Comparison between externally stented and unstented PTFE vascular grafts

It has been suggested that external stenting of synthetic vascular prosthetic material may improve patency rates in the low flow situation or across joints. This study compared externally stented polytetrafluoroethylene (PTFE) vascular grafts placed across the hip joint in dogs with nonstented PTFE grafts in regard to patency. Twenty animals underwent bilateral common iliac to common femoral artery bypass with proximal ligation of the femoral artery. In each animal one groin was randomly assigned to receive stented PTFE and the other nonstented PTFE. One animal was sacrificed at 2 weeks for graft infection. Nineteen animals received 38 grafts that remained in place 90-120 days. Patency was confirmed with angiography prior to sacrifice. Overall patency was 65 per cent with no significant difference between the two types of graft. Eighteen of 19 dogs (95%) had both the stented and nonstented PTFE grafts either open or closed. It is concluded that intrinsic factors, rather than external graft support, are a more important influence on graft patency in this model.     

Composite porosity of expanded polytetrafluoroethylene vascular prosthesis

Polytetrafluoroethylene (PTFE) prostheses were modified to produce two types of composite porosity PTFE grafts: type I — inner 60 μm/outer 20 μm and type II — inner 20 μm/outer 60 μm. These composite porosity PTFE designs were investigated for bleed through, graft healing and patency and compared with high porosity PTFE (60 μm) and standard PTFE (20 μm) grafts. The grafts were implanted into the carotid and femoral arteries of dogs and retrieved after 4, 12 and 18 weeks. Both composite porosity grafts showed significantly less bleed through than standard and high porosity grafts after reperfusion. In composite grafts, the 60-μm layer allowed fibrovascular tissue and histiocyte ingrowth from perigraft tissue, but the 20-μm layer did not. Neointima formation occurred earlier and endothelialization was more extensive in high porosity grafts, but seroma formation occurred in 25% of cases. In type I composite porosity grafts, smooth muscle cells of neointima migrated into the pores of the graft, providing a firmly anchored intima. Type II composite porosity grafts allowed better ingrowth of fibrovascular tissue at the outer layer from the perigraft tissue; however, endothelialization was not completed. Composite porosity grafts should be considered for evaluation in specific clinical situations.     

Fluoropolymer-coated dacron versus PTFE grafts for femorofemoral crossover bypass: randomised trial.

OBJECTIVES: To investigate whether patency of a thin walled 8 mm fluoropassivated Dacron graft was similar to that of a standard 8mm PTFE graft for femorofemoral crossover bypass surgery. DESIGN: A randomised multicentre clinical trial comparing two vascular grafts with participation of 10 departments of vascular surgery in Denmark, Sweden and Norway. PATIENTS AND METHODS: 198 patients were randomised to PTFE (n=107) or fluoropolymer-coated Dacron grafts (n=91), 63% underwent surgery for claudication, 27% for ischaemic rest pain and 10% for tissue loss. The median follow-up time was 24 months (IQR 19-26 months). RESULTS: The primary patency rate of the two grafts was similar (log rank test: p=0.35). The primary patency rates (95% CI) for coated Dacron and PTFE grafts were 92% (86-98) and 94% (89-99) at 12 months and 87% (74-95) and 93% (87-99) at 24 months, respectively. CONCLUSION: In patients with unilateral iliac artery disease not amenable to angioplasty, the femoral-femoral bypass is durable and effective. No difference in patency was found between the two graft materials (fluoropolymer coated Dacron and PTFE).     

Effects of omega-3 fatty acid supplementation on vascular access thrombosis in polytetrafluorethylene grafts.

