Rat epigastric pedicle model: a clinically relevant evaluation of 1-mm PTFE grafts

Twenty-eight Sprague-Dawley rats had 1.0-mm polytetrafluoroethylene (PTFE) interposition grafts placed in their femoral artery that supplied a 3.0 X 3.0 cm epigastric pedicle flap. The model is the first to evaluate 1.0-mm PTFE under rigorous, clinically simulating conditions. Anastomoses employed a new, continuous telescoping suture technique. Grafts were selected for histological and electron microscopic evaluation, which confirmed the development of a cellular neointimal lining. Viability of the flap model had a 90% correlation with graft patency. Overall graft patency was 50%. Patency was documented in some specimens harvested at 200 days. The flap model is a good indicator of graft patency. PTFE grafts of 1.0-mm internal diameter are not yet equivalent to autologous veins. Future refinements, particularly aseptic technique, are expected to result in even higher patency rates.     

Heparin-bonded Dacron or polytetrafluorethylene for femoropopliteal bypass: five-year results of a prospective randomized multicenter clinical trial

OBJECTIVE: Dacron was largely abandoned for femoropopliteal bypass 30 years ago, because better patency rates were achieved with saphenous vein. Despite the range of potential prosthetics, polytetrafluoroethylne (PTFE) clearly predominates in current femoropopliteal practice. We compared heparin-bonded Dacron (HBD) with PTFE in a randomized multicenter clinical trial. METHOD: Over 28 months, 209 patients (179 above-knee disease, 30 below-knee disease) were randomized to receive HBD (n = 106) or PTFE (n = 103) grafts. Aspirin, 300 mg/d, was started before surgery, and was continued if tolerated. RESULTS: At follow-up for a minimum of 5 years (mean, 76 months; range, 60-89 months), 37 patients (17.7%) had died with patent grafts and 121 (58%) grafts were occluded. Primary patency rate, measured with Kaplan-Meier survival analysis, was 46% (95% confidence interval [CI], 35%-57%) at year 5 for HBD, compared with 35% for PTFE (CI, 25%-45%; P < .055). Long-term patency was achieved in only 4 of 78 interventions performed in 55 thrombosed grafts. Secondary patency rate for HBD was 47% (CI, 36%-58%), and for PTFE was 36% (CI, 26%-46%). Risk factors for arterial disease did not significantly influence prosthetic patency. Major limb amputation was necessary in 9 patients with HBD grafts and 20 patients with PTFE grafts (P < .025). Two amputations in the HBD group and 8 amputations in the PTFE group were in patients undergoing bypass surgery to treat claudication only. Limb salvage rate was 86% (CI, 77%-95%) and 74% (CI, 64%-84%), respectively. CONCLUSIONS: Significantly better patency rates were achieved with HBD than with PTFE at 3 years (P < .044), but the difference was no longer statistically significant at 5 years (P < .055). The incidence of major limb amputation, however, was significantly greater (P < .025) in the PTFE group compared with the HBD group at both 3 and 5 years of follow-up.     

Expanded polytetrafluoroethylene as a microvascular graft: An experimental study

The patency rates of expanded polytetrafluoroethylene (PTFE) vascular grafts with internal diameters of 1.0–3.0 mm were evaluated in three different species (dogs, rabbits, and rats). An overall 2-week patency rate of 14 (23%) of 60 was obtained, with the exception of 10 (83%) of 12 grafts 1.8 mm in diameter inserted in the carotid arteries of rabbits. The presence of numerous variables in the structural properties of PTFE may explain the variable results reported in the literature and this study. Heparinization did not improve the results, nor did modification in suture technique. At the present time, PTFE cannot be considered an equivalent to or a substitute for autogenous vein grafts in microvascular surgery.     

Prospective randomized study on bilateral above-knee femoropopliteal revascularization: Polytetrafluoroethylene graft versus reversed saphenous vein

