ePTFE Grafts Research Articles

Matching the Diameter of ePTFE Bypass Prosthesis with a Native Artery Improves Neoendothelialization

Background and Aim: The undersizing of the bypass graft diameter compared to native artery changes blood flow characteristics and velocity which may affect conduit neo-endothelialization, intimal hyperplasia reaction and patency. The aim of this study was to evaluate conduit neoendothelialization, intimal hyperplasia reaction and patency results between undersized and matched ePTFE grafts. Material and Methods: In 16 male Sprague-Dawley rats, undersized (1-mm internal diameter) and matched (2-mm internal diameter) ePTFE grafts were anastomosed end-to-end in the infrarenal abdominal aorta. Blood flow volume per minute was measured and wall shear stress was calculated for each group. After 3 weeks of follow-up, angiography was performed via the left carotid artery just before sacrifice. Conduit neoendothelialization and intimal hyperplasia reaction were measured by computer-assisted morphometry. Results: Wall shear stress was 8 times higher for the undersized group (840.56 vs. 105.07 mPa). Three weeks after implantation, conduit neoendothelialization was better in matched grafts compared to undersized grafts (441 vs. 574 µm, p = 0.008). Intimal hyperplasia reaction was similar for both groups (8.7 vs. 6.7 µm²/µm for undersized and matched grafts, respectively). Patency rate was 7/8 for undersized and 8/8 for matched ePTFE grafts. Conclusion: Although the graft patency and the intimal hyperplasia reaction were not different between the two groups after 3 weeks, matched grafts had a significantly better endothelialization compared to undersized grafts. This short-term beneficial effect may influence long-term patency results.

Reduced Burst Release from ePTFE Grafts: A New Coating Method for Controlled Drug Release

Hemodialysis graft coated with paclitaxel prevents stenosis; however, large initial burst release of paclitaxel causes many negative effects such as drug toxicity and inefficient drug loss. Therefore we developed and tested a novel coating method, double dipping, to provide controlled and sustained release of paclitaxel locally. Expanded polytetrafluoroethylene (ePTFE) grafts were dipped twice into a solution of several different paclitaxel concentrations. In vitro release tests of the double dipping method showed that early burst release could be somewhat retarded and followed by sustained release for a long time. We observed the effect of paclitaxel coating by double dipping in porcine model of arterio-venous (AV) grafts between the common carotid artery and the external jugular vein. 12 weeks after constructing AV grafts, cross sections of the graft venous anastomosis were obtained and analyzed. Paclitaxel coated ePTFE grafts by double dipping were observed to prevent neointimal hyperplasia and therefore reduced stenosis of the arteriovenous hemodialysis grafts, especially at the graft venous anastomosis sites. Our results demonstrate that second dipping of ePTFE graft, which was already coated once with paclitaxel, washes off the drug on a surface of the graft and affects the ratio of paclitaxel on the surface to that of the inner space, possibly by diffusion: thus the early burst of drug can be somewhat reduced.

Inhibition of experimental neointimal hyperplasia by recombinant human thrombomodulin coated ePTFE stent grafts