OBJECTIVE: The purpose of this study was to investigate the effects of orally administered over-the-counter omega-3 (n-3) fatty acid supplements on primary patency of polytetrafluoroethylene (PTFE) grafts. DESIGN: This study was conducted with a triple-blind, permuted-block, randomized, placebo-controlled experimental design. SETTING: Dialysis clinics with patients who, in accordance with physician diagnosis, needed a new PTFE graft. PATIENTS AND OTHER PARTICIPANTS: Patients on long-term hemodialysis with newly placed PTFE grafts who were unable to receive a native arteriovenous fistula. INTERVENTION: Patients were followed prospectively for 8 months after they had been placed into an n-3 fatty acid or control group and were monitored for primary patency. MAIN OUTCOME VARIABLE: Primary patency of the PTFE graft. RESULTS: The n-3 fatty acid group had a mean PTFE graft primary patency rate of 254.2 days (SEM = 51.8), and the control group had a mean PTFE graft primary patency rate of 254.1 days (SEM = 34.6), revealing no significant difference in survival time between groups. CONCLUSIONS: No significant differences in primary patency rates were noted in the experimental and control groups.     

A small arterial substitute: expanded microporous polytetrafluoroethylene: patency versus porosity.

Eighty-nine grafts of expanded microporous polytetrafluoroethylene (PTFE) with a diameter of 4 mm, were placed in the carotid and femoral arteries of dogs. The animals were sacrificed at varying intervals beginning three days after operation. Four animals remain alive with patent grafts 10 months post-operatively. Twenty-four of 89 grafts were occluded, an overall patency of 73%. Fibril length (pore size) of the graft material was varied from 4 to 110 microns. Average pore size ranged from 9 to 65 microns. Wall thickness varied from 0.3 to 0.75 mm. Density ranged from 0.24 to 0.35 g/ml. Tissue ingrowth, neointimization and patency rate as compared to pore size, wall-thickness and density of expanded PTFE were observed. Pore size is the primary determinant of tissue ingrowth, neointimization and patency. Of 51 grafts with an average pore size of 22 microns or less, there were 6 occlusions, an 88% patency rate. There were 38 grafts with an average pore size of 34 microns or greater. In these 38 grafts, 18 occlusions were observed, a 53% patency rate. Patent grafts demonstrated tissue ingrowth, capillary formation an a thin neointima. Using small pore grafts, patency rates of 90% can be anticipated in the dog. Expanded microporous PTFE with its ease of handling, strength and pliability may be the vascular prosthesis of choice in man.     

Small-caliber Mesothelial Cell–layered Polytetraflouroethylene Vascular Grafts in New Zealand White Rabbits

Reduction in the thrombogenicity of small-caliber synthetic vascular grafts by lining them with mesothelial cell has been suggested as a method to reduce thrombosis. The purpose of this research is to determine whether creation of a mesothelial lining on the inner surface of a synthetic vascular graft would improve the patency rate of a small-caliber vascular grafts. Carotid interposition grafting was performed using mesothelial-lined grafts (MLG) in 30 New Zealand rabbits and compared with similar carotid interposition grafts using non-mesothelial-lined grafts (NLG) on the contralateral side. The mesothelial lining was created by suturing a piece of harvested peritoneum with the visceral surface toward the lumen onto a 2-mm polytetraflouroethylene (PTFE) graft. Graft patency was studied by in vivo Doppler. In vitro evaluations were done with hematoxylin-eosin stains, broadband cytokeratin staining, and monoclonal antibodies for macrophages. Explanation of the grafts was done in terminal operation at 7, 14, and 21 days. The MLG showed progressive fibroblastic proliferation in direct proportion to the age of the graft, but this did not lead to graft occlusion. However, a significant number of NLG were not patent at each time period studied. We concluded that mesothelial cell lining of small-caliber PTFE grafts could enhance the short-term patency more than using the PTFE without the mesothelial lining. The use of such hybrid small-caliber grafts has a potential for improving the patency of these artificial vascular graft substitutes.     

