ePTFE Grafts Research Articles

Nonanastomotic Pseudoaneurysm With Complete Disruption of an Expanded Polytetrafluoroethylene Axillofemoral Bypass Graft

Rupture of an expanded polytetrafluoroethylene (ePTFE) vascular graft is rare. We report a nonanastomotic pseudoaneurysm associated with complete disruption of an ePTFE graft that occurred 6 years after an axillofemoral bypass. The 81-year-old patient had undergone neither trauma nor infection. The aneurysmal segment was resected, and a new ePTFE graft was interposed. The patient recovered uneventfully and was well 4 years later. Histologic analysis revealed a torn graft edge, consistent with a rupture due to excessive force, but scanning electron microscopy showed that the internal structure of the prosthesis was intact. The cause of the midgraft rupture remains unknown.

High-dose Preoperative Fractionated Radiotherapy Does not Affect the Patency and Healing of ePTFE Vascular Prosthesis after Replacement of Canine Abdominal Aorta and Inferior Vena Cava

BackgroundFractionated radiotherapy allows for the safe administration of larger doses without the development of immediate or late toxicity. The influence of preoperative fractionated radiotherapy on neointima formation for expanded polytetrafluoroethylene (ePTFE) graft has not been determined. MethodsTwenty mongrel dogs were randomly divided into radiotherapy group (a total dose of 35 Gy) or control group (no radiation). The infrarenal abdominal aorta and inferior vena cava were replaced by ePTFE grafts at 3 months after irradiation in the radiotherapy group. Grafts were explanted at 4 weeks after surgery. Histopathological techniques were undertaken to evaluate graft neointima formation. The control group was managed the same as the radiotherapy group except for not receiving irradiation. ResultsFour grafts implanted into inferior vena cava in the irradiated group and three in the control group were found to be completely occluded. None of the grafts implanted into abdominal aorta were obstructed. In the case of the inferior vena cava graft, the thickness of the graft neointima did not differ significantly between the irradiated and control groups. However, for the abdominal aorta graft, the neointima thickness in the irradiated groups was significantly thinner than that in the control group. ConclusionPreoperative fractionated radiotherapy affects vascular healing via suppressing the development of neointima formation in the abdominal aorta graft.

Study on vascular transplantation with small-caliber decellularized matrix vascular grafts

Objective To explore the feasibility of smal-caliber decellularized matrix (DCM) vascular grafts in vascular transplantation.Methods 40 male dogs were randomly divided into three groups,and underwent right common carotid artery interposition with DCM (group Ⅰ,n =16),expanded polytetrafluoroethylene (ePTFE) (group Ⅱ,n =14 ) vascular grafts or autologous external jugular vein (group Ⅲ,n =10).Postoperative Doppler Ultrasound were done to detect the patency.Grafts were explanted at 4 and 8 weeks after implantation.The retrieved specimens were evaluated by morphology,hematoxylin and eosin (HE) stain,immunohistochemistry stain,and scanning electron microscopy.Results The patency rates at 1 week among the three groups (75.0％,64.3％,100.0％ respectively) were of no difference of significance (P ＞0.05).4 and 8 week patency rates of group Ⅲ ( 100.0％,88.9％ )are both higher than group Ⅰ (56.3％,26.7％ ) and group Ⅱ (57.1％,23.1％,P ＜0.05 ),however,no differences of significance were gained between the latter two (P ＞ 0.05).The thrombus formation area of DCM grafts was smaller than that of ePTFE grafts.DCM grafts achieved better endothelialization in the stomas neointima than ePTFE grafts within 8 weeks.Conclusion Compared with ePTFE grafts,DCM grafts show superiority in reducing thrombogeneity,and improving endothelialization. Key words: Small-caliber; Vascular grafts; Decellularized matrix; Expanded polytetrafluoroethylene; External jugular vein

A multicenter comparison between autologous saphenous vein and heparin-bonded expanded polytetrafluoroethylene (ePTFE) graft in the treatment of critical limb ischemia in diabetics

A multicenter comparison between autologous saphenous vein and heparin-bonded expanded polytetrafluoroethylene (ePTFE) graft in the treatment of critical limb ischemia in diabetics