The goal of this study was to evaluate the ability of recombinant human thrombomodulin (rTM) to inhibit neointimal hyperplasia when bound to expanded polytetrafluoroethylene (ePTFE) stent grafts placed in a porcine balloon injured carotid artery model. The left carotid artery of male pigs, weighing 25 to 30 Kg, was injured with an angioplasty balloon. Two weeks later either a non-coated standard ePTFE stent graft (Viabahn, 6 x 25 mm, W. L. Gore & Associates) or a rTM coated stent graft was implanted into the balloon-injured segment using an endovascular technique. Carotid angiography was performed at the time of the balloon injury, two weeks later and then at 4 weeks to assess the degree of luminal stenosis. One month after stent graft deployment, the grafts were explanted following in situ perfusion fixation for histological analysis. The specimens were then cross-sectioned into proximal, middle and distal segments, and the residual arterial lumen and intimal to media (I/M) ratios were calculated with computerized planimetry. rTM binding onto ePTFE-grafts was confirmed by functional activation of protein C and histopathology with immuno-scanning electron microscopy, backscatter electron emission imaging and x-ray microanalysis. All seven of the rTM coated stent grafts and six of the seven uncoated stent grafts were patent at the time of explantation. The mean luminal diameter of the rTM coated stents was 93% +/- 2.0% of the original diameter, compared with 67% +/- 23% (P = .006) in the control group. Histological analysis demonstrated that the area obliterated by intimal hyperplasia at the proximal portion of the rTM stent was -27% compared with the control group: (2.73 +/- 0.69 mm(2), vs 3.47 +/- 0.67 mm(2), P <.05). Neointimal hyperplasia is significantly inhibited in ePTFE stent grafts coated with rTM compared with uncoated grafts, as documented by improved luminal diameter by angiography and by computerized planimetry measurements of residual lumen area. These findings suggest that binding of recombinant human thrombomodulin onto ePTFE grafts may improve the long-term patency of covered stents grafts. Decrease of neointimal hyperplasia of the magnitude observed in this study could significantly improve blood flow and patency of small caliber prosthetic grafts. If the durability of these results can be confirmed by long-term studies, this technique may prove useful in preventing graft stenosis and arterial thrombosis following angioplasty or vascular bypass procedures.

QS364. Longterm Outcome of a Cuffed Expanded PTFE Graft for Hemodialysis Vascular Access

Introduction: Development of venous outflow stenosis has been a major obstacle in maintaining the patency of dialysis vascular grafts. In the current study, we retrospectively analyzed the long-term results of cuffed expanded polytetrafluoroethylene (ePTFE) and non-cuffed (standard) ePTFE grafts placed for hemodialysis access. Methods: A total of 67 patients who underwent placement of either cuffed (n=41) or standard (n=26) ePTFE grafts were retrospectively analyzed. There were no significant differences between the two groups in their age, gender, cause of ESRD and anatomic placement of the graft.

Benign superior vena cava syndrome: Stenting is now the first line of treatment

Endovascular repair (EVR) is emerging as first-line treatment for patients with superior vena cava (SVC) syndrome of benign etiology, but data on its durability remain scarce. The aims of this study were to assess the efficacy and durability of EVR and compare results of EVR with open surgical reconstruction (OSR). Data from 70 consecutive patients undergoing treatment for benign SVC syndrome between November 1983 and November 2006 were retrospectively reviewed. There were 30 males and 40 females (mean age, 41 years; range, 5-75 years). Etiology included indwelling catheters or pacemaker wires in 35 patients, mediastinal fibrosis in 31, idiopathic thrombosis in 2, hypercoagulable disorder in 1, and postsurgical thrombosis in 1. In 42 patients, OSR was done through a median sternotomy: repair was with spiral saphenous vein in 22, expanded polytetrafluoroethylene (ePTFE) in 13, femoral vein grafts in 6, and human allograft in 1. Fifteen OSRs followed failed EVR interventions. EVR was attempted in 32 patients and was successful in 28 (88%): 19 had stenting, 14 had percutaneous transluminal balloon angioplasty (PTA), 2 had thrombolytic therapy with PTA, and 3 had stenting. All four technical failures subsequently underwent OSR. There were no early deaths in either group. Periprocedural morbidity was 19% after OSR and 4% in the EVR group. Six early surgical graft failures were successfully treated with surgical revision; one restenosis after EVR was restented. During a mean follow-up of 4.1 years (range, 0.1-17.5 years) after OSR, 11 patients underwent 18 secondary interventions. Mean follow-up after EVR was 2.2 years (range, 0.2-6.4 years), and nine patients underwent 21 secondary EVR interventions. Primary, assisted primary, and secondary patency rates of surgical bypass grafts were, respectively, 45%, 68%, and 75% at 3 and 5 years. Primary, assisted primary and secondary patency rates after EVR were 44%, 96%, and 96% at 3 years. Assisted primary patency was significantly higher in vein grafts than in ePTFE grafts (P = .05). Assisted primary and secondary patency was significantly higher in patients undergoing stenting compared with PTA (P = .02). At last follow-up, 93% of patients in both OSR and EVR groups had significant relief from symptoms. OSR of benign SVC syndrome is effective, with durable long-term relief from symptoms. EVR is less invasive but equally effective in the mid-term, albeit at the cost of multiple secondary interventions, and is an appropriate primary treatment for benign SVC syndrome. OSR remains an excellent choice for patients who are not suitable for EVR or in whom the EVR fails.

