Preliminary experience with expanded polytetrafluoroethylene grafts.

This early clinical experience of members of the New England Society for Vascular Surgery with expanded polytetrafluoroethylene (PTFE) grafts was evaluated. Questionnaires were distributed to 52 active members of the Society and 32 answers were received. A total of 186 graft insertions were evaluated, of which 112 were positioned in the lower limb; 106 grafts were inserted for libm salvage. Patency rates for femoral-popliteal bypass grafts were determined by life-table analysis. Our results show a 6 to 9 month cumulative patency rate of 91% for PTFE grafts with a popliteal anastomosis above the knee, and a 52% patency rate for below-knee anastomosis. Two complications, aneurysmal dilatation and graft sepsis, were noted in this series. The new graft material exhibits an early patency rate higher than bovine or Dacron grafts which warrants long-term use and evaluation.     

Three year experience with expanded polytetrafluoroethylene arterial grafts for limb salvage

Polytetrafluoroethylene grafts were used for 175 femoropopliteal reconstructions with a cumulative 3 year life table patency rate of 77 percent. Reoperation for early or late failure was required in 27 patients to achieve this patency rate. If these 27 failures were calculated as nonpatent grafts, 3 year patency would be 62 percent. Thirty month life table patency rates were 94 and 91 percent for polytetrafluoroethylene axillofemoral and femorofemoral bypasses, respectively. Twenty-two polytetrafluoroethylene axillopopliteal bypasses were performed because of infection in the groin, previously failed reconstructions or unavailability of femoral vessels due to disease. The 2 year life table patency rate was 69 percent, with nine of the grafts patent for more than 1 year. Forty polytetrafluoroethylene bypasses to arteries at the ankle or in the foot resulted in a 2 year life table patency rate of 48 percent. Thus, polytetrafluoroethylene grafts show early promise as a vascular prosthesis. Although further study will be required to define the exact role of this new arterial substitute, it already can facilitate the performance of otherwise difficult or impossible limb salvage procedures.     

Six year experience with expanded polytetrafluoroethylene arterial grafts for limb salvage

We have used 822 polytetrafluoroethylene (PTFE) grafts in arterial reconstructions for limb salvage over the last 6 years at Montefiore Medical Center-Albert Einstein College of Medicine, Four hundred and twenty-seven femoropopliteal reconstructions with PTFE had a 6 year cumulative life table patency rate of 55% with follow-up of 76 grafts for more than 3 years and 28 grafts for more than 4 years. Seventy-nine bypasses to the isolated popliteal segment had a 6 year cumulative patency rate of 72%. There were 207 bypasses performed to the tibial, peroneal or dorsalis pedis arteries. Life table patency rates were 55% at 1 year, 40% at 2 years and 37% at 4 years. Ninety-two PTFE femorofemoral and 62 axillofemoral bypasses had 5 1/2 year cumulative life table patency rates of 83% and 75%, respectively. Axillopopliteal PTFE bypasses can salvage otherwise doomed limbs. Thirty-four such grafts had 74% 1 year and 45% 5 year patency rates. The overall infection rate in all 822 PTFE grafts was only 0.5%. Thus, PTFE is a promising vascular prosthetic material which facilitates otherwise difficult or impossible limb salvage procedures.     

One-year experience with a new expanded polytetrafluoroethylene vascular graft for hemodialysis

Hemodialysis access achieved through a prosthetic vascular graft has become more popular, especially in diabetic and older patients and those who have had several unsuccessful surgical accesses. From January to December 1996, we implanted a newly available expanded polytetrafluoroethylene (ePTFE) graft (DIASTAT Vascular Access Graft) that allows early cannulation in 18 patients (11 men and 7 women; mean age +/- SD, 63.7 +/- 11 years). Thirteen of these patients had at least one failed vascular access. All grafts were cannulated for dialysis within 7 days of implantation, with flow rates > or = 300 ml/min. The time to hemostasis after the first cannulation ranged from 2 to 4 min. The primary patency rate at one year was 56%. Four grafts developed thrombosis requiring surgical intervention; three were salvaged and one was removed. The one-year assisted or cumulative patency rate was 72%. One patient had persistent bleeding requiring graft revision immediately after surgery. The bleeding stopped and its origin was not determined. There were no graft infections or hematomas. Because of the early cannulation possible with the DIASTAT graft, as well as the lesser time to hemostasis than that generally achieved with standard ePTFE grafts, this prosthesis is a good alternative to autogenous access construction.     