Comparison of straight and Venaflo-type cuffed arteriovenous ePTFE grafts in an animal study

Comparison of straight and Venaflo-type cuffed arteriovenous ePTFE grafts in an animal study

In vitro biocompatibility evaluation of ePTFE graft with controlled release of heparin from mesoporous material

Heparin-loaded mesoporous-expanded poly(tetrafluoroethylene) (ePTFE) vascular prosthesis (HMVP-n) are prepared and the biocompatibility is studied by contact angle, heparin release, platelet resistance, chromogenic assay, endothelial progenitor cells (EPCs) proliferation and produced-NO function, in order to illustrate the relationship between the performance of artificial vessels and their mesostructure. Through in situ synthesis of mesoporous silica on ePTFE grafts, different mesoporous silica materials can be uniformly coated on the surface as well as the internal fibers of the artificial vessels to give various mesoporous vascular prosthesis, named as MVP-n. Structure analysis through scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX) analysis and nitrogen sorption experiment indicates that different MVP-n series own the similar nF/nSi ratio of both surface and cross-section, large Brunauer-Emmett-Tellerand (BET) surface area and average pore size located in meso range but different textural properties. Owning to the existence of mesostucture, controlled release and high bioactivity of heparin can be achieved, and the biocompatibility greatly enhance: surface hydrophilicity increases; no adherent platelet was observed on the surface of HMVP-n when they contacted with platelet-enriched plasma; endothelial progenitor cells proliferous potential and produced-NO function exhibit better endothelial coverage of grafts. And the performance is closely related to the mesostructure, suggesting a new way to improve the biocompatibility of biomaterials through controlling their mesostructure.

Modified Use of the HeRO Device for Immediate Salvage of a Threatened Dialysis Graft

The Hemodialysis Reliable Outflow (HeRO) device provides an additional access option for hemodialysis in patients with central venous occlusions. The HeRO device is a subcutaneously tunneled dialysis access device comprised of a standard 6mm ePTFE graft coupled to a nitinol reinforced 5mm venous outflow component. Standard placement involves tunneling the venous outflow component to the right atrium via the internal jugular vein and anastamosing the graft component to the brachial artery. This case illustrates a modified technique, employing the device for immediate salvage of a malfunctioning upper extremity dialysis graft with ipsilateral central venous occlusion. We report successful salvage of a failing arteriovenous graft by utilizing a HeRO device anastomosed to the graft and tunneled to the contralateral internal jugular vein. A 69-year-old male on hemodialysis for five years presented complaining of right upper extremity edema and pain worsened during hemodialysis. His dialysis access consisted of a right upper extremity 4-7 mm tapered brachio-axillary arteriovenous ePTFE graft (AVG) created two years prior to this admission (Figure, AVG). He had previously undergone a left basilic vein transposition and left brachio-axillary graft with subsequent removal of the graft due to infection. Despite adequate flow rates through the existing dialysis graft, his symptoms prompted a diagnostic fistulogram that demonstrated a patent right axillary vein (Figure, AXV), and occlusion of the right subclavian vein. Endovascular attempts at recanalization of the subclavian vein were unsuccessful. Central venography from a femoral vein approach demonstrated a right internal jugular vein occlusion, but patent superior vena cava, left innominate vein, and left internal jugular vein. Using ultrasound, the left internal jugular vein was accessed and a wire was passed into the right atrium under fluoroscopy. After establishing central venous access to the superior vena cava, the venous outflow component of the HeRO device was introduced following serial dilation of the tract. The device was then tunneled subcutaneously along the anterior chest wall to a counter incision at the right (contralateral) deltopectoral groove where the 6mm HeRO ePTFE graft was coupled to the venous outflow component (Figure, arrow). A 2.5 cm incision was made at the distal (venous) end of the AVG, and the HeRO ePTFE graft was further tunneled from the coupler incision site to the AVG incision site. The new ePTFE-HeRO system was finally anastamosed in end-to-side fashion to the AVG. A completion fistulogram was performed through the fistula, which revealed brisk flow via the HeRO, into the central venous system and right atrium (Figure, composite fistulogram). Dialysis was instituted the following day with flow rates of approximately 400 ml/min. The patient has successfully continued hemodialysis via his HeRO device for eight months without complications and with relief of his preoperative symptoms. This unique approach with the HeRO device allows graft salvage with immediate use while obviating the need for complex surgical reconstruction for dialysis access.

