Gore-Tex Vascular Grafts Research Articles

A Selective, Slow Binding Inhibitor of Factor VIIa Binds to a Nonstandard Active Site Conformation and Attenuates Thrombus Formation in Vivo

The serine protease factor VIIa (FVIIa) in complex with its cellular cofactor tissue factor (TF) initiates the blood coagulation reactions. TF.FVIIa is also implicated in thrombosis-related disorders and constitutes an appealing therapeutic target for treatment of cardiovascular diseases. To this end, we generated the FVIIa active site inhibitor G17905, which displayed great potency toward TF.FVIIa (Ki = 0.35 +/- 0.11 nM). G17905 did not appreciably inhibit 12 of the 14 examined trypsin-like serine proteases, consistent with its TF.FVIIa-specific activity in clotting assays. The crystal structure of the FVIIa.G17905 complex provides insight into the molecular basis of the high selectivity. It shows that, compared with other serine proteases, FVIIa is uniquely equipped to accommodate conformational disturbances in the Gln217-Gly219 region caused by the ortho-hydroxy group of the inhibitor's aminobenzamidine moiety located in the S1 recognition pocket. Moreover, the structure revealed a novel, nonstandard conformation of FVIIa active site in the region of the oxyanion hole, a "flipped" Lys192-Gly193 peptide bond. Macromolecular substrate activation assays demonstrated that G17905 is a noncompetitive, slow-binding inhibitor. Nevertheless, G17905 effectively inhibited thrombus formation in a baboon arterio-venous shunt model, reducing platelet and fibrin deposition by approximately 70% at 0.4 mg/kg + 0.1 mg/kg/min infusion. Therefore, the in vitro potency of G17905, characterized by slow binding kinetics, correlated with efficacious antithrombotic activity in vivo.

Surgical Treatment of Posttraumatic Radioulnar Synostosis in Children

The authors describe two children who underwent surgical treatment of radioulnar synostosis. One case involved simple excision; the other, excision and interposition of Gore-Tex vascular graft material. In a review of the literature, no other report of the latter type of surgical treatment was found. A discussion of the literature concerning this rare complication in children and the current surgical treatment options are included.

Repair of Bile Duct Injuries With Gore-Tex Vascular Grafts: Experimental Study in Dogs

Bile duct injury is the most feared complication related to biliary tract operations. The goal of this investigation was to offer an alternative treatment that might prevent this complication. Twelve mongrel dogs, thin-walled FEP-ringed Gore-Tex vascular grafts, and Gore-Tex sutures were used in this study. The dogs were randomized into three groups of four according to the length of time of graft implantation: group 1 = 1 month; group 2 = 2 months; and group 3 = 3 months. During the first part of the study, a biliary injury was induced by ligating the middle choledocus after performing a conventional cholecystectomy. During the second part of the study, biliodigestive and biliobiliary anastomosis were performed using Gore-Tex vascular grafts prior to resection of the stenotic area. Initially, an increase in serum bilirubin and alkaline phosphatase levels was noted. Two weeks later, after implantation of the grafts, these values returned to normal. Thin-walled FEP-ringed Gore-Tex vascular grafts were found to be useful in the repair of bile duct injuries, especially in complete transections of the common bile duct. The ductility and flexibility of the material allows any type of anastomosis to be performed, especially when bile duct–gut anastomosis is technically difficult. ( J Gastrointest Surg 2002;6:116–120.)

Limb Preservation by Gore-Tex Vascular Graft for Groin Recurrence after Postoperative Adjuvant Radiation in Vulvar Cancer

Background.Recurrent vulvar cancer involving the femoral artery after groin radiation is usually considered inoperable. A patient with such recurrent vulvar cancer successfully treated by femoral vascular graft and rectus abdominis myocutaneous flap reconstruction with limb salvage is described.Case. A 51-year-old woman had recurrent vulvar cancer involving the right femoral vessels 6 months after a radical vulvectomy plus inguinal lymphadenectomy and postoperative pelvic and groin radiation. Radical en bloc excision of tumor along with the involved femoral artery and vein followed by Gore-Tex vascular graft and rectus abdominis myocutaneous flap reconstruction led to a complete remission. However, occlusion of the grafted vessels occurred 21 months following bypass surgery. Since the compensatory collaterals were established, debridement and removal of the occluded graft were carried out. The patient has been clinically free of disease for more than 48 months since graft reconstruction surgery.Conclusion. It is highlighted that aggressive tumor resection with limb salvage is feasible even for patients with vulvar cancer of the groin recurrence involving the femoral artery after primary surgery and groin radiation.