The use of long synthetic microvascular grafts to vascularise free flaps in rabbits

A 5 cm length of 2 mm internal diameter (i.d.) synthetic, expanded polytetrafluoroethylene (PTFE, or Gore-Tex) vascular graft was used to connect 25 rabbit inferior epigastric flaps to the contralateral femoral vessels. In 15 animals an expanded PTFE graft connected the opposite femoral artery to the flap while the ipsilateral venous drainage remained intact. In the remaining 10 animals an expanded PTFE graft was used to replace the venous drainage of the flap and connected to the opposite femoral vein while the ipsilateral femoral artery supplied the flap. Flap survival and graft patency were evaluated over 3 weeks. Ten of 15 flaps with intra-arterial grafts survived at 3 weeks (67%). Only 27% (4/15) of their supplying grafts remained patent for 3 weeks, although 67% (10/15) were patent at 10 days. All 10 flaps, where expanded PTFE grafts replaced venous outflow, failed within 36 hours. At exploration these grafts were thrombosed or collapsed. In conclusion, currently available 2 mm (i.d.) expanded PTFE vascular graft cannot maintain patency in a low blood flow circulation supplying an isolated free flap.     

In Vitro and In Vivo Evaluation of a Small Caliber Vascular Prosthesis Fixed with a Polyepoxy Compound

Abstract: A small caliber vascular prosthesis obtained from an ovine internal thoracic artery (3. 8–4. 5 mm ID) fixed with a polyepoxy compound and treated with heparin has been evaluated. Cytocompatibility was evaluated in vitro using human endothelial cells (HEC). HEC were obtained from human saphenous vein and cultivated in culture medium supplemented with 25% human serum. Graft segments were rinsed using a standard protocol proposed by the manufacturer. Tissue reaction was tested on a rabbit model of subcutaneous implantation. The patency rate and healing patterns were evaluated comparatively with polytetrafluorethylene (PTFE) 4 mm ID prosthesis in a canine model of carotid interposition. Cytocompatibility assay showed that there was low adhesion on vascular grafts (20 ± 2% of endothelial cells seeded) and no growth of HEC on the graft surface. The graft patency rate was 55% in both groups, and actuarial freedom from occlusion was not different at 3 months (37. 7 ± 15% in Denacol–fixed grafts versus 38. 1 ± 14% in PTFE). Histological studies on the biological grafts shows a frequent neointimal hyperplasia at the anastomosis (5/12), a lack of endothelial cells lining the graft surface, a good preservation of the media, and a moderate inflammatory response in the adventicia. The Denacolfixed graft has presented excellent surgical properties and preservation of the histological structure. Nevertheless, the patency rate was not improved when compared with the PTFE control graft.     

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.     

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.     

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.     

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.     

Endothelial cell seeding of a new PTFE vascular prosthesis

Previous attempts to line polytetrafluoroethylene (PTFE) prostheses with enzymatically derived endothelial cells have not been as successful as similar work with Dacron grafts because of the failure of such prostheses to develop a satisfactory subendothelium. This article reports our experience with a new, highly porous, unreinforced PTFE prosthesis that appears to circumvent this problem. Segments (4 mm I.D., 10 cm in length) of this new graft were implanted in 41 mongrel dogs as carotid interposition grafts. One graft in each dog was seeded with the dog's own endothelial cells, whereas the contralateral graft was treated in an identical fashion except for the inclusion of endothelium. After a mean period of 7 weeks of implantation, the grafts were harvested, their patencies were noted, the thrombus-free area of their luminal surface was calculated with computerized quantitative planimetry, and graft segments were submitted for scanning and transmission electron microscopy. In seven dogs the luminal surface was scraped from each graft and measured quantitatively. Although seeded grafts failed to show a statistically significant increase in patency during the short course of this experiment, a trend in that direction was quite striking. Furthermore, seeded grafts had a significant increase in thrombus-free area on their luminal surface as well as a significant reduction in the volume of luminal thrombus. Histologically, seeded grafts developed a substantial 75 to 100 microns cellular subendothelium beneath a confluent endothelial lining. No endothelial lining was noted in control grafts. We believe that the superior handling characteristics of this new prosthesis and its ability to develop a substantial subendothelium with a confluent endothelial lining suggest potential future applications and warrant further investigation.     