Modelling ultrasound-induced mild hyperthermia of hyperplasia in vascular grafts.

BackgroundExpanded polytetrafluoroethylene (ePTFE) vascular grafts frequently develop occlusive neointimal hyperplasia as a result of myofibroblast over-growth, leading to graft failure. ePTFE exhibits higher ultrasound attenuation than native soft tissues. We modelled the selective absorption of ultrasound by ePTFE, and explored the feasibility of preventing hyperplasia in ePTFE grafts by ultrasound heating. Specifically, we simulated the temperature profiles of implanted grafts and nearby soft tissues and blood under ultrasound exposure. The goal was to determine whether ultrasound exposure of an ePTFE graft can generate temperatures sufficient to prevent cell growth on the graft without damaging nearby soft tissues and blood.MethodsUltrasound beams from two transducers (1.5 and 3.2 MHz) were simulated in two graft/tissue models, with and without an intra-graft cellular layer mimicking hyperplasia, using the finite-difference time-domain (FDTD) method. The resulting power deposition patterns were used as a heat source for the Pennes bioheat equation in a COMSOL® Multiphysics heat transfer model. 50°C is known to cause cell death and therefore the transducer powers were adjusted to produce a 13°C temperature rise from 37°C in the ePTFE.ResultsSimulations showed that both the frequency of the transducers and the presence of hyperplasia significantly affect the power deposition patterns and subsequent temperature profiles on the grafts and nearby tissues. While neither transducer significantly raised the temperature of the blood, the 1.5-MHz transducer was less focused and heated larger volumes of the graft and nearby soft tissues than the 3.2-MHz transducer. The presence of hyperplasia had little effect on the blood's temperature, but further increased the temperature of the graft and nearby soft tissues in response to either transducer. Skin cooling and blood flow play a significant role in preventing overheating of the native tissues.ConclusionsModelling shows that ultrasound can selectively heat ePTFE grafts and produce temperatures that cause cell death on the graft. The temperature increase in blood is negligible and that in the adjacent soft tissues may be minimized by skin cooling and using appropriate transducers. Therefore, ultrasound heating may have the potential to reduce neointimal hyperplasia and failure of ePTFE vascular grafts.

大腿-膝窩動脈バイパスにおける補強リング付きEPTFEグラフトの開存性―自家静脈グラフトとの比較

大腿-膝窩動脈バイパスにおける補強リング付きEPTFEグラフトの開存性―自家静脈グラフトとの比較

Prevention of neointimal hyperplasia associated with modified stretch expanded polytetrafluoroethylene hemodialysis grafts (Gore) in an experimental preclinical study in swine

Stenosis is the main cause of hemodialysis vascular graft failure and it is primarily caused by neointimal hyperplasia (NH) development at the vein-graft anastomosis. Even though NH development factors are well known, their activation pathway still remains disputed and the real role of the mismatch compliance between the vein and the graft wall has not yet been resolved. The purpose of this experimental study in swine was to verify the possibility of preventing the development of NH at the vein-graft anastomosis using a modified commercially available longitudinal stretch expanded polytetrafluoroethylene (ePTFE) Gore (W. L. Gore & Associates, Flagstaff, Ariz) graft (either standard or heparin-bonded) with an added handmade ePTFE radial stretch cuff at one end to reduce the compliance between the graft and the vein wall. Twelve ePTFE stretch grafts (6 modified and 6 unmodified) were surgically placed as arterovenous grafts (AVGs) between the carotid artery and the external jugular vein in 6 pigs. In each pig, one modified graft was placed on one side and one corresponding unmodified graft on the other side as a control. In 4 pigs, standard stretch ePTFE Gore grafts were used, and in 2 pigs, heparin-bonded stretch Gore grafts were used; 2 pigs were also treated with antiplatelet drugs. All the implanted grafts had a total length of 8 cm and a diameter of 6 mm. The modified graft was realized by cutting a short segment of the commercially available graft lengthwise which was then sewn crosswise (rotated 90°) with the same diameter as the original graft and was then added to it. A Doppler ultrasound scan was used for monitoring the graft patency immediately, weekly, and before death. At death (21-28 days after implantation), artery, vein, and graft specimens were collected "en bloc" for histopathology. The modified grafts in the antiplatelet-treated animals were able to completely prevent NH development on vein wall (100% in 2 subjects) which was also reduced in antiplatelet untreated animals (66.5%, 96.4%, and 100% in 3 subjects, respectively). The modified standard stretch grafts and similarly modified heparin-bonded stretch grafts obtained the same good results in NH prevention. Data provide evidence of the efficacy of modified stretch ePTFE grafts with an added radial stretch cuff for the prevention of NH in swine models and support the hypothesis of the pivotal role of mismatch compliance between the graft and the vein wall in NH development.