ADVANCEMENT OF THE UNDULATION PUMP TOTAL ARTIFICIAL HEART(UPTAH)

UPTAH is an implantable TAH developing in our laboratory in these 6 years. Many achievements concerning to the hard and software could survive TAH animal for long-term. Mechanism and merits: UPTAH is composed of 2 UPs 2 conversion mechanisms and 2 brushless DC motors, in which the motor revolution converts to the undulation motion of a disc by the conversion mechanism. The disc can squeeze blood from the inlet to the outlet of the pump. UPTAH has the following merits; very compact(76mm in diameter, 78mm in long), arbitrary flow pattern can be produced, the right and left heart can control independently, only one valve in the aortic cannula is required for the safety and no compliance chamber is required. Materials: Pump housing and disc was made of urethane resin. Atrial cuff was made of Gore-Tex sheet. Aortic cannula in which a jellyfish valve was incorporated, was attached Gore-Tex vascular graft. All blood contact surfaces were coated with segmented polyurethane. Measurement and control: Electromagnetic flow probes were installed into aortic and pulmonary artery cannulae to control the pump flow. The right and the left atrial pressure, aortic pressure and pulmonary artery pressure were measured by pressure transducers. The flow patterns, continuous, pulsatile and pulsatile on continuous, could change pulse width modulation(PWM) of the motor current. The basic control method was an automatic left atrial pressure control in which the sucking of the atrial wall and elevation of the left atrial pressure were automatically protected. I / R control which had succeeded to survive pneumatic driven TAH goat for more than 500 days without pathophysiological abnormality, was also applied after several days of the surgical operation. Animal experiments: UPTAH has been implanted into 40 goats' chest cavity weighing between 40 and 79 Kg since 1995. No anticoagulant was used after the surgery in these experiments. Until now, 7 goats survived over 2 weeks and 4 goats survived over one month including 50 days as the longest. And one goat is on going with a very good condition over 35 days

Incorporation of nitric oxide-releasing crosslinked polyethyleneimine microspheres into vascular grafts.

Over the years, many attempts have been made to increase the patency of small- to medium-sized prosthetic vascular grafts. However, none of them has greatly affected long-term rates. Recently, nitric oxide (NO) has been shown to inhibit thrombus formation in such grafts, suggesting that local delivery of NO may help to increase graft patency. This study describes the site-specific delivery of NO by entrapping NO-releasing microspheres in the pores of a vascular graft. NO-releasing polyethyleneimine microspheres (PEIX) were developed using a novel water-in-oil emulsion technique involving chemical crosslinking with a bis-epoxide. The PEIX microspheres were then derivatized with NO forming the [N(O)NO]- moiety of the diazeniumdiolates formerly known as NONOates. These polymeric NO-releasing particles were found to spontaneously release 194 nmol NO/mg with a half-life of over 66 h under physiologic conditions. Fluorescein isothiocyanate-labeled microspheres were then embedded into the pores of a 60-micron nonreinforced Gore-tex vascular graft using a simple evacuation technique and evaluated for microsphere placement and NO release. Scanning electron microscopic analysis showed the microspheres entrapped in the pores of the vascular graft releasing 10 nmol NO/mg with a half-life of 51 h. The microspheres remained entrapped in the graft even after immersion and NO release, as confirmed by fluorescence of the medium. These results suggest that NO-releasing particles can be incorporated into the pores of a vascular graft to deliver therapeutic amounts of NO for the prevention of thrombosis in small-diameter prosthetic grafts.

Effects of neurolytic concentrations of alcohol and phenol on Dacron and Gore-Tex vascular prosthetic grafts.

Neurolytic nerve block, using either alcohol (A) or phenol (P), is frequently used to treat intractable pain. However, these agents may disrupt the integrity of prosthetic vascular grafts. To investigate this possibility, the tensile strength of Dacron (Meadox Medicals, Oakland, NJ) and Gore-Tex (W.L. Gore Associates, Flagstaff, AZ) vascular grafts was determined after in vitro exposure to various clinically used concentrations of A or P. Segments of Dacron and Gore-Tex graft were placed in the following solutions: saline (S), 6% and 9% P, and 25%, 50%, 75%, and 100% A, and stored at 23 degrees +/- 1 degree C for 72 hours. Axial maximum load (in kilonewtons, KN) and strain (in mm/mm) were determined with an Instron universal testing machine (Instron Corporation, Camden, MA). Samples from the S, 9% P, and the 100% A groups were evaluated using a scanning electron microscope. Dacron tensile strength decreased a maximum of 23% after exposure to 50%, 75%, and 100% A. Dacron strain capacity decreased after exposure to A (50%, 75%, 100%) and P (6%, 9%). Scanning electron microscope of both P and A showed significant degradation. No changes were found in the Gore-Tex group after exposure to P or A, however, scanning electron microscope of the 100% A sample showed moderate fiber degradation. The study shows that Dacron woven grafts are degraded by concentrations of A of at least 50%, and to a lesser extent, concentrations of at least 6%, while Gore-Tex had only minimal changes. While neurolytic block offers distinct advantages in patients with terminal cancer pain, the findings suggest that the use of more conservative modalities, such as oral medication regimens, be considered for the treatment of intractable pain in patients with vascular prosthetic grafts that are proximate to the proposed site of neurolysis.