A heparin-bonded vascular graft generates no systemic effect on markers of hemostasis activation or detectable heparin-induced thrombocytopenia–associated antibodies in humans

Almost a third of patients who undergo peripheral bypass procedures do not have suitable veins, making the use of prosthetic materials necessary. Prosthetic materials can cause platelet adhesion and activation of the coagulation cascade on the graft. One potential strategy to reduce this thrombogenicity is to covalently bind heparin to the endoluminal surface of grafts. This human in vivo study examined systemic effects of the endoluminal heparin and addressed whether graft implantation results in (1) a measurable reduction of systemic markers of hemostasis activation compared with control grafts and (2) antibody formation against heparin, potentially responsible for heparin-induced thrombocytopenia (HIT). The study included 20 patients undergoing femoropopliteal bypass grafting, of whom 10 received a standard Gore-Tex Thin Walled Stretch Vascular Graft (W. L. Gore & Associates, Flagstaff, Ariz) and 10 received a heparin-bonded expanded polytetrafluoroethylene (ePTFE) graft (Gore-Tex Propaten Vascular Graft). Blood samples were drawn before and directly after the operation and at days 1, 3, 5, and week 6 after surgery. Established markers of in vivo activation of platelets and blood coagulation (prothrombin fragment 1+2, fibrinopeptide A, soluble glycoprotein V, thrombin-antithrombin complexes, and D-dimers) were measured using standard commercially available techniques. Antiplatelet factor 4/heparin antibody titers were measured using a commercially available enzyme-linked immunosorbent assay, and platelet counts were determined. No statistical differences were observed in any of the markers of in vivo activation of platelets and blood coagulation between patients receiving Propaten or control ePTFE. Moreover, no antibodies against heparin could be demonstrated up to 6 weeks after implantation. No measurable effect of heparin immobilization on systemic markers of hemostasis was found using a heparin-bonded ePTFE graft in vivo. Also, no antibodies against heparin could be detected up to 6 weeks after implantation.

Sutureless nonocclusive bypass surgery in combination with an expanded polytetrafluoroethylene graft

Cerebral aneurysms that cannot be treated by clip or coil placement can be treated with high-flow bypass surgery using techniques such as the excimer laser-assisted nonocclusive anastomosis (ELANA). To simplify the technique, a sutureless ELANA (SELANA) was developed in combination with an expanded polytetrafluoroethylene (ePTFE) graft. In 18 rabbits a bypass was constructed on the abdominal aorta using the SELANA technique with an ePTFE graft, resulting in 18 bypasses and 36 anastomoses. Short-term effects were analyzed in the first 2 weeks and at 2 and 3 months after the procedure. Patency was evaluated using quantitative ultrasound flowmetry. The anastomotic sites were studied using scanning electron microscopy. Construction of the bypass using the SELANA technique was easier and faster (15-25 minutes) compared with bypasses made with the ELANA technique (> 90 minutes). At the end of follow-up, 16 of 18 bypasses were patent. Of 36 SELANA anastomoses, 32 could be completed without short temporary occlusion of the recipient vessel. Scanning electron microscopy showed complete coverage of all anastomoses with neointimal repair tissue after 10 days. The SELANA technique provides further advantages over the conventional ELANA technique in ease of use and shortening of procedure time. The patency rate in this series was 89% and neointima repair tissue at the anastomosis site was complete after 10 days. Further experimental studies of the long-term patency and safety of this technique are necessary before clinical application.