Injuries of Adjacent Organs by the Expanded Polytetrafluoroethylene Grafts in the Venoplasty of Middle Hepatic Veins in Living-Donor Liver Transplantation

The objective of the study was to analyze computed tomography (CT) appearance and clinical features of adjacent-organ injuries related to expanded polytetrafluoroethylene (ePTFE) grafts after living-donor liver transplantation (LDLT). We evaluated follow-up CT images of 204 patients who underwent venoplasty with ePTFE during LDLT and encountered 4 patients (1.96%) with adjacent-organ injuries related to ePTFE. Clinical imaging records were reviewed in terms of imaging findings and possible risk factors. In 3 patients, ePTFE graft perforated gastric antrum or duodenal bulb; in another patient, the common bile duct was injured. The mean interval between transplantation and identification of injury was 30 months. In patients with adjacent-organ injuries, biliary or perihepatic interventional treatments, adhesion of bowel and early occlusion of ePTFE grafts were commonly observed. Adjacent-organ injuries by ePTFE graft after LDLT were rare but present. Interventional procedures, adhesion of the bowel wall and early occlusion of the grafts were possible risk factors.

A multicenter comparison between autologous saphenous vein and heparin-bonded expanded polytetrafluoroethylene (ePTFE) graft in the treatment of critical limb ischemia in diabetics

The aim of this study was to evaluate early and follow-up results of below-knee bypasses performed using a bioactive heparin-treated expanded polytetrafluoroethylene (ePTFE) graft in diabetic patients with critical limb ischemia (CLI) in a multicenter retrospective registry involving seven Italian vascular centers and to compare them with those obtained in patients operated on with autologous saphenous vein (ASV) in the same centers in the same period of time. Over an 8-year period, ending in 2009, a heparin-bonded prosthetic graft (Propaten Gore-Tex; W. L. Gore & Associates Inc, Flagstaff, Ariz) was implanted in 180 diabetic patients undergoing below-knee revascularization for CLI in seven Italian hospitals (group 1). In the same period in these seven centers, 133 below-knee bypasses with ipsilateral ASV in diabetics with CLI were performed (group 2). Data concerning these interventions were retrospectively collected in a multicenter registry with a dedicated database. Early (<30 days) results were analyzed in terms of graft patency, major amputation rates, and mortality. Follow-up results were analyzed in terms of primary and secondary graft patency, limb salvage, and survival. The interventions consisted of below-knee bypasses in 132 cases in group 1 (73%) and in 45 cases in group 2 (33%; P < .001); 48 patients in group 1 (27%) and 88 patients in group 2 (67%; P < .001) had distal tibial anastomosis. Patients in group 1 had more frequently adjunctive procedures performed at distal anastomotic sites to improve run-off status. Postoperative and long-term medical treatment consisted of single antiplatelet therapy in 93 cases (52%) in group 1 and in 64 cases (48%, P = ns) in group 2, of double antiplatelet therapy in 18 cases (10%) in group 1 and in four cases (3%; P = .05) in group 2 and of oral anticoagulants in 69 patients in group 1 (38%) and in 65 (49%; P = .02) in group 2. Mean duration of follow-up was 28.3 ± 21.4 months; 308 patients (98%) had at least one postoperative clinical and ultrasonographic examination and 228 (72%) reached at least a 1-year follow-up. Estimated 48-month survival rates were 76.6% in group 1 and 72.7% in group 2 (P = > .9, log-rank 0.08). Primary patency rate at 48 months was significantly better in group 2 (63.5%) than in group 1 (46.3%; P = .03, log-rank 4.1). Assisted primary patency rates at 48 months were 47.3% (SE 0.05) in group 1 and 69% (SE 0.05) in group 2 (P = .01, log-rank 6.3). The rates of secondary patency at 48 months were 57.5% in group 1 and 69.6% in group 2 (P = .1, log-rank 2.3); the corresponding values in terms of limb salvage and amputation free-survival rates were 75.4% and 82.4% (P = .3, log-rank 1), and 59.9% and 64.4% (P = .3, log-rank 0.9), respectively. Data from this large, retrospective registry confirmed that the indexed heparin-bonded ePTFE graft provides satisfactory early and midterm results in diabetic patients undergoing surgical treatment of CLI. While autologous saphenous vein maintains its superiority in terms of primary patency, secondary patency rates are not statistically different, even in the presence of a trend for improved secondary patency with vein graft; and also limb salvage rates are comparable.

