Long-term complication and patency rates of Vectra and IMPRA Carboflo vascular access grafts with aggressive monitoring, surveillance and endovascular management

The purpose of this study is to compare infection, pseudoaneurysm formation and patency rates during long-term follow-up of polyurethane and polytetrafluoroethylene (PTFE) vascular access grafts maintained with contemporary endovascular methods. During a 34-month period, 239 polyurethane and 125 carbon-impregnated PTFE vascular access grafts were placed in 324 consecutive patients. Thirty-six patients (9.9%) developed a pseudoaneurysm (anastomotic, n = 6 or at the needle-stick site, n = 30). An additional 19 patients (5.2%) required graft excision for infection. Three-year graft infection and pseudoaneurysm formation (at needle-stick site) rates were similar in polyurethane and PTFE grafts (11% versus 8%, P = 0.61, and 17% versus 23%, P = 0.72, respectively). Three-year secondary patency was better in polyurethane than PTFE grafts (69% versus 57%, respectively, P = 0.012). Straight upper arm polyurethane grafts had the best secondary patency (P = 0.001). Contemporary long-term secondary patency of vascular access grafts is satisfactory. Further follow-up is necessary to compare late infection and pseudoaneurysm formation rates.     

Transluminal angioplasty of venous stenoses in polytetrafluoroethylene vascular access grafts

Since 1984, percutaneous transluminal angioplasty (PTA) utilizing high pressure balloon catheters has been used as an initial approach to restore patency of PTFE (polytetrafluoroethylene, GORE-TEX) hemodialysis vascular access grafts. Seventeen stenotic lesions detected by fistulogram underwent elective PTA. Twelve of these lesions were detected after thrombectomy and five were detected because of increased venous pressures during dialysis. Fourteen attempts at PTA were completely successful in restoring functional patency to the vascular graft. Three attempts were unsuccessful; two of these three grafts were subsequently repaired surgically. Venous stenoses that extended far greater than 6 cm were not considered for PTA. We conclude that PTA is a technique of promise in the non-surgical salvage of failing PTFE grafts. PTA can prolong the useful life of PTFE vascular access grafts and can be performed on an outpatient basis, eliminating the hospitalization that is usually required for surgical revision.     

Angiotensin converting enzyme inhibitors maintain polytetrafluroethylene graft patency.

BACKGROUND: A patent vascular access is crucial for hemodialysis patients. Stenosis and thrombosis lead to access failure. Endothelial injury via angiotensin II may mediate a hyperplastic and prothrombotic response. Thus angiotensin II inhibition with angiotensin-converting enzyme inhibitors (ACEI) may prolong vascular access patency. This study determines the impact of ACEI use on access patency in both polytetrafluroethylene (PTFE) grafts and fistulas. METHODS: Demographics, access history and medication use were reviewed in 266 accesses from four dialysis centres. Primary patency, date of surgery to date of first access failure, was determined. Excluded accesses had incomplete history or <30 day patency. Groups divided into ACEI and non-ACEI based on patient use of ACEI during access patency. Statistical methods included: unpaired Student t to compare continuous variables, Chi-square and Fisher's Exact test to compare proportions and evaluate for risk estimation, univariate and multivariate Cox regression to investigate variables associated with duration of access patency. Cox-adjusted survival and Hazard curves were obtained for significant variables. RESULTS: Non-ACEI (PTFE) graft group included more males and older patients; however, when these covariates were adjusted during both univariate and multivariate regression, suggested, only ACEI use was associated with greater access patency duration, 671.7 days (ACEI) vs 460.0 days (non-ACEI), p=0.012. ACEI group had fewer clotting events, 55% versus 71% (non-ACEI) group, p=0.042. ACEI use had little effect on primary patency of the fistula however male gender increased time to fistula failure, p=0.002. CONCLUSIONS: Retrospective evaluation suggests ACEI use in patients with PTFE grafts may prolong and maintain patency. Fistula patency is affected by gender with longer patency noted in males. Further prospective studies are necessary to confirm the role of ACEI in maintaining vascular access patency.     

The expanded polytetrafluoroethylene graft. Three years' experience with 362 grafts.