Clinical experience with expanded polytetrafluoroethylene (Gore-Tex) grafts for femoropopliteal arterial bypass

Thirty-seven grafts of expanded polytetrafluo-roethylene were implanted in 28 patients in whom autogeneous saphenous vein was not available, either for symptoms of severe claudication or limb salvage. The length of follow-up ranges from 8 to 28 months. The patency rate is 86.9 percent for the patients with severe claudication and 71.4 percent in the limb salvage group; the overall patency rate is 81 percent. We believe that expanded polytetrafluoroethylene is a good prosthetic substitute when autogenous vein is unavailable.     

Paclitaxel-coated expanded polytetrafluoroethylene haemodialysis grafts inhibit neointimal hyperplasia in porcine model of graft stenosis.

BACKGROUND: The main pathology of haemodialysis graft stenosis is venous neointimal hyperplasia at graft-venous anastomoses. Neointimal hyperplasia is also observed in cases of coronary artery in-stent restenosis. Paclitaxel is a chemotherapeutic agent used to treat cancer, and has been proven to inhibit neointimal hyperplasia of coronary artery in-stent restenosis. In this study, we examined whether a paclitaxel-coated haemodialysis graft could inhibit neointimal hyperplasia and prevent stenosis. METHODS: We dip-coated paclitaxel on expanded polytetrafluoroethylene (ePTFE) grafts at a dose density of 0.59 microg/mm(2). In vitro release tests showed an initial paclitaxel burst followed by a long-term slow release. Using ePTFE grafts with (coated group, n = 8) or without a paclitaxel coating (control group, n = 11), we constructed arteriovenous (AV) grafts connecting the common carotid artery and the external jugular vein in Landrace pigs. RESULTS: After excluding seven pigs for technical failure, cross-sections of graft-venous anastomoses obtained 6 weeks after placing the AV grafts were analysed. Percentage luminal stenosis, ratios of intima to media in whole cross-sections, areas of intima in the peri-junctional areas (within 2 mm above and 2 mm below the graft-venous junction), and the mean thickness of intima within venous sides of cross-sections, were 60.5% (range, 41.5-60.7), 13.0 (range, 8.6-20.4), 23.7 mm(2) (range, 10.8-32.1) and 2.1 mm (range, 1.1-3.0), respectively, in the control group, whereas corresponding median values in the coated group were 10.4% (range, 1.0-17.8), 1.0 (range, 0.7-5.1), 1.6 mm(2) (range, 0.2-8.0) and 0.3 mm (range, 0.1-2.2). All parameters were significantly different between the two groups (P<0.05 by Mann-Whitney test). CONCLUSION: Paclitaxel-coated ePTFE grafts could prevent neointimal hyperplasia and the stenosis of AV haemodialysis grafts.     

Enhanced graft healing of high-porosity expanded polytetrafluoroethylene grafts by covalent bonding of fibronectin

(Received for publication on Jan. 5, 1999; accepted on Sept. 17, 1999)     

Surgical experience with expanded polytetrafluoroethylene (PTFE) as a replacement graft for traumatized vessels.

With the increased nationwide incidence of major vascular injuries, the need for interposition grafting has become quite common in major trauma centers. Despite extensive experience with such injuries, the choice of a substitute conduit remains controversial. Recent studies have demonstrated the potential of expanded polytetrafluoroethylene (PTFE) as a replacement graft for small arteries and veins. The surgical services at the Ben Taub General Hospital began to use PTFE grafts in traumatic vascular wounds approximately 2 years ago. Eight axillary arteries and 12 brachial arteries have had interposition grafting with PTFE prostheses. Eleven patients have required PTFE interposition grafts in repair of traumatized common, superficial, and profunda femoris arteries and common femoral veins; eight patients had reconstruction in the popliteal artery or vein. Three patients had renal artery revascularization procedures following blunt abdominal trauma, three patient had segmental replacement of the superior mesenteric artery following gunshot wounds, and one carotid artery, one iliac vein, and two axillary veins were grafted with PTFE. All patients with segmental repair of axillary, brachial, femoral, and popliteal vessels have maintained good distal pulses and viable extremities. No grafts have thrombosed, nor become infected, in spite of soft-tissue injury encountered at time or repair. In situations requiring interposition graft placement for reestablishment of distal flow in small arteries and veins, PTFE grafts appear to be an acceptable prosthesis.     