Accelerated neovascularization and endothelialization of vascular grafts promoted by covalently bound laminin type 1

Development of a small diameter (<6 mm) synthetic vascular graft with clinically acceptable patency must overcome the inherent thrombogenicity of polymers and the development of neointimal thickening. Establishment of an endothelial cell lining on the lumenal surface has been hypothesized as a mechanism to improve the function of vascular grafts. The major aim of this study is to evaluate the use of laminin type 1, covalently bound to all surfaces of expanded polytetrafluoroethylene (ePTFE) grafts, on neovascularization of the interstices and lumenal surface endothelialization. One millimeter i.d. vascular grafts were surface modified through covalent attachment of laminin type 1. Grafts were subsequently implanted as interpositional aortic grafts in rats. Following 5-weeks implantation, the grafts were explanted and morphologically evaluated using scanning electron microscopy and light microscopy. Scanning electron microscopy identified an extensive coverage of antithrombogenic cells on the lumenal flow surface of laminin type 1 modified grafts. Histological evaluation confirmed the presence of endothelial cells on the midgraft lumenal surface of laminin 1 modified grafts. Extensive neovascularization of the interstices of the laminin-modified grafts occurred as compared with control grafts. We conclude that surface modification using laminin type 1 accelerates both the neovascularization and endothelialization of porous ePTFE vascular grafts.

Midterm Results of Autologous Saphenous Vein and ePTFE Pre-Cuffed Bypass Surgery in Peripheral Arterial Occlusive Disease

The graft of choice in lower limb bypass surgery is the autologous saphenous vein (ASV). However, a prosthetic graft is needed in the absence of an ASV. In such situations, we used an expanded polytetrafluoroethylene (ePTFE) pre-cuffed Dynaflo graft as supragenicular bypass or Distaflo graft as infragenicular or femorocrural bypass. In respect to the expanding possibilities of percutaneous transluminal angioplasty (PTA), the indication for bypass surgery moved toward patients with advanced stages of peripheral arterial occlusive disease. For this reason, this study analyzed the current performances of these ePTFE grafts and ASV grafts with special attention to limb salvage. In a retrospective study all patients who underwent peripheral bypass surgery between 2004 and 2008 were included. Kaplan-Meier curves were used to express primary patency, secondary patency, and limb salvage rates at 1 and 3 years. Log-rank tests were performed to compare graft types. A total of 272 grafts (ePTFE/ASV: 110/162) were performed in lower limb bypass surgery. The mean follow-up was 20.3 months. The secondary 3-year patency rates were for (n=78) supragenicular grafts (ePTFE/ASV: 45%/94%)*, for (n=124) infragenicular grafts (24%/74%), and 70 for femorocrural grafts (26%/52%). Limb salvage after 3 years was 59% in the ePTFE group versus 78% in the ASV group (P < .05). In the current population of vascular patients where no PTA is possible and a peripheral bypass is necessary, the ASV remains the graft of first choice. However, the pre-cuffed ePTFE graft is a good alternative, especially in cases of critical limb ischemia, in respect to an acceptable limb salvage rate.