OBJECTIVE: Some controversy exists as to whether polytetrafluoroethylene (PTFE) is equivalent to reversed saphenous vein (SV) as bypass graft material for above-knee femoropopliteal revascularization. We compared the 5-year patency rate with reversed SV and PTFE grafts in patients with claudication who underwent bilateral above-knee femoropopliteal revascularization. METHODS: Between January 1994 and December 1997, 51 patients (102 limbs) with bilateral disabling claudication due to superficial femoral artery occlusion underwent above-knee femoropopliteal bypass grafting, with SV in one limb and PTFE graft in the other limb. Patients were randomly selected for sequential surgical treatment with either SV-PTFE or PTFE-SV. Kaplan-Meier analysis was used to estimate patency rate, and various factors were analyzed to ascertain any association with revascularization failure. RESULTS: There was no perioperative (30 day) limb loss or death, but five late deaths (late survival rate, 90%). Mean follow-up was 59 months. In the SV group, three bypass grafts failed, requiring repeat operation in only one patient. In the PTFE group, eight bypass grafts failed, leading to five repeat operations. There was no statistically significant difference in primary "assisted" patency rate for the two grafts: 100%, 98%, and 94% for SV grafts, and 96%, 84%, and 84% for PTFE grafts (P =.09), after 1, 3, and 5 years, respectively. CONCLUSIONS: The overall results of this randomized study show that SV and PTFE grafts have a statistically comparable patency rate when used above the knee in patients with claudication. Use of SV, however, leads to fewer occlusions and repeat operations.     

An Animal Model for Small-Diameter Arterial Grafts

A rabbit model was developed to study small-diameter arterial grafts. A total of 158 2-mm-diameter polytetrafluoroethylene (PTFE) grafts und 35 autogenous carotid artery (AA) grafts were interposed in the carotid arteries of New Zealand white rabbits. A pilot study of 16 PTFE grafts used to develop operative and anesthetic techniques had a 20% mortality and 38% early (<2 day) thrombosis rate. Subsequent to the pilot study 177 grafts were placed and a 92% postoperative survival with 100% AA graft patency and 93% PTFE graft patency at 2 weeks was observed. AA grafts followed beyond 16 weeks continued to have 100% patency, while PTFE grafts began to show increased failure. Closure was found to be due to the development of anastomotic myointimal hyperplasia.     

One hundred percent patency of one-millimeter polytetrafluoroethylene (Gore-tex) grafts in the carotid arteries of rats

Expanded polytetrafluoroethylene arterial interposition grafts with an internal diameter of 1.0 mm were placed in the carotid arteries of rats. At 2 weeks, 100% patency rate was achieved by the use of strict sterile technique in 23 rats. In contrast, only 1 out of 21 grafts remained open in rats operated using standard clean but nonsterile technique, 5% patency. All thrombosed grafts showed evidence of infection. Orally administered aspirin at therapeutic doses prolonged bleeding times in the rats but did not affect patency results in either group.     

A clinical survey of aortobifemoral bypass using two inherently different graft types.

The performance of knitted Dacron and polytetrafluoroethylene (PTFE) bifurcated grafts are compared in this study of 312 patients at a single institution. Patients of the two graft groups were statistically well-matched in risk factors and degree of distal obstructive disease. Operating time needed to implant either graft was approximately equal. For patients with abdominal aortic aneurysms, mean volume of blood transfused was 2.2 units for Dacron grafts and 0.2 units for PTFE grafts; for patients with aortoiliac occlusive disease, the comparable figures were 1.1 units and 0.1 units, respectively. Four-year cumulative patency for Dacron (90%) and PTFE (97%) grafts were not significantly different (p greater than 0.01). Complications affected 13% of the patients of the Dacron group and 4% of the PTFE group. All six graft infections and all seven graft double-limb thromboses occurred in Dacron grafts. Anastomotic aneurysms, amputations, and late graft revisions occurred with greater frequency in patients with Dacron grafts.     

Six-year prospective multicenter randomized comparison of autologous saphenous vein and expanded polytetrafluoroethylene grafts in infrainguinal arterial reconstructions

