined microscopically. The mean forces required to disrupt the anastomoses of velour woven Dacron, velour knitted Dacron and E-PTFE were greater than those of woven Teflon and woven Dacron. At the disrupted sites of woven Teflon and woven Dacron, which were non-velour grafts, fibrous outer sheath were remarkably separated from the grafts. This results indicate that organization and fixation of fibrous outer sheath are the most important factors in the strength of arterial prosthetic anastomoses and velour grafts have superiority over non-velour grafts. The organization of E-PTFE was poor, but its tensile strength was equal to velour grafts. It is considered E-PTFE has an advantage due to non-crimped structure and requires further evaluation over longer period.     

The effect of pancreatopeptidase E (elastase) on anastomotic intimal thickness in two types of vascular prosthesis

To determine the effects of pancreatopeptidase E (elastase) on anastomotic intimal thickness in vascular prostheses, expanded polytetrafluoroethylene (ePTFE) and Dacron grafts were implanted in the infrarenal aortas of 28 adult mongrel dogs, divided into four groups of seven dogs each according to the type of graft used and whether or not elastase was given. Thus, group E received ePTFE grafts without elastase; group D received Dacron grafts without elastase; group E + Ela received ePTFE grafts with concomitant oral elastase, 8 mg/kg per day; and group D + Ela received Dacron grafts with elastase given at the same dosage as in group E + Ela. Each graft was harvested 4 months following surgery for histologic examination. It was clearly observed that elastase suppressed intimal growth at the proximal and distal anastomoses in the ePTFE grafts (P<0.05), but not in the Dacron grafts. Furthermore, when we measured the smooth muscle cell percent extinction (%E) on microspectrophotometry in the intima within 2 mm of the proximal and distal anastomoses, it was found that elastase reduced intimal smooth muscle proliferation at the anastomosis of the ePTFE grafts, but not the Dacron grafts (P<0.05). These data suggest that elastase suppresses intimal growth by inhibiting smooth muscle cell migration and proliferation in the vascular prostheses of low but not of high porosity.     

Infrainguinal ePTFE vascular graft with bioactive surface heparin bonding. First clinical results

AIM: The ultimate aim of improved expanded polytetrafluoroethylene (ePTFE) vascular graft design is to achieve patency rates in femoropopliteal bypass grafting comparable with autologous saphenous vein grafts. Enhanced thromboresistance of the ePTFE material by bioactive surface heparin bonding is one conceivable path toward this goal. This retrospective study was performed to collect the first clinical data for a new ePTFE graft with bioactive surface heparin immobilization. METHODS: Between March 2003 and February 2004, 43 femoropopliteal or femorocrural ePTFE vascular prostheses with bioactive end-point immobilized heparin (Gore-Tex Propaten Vascular Graft), using the Car-meda BioActive Surface technology, were implanted in 40 patients. Twelve prostheses were implanted in above-knee and 31 in below-knee position. The indication for bypass grafting was limb-threatening ischemia in 88% of the patients. The mean follow-up was 16.6 months. RESULTS: The primary 1-year patency was 91% for above-knee bypass grafts and 92% for below-knee bypass grafts. The 2-year primary patency rate for above-knee bypass grafts was 68% and 81% for below-knee bypass grafts. Limb salvage was achieved in 98%. The perioperative mortality was 0%, but during follow-up 22% of the patients died with patent bypass grafts. CONCLUSIONS: While conventional ePTFE grafts, particularly in the below-knee position, have shown poor results even in the short-term, the bioactive heparinized ePTFE graft evaluated in this study provides patency rates comparable with autologous vein grafts. Because the influence of luminal heparin bonding is not only limited to thromboresistance but has impact on, amongst other elements, protein adsorption (thereby improving hemocompatibility), a continuous effect for long-term patency could also be expected.     