Effect of postoperative fractionated radiotherapy on canine ePTFE graft neointima and anastomotic stoma healing: A preliminary experimental study

The present study aimed to determine whether postoperative fractionated radiotherapy, at a total dose of 35Gy, affected expanded polytetrafluoroethylene (ePTFE) graft anastomotic stoma healing and neointima formation. The subrenal abdominal aortas of 20 mongrel dogs were replaced with an ePTFE graft. The dogs were randomly divided into either a radiotherapy or nonradiotherapy control group. Grafts were harvested at 4 or 8 weeks after surgery. Hematoxylin-eosin staining, and immunohistochemistry tests for proliferating cell nuclear antigen (PCNA) and CD34 were undertaken to analyze the anastomotic healing and neointima formation. The patency rate of grafts was 100% in each group. No disunion, rupture, or aneurysm was observed in the anastomotic stoma. Eight weeks after surgery, the graft neointima and anastomotic vessel wall of the radiotherapy group were significantly thinner than those of the control group (p<0.05). Immunohistochemical examination was carried out in accordance with histomorphology. Postoperative fractionated radiotherapy after an ePTFE graft replacement of the abdominal aorta did not affect the healing of the anastomotic stoma. However, it suppressed the development of hyperplasia in the anastomotic stoma neointima and graft neointima formation in the short term.

Surgical Thrombectomy of Thrombosed Arteriovenous Grafts by Interventional Nephrologists

The aim of our retrospective study was to present the success of surgical thrombectomy in acutely thrombosed, arteriovenous (AV), expanded polytetrafluoroethylene (ePTFE) grafts. Patients from hemodialysis centers in Slovenia were admitted to our dialysis center after acute thrombosis of their AV graft to undergo surgical thrombectomy under local anesthesia as an outpatient procedure. In 55 chronic hemodialysis patients, of whom 26 were men (47.3%), with a mean age of 63 ± 13 years (range 35-84 years), and diabetes mellitus in 11 patients (20%), 59 ePTFE AV grafts thrombosed. A total of 129 thrombectomies were performed, on average 2.2 ± 2.1 per graft (range 1-13). Primary patency (defined as the time from AV graft creation to first thrombosis) was 638 ± 633 days (range 10-2586, median 418 days), secondary patency (defined as the time from first thrombectomy to abandonment) was 451 ± 472 days (range 0-1994, median 305 days), and cumulative patency (defined as the time from creation to abandonment) was 1089 ± 685 days (range 25-3020, median 1031 days). In 46 (78%) of the AV grafts, the first thrombectomy was successful. The secondary patency rates after 1, 2, 3, 4, and 5 years were 76%, 66%, 54%, 14%, and 14%, respectively (13/59 unsuccessfully thrombectomized grafts were excluded). Cumulative patency after 1, 2, 3, 4, and 5 years was 88.1%, 67.8%, 44.7%, 27.1%, and 16.9%, respectively. In conclusion, surgical thrombectomy after thrombosis of an AV graft in the arm or thigh, performed by interventional nephrologists and followed, if required, by angioplasty, significantly prolonged the patency of the majority of thrombosed AV grafts.

A prospective, randomized comparison of bovine carotid artery and expanded polytetrafluoroethylene for permanent hemodialysis vascular access

Many patients on hemodialysis do not have adequate anatomy for native arteriovenous fistulas. In these patients, synthetic conduits remain an alternative option for permanent hemodialysis access. We sought to compare the standard cuffed expanded polytetrafluoroethylene (ePTFE) graft with the bovine carotid artery (BCA) graft. This was a prospective, randomized controlled trial that was set in an academic medical center. We enrolled 26 patients in the BCA group and 27 patients in the ePTFE group. Primary, assisted primary, and secondary patency were calculated using the Kaplan-Meier method. Complications were monitored and are reported. Although there was no significant difference in secondary patency rates, primary and assisted primary patency rates were significantly higher in BCA than in the ePTFE grafts (60.5% vs 10.1% and 60.5% vs 20.8% at 1 year, respectively). The BCA graft survival advantage was most profound in the upper arm grafts with significantly higher primary and assisted patency rates (P < .0001 and .0005, respectively). The total number of interventions (upper arm grafts) and total number of angioplasties (overall and upper arm) required to maintain patency were significantly fewer in the BCA group. The most common complication was graft thrombosis which occurred 0.34 ± 0.09 times per patient year in the BCA group compared to 0.77 ± 0.16 times per patient year in the ePTFE group, P = .01. The BCA graft is an excellent option for patients on hemodialysis that are not suitable for native arteriovenous fistulas, as these grafts required fewer interventions than the ePTFE grafts to maintain patency.