Lipid uptake in expanded polytetrafluoroethylene vascular grafts

Purpose: The mechanisms of vascular prosthesis failure are reported to be associated, in part, with an atherosclerotic degenerative process that is related to an abnormal lipid infiltration. The lipid uptake in expanded polytetrafluoroethylene (ePTFE) vascular grafts was reproduced in vitro, and the effect of time on the permeability of these prostheses was studied. Methods: Water permeability tests were carried out under dynamic flow conditions at various hydrostatic pressures. Lipid uptake was simulated by circulating a phosphatidylcholine suspension inside an expanded Teflon prosthesis under pulsatile or continuous transmural pressure ranging between 80 mm Hg and 180 mm Hg, at a flow rate of 500 mL/min and 2000 mL/min, for a duration ranging from 2 hours to 1 month. Results: Water permeability tests indicated that under hydrostatic pressures of 180 mm Hg and 300 mm Hg, water percolated through the prosthesis wall after an exposure of 720 minutes and 75 minutes, respectively. After exposing the prostheses to the lipid dispersion under the various flow conditions, the fluid convection through the wall occurred. Preferential convection pathways with a constant periodicity were observed across the length of each prosthesis and were, therefore, associated with regularly spaced perforations depicted in the structure of the devices. Phospholipids gradually agglomerated within the prosthesis wall, allowing a restrictive molecular mobility. Infrared spectroscopy results indicated that the lipid uptake depended on the transmural pressure and time of exposure. Conclusion: The occurrence of the membrane permeability may be associated with the dilatation and plastic deformation of the prosthesis. Lipid uptake occurs in ePTFE grafts after an aggressive kinetic process. (J Vasc Surg 1998;28:527-34.)     

Long-term results with the above-knee popliteal expanded polytetrafluoroethylene graft

Since approximately 30% to 40% of autogenous vein bypass grafts to the femoropopliteal level may occlude within 5 years of implantation, additional vein will be required for subsequent revisions. We undertook a study to determine whether the preferential use of an above-knee expanded polytetrafluoroethylene bypass graft to save vein is an appropriate option. We reviewed our experience with 114 above-knee expanded polytetrafluoroethylene bypass reconstructions. Life-table analysis of primary and secondary graft patency was carried out by the method of Peto and statistically analyzed for the influence of clinical indication, runoff as determined by both preoperative and intraoperative completion arteriography, smoking, and diabetes. The 5-year primary patency rate of 57% for patients with claudication was comparable to contemporary randomized or retrospective series with below-knee autogenous vein for that indication, and it was superior to the patency rate for limb salvage. The status of the runoff vessels was an important determinant of outcome. The 59 limbs with good arteriographic runoff (2 to 3 vessels) had a markedly higher 5-year patency rate (70%) than the poor arteriographic runoff (0 to 1 vessels) group (30%). Continued cigarette smoking and diabetes mellitus also appeared to affect adversely primary graft patency in our hands. Our data support the use of preferential above-knee expanded polytetrafluoroethylene grafts in patients with good angiographic runoff. This approach does not appear to prejudice the limb against secondary revisionary procedures or the use of a new autogenous graft, if required.     

Three years' experience with esophageal stapling device.

The authors report their experience with forty patients undergoing resection of middle and lower thirds carcinomas of the esophagus or proximal stomach, with esophagogastric or esophagojejunal anastomosis using an end-to-end anastomosis (EEA) stapler. A fatal anastomotic leak occurred in the first two patients and seven other patients died in the early postoperative period from respiratory and cardiovascular complications. Four other patients developed fibrotic strictures between 6 and 24 months after their operation. The strictures were easily dilated and did not recur. The use of an EEA stapler is recommended because it reduces the operating time, the incidence of anastomotic leaks, and probably the blood loss. The majority of anastomoses can be accomplished exclusively through the left chest by using the stapler.     

Precoating expanded polytetrafluoroethylene grafts alters production of endothelial cell-derived thrombomodulators.

Although the use of extracellular matrix proteins to precoat small-caliber vascular grafts before endothelial cell seeding has been shown to improve cell attachment, proliferation, and adherence, the effect of precoating on the thrombomodulatory properties of the seeded cells is unknown. The use of vascular prostheses lined with confluent endothelial cell monolayers expressing optimal thromboresistant properties may enhance patency rates. In this study human saphenous vein endothelial cells were seeded onto expanded polytetrafluoroethylene (ePTFE) graft material, both unmodified and precoated with fibronectin, type I collagen, or fibronectin and type I collagen (fibronectin/type I collagen). After 3 days of in vitro cultivation, endothelial cell production of prostacyclin, tissue plasminogen activator, and plasminogen activator inhibitor was evaluated under basal conditions and after stimulation with arachidonate or thrombin. Production of tissue plasminogen activator by endothelial cells cultured on fibronectin-ePTFE was significantly greater compared with production by endothelial cells grown on noncoated or fibronectin/type I collagen-ePTFE under basal conditions (p values less than 0.01 and less than 0.05, respectively) and in response to thrombin (p values less than 0.002 and less than 0.003, respectively). Plasminogen activator inhibitor-1 production was not detected in any of the four experimental groups. Endothelial cells cultured on fibronectin-ePTFE also synthesized significantly more prostacyclin than endothelial cells grown on type I collagen- or fibronectin/type I collagen-ePTFE, under basal conditions (p values less than 0.02 and less than 0.01, respectively) and in response to arachidonate (p values less than 0.03 and less than 0.002, respectively) and thrombin (p values less than 0.003 and less than 0.002, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Aorta--coronary artery revascularization with an expanded polytetrafluoroethylene vascular graft. A preliminary report.