The influence of endothelial seeding and platelet inhibition on the patency of ePTFE grafts used to replace small arteries--an experimental study

Previous studies on the influence of endothelial seeding on graft patency have shown that significant improvement has only been achieved with Dacron and an experimental, porous PTFE graft. Methods of assessing patency or showing statistical significance could be questioned in some of these studies. To determine if the combination of endothelial cell seeding and antiplatelet agents would improve patency in small-diameter, commercially available expanded polytetrafluorethylene (ePTFE) grafts, we placed ePTFE grafts into the left carotid position in two groups of mongrel dogs. All grafts were 4 mm internal diameter and 60 mm long, and were interposed in an end-to-end fashion. Both groups received aspirin (80 mg daily) and dipyridamole (25 mg daily) for 14 days, beginning immediately prior to surgery. In Group I (n = 12), the grafts were seeded with enzymatically harvested autogenous endothelium just prior to implantation; in Group II (n = 10) the grafts were not seeded. All grafts were removed at 30 days. Seven of 12 (58%) seeded grafts, but only one control graft (10%) remained patent (P = 0.03). Six of the seven seeded grafts exhibited surface endothelium, but the single patent control graft did not. The inner capsule of the seeded grafts consisted of a monolayer of endothelium and a thin acellular subendothelial matrix with an average thickness of 8 mu. We conclude that a 14-day course of anti-platelet agents combined with endothelial seeding of ePTFE resulted in significantly improved patency compared to controls, with most patent, seeded grafts developing an endothelial lining in 30 days.     

Dacron inhibition of arterial regenerative activities

These biocompatibility studies evaluate the effects of Dacron, absorbable polymeric, and compound prostheses containing both elements in various constructions on the migration, proliferation, and functional characteristics of regenerating endothelial and smooth muscle—like cells in the rabbit aorta model. Prosthesis/tissue complexes explanted after 2 weeks to 9 months were studied grossly, photographed, sectioned for light microscopy and scanning and transmission electron microscopy, and assayed for 6-keto-PGF_1α contents in inner capsular tissues. Polyglycolic acid, polyglactin 910, or polydioxanone prostheses elicited a transinterstitial migration and proliferation of primitive mesenchymal cells that differentiated into smooth muscle—like myofibroblasts and a surface repopulation of confluent endothelial-like cells paralleling the time course of macrophage-mediated prosthetic dissolution. Even small Dacron components (20%) woven into or surrounding the absorbable polymer significantly inhibited these processes, yielding significantly thinner, less cellular inner capsules with lower 6-keto-PGF_1α contents. These studies show the augmentation of clinically efficacious arterial regenerative activities by polymers phagocytosed by macrophages and the inhibition of these activities by Dacron. (J VASC SURG 1986;3:747-56.)     

Histopathological evaluation of woven and knitted Dacron grafts for right ventricular conduits: a comparative experimental study

Composite extracardiac conduits consisting of a low-porosity woven graft and a high-porosity knitted double-velour Dacron graft presealed with fibrin glue were implanted between the right ventricle and the pulmonary artery in 6 dogs under partial heparinization. Two grafts were explanted after 6 weeks, 2 after 12 weeks, and 2 after 6 months. The healing properties of both types of prosthesis were studied macroscopically, under light microscopy, and with scatter electron microscopy. Spontaneous peeling of both the inner and outer capsules of the graft occurred in 3 of 6 woven prostheses during transection. In the remaining 3, peeling could be easily induced by blunt dissection; this was impossible in the knitted grafts. Microscopically, in a comparison of the different weaves after identical time intervals, the inner capsule was noticeably thicker in woven than in knitted grafts. Transtitial ingrowth of fibroblastic tissue could be observed in knitted grafts after 6 weeks; only poor transmural tissue bridging was detectable in woven prostheses after 6 months. Neovascularization of the inner capsule was detectable earlier and was more advanced toward the luminal surface of highly porous grafts. In conclusion, knitted grafts in the position of extracardiac right ventricular conduits showed firmer attachment of both inner and outer capsules to the prosthetic material. Also, the inner capsule remained thinner and revealed a higher degree of neovascularization than in the woven Dacron grafts.     