Bilateral Persistent Sciatic Arteries Complicated with Acute Left Lower Limb Ischemia

Persistent sciatic artery (PSA) is a rare congenital malformation. In the early embryonic stage, the sciatic artery is the major blood supply for the lower limb bulb and is later replaced by the iliofemoral artery as the limb develops. Its failure to regress, sometimes associated with femoral arterial hypoplasia, and therefore becoming the dominant inflow to the lower extremity is called PSA. This anomaly is often associated with a higher rate of aneurysm formation or thromboembolic complications causing lower extremity ischemia. Here, we describe a 79-year-old male patient who presented with acute left lower extremity ischemia. He was treated initially with conventional embolectomy through inguinal and popliteal incisions. The bilateral PSA with thrombosed aneurysms was not identified at first on computed tomographic angiography. It was later diagnosed intraoperatively due to the discontinuity of the superficial femoral artery and popliteal artery found with embolectomy catheter, and was managed successfully with ePTFE graft bypass. Careful interpretation of the imaging study may be helpful in preoperative diagnosis.

Lower Limb Revascularization with a New Bioactive Prosthetic Graft: Early and Late Results

The aim of the study was to evaluate the immediate and long-term results of femoropopliteal bypasses performed with a new bioactive heparin-treated expanded polytetrafluoroethylene (ePTFE) graft in a single-center experience. From March 2002 to April 2006, 51 patients underwent lower limb revascularization with a new bioactive ePTFE prosthetic graft with covalent end-point attachment of heparin to the graft surface. Data concerning preoperative assessment, intraoperative strategy, drug administration, and follow-up surveillance program were prospectively collected in a dedicated database; early results were analyzed in terms of graft patency, amputation rate, and deaths. Follow-up consisted of clinical and duplex scan examination at 1, 6, and 12 months and yearly thereafter. Midterm results in terms of primary and secondary patency, limb salvage, and survival were analyzed. Patients were predominantly male (35 patients, 71%), with a mean age of 71 years (SD = 9.05). Indications for surgical revascularization were critical limb ischemia in 36 patients and severe intermittent claudication in 15 patients. Interventions were performed for occlusion of a native vessel in 35 cases, whereas 12 patients had late thrombosis of a femoropopliteal bypass; the remaining four patients were operated on for an occluded popliteal artery aneurysm. Intervention consisted of below-knee bypass in 34 patients, while the other 17 had an above-knee revascularization. No perioperative deaths occurred. Cumulative 30-day graft patency was 88%, with an amputation rate of 4% (two cases). Results were similar in above- and below-knee revascularizatons. Mean duration of follow-up was 18 months (SD = 7). Cumulative estimated 24-month survival and primary patency rates were 97% and 80.2%, respectively; the corresponding limb salvage rate was 85.7%. Long-term results did not significantly differ in above- and below-knee revascularizatons. In our experience, the use of a modified ePTFE graft with covalent end-point linkage of heparin molecules on the graft surface provides good early and midterm results, with low rates of graft thrombosis and amputation.

Abstract 2053: Biodegradable Small Calibre Polydioxanone-based Vascular Prostheses: Potential as Coronary Bypass Grafts

Aims : Shelf-ready synthetic small calibre prostheses are needed for coronary artery bypass grafting. Biodegradable scaffolds resistant to degradation-induced aneurysm formation in the systemic arterial circulation have been developed for in vivo vascular tissue engineering. We evaluated patency, biocompatibility and mechanical properties (remodelling) of 3 electrospun biodegradable random nano-fibre polymer prostheses: polydioxanone (PDO) alone; blended with: poly(lactic-acid) (PDO-PLA); with polycaprolactone (PDO-PCL). Methods: In 30 anaesthetised Sprague Dawley rats, 2mm ePTFE grafts controls(n=9), PDO(n=3), PDO-PLA(n=9), PDO-PCL(n=9), were interposed in the infrarenal abdominal aorta and followed for 3, 6 and 12 weeks. Digital substraction angiography was made for patency, stenosis and aneurysmal dilatation before euthanasia. Grafts were harvested for SEM, histology and computed morphometry for assessment of neo-endothelialisation and intimal hyperplasia. Results: Patency rates were excellent for all grafts (100%) and no relevant stenoses were found. Angiography follow-up showed aneurysmal formation for all PDO-alone grafts at 3 weeks (therefore no further implantations were made) and 1/3 for PDO-PLA at 6 and 12 weeks. No aneurysms were found for PDO-PCL grafts. All PDO-based grafts show slow degradation, a significantly better neoendothelialisation and insignificant neointimal formation compared to ePTFE. Conclusion(s): Patency of electrospun biodegradable PDO-based prostheses is excellent. Using slow, biodegrading polymer blends, e.g. PDO-PCL can avoid aneurysm formation and the neoendothelialisation (blood compatibility) of such prostheses is significantly better compared to ePTFE. Therefore, biodegradable, electrospun PDO-based vascular prostheses may be a promising alternative as shelf-ready cardiopulmonary bypass grafts. RESULTS AFTER 12 WEEKS IMPLANTATION:

Repairing Large Duodenal Injuries in Dogs by Expanded Polytetrafluoroethylene Patch

One of the most challenging problems in clinical surgery is management of injured duodenum. In this experimental study, we treated large duodenal defects by an expanded polytetrafluoroethylene (ePTFE, Gore-Tex; W.L. Gore, Elkton, MD) soft-tissue patch and compared it with the jejunal serosal patch. A duodenal defect (about 50% of the total circumference) was created in the second portion of the duodenum in 20 dogs. The effectiveness and gross and histological examinations of the ePTFE patch technique was compared with the jejunal serosal patch. No significant difference was found in early survival rates (90.9% versus 88.9%; P = 0.711). The whole grafted area was covered by neomucosa at the end of the sixth week in all animals with the ePTFE patch. The scar was small; no significant narrowing of lumen was noted and serosal healing was uniformly complete. In histological examination, complete coverage of the ePTFE grafts by neomucosa consisting of columnar epithelium with short villous formations was observed. Use of the ePTFE patch method is easy, reliable, and comparable to the jejunal serosal patch. It can be used in the treatment of large duodenal defects, which cannot be repaired by duodenorraphy.

Aspirin

Dependence on an expanded polytetrafluoroethylene graft for provision of pulmonary blood flow is a common yet precarious interval through which a population of patients with congenital heart disease must pass. The goals of the systemic-to–pulmonary artery shunt are to relieve cyanosis and to provide time before establishing in-series circulation by either complete repair of 2-ventricle lesions or, in the case of the single-ventricle patient, a bidirectional Glenn shunt. In the case of patients with single-ventricle anatomy, this period of parallel circulation is necessary to permit the lung maturation and the reduction in pulmonary vascular resistance that are necessary for subsequent palliation. For patients who will ultimately achieve a 2-ventricle repair, the goals of a preliminary shunt may include increasing the size of the pulmonary artery size or having a larger, older patient at the time of repair. This period of parallel circulation is tenuous, and the patient remains at increased risk during this period of altered circulation. Article p 293

Use of a Bifurcated ePTFE Graft for Off-Pump Extracardiac Fontan Completion

A 6-year-old girl underwent off-pump extracardiac Fontan completion. Intrapericardial inferior caval vein was found to be accompanied by the hepatic vein on the left side; a 20 x 10 x 10-mm bifurcated ePTFE graft was used without external shunting. This approach is practical for the surgeons and may result in lower perioperative Fontan pressures/transpulmonary gradients as well as a shorter intubation period and hospital stay.

Use of Stretch Expanded Polytetrafluoroethylene as a Microvascular Graft in a Low-pressure Situation