Autologous saphenous vein (ASV) and polytetrafluoroethylene (PTFE) grafts were compared in 845 infrainguinal bypass operations, 485 to the popliteal artery and 360 to infrapopliteal arteries. Life-table primary patency rates for randomized PTFE grafts to the popliteal artery paralleled those for randomized ASV grafts to the same level for 2 years and then became significantly different (4-year patency rate of 68% +/- 8% [SE] for ASV vs. 47% +/- 9% for PTFE, p less than 0.025). Four-year patency differences for randomized above-knee grafts were not statistically significant (61% +/- 12% for ASV vs. 38% +/- 13% for PTFE, p greater than 0.25) but were for randomized below-knee grafts (76% +/- 9% for ASV vs. 54% +/- 11% for PTFE, p less than 0.05). Four-year limb salvage rates after bypasses to the popliteal artery to control critical ischemia did not differ for the two types of randomized grafts (75% +/- 10% for ASV vs. 70% +/- 10% for PTFE, p greater than 0.25). Although primary patency rates for randomized and obligatory PTFE grafts to the popliteal artery were significantly different (p less than 0.025), 4-year limb salvage rates were not (70% +/- 10% vs. 68% +/- 20%, p greater than 0.25). Primary patency rates at 4 years for infrapopliteal bypasses with randomized ASV were significantly better than those with randomized PTFE (49% +/- 10% vs. 12% +/- 7%, p less than 0.001). Limb salvage rates at 3 1/2 years for infrapopliteal bypasses with both randomized grafts (57% +/- 10% for ASV and 61% +/- 10% for PTFE) were better than those for obligatory infrapopliteal PTFE grafts (38% +/- 11%, p less than 0.01). These results fail to support the routine preferential use of PTFE grafts for either femoropopliteal or more distal bypasses. However, this graft may be used preferentially in selected poor-risk patients for femoropopliteal bypasses, particularly those that do not cross the knee. Although every effort should be made to use ASV for infrapopliteal bypasses, a PTFE distal bypass is a better option than a primary major amputation.     

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.     

Patency Rates and Complications of Exxcel Yarn-Wrapped Polytetrafluoroethylene Grafts Versus Gore-Tex Stretch Polytetrafluoroethylene Grafts: A Prospective Study

Purpose. Polytetrafluoroethylene (PTFE) has long been used for hemodialysis access when there is no suitable superficial vein. We conducted a prospective randomized study to compare two PTFE grafts; the stretch Gore-tex graft and the Exxcel graft.Methods. Between May 2000 and February 2001, PTFE grafts were implanted for hemodialysis access in the upper extremities of 94 consecutive patients with end-stage renal disease. Graft selection was randomized, with patients receiving either a Gore-tex or an Exxcel graft. All grafts were monitored for signs of thrombosis or other complications. Graft survival was analyzed using a life-table analysis and the log-rank test was applied to compare graft patency.Results. The primary patency rates 1 and 2 years after implantation were 51% and 36% for the Exxcel grafts, and 71% and 45% for the Gore-tex grafts, respectively. The difference between the two groups was not significant at any time. The incidence of complications needing further surgical management was 8.2% in the Exxcel group and 6.7% in the Gore-tex group, without a significant difference.Conclusion. Exxcel grafts or Gore-tex stretch grafts can be used for dialysis access with similar expected outcomes for up to 2 years, despite the differences in their outer surface design. The yarn-wrapped design does not appear to enhance the graft patency and we found no remarkable difference.     

Bovine carotid artery and expanded polytetrafluroethylene grafts for hemodialysis vascular access

Seventy-six bovine carotid artery heterografts (BCAH) and 100 expanded polytetrafluroethylene (PTFE) grafts were inserted as chronic hemodialysis arteriovenous fistulas. Cumulative patency at 1 year was 70% for the BCAH group and 87% for the PTFE group and at 2 years was 45 and 73%, respectively. Infection accounted for 38% of BCAH failures and none of the PTFE failures. BCAH required twice as many revisions per dialysis month to maintain patency as did the PTFE grafts (0.036 vs 0.019, respectively). Graft configuration and location did not affect patency rates. At present the PTFE grafts appear superior to the BCAH for construction of arteriovenous dialysis fistulas.     

Heparin and small caliber polytetrafluoroethylene grafts in the carotid arteries of rats

Polytetrafluoroethylene (PTFE) grafts having an internal diameter of 1 mm were implanted in the common carotid arteries of rats with or without the simultaneous application of various heparin regimens. Graft patency was determined from postoperative angiograms, and grafts that were patent 40 days after surgery were harvested for light microscopic examination. The level of anticoagulation produced by the various heparin regimens was measured in separate groups of rats and found to be clinically therapeutic. All of the grafts from rats that did not receive heparin were occluded at 24 hours. In the two groups of rats that received high doses of heparin, 5 of 10 and 4 of 11 grafts were patent 40 days postoperatively. There were no patent grafts three days postoperatively in the group receiving low doses of heparin. The grafts that were patent 40 days postoperatively had lumens that were completely lined with presumptive endothelial cells. Further laboratory experimentation is needed before PTFE small caliber grafts can be recommended for use in humans.     