Bacterial adherence to vascular prostheses: A determinant of graft infectivity

An in vitro model was developed to quantitatively measure bacterial adherence to the surface of prosthetic vascular graft material. Four strains of bacteria (Staphylococcus aureus, nonmucin-producing S. epidermidis [SP-2], mucin-producing S. epidermidis [RP-12], and Escherichia coli) were used to inoculate expanded polytetrafluoroethylene (ePTFE), woven Dacron, and velour knitted Dacron graft material. After graft specimens were incubated in a 10⁷ suspension of bacteria, they were washed to remove nonadherent organisms and ultrasonically oscillated to dislodge adherent organisms. Quantitative culture of the sonication effluent was used to calculate bacterial adherence, expressed as the number of colony-forming units found in each square centimeter of graft material per 10⁷ inoculum. All bacterial strains had a greater affinity to velour knitted Dacron graft than to ePTFE (p < 0.025). E. coli and S. aureus adhered to velour knitted Dacron in greater numbers than to woven Dacron (p < 0.04). The production of extracellular polysaccharide (mucin) by the RP-12 strain significantly increased adherence to both ePTFE and Dacron grafts compared with the other three bacterial strains tested (p < 0.04). Although E. coli was less adherent to ePTFE than nonmucin-producing staphylococcal strains (S. aureus and SP-2), no difference in adherence to knitted or woven Dacron graft material was demonstrated. The differential adherence of bacteria to prosthetic vascular grafts pays an important role in the pathogenesis of graft sepsis and determines relative graft infectivity. The in vitro model developed is well suited for further study of the mechanisms by which bacteria adhere to and colonize vascular grafts. (J VASC SURG 1986;3:732-40.)     

In vitro adherence and kinetics studies of adult human endothelial cell seeded polytetrafluoroethylene and gelatin impregnated Dacron grafts.

Lining the luminal surface of small diameter vascular prostheses with living endothelial cells reduces thrombogenicity, decreases infection and improves patency. In vitro adherence and kinetics studies of adult human endothelial cell seeded Polytetrafluoroethylene (ePTFE) and Gelatin impregnated Dacron (Gelseal) were performed. Endothelial cell adherence on ePTFE and Gelseal coated with collagen IV, fibronectin and preclot matrices was compared. Untreated ePTFE and Gelseal were also used. Ten graft segments in each group coated with these matrices were incubated with radio-labelled adult human endothelial cells for 30, 60 and 90 min. Labelled endothelial cells seeded in supra-confluent densities on fibronectin coated ePTFE and Gelseal grafts were used for kinetic studies. Resultant endothelial cell monolayers were then exposed to varying shear stress at flow rates of 200 and 300 ml/min in an artificial flow circuit. Endothelial cell attachment to untreated grafts was poor and a suitable matrix significantly improved adherence with fibronectin and preclot but less so with collagen. A 30 min incubation was sufficient for optimum cell attachment. Cell adherence to ePTFE was significantly better than Gelseal. Scanning electron micrographs (SEM) of ePTFE showed preferential attachment to the nodes whilst on Gelseal, cells conformed to Dacron fibres at different levels and directions. Rapidly formed endothelial cell monolayers on ePTFE and Gelseal grafts resisted shear stress of flow with significant cell retention at 2 h. There was patchy coverage of both grafts with evidence of bridging of gaps between individual fibres in Gelseal.     

High-Porosity expanded polytetrafluoroethylene grafts with omentum wrap for portal vein replacement: Intermediate results

The purpose of this study was to examine the intermediate (6-month) patency and healing characteristics of high-porosity expanded polytetrafluoroethylene (ePTFE) grafts with and without omentum wrap in a dog portal vein replacement model, compared with short-term (1-month) results. The grafts, either wrapped by omentum or not, were placed as portal vein replacements in 22 mongrel dogs. After 1 and 6 months, the grafts were retrieved and examined for patency and subjected to pathology study. Although the short-term patency rate in all grafts was 100%, regardless of the presence or absence of omentum wrap, the intermediate patency of high-porosity ePTFE without omentum wrap was very poor (20%). On the other hand, high-porosity ePTFE with omentum wrap had an intermediate patency rate of 100%. At 6 months, the high-porosity ePTFE grafts with omentum wrap were completely healed. The pseudointima was entirely replaced by thin fibrous tissue, with complete endothelial-like cell coverage throughout the graft. This result suggests that high-porosity ePTFE with omentum wrap could be a suitable prosthetic alternative to autogenous vein graft in portal vein reconstruction.     