Effects of angiotensin converting enzyme inhibition with cilazapril on intimal hyperplasia in injured arteries and vascular grafts in the baboon.

To determine the importance of angiotensin converting enzyme (ACE) activity in the development of arterial proliferative lesions in a primate model, the response to vascular injury was studied in five baboons treated with oral cilazapril (20 mg/kg/day) and in five untreated control animals. Each animal underwent three procedures: 1) carotid artery endarterectomy, 2) balloon catheter deendothelialization of the superficial femoral artery, and 3) surgical placement of bilateral aorto-iliac expanded polytetrafluoroethylene (Gore-Tex) vascular grafts. Cilazapril therapy was initiated 1 week preoperatively and continued throughout the study interval. At 1 and 3 weeks postoperatively, plasma ACE activity was inhibited by more than 96% versus control values. After animals were killed at 3 months, injured vessel and graft segments were evaluated morphometrically. Although the response between animals was variable, average cross-sectional areas of neointima did not differ between the cilazapril-treated and control groups at sites of carotid endarterectomy (0.26 +/- 0.12 versus 0.34 +/- 0.17 mm2, respectively; p greater than 0.5), femoral artery ballooning (0.15 +/- 0.08 versus 0.11 +/- 0.01 mm2; p greater than 0.5), or at graft anastomoses (1.86 +/- 0.50 versus 1.72 +/- 0.50 mm2; p greater than 0.5). Thus, cilazapril did not reduce intimal thickening over 3 months in these primate arterial injury models. However, a possible beneficial effect of cilazapril, which might be apparent at earlier time points or with larger animal groups, cannot be excluded.

Reconstruction of Superior Vena Cava in Invasive Thymoma

Aggressive en-bloc resection of the superior vena cava was performed in a 50-year-old man who had superior vena caval syndrome caused by invasive thymoma. After the superior vena cava was resected, a Gore-Tex vascular graft was used to reconstruct the lower end of the right innominate vein and lower end of the superior vena cava. The patient was treated with postoperative radiotherapy to the mediastinum and has been asymptomatic for 14 months following surgery.

Salvage of chronically exposed Gore-Tex vascular access grafts in the hemodialysis patient.

Exposure and infection of a Gore-Tex vascular access graft often results in removal of the graft. Salvage of the graft is possible, however, with the use of well-vascularized muscle flaps. In 1982, Hodgkinson was the first to use a sublimis muscle flap to cover an exposed vascular access graft. We used the flexor carpi ulnaris and flexor digitorum superficialis to cover exposed Gore-Tex grafts in nine patients. The sublimis was used to cover distal graft exposures, and the longer flexor carpi ulnaris muscle was used to cover more proximal sites. Multiple exposures required both flaps or combinations of muscle flaps and local rotation flaps. Eight of nine chronically exposed grafts were salvaged using these techniques; a graft was removed from one patient because of diffuse unrecognized graft bed infection. Disability is minimized by using only part of the sublimis, and loss of the flexor carpi ulnaris is compensated by local muscles with similar actions. Vascular puncture can be continued during healing.

Salvage of Chronically Exposed Gore-Tex Vascular Access Grafts in the Hemodialysis Patient

Salvage of Chronically Exposed Gore-Tex Vascular Access Grafts in the Hemodialysis Patient

Aortocoronary Gore-Tex Graft: 18-Month Patency

Despite widespread success with Gore-Tex (polytetrafluoroethylene) vascular grafts in peripheral artery operations, very little use has been made of this material in aortocoronary bypasses. We present the case of a 61-year-old woman with a 6-month history of angina who was found to have no suitable saphenous vein available at operation and who therefore underwent Gore-Tex bypass grafting to the right coronary artery. Coronary angiograms made 6 months and 18 months postoperatively showed patency of the 6 mm Gore-Tex replacement graft as well as the internal mammary artery placed to the left anterior descending coronary artery. Although frequent follow-up and close observation are recommended in patients with aortocoronary Gore-Tex grafting, the unique design of this material has made it the best alternative for synthetic coronary bypass conduit in the absence of the saphenous veins, particularly when these veins are found to be inadequate only at the time of operation.

Aorta-coronary artery revascularization with an expanded polytetrafluoroethylene vascular graft

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.

Coronary bypass with Gore-Tex graft

The case is presented of a 68-year-old man who previously had undergone aorta-coronary bypass. During a 3 year interval the coronary disease progressed, so that a once insignification lesion necessitated reoperation. A Gore-Tex vascular graft was chosen as a substitute because of the lack of saphenous vein. Three months posoperatively the patient's recatheterization study showed patency of the Gore-Tex graft placed in the distal righ coronary artery, and there was a satisfactory clinical result. No anticoagulants have been given to the patient after the operation.