A total of 362 polytetrafluoroethylene (PTFE) grafts were implanted in patients as vascular substitutes in a variety of vascular reconstructive procedures. A total of 184 were used in femoropopliteal bypass operations. Cumulative patency rates showed 74% patency at the end of the first year of observation and 58% after two and three years. Seventeen grafts were used for femorotibial bypasses, with a cumulative patency rate of 40.4% after one year. Ninety-eight grafts were implanted in the upper or lower extremity to serve as vascular access for hemodialysis. For this group, the cumulative one-year patency rate was 83%. Sixty-three additional grafts were implanted in various other anatomic locations. Based on this experience, the PTFE graft seems to be a promising and versatile vascular prosthesis, although it should be used cautiously.     

An evaluation of expanded polytetrafluoroethylene (PTFE) loop grafts in the thigh as vascular access for haemodialysis in patients with access problems.

A total of 21 patients with vascular access problems received 22 PTFE loop grafts in the thigh as vascular access for haemodialysis. Eighteen of 22 grafts supported haemodialysis during the patients' lifetime. Actuarial patient survival was 50% at 2 years with a cumulative graft patency in the survivors of 80.5%. Although early thrombosis has been a problem, no graft has been lost from infection. We feel that these results are encouraging enough to recommend the use of PTFE grafts in the thigh of patients with vascular access problems.     

Long-term Follow-up of Polyurethane Vascular Grafts for Hemoaccess Bridge Fistulas

The new polyurethane vascular graft (PVG) has been reported to be better than the expanded polytetrafluoroethylene (PTFE) graft in terms of early access and prompt hemostasis, but long-term patency and safety of PVGs have not been investigated objectively. To evaluate late clinical outcome of the PVG, we compared the complication and patency rates of stretch PTFE grafts with those of PVGs implanted for hemodialysis vascular access. Subjects were 53 patients who received 58 arteriovenous grafts between October 1997 and July 2000. They were divided in a prospective fashion into two groups according to the type of implanted graft: PVG (n = 30) or PTFE (n = 28). The study group comprised 27 men and 31 women with a mean age of 61.7 ± 10.9 years (range: 23-84 years). The average number of previous accesses was 5.1 ± 3.1 (range: 0-12). There were no differences between the groups in term of age, sex, body surface area, etiology of renal disease, presence of diabetes, previous access procedures, anatomical positions of grafts, or mean follow-up period. Primary patency rates for the PVG and PTFE grafts were equivalent at 1 year (60.7% vs. 56.5%) and at 2 years (54.7% vs. 51.8%). Similarly, secondary patency rates for the two groups did not differ at 1 year (78.7% vs. 79.9%) or at 2 years (78.7% vs. 69.3%). These findings indicate that the PVG is an acceptable alternative to the PTFE graft for blood access.     

In vivo study of an elastomer end-coated polytetrafluoroethylene vascular prosthesis.

Polyurethane end-coated polytetrafluoroethylene (PTFE) grafts (elastomer PTFE grafts) were implanted in 12 female adult mongrel dogs to assess patency, intimalization, tissue incorporation, and technical suitability of the material as a vascular graft. Each dog had bilateral aortoiliac grafts placed, one a standard PTFE and the other an elastomer PTFE graft. The length of the grafts was 7-8 cm and the diameter was 6 mm. The grafts were harvested at intervals to 120 days postoperatively. The elastomer PTFE grafts showed superior longitudinal elasticity, retention of shape, and no graft tearing with suture tension; however, no significant difference in bleeding was noted at the anastomoses between the standard and elastomer PTFE grafts. Satisfactory patency was obtained with both standard (8/10) and elastomer PTFE grafts (9/10) at 90-120 days. No significant difference in the thickness of intima and the length of pannus ingrowth was noted between the standard and elastomer PTFE grafts. No outer tissue incorporation was seen at the elastomer-treated graft segments as opposed to the well-incorporated untreated segments. In conclusion, elastomer end-coating of a PTFE vascular prosthesis provided excellent handling characteristics without detracting from patency; however, the lack of outer tissue incorporation may be a potential disadvantage in its clinical use.     