Long-term dilatation of polyester and expanded polytetrafluoroethylene tube grafts after open repair of infrarenal abdominal aortic aneurysms

Since 1995, expanded polytetrafluoroethylene (ePTFE) grafts have been implemented in open surgical repair (OSR) of abdominal aortic aneurysms (AAA) and are supposed to show less dilatation than polyester grafts. This study examined differences in graft dilatation and clinical outcome. This single-center long-term, prospective randomized study monitored 99 consecutive patients after OSR of AAA. Implanted were 90 tube ePTFE Gore-Tex Stretch grafts, 56 tube Dacron grafts (Uni-Graft KDV, polyester, B. Braun, knitted), and 51 tube Dacron grafts (Gelseal Plus, polyester, Vascutek, triaxial knitted). Follow-up with ultrasound examination was performed at discharge, at 12 months, and at 6 years. Patients were a mean age of 67 years. Thirty-day mortality was 2.5% (n = 5 of 199), without significant differences among the groups. The Kaplan-Meier analysis showed 5-year survivals of 0.82 (ePTFE/Gore), 0.81 (polyester/Braun), and 0.83 (polyester/Vascutek). Mean ± standard deviation dilatation of the midgraft segment was 1% ± 5% (ePTFE/Gore), 10% ± 9% (polyester/Braun), and 7% ± 8% (polyester/Vascutek) (P ≤ .001) at discharge; 8% ± 11% (ePTFE/Gore), 24% ± 7% (polyester/Braun), and 20% ± 13% (polyester/Vascutek; P ≤ .001) after 12 months; and 19% ± 21% (ePTFE/Gore), 33% ± 22% (polyester/Braun), and 23% ± 19% (polyester/Vascutek; (P ≤ .001) after 6 years. No graft failure or rupture occurred. Graft patency was 100%. After a mean implantation of 6 years, the ePTFE/Gore, polyester/Braun, and polyester/Vascutek tube grafts presented with significant differences. The ePTFE grafts showed a stronger resistance against dilatation than the two types of polyester grafts. Owing to similar perioperative and postoperative courses, no advantage could be identified in any group concerning the overall outcome. Vascular implants for OSR of AAA made of ePTFE and polyester are safe, even after a long implantation time. Therefore, the choice of the suitable graft does not depend on its postimplantation dilative characteristics. The outcome is not likely to be connected with dilatation of the implanted graft, because a causal connection between graft dilatation and death cannot be made. The study does not offer a basis for the preference of one of the three graft types. Nevertheless, continuous ultrasound examinations should be performed after implantation of an aortic tube graft to identify possible problems arising from changes in the graft and the residual vascular branches over time.

Is a Vein Patch Worthwhile for Femoropopliteal Bypass With ePTFE Grafts?

One of the factors contributing to late graft occlusion after peripheral arterial bypass with prosthetic grafts is anastomotic intimal hyperplasia. The purpose of this study was to evaluate, experimentally and clinically, the effect of placing a vein patch over the site of distal anastomosis of a ePTFE graft in peripheral arterial bypass (DAPP). After heparinization, the infrarenal abdominal aorta in 14 beagle dogs was resected, and an ePTFE graft was interposed between the resected ends. The dogs were divided into a control group without DAPP and a DAPP group. These animals were killed 3 months after surgery. A total of 89 femoropopliteal bypasses using ePTFE grafts, 71 patients were divided into two groups for analysis; namely, a direct suture group without DAPP being the DS group (n = 62 limbs) and a DAPP group with DAPP (n = 27 limbs). The mean follow-up period was 1010 days in the DS group and 302 days in the DAPP group. All the grafts were patent in both groups of dogs. The thrombus adhering to the entire intraluminal surface of the graft defined as the mean thrombus-covering ratio, in the DAPP group was significantly less than that in the control group, although there were no significant differences in the length of proximal or distal intimal ingrowth into the ePTFE grafts between the two groups. The maximal intimal thickness did not differ significantly between the control group and the DAPP group, at 541 +/- 349 µm and 353 +/- 76 µm, respectively. The 1- and 3-year cumulative patency rates of femoropopliteal bypasses were 86% and 71%, respectively, in the DS group, whereas they were both 91% in the DAPP group. Although the numbers of subjects in this study was too limited for a final evaluation, the trend was unmistakable. The findings of this study indicate that DAPP may improve the cumulative patency of femoropopliteal bypasses with ePTFE grafts.http://link.springer-ny.com/link/service/journals/00547/bibs/8n4p193.html</hea