The reverse J arteriovenous graft configuration for hemodialysis access: rationale, technique, and outcomes

The long-term survival of patients on hemodialysis is often limited by the exhaustion of vascular access sites. A fundamental principle of vascular access surgery is that the arteriovenous (AV) access be placed as far distally in the arm as possible. This principle enhances the secondary patency of the AV grafts by preserving the proximal veins for AV graft revision and provides venous outflow for a new AV access to be placed more proximally in the extremity. The standard straight and looped AV graft configurations violate this principle by bypassing long segments of vein in the extremity that could be used for AV graft revision or new AV graft placement. We have developed a novel AV graft configuration that preserves venous outflow and enhances the longevity of each AV access site. The purpose of this review is to describe the reverse J AV graft technique and to report our outcomes with the procedure. Between February 2004 and April 2007, 26 AV grafts were placed using the reverse J configuration. Eighteen (69%) AV grafts were placed in the upper arm, 7 (27%) were placed in the forearm, and 1 (4%) was placed in the thigh. Median follow-up was 320 days. The secondary AV graft patency was 90 per cent at 6 months, 84 per cent at 12 months, and 84 per cent at 18 months. Five AV grafts were subsequently revised to a loop configuration. Overall patient survival was 85 per cent at 6 months, 68 per cent at 12 months, and 62 per cent at 18 months. Compared with the standard straight and looped AV graft configurations, the reverse J AV graft configuration preserves the length of venous outflow in the extremity for AV graft revision or new AV graft placement. Therefore, the reverse J configuration enhances the secondary patency of AV graft patency and AV access site longevity.     

The effect of preformed confluent endothelial cell monolayers on the patency and thrombogenicity of small calibre vascular grafts

Endothelial cell seeding has been proposed as a method to improve the patency rates in small calibre prosthetic vascular grafts. The seeding methods used at present leave much of the graft luminal surface devoid of endothelial cells and thus still significantly thrombogenic. We have developed a method to preform confluent endothelial cell monolayers, on the grafts prior to implantation, and this study investigates the effect of these monolayers on the early thrombogenicity and patency of polytetrafluoroethylene (PTFE) grafts. Small diameter PTFE grafts were seeded with canine endothelial cells obtained from the external jugular vein. Each of five dogs then received a graft seeded with its own cells and a contralateral, non-seeded control graft. At 1 and 10 weeks after graft implantation graft thrombogenicity was assessed by the use of Indium labelled platelets. The thrombogenicity index (TI) of each graft was determined from counts of gamma activity recorded over a period of 7 days. Grafts were subsequently removed at 12 weeks. At 1 week the mean TI for the seeded grafts was 0.123 (SD 0.019) and that for the controls 0.183 (SD 0.017) (p = 0.005). At 10 weeks only the seeded grafts could be assessed because all of the control grafts had occluded. At this point in time the seeded grafts had a mean TI of 0.159 (SD 0.011) (p = 0.047 vs. seeded at 1 week). By the time of removal at 12 weeks, all control grafts were occluded but only one of the seeded grafts had occluded (p = 0.025). In conclusion, the use of preformed, confluent endothelial cell monolayers for seeding prosthetic grafts significantly reduces the early graft thrombogenicity and improves graft patency. It does not, however, completely halt the increase in thrombogenicity which occurs during the early post-implantation period.     

Patency of polytetrafluoroethylene microarterial prostheses improved by ibuprofen

Because of the increasing need for a reliable prosthetic microvascular graft, we investigated the patency of expanded PTFE with and without platelet inhibitor medication as an arterial prosthesis (1 by 10 mm) placed in the aorta of the rat using standard microsurgical technique. In 10 animals without platelet-inhibitor medication, one graft (10 percent) was patent at 30 days. When the platelet inhibitor ibuprofen was given for the initial 15 days to 10 animals, all 10 grafts (100 percent) remained patent at 30 days without further use of the drug. There was a significant difference between the patency achieved with the drug and that obtained without it (p < 0.0001). The results of this experimental study demonstrate that expanded PTFE can successfully be used as a microvascular graft in the rat with excellent patency (100 percent at 30 days) when combined with ibuprofen therapy.     