An animal model for small-diameter arterial grafts

A rabbit model was developed to study small-diameter arterial grafts. A total of 158 2-mm-diameter polytetrafluoroethylene (PTFE) grafts and 35 autogenous carotid artery (AA) grafts were interposed in the carotid arteries of New Zealand white rabbits. A pilot study of 16 PTFE grafts used to develop operative and anesthetic techniques had a 20% mortality and 38% early (less than 2 day) thrombosis rate. Subsequent to the pilot study 177 grafts were placed and a 92% postoperative survival with 100% AA graft patency and 93% PTFE graft patency at 2 weeks was observed. AA grafts followed beyond 16 weeks continued to have 100% patency, while PTFE grafts began to show increased failure. Closure was found to be due to the development of anastomotic myointimal hyperplasia.     

Axillopopliteal bypass for limb salvage.

Forty-one axillopopliteal bypass grafts have been placed in 30 patients for limb salvage in the past 12 years. The mean patient age was 65.6 years; 8 were women; 19 smoked; and six had diabetes. Sixteen grafts were straight axillopopliteal bypass grafts, and 25 were sequential axillopopliteal bypass grafts. Cumulative life-table primary patency rates at 1, 2, and 3 years were 70%, 56%, and 43%, respectively; secondary patency rates were 73%, 57%, and 50%, respectively. Corresponding limb salvage rates were 86%, 69%, and 69%, respectively. Ringed polytetrafluoroethylene (PTFE) graft patency at 3 years was 61% versus 40% for unsupported PTFE grafts (p = 0.35). Ringed PTFE axillofemoral grafts with sequential femoropopliteal saphenous vein grafts had a 3-year patency of 67%. Graft patency was restored in 25% of occluded grafts by thrombectomy and in 80% of occluded grafts by thrombectomy with graft revision (p = 0.21). Cumulative 3-year patient survival was 48%. The 30-day operative mortality rate was 20%; patients operated on for graft infection had a 30-day operative mortality rate of 36%. The data support the use of axillopopliteal bypass for limb salvage when standard revascularization techniques are contraindicated. Long-term patency is enhanced by use of externally supported PTFE and sequential femoropopliteal saphenous vein.     

Collagen- versus gelatine-coated Dacron versus stretch PTFE bifurcation grafts for aortoiliac occlusive disease: long-term results of a prospective,randomized multicenter trial

BACKGROUND: In this prospective randomized multicenter trial, knitted gelatine-coated Dacron, knitted collagen-coated Dacron, and stretch polytetrafluoroethylene (PTFE) aortic bifurcation grafts were compared for their long-term results. METHODS: Between 1991 and 1998, 149 patients undergoing elective revascularization for aortoiliac occlusive disease were prospectively randomized at 3 tertiary referral centers of vascular surgery. The patients received either gelatine-coated Dacron (GEL-D) grafts (n = 52), collagen-coated Dacron (COL-D) grafts (n = 49), or stretch PTFE grafts (n = 48). RESULTS: No intraoperative deaths were recorded. The 30-day mortality was 4%. The mean follow-up time was 97 months. Primary patency rates were 77% for GEL-D, 78% for COL-D, and 79% for PTFE at 8 years. The differences were not different (P >.8). Secondary corrected 8-year patency rates were also not significantly different (P >.5): 91% for GEL-D, 96% for COL-Dm and 90% for PTFE. Five Dacron and 1 PTFE grafts were affected by infections. CONCLUSIONS: Bifurcation grafts for revascularization of aortoiliac occlusive disease using these 3 materials were comparable in terms of primary and secondary patency and long-term complication rates.     

Intraarterial 9-beta-methyl carbacyclin improves canine polytetrafluoroethylene graft patency

This study examined the effect of 9-beta-methyl carbacyclin, a synthetic, stable prostacyclin analog, on canine polytetrafluoroethylene (PTFE) graft patency. Twenty-five dogs had 4 mm x 7 cm PTFE grafts implanted bilaterally into the femoral arteries. A subcutaneous infusion pump was used to deliver either saline solution (control) or 9-beta-methyl carbacyclin (Ciprostine) at 100 (CARB-100) or 200 ng/kg/min (CARB-200) through a femoral artery branch just proximal to one of the femoral grafts, with the contralateral graft serving as a noninfused control. Graft-platelet deposition (with 111In-labeled platelets) was measured between the fifth and seventh days, with patency determined on the seventh day. Dogs were classified as aggregators (AGG [+]) if the preoperative epinephrine-enhanced sodium arachidonate platelet aggregation was greater than 20%. CARB-200 infusion significantly improved ipsilateral graft patency (80%) compared with noninfused grafts (50%, p less than 0.05), or grafts in control and CARB-100 dogs (43%, p less than 0.05). Anastomotic platelet deposition was decreased bilaterally in CARB-200 dogs by 45% to 59% compared with CARB-100 and control dogs (p less than 0.05). With the exception of grafts infused with CARB-200, AGG (+) dogs had significantly lower graft patency (26%) than nonaggregator AGG (-) dogs (71%, p less than 0.01). CARB-200 infusion significantly improved graft patency in AGG (+) dogs (71%), compared with control and CARB-100-infused grafts (19%, p less than 0.025). Intra-arterial 9-beta-methyl carbacyclin improved early PTFE graft patency and inhibited platelet deposition in a severe canine model, independent of baseline platelet aggregation status, which also had an important effect on graft patency.     