POLYTETRAFLUOROETHYLENE (PTFE) GRAFTS FOR HAEMODIALYSIS IN CHRONIC RENAL FAILURE: ASSESSMENT OF DURABILITY AND FUNCTION AT THREE YEARS

The utilization of 162 PTFE grafts for anglo access in 131 patients over a three year period is reported. One hundred and three new PTFE arterlo-venous flstulae were constructed in addition to 59 patch and tube incorporations Into pre-existing graft flstulae. At three years, the cumulative patency of newly constructed grafts was 85%. Seventy four per cent of the grafts have had no thrombosis and are functioning up to 38 months following insertion. An aggressive approach was adopted towards the 15% of grafts that had at least one episode of thrombosis prior to flow being successfully restored. Graft occlusion which occurred up to 18 months following Insertion, represented 11% of the group In this series. PTFE has provided an important advance In angio access for chronic renal failure with high patency and excellent durability after three years.     

Vascular access for hemodialysis. Patency rates and results of revision.

Over a 4-year interval, 324 arteriovenous conduits were created in 256 patients with end-stage renal disease as access for chronic hemodialysis. These included 154 Cimino fistulae, 163 polytetrafluoroethylene (PTFE) grafts, and seven miscellaneous grafts. Satisfactory patency rates were demonstrated for as long as 4 years for both Cimino fistulae and PTFE grafts by life-table analysis. Failures of Cimino fistulae usually occurred early in the postoperative period, secondary to attempts to use inadequate veins. Thrombosis caused the majority of PTFE graft failures and was generally the result of venous stenosis. Correction of such venous stenosis is mandatory to restore graft patency and can result in prolonged graft survival.     

Use of short PTFE segments (<6 cm) compares favorably with pure autologous repair in failing or thrombosed native arteriovenous fistulas

OBJECTIVE: The re-establishment of patency in a stenosed or thrombosed native arteriovenous fistula (AVF) is fundamental to regaining adequate hemodialysis through the same cannulable vein. Many surgeons have been reluctant to use even small segments of synthetic grafts in AVF revisions because of a perception that these would lead to poor results; however, studies comparing various treatment options are scarce. This study compared the use of short (<6 cm) polytetrafluoroethylene (PTFE) segments with pure autologous repair in stenosed or thrombosed native fistulas. METHODS: The cumulative postintervention primary patency rates of two groups of hemodialysis patients receiving different surgical revision operations of their vascular accesses were prospectively compared. Group I (n = 30) comprised patients who presented with stenosed or thrombosed native fistulas and received short (2 to 6 cm) interposition PTFE grafts placed after the stenosed or thrombosed outflow vein segment was resected. These short PTFE grafts were not used for cannulation. Group II (n = 29) comprised patients who presented with dysfunctional or failed AVFs and underwent various types of pure autogenous corrections. AVF dysfunction or thrombosis was detected with clinical examination and color duplex ultrasound scanning. In all cases, on-table arteriography-fistulography was performed before surgical repair. Access adequacy was assessed in all patients postoperatively after the first puncture and every month thereafter (mean follow up 16.7 months). RESULTS: No statistically significant difference in patency was observed between the two groups. Postintervention cumulative patencies were 100%, 88%, and 82% for group I and 90%, 82%, and 71% for group II at 6, 12, and 18 months, respectively ( P = .8). CONCLUSIONS: Short (<6 cm) interposition PTFE segments used for the revision of failing or failed AVFs compare favorably to purely native repair and do not alter the autologous behavior of the initial access. These short PTFE revisions resulted in satisfactory midterm primary patency without further consumption of the venous capital by harvesting segments of vein from other locations and without compromising more proximal access sites. This practice is recommended and is justified as part of an aggressive access salvage policy addressed by many authors so far.     

Expanded polytetrafluoroethylene as dialysis access grafts: serial study of histology and fibrinolytic activity.

Expanded polytetrafluoroethylene (Gore-Tex) grafts were evaluated as hemodialysis access shunts. A serial study of cellular ingrowth and endothelialization was performed. The development of fibrinolytic activator was sequentially monitored and shown to be consistently higher in the Gore-Tex grafts than in either knitted or woven Dacron prostheses. Functional assessment by repeated needle puncture demonstrated that PTFE grafts were durable, had uniform patency (6 mm ID size) and showed no evidence of degeneration during the time limit of this study. Although these are favorable characteristics, further long-term evaluation of PTFE grafts is necessary before its role as a vascular prosthesis applicable to clinical practice, can be established.     