Development of intimal hyperplasia in six different vascular prostheses.

OBJECTIVES: to compare six vascular prostheses for the development of intimal hyperplasia (IH) in a sheep model. MATERIAL AND METHODS: prostheses tested were gelatin sealed Dacron (GSD), fluoropassivated Dacron (FPD), FluroIpassiv TM (FD), expanded polytetrafluoroethylene (ePTFE), carbon-lined expanded polytetrafluoroethylene (CL-ePTFE) and vascular access graft (VAG). Sixty-two adult female Merino sheep (35-45 kg) were used. Elliptical graft patches were implanted into the left common carotid artery using one of the six graft types: GSD (n=10), FPD (n=10), FD (n=12) VAG (n=10), ePTFE (n=10), or CL-ePTFE (n=10). Four weeks later grafts were removed for histopathological assessment and measurement of the degree of IH obtained on a computerised image analysis system. RESULTS: IH indices were significantly less for FPD (0.191+/-0.095, p<0.05), FD (0.199+/-0. 081, p<0.05), ePTFE (0.213+/-0.078, p<0.05) and CL-ePTFE (0.161+/-0. 066,p<0.01), compared to the GSD group (0.287+/-0.077). The VAG group (0.257+/-0.091) showed no difference compared to GSD. There was no significant difference between the FPD, FD, ePTFE and CL-ePTFE grafts. CONCLUSION: this study indicates that less IH occurred in the two-ePTFE grafts and two fluoropolymer coated Dacron grafts than in gelatin sealed Dacron or polyurethane grafts.     

Comparison of different vascular prostheses and matrices in relation to endothelial seeding.

Thin-walled expanded polytetrafluoroethylene (ePTFE), woven Dacron and gelatin-impregnated Dacron (Gelseal) vascular grafts were compared, the grafts being coated with three different matrices: collagen IV, fibronectin and preclot matrix. In addition, untreated ePTFE and Gelseal were examined. The graft segments, coated with these matrices, were incubated with radiolabelled adult human endothelial cells for 30, 60 and 90 min. Endothelial cell adherence was calculated from the ratio of radioactive counts in the grafts to counts in grafts plus supernatants. Endothelial cell attachment to untreated grafts was poor, but a suitable matrix significantly improved adherence. All three matrices tested gave good results, although preclot was best; 30-60 min incubation was sufficient for optimum cell attachment. Cell adherence to both Dacron and ePTFE was significantly better than to Gelseal. The type of prosthetic polymer and the substrate protein coating used to promote endothelial cell adherence are two important factors which may determine the ultimate success of endothelial seeding in the operating room.     

Dacron or ePTFE for Femoro-popliteal Above-Knee Bypass Grafting: Short- and Long-term Results of a Multicentre Randomised Trial

ObjectivesTo compare expanded polytetrafluoroethylene (ePTFE) prosthesis and collagen-impregnated knitted polyester (Dacron) for above-knee (AK) femoro-popliteal bypass grafts.DesignA prospective multicentre randomised clinical trial.Patients and MethodsBetween 1992 and 1996, 228 AK femoro-popliteal bypass grafts were randomly allocated to either an ePTFE (n = 114) or a Dacron (n = 114) vascular graft (6 mm in diameter). Patients were eligible for inclusion if presenting with disabling claudication, rest pain or tissue loss.Follow-up was performed and included clinical examination and duplex ultrasonography at all scheduled intervals. All patients were treated with warfarin.The main end-point of this study was primary patency of the bypass graft at 2, 5 and 10 years after implantation. Secondary end-points were mortality, primary assisted patency and secondary patency. Cumulative patency rates were calculated with life-table analysis and with log-rank test.ResultsAfter 5 years, the primary, primary assisted and secondary patency rates were 36% (confidence interval (CI): 26–46%), 46% (CI: 36–56%) and 51% (CI: 41–61%) for ePTFE and 52% (CI: 42–62%) (p = 0.04), 66% (CI: 56–76%) (p = 0.01) and 70% (CI: 60–80%) (p = 0.01) for Dacron, respectively. After ten years these rates were respectively 28% (CI:18-38%), 31% (CI:19-43%) and 35% (CI: 23-47%) for ePTFE and 28% (CI: 18-38%), 49% (CI: 37-61%) and 49% (CI: 37-61%) for Dacron.ConclusionDuring prolonged follow-up (10 years), Dacron femoro-popliteal bypass grafts have superior patency compared to those of ePTFE grafts. Dacron is the graft material of choice if the saphenous vein is not available.     