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.     

Experimental and clinical use of polytetrafluoroethylene vascular grafts

Synthetic textiles, saphenous veins and now expanded polytetrafluoroethylene (PTFE) allow the surgeon a wide range of vascular operations. Two sets of studies are reported testing PTFE under a variety of circumstances. Twenty-four dogs underwent either replacement of a segment of the abdominal aorta or aortoiliac bypass with PTFE or Dacron grafts. PTFE was the easiest to use and to suture. Patency was better (six of seven versus four of seven) although not statistically significant, and microscopic examination showed better tissue ingrowth and less inflammatory and fibrous reaction than the woven or knitted grafts. Twenty-two PTFE grafts (6 mm in internal diameter) were implanted in 19 patients for use as vascular access during hemodialysis. All patients presented with damaged blood vessels and had undergone multiple vascular access procedures previously. Graft patency was excellent (three grafts were removed because of infection, vascular steal or occlusion and three grafts were revised because of obstruction or bleeding); the grafts allowed good flows during dialysis and they were easy and convenient to implant. PTFE tolerates pressure and flows in medium and large arteries, its patency rate is excellent, it is easy to use, and its interactions with tissues are adequate.     

Microvascular repair with 1-mm polytetrafluoroethylene (PTFE) grafts: effect of recombinant tissue-type plasminogen activator (rt-PA) on the patency rate and healing process

The present study assesses the effect of recombinant tissue-type plasminogen activator (rt-PA) on the patency rate and healing process of microvascular polytetrafluoroethylene (PTFE) grafts. Wistar rats were used, divided into four groups of 25 animals each. After dissection of the carotid artery a segment of the vessel, 1 cm long, was resected and replaced by equal length graft. Two different type fibril length (30- or 60-microm) grafts of the same wall thickness (0.18 mm) were used. Normal saline or 3 mg/kg of body weight of rt-PA was applied locally in each group of different fibril length grafts. Patency tests were performed at 15 min and 4 weeks after blood flow was reestablished. All grafts were harvested and examined histologically. The results showed that local application of rt-PA improves patency statistically significantly in both types of fibril length grafts. Patency in 60-microm fibril length grafts was statistically significantly higher than that of 30-microm fibril length grafts, whether rt-PA was used or not. The use of rt-PA had no influence on the healing process of either type of graft.     

Optimal grafting methods for the small abdominal aorta

Aortobifemoral bypass procedures were performed on 42 patients with the hypoplastic aortoiliac syndrome over an eight year period. During the first five years, 22 patients had either a 13 X 6.5 mm or a 14 X 7 mm knitted Dacron graft and served as historic controls for a second group of 20 others who had 14 X 7 mm grafts of expanded polytetrafluoroethylene (PTFE), during the last three years of the study. Although the two groups were neither concurrent nor randomized, they were nonetheless well matched with regard to age, sex, risk factors, indications for operations, distribution and severity of distal occlusive disease, and type of distal anastomosis. There was only one early graft limb occlusion in the PTFE group after a median follow-up of 14 months, compared to nine occlusions and one amputation in the Dacron group after a median follow-up of 26.2 months. The cumulative patency of the PTFE grafts was 95% at four years compared to only 52% for Dacron (p = 0.11). If the single postoperative occlusion which occurred in each group is excluded, then the difference in patency rates bordered on statistical significance (p = 0.06). Inclusion of the profunda femoris orifice in the distal anastomosis was also found to be an important factor contributing to long-term patency which approached statistical significance (p = 0.075). The configuration of the proximal aortic anastomosis (end to end vs. end to side), or the concomitant use of lumbar sympathectomy or the postoperative infusion of Dextran did not have a statistically significant influence on patency.(ABSTRACT TRUNCATED AT 250 WORDS)