ePTFE Grafts Research Articles

Paclitaxel Coating Inhibits Inflammation Surrounding Subcutaneously Implanted Expanded Polytetrafluoroethylene (ePTFE) Hemodialysis Grafts in Rabbit Model

Hemodialysis vascular access dysfunction (HVAD) due to the aggressive development of venous neointimal hyperplasia remains a major complication for patients with synthetic arteriovenous grafts. Paclitaxel-coated expanded polytetrafluoroethylene (ePTFE) grafts effectively prevent neointimal hyperplasia and stenosis. However, peri graft inflammation or edema can be another complication of ePTFE grafts, preventing early cannulation. Three different types of ePTFE grafts, including grafts without paclitaxel coating (control group, n = 12), grafts with paclitaxel coating at a dose density of 0.61 ug/mm 2 (low concentration group, n =12), and grafts with paclitaxel coating at a dose density of 1.15 ug/mm 2 (high concentration group, n = 12) were placed in the backs of 12 rabbits, simultaneously. Six rabbits were euthanized after one week and the remaining six were euthanized two weeks after implantation. Perigraft inflammation, graft wall inflammation, stromal cell proliferation, blood vessel formation, tissue necrosis and edema were analyzed for the grafts in each animal. Inflammation surrounding the paclitaxel-coated grafts was significantly reduced compared to the control group. Stromal cell layers were detected at the interface between the graft and the surrounding tissue in the control group, infiltrated into the graft interstices, and differentiated into myofibroblasts for graft healing. Paclitaxel-coated grafts inhibited stromal cell proliferation and infiltration into the graft wall. Tissue necrosis and edema were not detected in either of the paclitaxel-coated graft groups.

Cryoplasty of the Venous Anastomosis for Prevention of Intimal Hyperplasia in a Validated Porcine Arteriovenous Graft Model

Objectives Cryoplasty combines conventional angioplasty – percutaneous transluminal angioplasty (PTA) – with cold thermal energy. In this animal study, we investigated if preventive cryoplasty could reduce intimal hyperplasia (IH) at the venous anastomosis. Design We investigated cryoplasty versus PTA of the venous anastomosis in a validated porcine, bilateral, arteriovenous graft model. Animals and methods In 12 pigs, 24 expanded polytetrafluoroethylene (ePTFE) grafts were bilaterally inserted between the common carotid artery and internal jugular vein. Directly after surgery, one venous anastomosis was treated with cryoplasty at −10 °C, the contralateral anastomosis with conventional PTA. At 4 weeks, graft flow was measured, quantitative angiography was performed and grafts with adjacent vessels were excised for histological analysis. Results Due to a number of thromboses, data for paired analysis were available from eight pigs. Angiographic outflow vein diameter and graft blood flow were not different between treatment groups. Compared with the control group, IH at the venous anastomosis was reduced by 47% ( P = 0.21) and intima/media ratio was reduced by 45% ( P = 0.07) by cryoplasty. Effects were most profound in those animals that tended to develop most IH. Conclusion Our results suggest that preventive cryoplasty of the venous anastomosis might help to reduce IH in those cases that develop most profound IH.

Dacron or ePTFE graft for above-knee femoropopliteal bypass reconstruction. A bi-centre randomised study

The objective of this study was to compare polyester (Dacron) and expanded polytetrafluorethilene (ePTFE) grafts for above-knee femoropopliteal bypass. Eighty five patients with disabling claudications or limb threatening ischemia suitable for above-knee femoropopliteal reconstruction were randomized into two groups. In the first group the surgery was performed using 8 mm Dacron graft, whereas the patients in the second group were operated using ePTFE grafts. The primary patency rates for Dacron and ePTFE were 100 %, and 88.37 % (p < 0.05), while secondary patency rates were 83.3 % and 75 % (p > 0.05) respectively. The early limb salvage rates for Dacron and ePTFE were 100 % and 97.7 % (p > 0.05). Early (30-day) complications (bleeding 2.38 % and 2.32 %; wound infection 11.9 % and 11.63 %) occurred in both groups with similar frequency (p > 0.05). The patients were followed up over a period of 6 to 12 months (mean 8.3 +/- 3.6 months). The overall mortality rate in the follow-up period was 2.38 % (one patient) for Dacron and 6.98 % (three patients) for ePTFE group (p > 0.05). Late graft infection was noted in three patients (7.1 %) in Dacron, and two patients (4.65 %) in ePTFE group (p > 0.05). Primary patency rates were not significantly influenced by obesity, diabetes, hypertension, hyperlipidemia, cigarette smoking, (p > 0.05). However, poor run-off (only one crural artery patent on preoperative angiography) significantly decreased patency of both grafts and favored the use of ePTFE graft (p < 0.05). This study confirms that both materials are suitable for above-knee femoropopliteal reconstructions. Above-knee femoropopliteal bypass does not have a good long-term prognosis in the presence of poor run-off.