Heparin-bonded Dacron or polytetrafluoroethylene for femoropopliteal bypass grafting: a multicenter trial

BACKGROUND: Dacron (polyester fiber) was largely abandoned for femoropopliteal bypass grafts 30 years ago because saphenous vein achieved better patencies. However, in patients taking aspirin, patency in above-knee femoropopliteal bypass grafts has recently been shown to be equivalent to that with saphenous vein. We compared heparin-bonded Dacron (HBD) and polytetrafluoroethylene (PTFE) in a randomized multicenter trial including below-knee popliteal or tibioperoneal trunk bypass graft where the long saphenous vein was absent or inadequate. METHODS: Over 28 months, 209 patients undergoing femoropopliteal bypass grafts (180 above-knee, 29 below-knee) were randomized to HBD (n = 106) or PTFE (n = 103). Each patient was given aspirin (300 mg/d) before surgery, and this continued unless the patient had intolerance to the aspirin. RESULTS: The mean follow-up was 42 months (range, 28-55). Fifteen (7.1%) patients died with patent grafts, and three (1.4%) infected grafts were removed. Patency (measured with Kaplan-Meier survival analysis) at 1, 2, and 3 years for HBD was 70%, 63%, and 55% compared with 56%, 46%, and 42%, respectively, for PTFE (P =.044). A total of 67 secondary interventions were performed on 48 thrombosed grafts; long-term patency was achieved in only three. Risk factors for arterial disease did not significantly influence patency. Amputations have been performed in 23 patients, six after HBD and 17 after PTFE bypass grafts (P =.015). CONCLUSIONS: HBD achieved better patency than PTFE, which carried a high risk of subsequent amputation.     

Long-term patency rates, complications and cost-effectiveness of polytetrafluoroethylene (PTFE) grafts for hemodialysis access: a prospective study that compares Impra versus Gore-tex grafts.

Manufacturers of polytetraflouroethylene (PTFE) grafts used for chronic hemodialysis access describe specific advantages for their respective grafts, which presumably result in greater graft patency rates, reduced complications and decreased overall costs. There are few data available in the literature to support or contradict these alleged benefits. Therefore, this prospective study was undertaken to evaluate and compare patency rates, complications and costs between two of the leading brands of PTFE that are currently being marketed for use as hemodialysis access grafts. Totals of 190 primary PTFE grafts (100 Gore-tex (W. L. Gore and Associates, Flagstaff, AZ) and 90 Impra (C. R. Bard Inc., Tempe, AZ)) were implanted in 168 consecutive patients with end-stage renal disease. A policy of non-interventions was employed for patent grafts, as no attempt was made to assist primary patency. Grafts that occluded during follow-up underwent secondary revision to maintain patency. There was no difference in primary and secondary patency by life-table analysis between Gore-tex and Impra grafts at 2 years (P > 0.53 and P > 0.13, respectively). There was also no significant difference between Gore-tex and Impra in the number of days before the first thrombectomy or in the number of thrombectomies or revisions per graft (P > O.50). Likewise, the incidence of complications was similar between the two grafts. The cost of graft implantation and maintenance of patency was not significantly different between Gore-tex and Impra grafts. It is concluded that either graft can be used for hemodialysis access with similar expected outcomes for at least 2 years following implantation.     

Reduction of Vascular Intimal-Medial Hyperplasia in Polytetrafluoroethylene Arteriovenous Grafts via Expression of an Inhibitor of G Protein Signaling