Microvascular reconstruction is often limited by the availability and length of the pedicle. The harvesting of autologous vein grafts adds morbidity and may not provide a good match. Expanded polytetrafluoroethylene (ePTFE) grafts have been used routinely in macrovascular surgery. However, there are no conclusive data on the performance of small-diameter PTFE grafts for pedicle lengthening in free flaps in a low-pressure situation. In this study, we evaluated the efficacy of 3-mm diameter stretch ePTFE grafts to lengthen the venous pedicle of a free flap. Fifteen male New Zealand white rabbits were operated on under sterile conditions. Using an operating microscope, an epigastric flap was raised and the pedicle was exposed and dissected to its origin from the superficial femoral vessels. A segment of the vein of 1 cm to 3 cm was replaced with a stretch ePTFE graft. Microsurgical anastomoses were performed using 9-0 nylon sutures. Four weeks postoperatively, the flaps were raised again with the pedicles re-explored. The graft was then removed and examined histologically. All the grafts demonstrated immediate patency. There were no cases of flap loss on the control side at 4 weeks postoperatively. When re-explored, the patent ePTFE grafts appeared to be covered by connective tissue. Light microscopy showed neoendothelialization with fibrovascular in growth. From this study, we can conclude that 3-mm diameter stretch ePTFE grafts can be used successfully as an alternative to bridging autologous vein grafts in free-flap pedicles.

Persistent Sciatic Artery with Monoplegia in Right Lower Leg Without Vascular Complication Symptoms in an Obese Woman

A rare case of a persistent sciatic artery (PSA) in a patient with monoplegia of the right lower leg without vascular complication symptoms is presented. A 44-year-old nervous and obese woman was referred with monoplegia of the right lower extremity. She was referred with an impression of a peripheral neuropathy due to nerve compression by a large uterine cyst. This impression was derived from a computed tomography (CT) scan that had been performed at the referring hospital the day before. On admission to our hospital, we repeated the CT scan and also obtained angiography that demonstrated that the problem was due to a persistent sciatic artery (PSA). The cyst was proved not to compress any vessels or nerves. The PSA was an aneurysmal dilatation from the internal iliac artery to the popliteal artery. It intermittently compressed the sciatic nerve. A persistent sciatic artery was noted to be the dominant blood supply to the right lower extremity. A right ilio-popliteal artery bypass using a 6-mm ringed ePTFE graft was performed. After arterial reconstruction, she recovered completely.

Novel thromboresistant materials

The development of a clinically durable small-diameter vascular graft as well as permanently implantable biosensors and artificial organ systems that interface with blood, including the artificial heart, kidney, liver, and lung, remain limited by surface-induced thrombotic responses. Recent breakthroughs in materials science, along with a growing understanding of the molecular events that underlay thrombosis, has led to the design and clinical evaluation of a variety of biologically active coatings that inhibit components of the coagulation pathway and platelet responses by surface immobilization or controlled release of bioactive agents. This report reviews recent progress in generating synthetic thromboresistant surfaces that inhibit (1) protein and cell adsorption, (2) thrombin and fibrin formation, and (3) platelet activation and aggregation.

Secondary Endovascular Repair of a Reconstructed Superior Vena Cava in a Patient with a Malignant Thymic Epithelial Neoplasm

Thymic epithelial tumors can cause venous obstruction from compression or direct invasion of the superior vena cava (SVC) or the innominate veins. We report a case of a 40-year-old patient with a Masaoka stage III thymoma that resulted in obstruction of the left innominate vein and extrinsic compression of the SVC. All macroscopic tumors were resected together with ligation of the left innominate vein and reconstruction of the SVC with an ePTFE graft. Early graft thrombosis occurred in the first postoperative month with clinical signs of SVC syndrome. Endovascular repair was performed with the deployment of self-expanding nitinol stents, resulting in immediate relief of symptoms. The stented graft has remained patent for a follow-up period of 7 months.

New vessels: Vascular tissue engineering

The use of vascular bypass grafts in patients is not new. The high prevalence of atherosclerosis has seen them being used in the treatment of some of the 800 000 cases of myocardial infarction in the UK. So, is there a need for tissue-engineered blood vessels if there is a functional prosthetic alternative? While this may hold true for vessels with high-blood-flow rates1, the patency rates of poly(ethylene terephthalate) (Dacron®) and expanded polytetrafluoroethylene (ePTFE) grafts are less satisfactory at lower flow rates. Given the limitations with synthetic materials alone, a biological or bio-hybrid vascular prosthesis could provide us with the ideal blood-vessel substitute.