Patients requiring coronary artery surgery may have had bilateral saphenous vein stripping, and the arm veins may not be adequate for use for coronary artery grafting. The internal mammary artery may not be long enough for use for the circumflex or right coronary artery anastomoses. A suitable substitute would be most welcome for these patients or for those with marked varicosities of the saphenous vein. Five patients received expanded polytetrafluoroethylene (PTFE) grafts (Gore-Tex vascular grafts) for coronary artery revascularization because veins of adequate size or length were not available at the time of operation. These five patients are alive 9 to 14 months after graft insertion. Four of the five grafts were patent at the time of restudy 3 to 6 months postoperatively. More follow-up studies for far longer periods of time will be necessary before Gore-Tex vascular grafts can be recommended as the ideal material for coronary artery bypass surgery.     

Nine year patent femorotibial expanded polytetrafluoroethylene graft bypass

A 65-year-old patient with a trophic lesion and severe intermittent claudication in the right lower extremity was surgically treated by femoro-distal-tibial bypass employing a prosthetic 6 mm diameter PTFE (Gore-Tex) graft. It is still patent nine years later as shown by a follow-up arteriogram. The patient's trophic lesion disappeared, and there are presently no symptoms of intermittent claudication. When arterial revascularization in the leg is indicated, an option to a saphenous vein graft for long bypass is the use of a PTFE graft.     

Production of endothelium-derived factors from sodded expanded polytetrafluoroethylene grafts

Purpose: Experiments were designed to determine whether endothelium isolated from adipose tissue and sodded onto expanded polytetrafluoroethylene grafts release endothelium-derived vasoactive factors.Methods: Thin-walled expanded polytetrafluoroethylene grafts (6 mm internal diameter, 6 cm length, 30 μm pore size), one sodded with autogenous endothelial cells, the other unsodded, were implanted bilaterally in carotid arteries of 30 male mongrel dogs. Dogs were treated with 325 mg aspirin daily. After 6 weeks grafts were excised and perfused in a bioassay system. Effluent from the grafts stimulated with either acetylcholine, thrombin, adenosine 5-diphosphate, or the calcium ionophore A23187 was superfused over rings of canine femoral arteries without endothelium contracted with phenylephrine. Effluent from the grafts was analyzed by radioimmunoassay for thromboxane B₂, 6-keto-prostaglandin F_1α, endothelin-1, and C-type natriuretic peptide.Results: Ninety percent of the sodded grafts and 87% of the unsodded grafts were patent after 6 weeks. Bioassay rings superfused with effluent from sodded grafts stimulated with acetylcholine relaxed significantly more than rings superfused with effluent from similarly stimulated unsodded grafts. Biochemical analysis of the effluent showed an increase in 6-keto prostaglandin F_1α and C-type natriuretic peptide and a decrease in endothelin-1 and thromboxane B₂ release from the sodded compared with the unsodded grafts. Scanning electron microscopy showed a continuous layer of endothelial cells lining only the sodded grafts. Staining for α-actin and heavy-chain myosin showed a differentiated layer of smooth muscle below the endothelial layer on the sodded grafts. Finally, there was positive staining for C-type natriuretic peptide and endothelin-1 in the endothelium of the sodded grafts.Conclusions: These results indicate that endothelial cells of sodded expanded polytetrafluoroethylene grafts produce endothelium-derived vasoactive factors. In addition, receptor-coupled synthesis/release of these factors is retained in sodded endothelial cells. (J Vasc Surg 1997;25:187-97.)     