Polytetrafluoroethylene (PTFE) arteriovenous (AV) grafts are performed routinely for vascular access. The limited life span of PTFE grafts is a major cause of morbidity. Graft failure is attributed to venous outflow tract vascular smooth muscle (VSM) hyperplasia, which is linked to heterotrimeric G protein signaling. We proposed that expression of a peptide inhibitor of G_βγ signaling (βARKct) in the venous outflow of PTFE grafts would reduce hyperplasia and prolong graft patency. Left carotid to right external jugular vein PTFE AV grafts were placed in swine. The isolated external jugular vein was treated with an adenovirus encoding βARKct, empty adenovirus, or phosphate-buffered saline for approximately 25 min. After 7 or 28 days, flow probe analysis was performed and the vein was harvested and analyzed for cross-sectional area comparison. After both 7 and 28 days, when compared to controls, treated animals demonstrated a statistically significant reduction in VSM hyperplasia with a reduction in cross-sectional intimal and medial areas of >40% (p < 0.05). Flow was maintained in treated grafts, while control groups demonstrated a >50% reduction (p < 0.05) at 7 days. Further, treated grafts demonstrated significant improvement in graft patency at 28 days (100% vs. 12% for treated and untreated grafts, respectively). The inhibition of G_βγ signaling reduces intimal-medial hyperplasia and prolongs graft patency in PTFE AV grafts. This represents a novel molecular therapeutic strategy for improving the patency of vascular access grafts.Part of this work was presented at the American Heart Association Annual Meeting, Chicago, IL, September 2002.     

Regular ultrasonographic screening significantly prolongs patency of PTFE grafts

BACKGROUND: Polytetrafluoroethylene (PTFE) dialysis grafts have considerably shorter patency than native arteriovenous fistulas, despite the use of a complex of screening monitoring methods (venous pressure, access flow). PTFE grafts are used often in subjects with depleted subcutaneous veins after previous abandoned accesses, so keeping the access patent is crucial. We hypothesized that regular duplex Doppler ultrasound screening for access stenoses, together with their sooner treatment, would prolong PTFE graft patency. METHODS: We performed a randomized, prospective study of PTFE grafts' cumulative patency in 192 subjects. In group 1, regular ultrasound examinations performed every 3 months was added to traditional screening (i.e., regular access examination at hemodialysis unit, monitoring of venous pressure and access flow). Group 2 was screened only traditionally (without ultrasound). Interventions of suspected stenoses were indicated by nephrologists, vascular surgeon, and, in group 1, also by ultrasonography. Classic ultrasound criteria for significant stenosis were used, even if the access flow had not been decreased. The mean follow-up lasted 392 +/- 430 days. RESULTS: Groups were similar with respect to age, gender, diabetes status, and number of previous abandoned accesses. Group 1 had significantly longer access patency (P < 0.001). Number of interventions per graft was 2.1 +/- 1.8 and 1.3 +/- 1.0 in group 1 and group 2. CONCLUSIONS: Regular screening duplex Doppler ultrasonography results in significantly longer PTFE graft patency due to early detection of access stenosis and, thus, more frequent elective interventions of access stenoses.     

Microsurgery in gaining paediatric vascular access for haemodialysis

One hundred and one surgical procedures performed in children for construction and maintenance of vascular accesses for haemodialysis were retrospectively analyzed. There were 86 operations performed to create a new fistula in patients without vascular access or with nonrecoverable failed angioaccess. Fifteen surgical procedures were performed to treat fistula complications. The new fistulas were radiocephalic n = 60 (70%), ulnar-basilic n = 5 (5.8%), antecubital n = 9 (10.3%), and PTFE grafts n = 12 (14%). Microsurgical techniques were used in all cases, including PTFE graft fistulas. A microscope was used in 56 cases (55.4%) and magnifying loupes (× 2.5 magnification) in the rest of the operations. Early-failure rate for radiocephalic fistulas was 10%. Cumulative patency rates in radiocephalic fistulas were 79%, 75%, and 70% at 1, 2, and 5 years, respectively. No statistical differences were found from the cumulative patency curve of 730 radial-cephalic fistulas performed in adults during the same period of time. Radiocephalic fistulas can be constructed in most paediatric cases using microsurgical technique. Elbow fistulas can be the second-choice vascular access, and PTFE grafts can be reserved for children with exhaustion of autologous veins. Brachial-jugular PTFE grafts can be used in cases of subclavian vein stenosis. © 1993 Wiley-Liss Inc.     

Lack of evidence for use of heparin-bonded grafts in access surgery: a meta-analysis

The aim of this study was to evaluate the efficacy of heparin-bonded vascular grafts to offer improved outcomes compared with standard prosthetic grafts in access surgery. A systematic review and meta-analysis was performed and eight studies (seven observational studies and one randomized controlled trial) were included. The pooled 6-month and 1-year primary patency was not significantly different between heparin-bonded arteriovenous (AV) grafts and standard prosthetic AV grafts in seven studies reporting on 1,209 access procedures. The assisted primary patency and secondary patency at 1-year was not significantly different either. Heparin-bonded AV grafts offer no distinct advantage over standard prosthetic AV grafts and their preferential use in access surgery cannot be recommended based on the available evidence.     