Collagen versus gelatin-coated Dacron versus stretch polytetrafluoroethylene in abdominal aortic bifurcation graft surgery: results of a seven-year prospective, randomized multicenter trial

BACKGROUND: A prospective randomized multicenter trial was performed to compare knitted gelatin-coated Dacron bifurcation grafts, knitted collagen-coated Dacron grafts, and stretch polytetrafluoroethylene (PTFE) grafts. METHODS: Between 1991 and 1998, 315 elective patients were randomized by age, gender, diabetes, runoff, indication (aneurysm, aortoiliac occlusive disease), and nicotine consumption at 3 centers of vascular surgery in Austria. The patients received gelatin-coated Dacron (GEL-D) grafts (n = 109), collagen-coated Dacron (COL-D) grafts (n = 100), or stretch PTFE grafts (n = 106). RESULTS: No intraoperative deaths occurred. The 30-day mortality was 3%. No difference was found between the 3 graft materials in long-term patency. The primary 5-year patency rates were 92% for GEL-D, 89% for COL-D, and 91% for stretch PTFE (P =.6001). The secondary 5-year patency rates also differed: 97% for GEL-D, 100% for COL-D, and 97% for stretch PTFE (P =.2062). Early occlusions were observed overall in 3% and late occlusions in 5% of patients. When both Dacron grafts were compared collectively with stretch PTFE, a difference was found in infection rate: Dacron 3% (6/209) versus PTFE 0% (0/106); P <.03. CONCLUSIONS: The bifurcation grafts of all 3 materials were comparable in primary and secondary patency rates, incidence of false aneurysms, and rate of perioperative complications. Graft infections were confined to the 2 Dacron grafts and did not occur in stretch PTFE grafts.     

Results of bypasses to the anterior tibial artery through the interosseous membrane

The purpose of the present study was to retrospectively evaluate the results of anatomically tunneled grafts to the anterior tibial artery for distal revascularization in terms of patency and limb salvage rates as well as local morbidity, which can lengthen the postoperative hospital stay. Twenty-three patients received 24 bypasses to the anterior tibial artery, with grafts tunneled through the interosseous membrane. The mean age was 67 years; 10 patients were diabetic, 12 were smokers, 9 presented with significant coronary artery disease, and 2 with chronic renal insufficiency. The donor vessel was the common femoral artery in 17 cases, the superficial femoral artery in 4, and the infra-articular popliteal artery in 3. The graft material consisted in the reversed saphenous vein in 4 cases, the non-reversed devalvulated ex situ saphenous vein in 11, composite polytetrafluoroethylene (PTFE) + inversed saphenous vein in 6, and PTFE alone in 3 cases. No postoperative mortality was observed, nor was there postoperative graft occlusion or need for major amputation. The average postoperative length of stay in the hospital was 9.7 days. Two local surgical wound complications were observed, which did not necessitate a postoperative hospital stay exceeding 15 days. Cumulative primary patency and limb salvage rates at 3 years were 50% and 70%, respectively. Anatomic tunneling of grafts to the anterior tibial artery yields patency and limb salvage rates comparable to those reported in the literature for distal bypasses and, considered overall, an acceptably low local morbidity and short hospital stay. Definitive superiority over externally tunneled grafts, however, is not definitely demonstrated by this study and should be prospectively tested. Received: 9 May 1997     

Forskolin impregnation of small calibre PTFE grafts lowers early platelet graft sequestration and improves patency in a sheep model

Synthetic vascular grafts have a thrombogenic surface which plays a role in graft failure. Systemic pharmacologic interventions have been used to lower platelet sequestration onto the graft surface but are associated with side effects. In this communication we describe the results of a new therapeutic principle of applying forskolin, a powerful cyclic adenosine monophosphate stimulator (cAMP) to the inner surface of PTFE vascular grafts. The grafts were evaluated with Indium-III-oxine labelled platelets and by graft patency on 3 consecutive days after implantation at 1 month and 3 months. Forskolin significantly lowered early platelet sequestration onto the treated graft surface when compared with controls. Graft potency at 1 and 3 months was also significantly higher in the forskolin treated grafts.     

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.