Infrainguinal polytetrafluoroethylene grafts: Saved limbs or wasted effort? A report on ten years' experience

Two-hundred and twenty-four infrainguinal polytetrafluoroethylene reconstructions were performed for critical ischemia over a 10 year period: 48 to the above-knee popliteal artery, 113 to the below-knee popliteal artery, and 63 to the tibial vessels. The cumulative patency rates were 84±6% and 63±9% for above-knee popliteal, 53±5% and 35±7% for below-knee popliteal, 45±6% and 30±9% for tibial vessels at one and five years respectively. Limb salvage rates were 81±6% and 73±9% (above-knee popliteal), 69±5% and 57±9% (below-knee popliteal), 64±7% and 32±10% (tibial vessels) at one and five years respectively. Graft occlusion did not result in limb loss in 32 cases. Preoperatively, 54% of the patients had limited mobility while 43% were regarded as severely restricted. At follow-up, 57% of the patients were considered to be independent, 26% had limited mobility, and 17% were still severely restricted. Polytetrafluoroethylene provides good short-term limb salvage and improved mobility in patients with critical ischemia and poor life expectancy. Its use is well worth the effort.     

Longevity of expanded polytetrafluoroethylene grafts for superior vena cava

We previously reported that the expanded polytetrafluoroethylene (ePTFE) graft for superior vena cava (SVC) substitution presents the problems of flexion and kinking when the graft is long. We therefore replaced the SVC of dogs with two types of prosthetic substitutes, ePTFE (Gore-Tex) and spiral-supported ePTFE (Im/praflex), and evaluated the long-term patency of the prosthetic substitutes. Total replacement of the SVC was performed in 9 adult mongrel dogs. The substitutes were ePTFE and spiral-supported ePTFE in 5 and 4 dogs, respectively. The animals were killed about 3 years after replacement of the SVC, and the harvested specimens were histologically examined by light microscopy and scanning electron microscopy. Evaluation of ePTFE revealed late occlusion in 1 of 5 dogs. The spiral-supported ePTFE showed patency in all dogs. In the group with ePTFE grafts, light microscopic examination revealed abnormalities of endothelial cells, granulation, and necrosis. There was no hyperplasia of the subendothelial connective tissue near the center. In the animals with spiral-supported ePTFE grafts, the subendothelial connective tissue showed favorable growth even in the center of the reconstructed site. There was no granulation in the spiral-supported ePTFE group. Scanning electron microscopic examination in the ePTFE group showed that endothelial cells were spindle-shaped and had an irregular surface. The spiral-supported ePTFE group showed an almost regular form of endothelial cells and no abnormalities except for the slightly spindled shape in the center. Therefore, we recommend that spiral-supported ePTFE should be used as an SVC substitute in clinical situations.     

Heparin immobilization reduces thrombogenicity of small-caliber expanded polytetrafluoroethylene grafts

OBJECTIVE: The patency of small-diameter expanded polytetrafluoroethylene (ePTFE) grafts for vascular reconstruction is impaired by acute thrombotic occlusion. Prosthetic materials are thrombogenic and cause platelet adhesion and activation of the coagulation cascade. Heparin is a potent anticoagulant drug widely used to prevent and treat thrombosis. A new ePTFE graft with long-term bonding of heparin is now commercially available in several European countries, but a basic analysis of its mechanism of action in humans has never been performed. This study was performed to evaluate the thrombogenicity of heparin-bonded ePTFE grafts compared with standard ePTFE in a newly developed human ex vivo model. METHODS: Nonanticoagulated blood was drawn from antecubital veins of 10 healthy donors with a 19-gauge needle. The proximal end of a 60-cm ePTFE vascular graft with a diameter of 3 mm was connected to the needle while the distal end was connected to a syringe, which was placed in a syringe pump. Every volunteer served as his or her own control by using a heparin-bonded ePTFE graft on one arm and a standard ePTFE graft on the other arm. The perfusions were performed over 6 minutes with a flow rate of 20 mL/min, corresponding to a shear rate of 74/s. Serial samples were taken at the distal end of the graft for determination of prothrombin fragment 1 + 2, fibrinopeptide A, and P-selectin expression on perfused platelets. Fibrin deposition and platelet deposition were studied by using scanning electronic microscopy. RESULTS: Fibrinopeptide A production over time was significantly reduced on the heparin-bonded ePTFE grafts compared with standard ePTFE grafts (P < .05). There was no increase in the production of prothrombin fragment 1 + 2 or P selectin over time on either type of graft. Scanning electronic microscopy scanning showed platelet deposition and fibrin formation on standard ePTFE grafts, whereas no platelets or fibrin were observed on heparin-bonded ePTFE grafts. CONCLUSIONS: Heparin immobilization substantially reduces the thrombogenicity of small-diameter ePTFE in a newly developed human ex vivo model. In this study, we provide evidence that the mechanism of action of the heparin bonding is due not only to anticoagulant but also to antiplatelet effects. Heparin bonding may be an important improvement of ePTFE, resulting in better patency rates for vascular reconstructions.