In vivo h-VEGF165 gene transfer improves early endothelialisation and patency in synthetic vascular grafts☆

Small-diameter synthetic vascular graft performance is inferior to autologous vein grafts. This study tested the hypotheses that local in vivo administration of plasmids encoding for human vascular endothelial growth factor (VEGF), or co-administration of plasmids encoding for human vascular endothelial growth factor/plasmids encoding for fibroblast growth factor-2 in the tissues surrounding a porous synthetic vascular graft would enhance graft endothelialisation and, consecutively, graft patency. First, optimal gene for small-diameter synthetic graft endothelialisation was studied in rat abdominal aorta model (n=132): plasmids encoding for human vascular endothelial growth factor; co-administration of plasmids encoding for human vascular endothelial growth factor/plasmids encoding for fibroblast growth factor-2; or control plasmids were injected around 60 microm ePTFE graft. Second, optimal small-diameter synthetic graft design for endothelialisation was explored in rabbit abdominal aorta model (n=90). Various ePTFE grafts or pre-clotted polyester grafts were used with/without plasmids encoding for human vascular endothelial growth factor. Third, clinically used medium-size synthetic grafts were investigated with/without plasmids encoding for human vascular endothelial growth factor in dog carotid (n=20) and femoral arteries (n=15). Endothelialisation was assessed in midgraft area with scanning electron microscopy. In rats, plasmids encoding for human vascular endothelial growth factor enhanced endothelialisation; whereas co-administration of plasmids encoding for human vascular endothelial growth factor/plasmids encoding for fibroblast growth factor-2 had worst outcome at 1 week (NS), 2 weeks (P=0.01) and 4 weeks (P=0.02). In rabbits, pre-clotted polyester grafts had a trend for faster endothelialisation than ePTFE grafts (P=0.08); whereas plasmids encoding for human vascular endothelial growth factor enhanced endothelialisation compared to controls at 2 weeks (P=0.06), however, the effect reversed at 4 weeks (P=0.03). In dogs, synthetic graft patency was improved by plasmids encoding for human vascular endothelial growth factor in femoral position (P=0.103); whereas all carotid grafts were patent at 6 weeks. Thus, these data suggested that endothelialisation was fastest in pre-clotted polyester grafts; and that local application of plasmids encoding for human vascular endothelial growth factor had a potential to improve early endothelialisation and patency in synthetic vascular grafts.

An artificial vascular graft is a useful interpositional material for drainage of the right anterior section in living donor liver transplantation

Congestion in the anterior section in a right liver (RL) without a middle hepatic vein (MHV) may lead to graft dysfunction. To solve this problem, an RL draining MHV branches with autologous or cryopreserved vessels can be introduced. However, these vessels are often unavailable, and their preparation is time-consuming. An expanded polytetrafluoroethylene (ePTFE) graft may be used for anterior section drainage. Between February and November 2005, 26 recipients underwent RL liver transplantation draining MHV branches with an ePTFE graft (group P). Twenty-six ePTFE grafts (6 or 7 mm in internal diameter) drained 35 MHV branches on the back table to the graft right hepatic vein or to the recipient's inferior vena cava. The patency of the ePTFE graft was checked with computed tomography scans of the liver. The outcome of group P was compared with those of an RL group with MHV (group M, n=17) and an RL group without reconstruction of MHV or its tributaries (group R, n=85). The 1-month and 4-month patency rates (PRs) of the ePTFE grafts were 80.8% (21/26) and 38.5% (10/26). All showing early obstruction of the ePTFE graft had congestion in the anterior section, but all showing late obstruction were asymptomatic. The 1-month PRs of group P were comparable to, but the 4-month PRs were lower than, those of group M (both 94.1%; P<0.05). However, 1-year patient and graft survival rates of group P (both 100%) were comparable to those of group M (94.1% and 100%) and better than those of group R (83.5% and 88.2%; P<0.05). In conclusion, the early PR of group P was good, and late obstruction of the ePTFE graft had no impact on congestion in the anterior section or patient survival. Therefore, an ePTFE graft may be a useful interposition material for anterior section drainage in RL transplantation without serious complications.