Expanded polytetrafluoroethylene grafts for severe lower limb ischaemia

Identification of dendritic cells in ePTFE grafts explanted from humans

Following implantation different cell types interact with synthetic vascular prostheses resulting in a complex immuno-inflammatory response. Dendritic cells are responsible for activating the primary T-lymphocyte immune response in various pathological conditions by their role as antigen-presenters. This study aimed at examining whether dendritic cells accumulate within small diameter expanded polytetrafluoroethylene (ePTFE, Goretex(R)) grafts explanted from humans. Segments of expanded polytetrafluoroethylene were explanted from 11 patients (6 male, 5 female), aged between 60 and 83 years (mean 70.7 years) at secondary or revision bypass operation. The graft implant duration varied from 4 months to 12 years (mean 40.5 months). Dendritic cells were identified immunohistochemically using S-100 antibody, as well as by electron microscopy. Immunohistochemical examination showed that all 11 explanted synthetic grafts contained S-100(+) cells colonising both the synthetic matrix itself, and the adjacent perigraft tissue. Electron microscopic analysis confirmed the presence of cells with a characteristic dendritic cell morphology within the grafts. Dendritic cells which accumulated within synthetic grafts were found to co-localise with T-lymphocytes. Based on these observations, we speculate that dendritic cells may be involved in the immuno-inflammatory responses following the implantation of synthetic vascular prostheses through their interaction with T-lymphocytes.

Polytetrafluoroethylene (PTFE) femorodistal grafts with a distal vein cuff for critical ischaemia

OBJECTIVE

To analyse the results of PTFE femorodistal bypass grafts using a distal anastomotic vein cuff in the treatment of critical ischaemia.

DESIGN

Prospective study of consecutive patients under the care of a single Vascular Surgeon.

SETTING

A dedicated Vascular Surgical Unit in a University teaching hospital.

SUBJECTS

Fifty-one consecutive femorodistal PTFE grafts were performed on 50 patients (median 74 years, range 58-94 years, 25 men; median ankle:brachial index 0.4). In 28 (55%) a common ostium arteriovenous fistula (AVF) was fashioned at the distal anastomosis.

RESULTS

The 30-day postoperative mortality was 8%, with 10 (21%) major complications. The 1 and 2 year primary patency was 64% and 51%, respectively, with corresponding limb salvage rates of 85% and 80%. The presence of an AVF did not significantly affect graft patency or patient survival, but appeared to hinder limb salvage. The latter effect may be due to bias in patient selection.

CONCLUSION

PTFE femorodistal grafts with a distal vein cuff are a suitable alternative to autogenous saphenous vein in distal reconstructions for critical ischaemia. No conclusions can be made about the efficacy of an AVF in this context.

Below-knee bypass using fresh arterial allografts for limb salvage: early results

The purpose of this study was to evaluate early results of below-knee bypass using fresh arterial allografts as arterial substitutes for limb salvage. From April 1991 to September 1993, we performed 28 below-knee bypass procedures using fresh arterial allografts in patients without a suitable autologous vein. Allografts were obtained by multiorgan harvesting from brain-dead subjects and preserved at 4 degrees C. Histologic examination of grafts was carried out. Secondary patency at 2 years calculated using the Kaplan-Meier method was 64% (confidence interval [CI] 45%-79%). No signs of graft deterioration or rejection were noted. These preliminary results are encouraging but long-term assessment is needed before expanding the range of application.

Influence of a vein cuff on polytetrafluoroethylene grafts for primary femoropopliteal bypass

A retrospective investigation was performed to study the benefit obtained from a vein cuff inserted at the distal anastomosis of a primary femoropopliteal bypass graft with polytetrafluoroethylene (PTFE). When PTFE was preferred to vein an attempt was made to assess whether there was subsequent use for the spared vein. A series of 559 primary PTFE bypasses was studied and found to have a cumulative patency rate of 62 per cent at 36 months. Subgroups were also studied for a similar period. In the above-knee position there was no difference in the primary patency rate of PTFE with or without a cuff at 36 months (69 versus 68 per cent, P = 0.89). Below the knee, grafts with a cuff had a better 36-month patency rate than those without (57 versus 29 per cent, P = 0.01). Cuffed PTFE for claudication had a better patency rate than that for threatened limbs at 36 months (68 versus 60 per cent, P = 0.03). Thrombectomy of occluded cuffed PTFE grafts improved the 36-month patency rate from 64 to 74 per cent. The limb salvage rate at 36 months was 97 per cent for claudication and 89 per cent for threatened limbs with cuffed PTFE. Occlusion of cuffed PTFE was associated with preservation of outflow in 91 (51 per cent) of 179 cases, permitting subsequent graft thrombectomy or insertion of a new bypass. Spared vein was rarely used to salvage an occluded PTFE graft, and was associated with poor patency and a high amputation rate. Although this study does not support the use of PTFE for the primary graft, PTFE with a vein cuff interposed at the distal anastomosis is a reasonable substitute when vein is not available.

Improved technique for polytetrafluoroethylene bypass grafting: long-term results using anastomotic vein patches

Results of peripheral arterial bypass using polytetrafluoroethylene grafts have remained poor in comparison with those using saphenous vein grafts, particularly for anastomoses to tibial and peroneal vessels. A simple modification to the conventional operative technique, involving the incorporation of a vein patch into the distal anastomosis, has enabled considerable improvement. Five-year patency rates of 71 per cent for popliteal and 54 per cent for infrapopliteal grafts have been achieved in a series of 256 patients operated on between 1982 and 1989.

A review of structural and material properties of vascular grafts

A brief review of the textile structures employed in the construction of vascular grafts is followed by a survey of the causes of failure cited in the literature. An attempt is made to determine the structural factors contributing to the failure of vascular grafts, and attention is given to material properties and methods for determining these attributes. Need for further research is emphasized.

An investigation into the causes of failure of PTFE grafts

In an attempt to improve the results of PTFE bypass grafting in the lower limb, a consecutive series of 159 grafts has been analysed in detail to determine the causes of failure. The majority were performed for limb salvage (76%) and the remainder for severe claudication. Forty-five grafts (28%) were to tibial or peroneal vessels. All patients were studied by preoperative arteriographic and Doppler studies, operative arteriography and postoperative Doppler and vasoscan studies. In selected cases postoperative arteriography was carried out with the knee straight and flexed. Thirty-seven failures occurred during a follow-up period of between 6 months and 6 years. The findings indicated four main causes of failure, extension of disease (30%), anastomotic hyperplasia (19%), graft kinking (13%) and technical faults (5%). Each of these is considered in detail and illustrative examples described. Overall patency rates for all popliteal bypasses (AK 43%; BK 57%) were 90 +/- 3% at one year, 78 +/- 5% at 3 years and 69 +/- 8% at 5 years. Comparable figures for tibial grafts were 86 +/- 6% at one year, and 60 +/- 14% at three years. As a consequence of the study, operative techniques have now been modified and preliminary results indicate that these patency rates can be significantly improved.

An appraisal of the role of the PTFE graft in lower limb arterial reconstruction

In the period between April 1977 and April 1981, 105 femoropopliteal bypass grafts were performed for atherosclerotic occlusive arterial disease below the inguinal ligament. Forty-six of these were done using polytetrafluoroethylene (PTFE) and the remaining 59 using autogenous saphenous vein. In April 1982 a retrospective evaluation of the efficacy of the PTFE graft was undertaken. Patency rates between the two groups were found to be comparable when disabling claudication was the indication for surgery. No difference in patency rates was found between the PTFE graft inserted above or below the knee irrespective of whether the graft was undertaken for claudication or limb salvage.