Comparison of polytetrafluoroethylene (PTFE) and dacron as long, small-diameter arterial grafts in dogs

A canine model in which joined carotid arteries were anastomosed to 6-mm grafts (average length, 45 cm) of polytetrafluoroethylene (PTFE) or Dacron double velour and the grafts were anastomosed to the ligated distal abdominal aorta was used to study long-term graft patency. The 16 dogs with PTFE grafts and the 15 dogs with Dacron grafts were sacrificed at three-, six-, and 12-month intervals, or whenever a graft occluded. At three months, eight of 11 PTFE and 11 of 11 Dacron grafts were patent; at six months, two of three PTFE and three of three Dacron grafts were patent; at 12 months, one of two PTFE grafts and the one remaining Dacron graft were patent. All grafts were examined grossly and microscopically. The PTFE grafts showed increasing degrees of calcification and intimal fibrin deposition; the Dacron grafts had no calcification and less intimal fibrin deposition. The model was satisfactory for studying long, small-diameter vascular grafts, but PTFE was not found to be superior to Dacron in this study.     

Difficult vascular access in patients with end-stage renal failure

BACKGROUND/AIM: End-stage renal failure patients requiring long-term hemodialysis need a durable vascular access. The arteriovenous fistula (AVF) with its long patency rate and low complication profile is usually the first choice for vascular access creation. However, when superficial veins are not suitable for AVF creation or all have been exhausted as a result of repeated AVF procedures, arteriovenous grafts (AVGs) using expanded polytetraflouroethylene (ePTFE) is an alternative. This study reviewed our experience in using PTFE AVGs for vascular access in patients requiring chronic hemodialysis. MATERIALS AND METHODS: In a prospective study, from September 2002 to October 2004, 21 PTFE AVGs were placed in 21 patients. We evaluated the complications and patency. RESULTS: There were 12 female and nine male patients of mean age 58+/-8.7 years (range=45 to 76 years). Nine patients (43%) had hypertensive nephrosclerosis, 6 (29%) diabetic, 2 (10%) glomerulonephritis, 3 (14%) systemic lupus erythematosis requiring long-term steroids, and 1 (4.7%) unknown cause. The patency rate at 24 months was 85.7%. Complications included graft thrombosis (three; 14.3%), wound infection (three; 14.3%) and graft infection (one; 4.8%). CONCLUSION: ePTFE AVGs offer reasonable patency and serviceability rates as a vascular access modality, but in view of their complication profile, the native vein arteriovenous fistula should continue to be the first choice for vascular access for patients requiring chronic hemodialysis.     

Evaluation of Gore-Tex graft patency in hemodialysis access

Aim: The purpose of this retrospective study was to analyze the patency and complications of Gore-Tex grafts used in hemodialysis (HD) access. Methods: In the last 16 years, 1649 surgical procedures were performed on 655 patients to ensure and maintain permanent HD access. The study group consisted of 64 HD patients on whom 81 vascular synthetic PTFE Gore-tex grafts were performed. There were 28 males and 36 females, 3 of them were children (4.7%). Mean age was 54.2 years (range 15-77). Two types of Gore-Tex prosthesis were used: Diastat and Stretch. All grafts were implanted in the upper extremities. Kaplan-Meier survival curves were calculated to determine primary and secondary patency. Log-rank analysis was used to determine differences between curves. Results: Primary and secondary patency at 12 months was 52.5% and 67.5%, and at 18 months respectively 41.5% and 58.2%. The Diastat graft had a lower primary and secondary patency compared with the Stretch graft (respectively p = 0.02 and p = 0.008). Factors such as gender, coexisting diabetes and hypertension did not determine graft patency. Thrombosis was one of the most frequent complications. The remaining complications included stenosis, pseudoaneurysms, infection, steal syndrome and seroma. Conclusion: On the basis of our experience Stretch grafts appear a better option for creating vascular access for HD than Diastat grafts.