Evaluation of the Hemodynamics of a Tissue-engineered Hybrid Graft

We evaluated the hemodynamics of tissue-engineered hybrid graft in vivo. The hybrid expanded polytetrafluoroethylene (ePTFE) scaffold was fabricated by coating the ePTFE graft with poly (lactide-co-glycolide) (PLGA) solution. This scaffold was turned into an engineered hybrid graft by culturing smooth muscle cells on its surface. Both the ePTFE (n = 6) and the engineered hybrid grafts (n = 8) were implanted in the carotid arteries of mongrel dogs. The length of intima in the engineered hybrid graft was greater than the ePTFE. The neoarterial thickness in the engineered hybrid group was greater, and the foreign body reaction was more severe. We compared the hemodynamics (diameter, flow rate, pulsatile index, mean velocity, shear stress, resistance index, and systolic/diastolic ratio) of the native arteries in the distal anastmosis. The shear rate in the engineered hybrid group was higher immediately after implantation, and the resistance index was lower, but there was no significant difference after 4 weeks. The engineered grafts demonstrated similar hemodynamics with the ePTFE grafts after 4 weeks implantation.

Hemodynamic Comparison of Differing Anastomotic Geometries Using Magnetic Resonance Velocimetry

Hemodynamic factors at the distal anastomosis play an important role in prosthetic graft performance. A new magnetic resonance imaging (MRI) technique was used to determine the effect of anastomotic geometry on hemodynamic flow patterns. Four dimensional (4D) magnetic resonance velocimetry (4D-MRV) is a noninvasive method of analyzing pulsatile flow in three dimensions (3D). End-to-side anastomotic models were constructed by suturing 6 mm polytetrafluoroethylene (ePTFE) grafts to silicone tubing (4 mm i.d.). The models included straight ePTFE, precuffed ePTFE, and patched ePTFE configurations in a pulsatile system, which created flow consistent with physiologic flow rates and pressures. Blood was simulated by a solution of 40% glycerol in distilled water with trace gadolinium. The different models were imaged using MRV techniques in a three-dimensional (3D) coronal slab (0.5 mm thick coronal slices, in-plane field of view (FOV) 18 cm.) The data were reconstructed, resulting in an interpolated resolution of 0.35 mm in each coronal plane. The 3D flow fields were represented as isosurfaces, visualizing the internal geometry of the models with streamlines tangent to the velocity vectors identifying the path of the fluid. Volumetric flow rates for each time phase were calculated by integrating the flow through cross sections of each anastomotic model. Analysis of the flow patterns focused on the anastomotic regions prone to the development of intimal hyperplasia and graft failure as identified in the literature; the toe, floor, heel, and hood. Conventional end-to-side geometry resulted in uniform flow with a low angle of impingement on the recipient vessel floor. A small vortex at the anastomotic heel created minimal recirculation. The precuffed geometry resulted in a large recirculation vortex of chaotic, low flow that increased throughout the pulsatile cycle. Regions of low flow velocity were noted in a substantial portion of the precuffed anastomotic configuration. Flow separation distal to the toe occurred in both geometries, but was more apparent in the precuffed configuration. The patch model had flow characteristics similar to the straight end-to-side geometry. Magnetic resonance velocimetry produces 3D, time varying velocity measurements with sufficient accuracy and resolution to analyze hemodynamics in anastomotic geometries. Flow structures in different graft configurations were effectively captured with marked differences noted between standard and precuffed anastomotic geometries. The findings support a conventional end-to-side anastomosis with a low incidence angle using a straight graft as producing favorable hemodynamics as compared to a cuffed configuration. The vein patch configuration closely approximates the conventional, straight anastomotic pattern. We believe the MRV technique has been sufficiently developed to warrant additional in vitro and in vivo studies providing insight into hemodynamic implications for the development of optimal prosthetic graft performance.