Thromboembolic potential of synthetic vascular grafts in baboons

We have compared in baboons the capacity of two types of synthetic vascular grafts to accumulate thrombus, activate circulating platelets, and generate occlusive platelet microemboli. Grafts were incorporated into femoral arterial-arterial shunts placed unilaterally in 10 baboons; the unoperated contralateral limbs served as controls. The accumulation of indium 111 (111In)-labeled platelets onto the grafts (expanded polytetrafluoroethylene [ePTFE] or knitted Dacron, 4 mm inner diameter) and the appearance of 111In radioactivity in distal microcirculatory beds (calf and foot) were quantified by dynamic scintillation camera imaging. After 1 hour total platelet deposition per graft was higher with Dacron (49.0 +/- 8.0 x 10(9) platelets) than with ePTFE (3.7 +/- 0.6 x 10(9) platelets, p less than 0.01). Platelet counts decreased and beta-thromboglobulin levels increased with Dacron graft placement but were unaffected by ePTFE graft placement (p less than 0.05 and p less than 0.01, respectively). Emboli shed from Dacron grafts were detected as multifocal, irregular, and changing deposits in the calves and feet. Indium 111 platelet activity in the feet distal to the Dacron grafts increased 81.1% +/- 21.4% from baseline values over 1 hour, whereas the activities in the feet distal to the ePTFE grafts were unchanged (p less than 0.05). The increase 111In-platelet radioactivity above the control limb values (excess radioactivity) was higher for the Dacron graft group than for the ePTFE group in both the feet (139.6% +/- 46.9% vs 6.2%, p less than 0.05) and the calves (86.7% +/- 21.7% vs 7.3% +/- 3.6%, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

The response of rapidly formed adult human endothelial-cell monolayers to shear stress of flow: a comparison of fibronectin-coated Teflon and gelatin-impregnated Dacron grafts.

Endothelial cells labeled with indium 111-oxine were seeded in supraconfluent densities onto fibronectin-coated expanded polytetrafluoroethylene (ePTFE) and gelatin-impregnated Dacron graft segments. These grafts with rapidly formed endothelial-cell monolayers were then exposed to varying shear stresses at flow rates of 200 and 300 ml/min, using tissue culture medium in an artificial flow circuit. As the loss of radioactivity represented endothelial-cell loss, cell retention was calculated by the ratio of counts recorded at different time points during 2 hours of flow to initial counts. Although initial cell adherence to gelatin-impregnated Dacron graft segments was poor compared to ePTFE, once cells were attached they resisted shear stress of flow better at 200 ml/min and equally well at 300 ml/min. The cell retention on fibronectin-coated ePTFE was 55.4 +/- 12.9% at 200 ml/min and 56.5 +/- 15.2% at 300 ml/min; cell retention for gelatin-impregnated Dacron graft segments was 69.0 +/- 6.0% and 66.5 +/- 5.5%, respectively. Qualitatively scanning electron microscopy of both ePTFE and gelatin-impregnated Dacron graft segments showed patchy coverage of grafts with cells. There was preferential attachment of endothelial cells to the nodes on ePTFE, although on gelatin-impregnated Dacron graft segments, cells conformed to the Dacron fibers at different levels and directions with evidence of bridging in the gaps between individual fibers. This study shows conclusively that rapidly formed endothelial-cell monolayers on ePTFE and gelatin-impregnated Dacron graft segments resisted a shear stress of flow equal to that seen in a femoropopliteal vein graft with significant cell retention at 2 hours.