Use of Fibrin Sealant as a Hemostatic Agent in Expanded Polytetrafluoroethylene Graft Placement Surgery

The low thrombogenicity, porosity, and limited elasticity of expanded polytetrafluoroethylene (ePTFE) vascular grafts, although beneficial, may exacerbate the problem of suture-line bleeding at vascular anastomoses and consequently lead to increased operating times. The overall objective of this prospective, randomized, controlled, subject-blinded, multicenter phase 2 study was to evaluate the efficacy and safety of a fibrin sealant containing 500 IU/mL thrombin and synthetic aprotinin (FS; marketed in the United States under the name TISSEEL) for hemostasis in subjects undergoing vascular surgery and receiving prosthetic ePTFE vascular grafts. FS was compared with manual compression with surgical gauze pads, a standard of care for hemostasis in vascular surgery. Two FS polymerization/setting times (60 and 120 seconds) were investigated to evaluate influence on the efficacy results. Patients undergoing ePTFE graft placement surgery (N = 73) who experienced bleeding that required treatment after surgical hemostasis were randomized to be treated with FS with clamps opened at 60 seconds (FS-60; N = 26), with FS with clamps opened at 120 seconds (FS-120; N = 24), or with manual compression with surgical gauze pads (control; N = 23). The proportion of subjects achieving hemostasis at 4 minutes (primary endpoint) as well as at 6 and 10 minutes (secondary endpoints) in the three treatment groups was analyzed using logistic regression analysis, taking into account gender, age, type of intervention, severity of bleeding, systolic blood pressure, diastolic blood pressure, heparin coating of the ePTFE graft, and platelet inhibitors. There were substantial differences in the proportion of subjects who achieved hemostasis at the study suture line at 4 minutes from treatment application between FS-120 (62.5%) and control (34.8%) groups (a 79.6% relative improvement). Logistic regression analyses found a statistically significant treatment effect at the 10% level in the odds ratio (OR) of achieving hemostasis at 4 minutes between the FS-120 and control groups (OR = 3.98, p = 0.0991). Furthermore, it has been shown that the perioperative administration of platelet inhibitors significantly influences (OR = 3.89, p = 0.0607) hemostasis rates at the primary endpoint. No statistically significant treatment effects were found for the other factors. Logistic regression analyses performed on the secondary endpoints demonstrated a significant treatment effect of achieving hemostasis at 6 minutes (OR = 9.92, p = 0.0225) and at 10 minutes (OR = 6.70, p = 0.0708) between the FS-120 and control groups. Statistically significant effects in the logistic regression analyses were found at the 10% level in the OR of achieving hemostasis at 6 and 10 minutes, respectively, for the following factors: FS-120 versus control group (OR = 9.92; p = 0.0225 and OR = 6.70; p = 0.0708, respectively), type of intervention (OR = 0.3; p = 0.0775 and OR = 0.25; p = 0.0402, respectively), and heparin coating of the ePTFE prosthesis (OR = 4.83; p= 0.0413 and OR = 3.65; p = 0.0911, respectively). FS was safe and well-tolerated, as indicated by the lack of any related serious adverse events. The findings from this phase 2 study support the strong safety profile of FS and suggest that it is an efficacious hemostatic agent in ePTFE graft placement surgery, as well as a useful tool in peripheral vascular surgery applications.