Biomechanical, morphological and zero-stress state characterization of jugular vein remodeling in arteriovenous fistulas for hemodialysis

While the role of hemodynamic variables on the development of intimal hyperplasia in arteriovenous fistulas for hemodialysis has been examined, less is known about the intramural biomechanical factors. In this study, arteriovenous fistulas were created by implantation of e-PTFE grafts between carotid artery and jugular vein in healthy pigs. In vivo recordings exhibited a three-fold pressure and flow elevation in grafted veins after fistula creation, remaining so until sacrifice. The chief morphological observation in grafted vessels was wall thickening at two weeks, serving to restore intramural stresses to homeostatic levels, and a less marked internal diameter enlargement, gradually normalizing intimal shear after four weeks. The residual strains and opening angle, specifying the zero-stress configuration, increased with differences reaching significance at twelve weeks. Association with histomorphological findings on intima, media and adventitia growth disclosed a correlation between intimal hyperplasia and opening angle increase. Elastin and cellular contents diminished opposite to collagen content, most differences occurring within the first four weeks after grafting. Inflation/extension testing showed that post-fistula the vein wall became progressively thicker and stiffer, lacking restoration of compliance to baseline levels. The present data may further our understanding of the dynamics of venous biomechanical remodeling under pressure and flow-overload conditions.

Heparin-bonded ePTFE grafts compared with vein grafts in femoropopliteal and femorocrural bypasses: 1- and 2-year results

Heparin-bonded ePTFE grafts compared with vein grafts in femoropopliteal and femorocrural bypasses: 1- and 2-year results

Long term performance of small-diameter vascular grafts made of a poly(ether)urethane–polydimethylsiloxane semi-interpenetrating polymeric network

In the past years considerable research efforts have been directed at developing more suitable synthetic vascular grafts, but small-diameter vascular grafts (SDVGs) perform less well than autogenous arterial or venous grafts. Grafts such as Dacron ® and ePTFE have often been used as alternatives to autologous grafts, but they have shown poor patency rates when used in small-diameter sizes or low-flow locations. Nevertheless, despite these efforts no alternative concepts have emerged yet that promises to replace the current generation of synthetic grafts soon. The purpose of this preliminary in vivo study was to assess the blood and tissue compatibility behaviors of a novel compliant SDVGs, fabricated with a poly(ether)urethane–polydimethylsiloxane (PEtU–PDMS) semi-interpenetrating polymeric network (semi-IPN) and featuring two different porous layers in the wall thickness. Grafts were implanted according to anastomotic techniques which emulate the flow conditions clinically adopted for peripheral or aorto-coronary bypass procedures. Relatively long grafts were implanted in the common carotid artery of adult sheep and compared to standard ePTFE grafts of the same size and length implanted controlaterally. The animal experimentation showed superior handling and compliance characteristics, and patency rates of PEtU–PDMS grafts in comparison with a standard ePTFE graft, and the ability of remodelling in vivo while being gradually replaced by a natural tissue with no sign of calcification.

Human Blood Vessel–Derived Endothelial Progenitors for Endothelialization of Small Diameter Vascular Prosthesis

BackgroundCoronary bypass graft failure as a result of acute thrombosis and intimal hyperplasia has been the major challenge in surgical procedures involving small-diameter vascular prosthesis. Coating synthetic grafts with patients' own endothelial cells has been suggested to improve the patency rate and overall success of bypass surgeries.Methodology/Principal FindingsWe isolated endothelial progenitor cells (EPCs) from leftover pieces of human saphenous vein/mammary artery. We demonstrate that EPCs can be expanded to generate millions of cells under low-density culture conditions. Exposure to high-density conditions induces differentiation to endothelial cell phenotype. EPC–derived endothelial cells show expression of CD144high, CD31, and vWF. We then assessed the ability of differentiated endothelial cells to adhere and grow on small diameter expanded polytetrafluoroethylene (ePTFE) tubings. Since ePTFE tubings are highly hydrophobic, we optimized protocols to introduce hydrophilic groups on luminal surface of ePTFE tubings. We demonstrate here a stepwise protocol that involves introduction of hydrophilic moieties and coating with defined ECM components that support adhesion of endothelial cells, but not of blood platelets.Conclusion/SignificanceOur data confirms that endothelial progenitors obtained from adult human blood vessels can be expanded in vitro under xenoprotein-free conditions, for potential use in endothelialization of small diameter ePTFE grafts. These endothelialized grafts may represent a promising treatment strategy for improving the clinical outcome of small-caliber vascular grafts in cardiac bypass surgeries.

Superior vena cava (SVC) reconstruction using autologous tissue in two cases of differentiated thyroid carcinoma presenting with SVC syndrome

Herein, we report two extremely rare cases of differentiated thyroid carcinoma (DTC) with extended tumor thrombus or mediastinum lymph node metastasis (LNM) involving the superior vena cava (SVC), causing SVC syndrome. Both of these patients were successfully treated with radical resection and reconstruction of the SVC using autologous tissue instead of an expanded polytetrafluoroethylene (ePTFE) graft. The left brachiocephalic vein was used to reconstruct the SVC in a papillary thyroid carcinoma patient with mediastinum LNM and a pericardial patch was used in a follicular thyroid carcinoma patient with tumor thrombus. Our search of the English-language literature found sporadic reports of SVC resection with reconstruction by vascular graft (ePTFE), interposed between the brachiocephalic vein and the right atrium. However, SVC reconstruction using autologous tissue in thyroid carcinoma has not been reported to date. To our knowledge, this is the first report describing such an unusual technique in DTC patients.

Response to Letter to Editor

We would like to thank Dr Chaudhuri for his in-depth response on our recent publication “Dacron or ePTFE for femoro-popliteal above-knee bypass grafting: short and long-term results of a multicentre randomised trial.” Eur J Vasc Endovasc Surg 2009; 37: 457–463. Indeed it was mentioned that the patency rates with large-caliber prosthetic grafts in the fem-distal position (8 mm instead of 6 mm) were maybe better.1Abbott W.M. Green R.M. Matsumoto T. Wheeler J.R. Miller N. Veith F.J. et al.Prosthetic above-knee femoropopliteal bypass grafting: results of a multicenter randomized prospective trial. Above-Knee Femoropopliteal Study Group.J Vasc Surg. 1997 Jan; 25: 19-28Google Scholar, 2Green R.M. Abbott W.M. Matsumoto T. Wheeler J.R. Miller N. Veith F.J. et al.Prosthetic above-knee femoropopliteal bypass grafting: five-year results of a randomized trial.J Vasc Surg. 2000 Mar; 31: 417-425Google Scholar Unfortunately all these studies were flawed by nonrandomised design and potential selection bias. There is no level 1 evidence which clearly showed the better results of 8 mm prostheses in the femoro-distal position. We agree that new graft technologies might give better results compared to both, the standard Dacron and ePTFE, we used in our study. The older vascular surgeons remembered the “strong expert opinion” that patency rates with PTFE femoro-popliteal bypass above and below the knee were equal to or better than those with the same operation performed with saphenous vein.3Veith F.J. Moss C.M. Fell S.C. Rhodes B.A. Somberg E. Weiss P. et al.Expanded polytetrafluorethylene grafts in reconstructive arterial surgery. Preliminary report of the first 110 consecutive cases for limb salvage.JAMA. 1978 Oct 20; 240: 1867-1869Google Scholar This “evidence” was the background of our prospective RCT which clearly showed the opposite of the opinion of the experts in the 80th. Our group was also involved in the prospective non-consecutive cohort study of the Gore–Tex Propaten Vascular Graft in the femoro-distal position. The design of this study lodged all the potential risks of bias.4Gurusamy K.S. Gluud C. Nikolova D. Davidson B.R. Assessment of risk of bias in randomised clinical trials in surgery.Br J Surg. 2009; 96: 342-349Google Scholar The primary patency result of 91% of the Gore Propaten resembles our 1-year patency result of Dacron.5Walluscheck K.P. Bierkandt S. Brandt M. Cremer J. Infrainguinal ePTFE vascular graft with bioactive surface heparin bonding. First clinical results.J Cardiovasc Surg (Torino). 2005; 46: 425-430Google Scholar The two-year primary patency was also comparable with our Dacron result.6Peeters P. Verbist J. Deloose K. Bosiers M. Results with heparin bonded polytetrafluoroethylene grafts for femorodistal bypasses.J Cardiovasc Surg (Torino). 2006 Aug; 47: 407-413Google Scholar We agree with Dr Chaudhuri that we should not ignore possible renewals of allograft materials but he should also agree with us that we should learn from the past. Only proper designed RCTs without a mix of above-knee and below-knee bypass grafts could prove that heparin bounding ePTFE grafts should become the first choice allograft material in the femoro-distal position. Lacking this evidence so far we still conclude that Dacron is the preferential graft material in the above-knee fem-pop position if a suitable saphenous vein is absent. Re: Dacron or ePTFE for Femoro-popliteal Above-Knee Bypass Grafting: Short- and Long-term Results of a Multicentre Randomised Trial, van Det et al. in Eur J Vasc Endovasc Surg (2009) 37, 457–463European Journal of Vascular and Endovascular SurgeryVol. 38Issue 2PreviewI read with interest the paper by the above authors that challenges the more conventional use of ePTFE for prosthetic above-knee femoropopliteal bypasses. A few issues arise: firstly, the use of grafts of 6 mm diameter when an 8 mm graft is an option, which is not an unconventional one. The authors have also ignored the issue of heparin-bonded ePTFE grafts such as the Gore Propaten vascular graft in the discussion, which has demonstrated 84% and 91% 1-year primary patency rates,1,2 which is also supported on a haematological basis. Full-Text PDF Open Archive

Heparin Bonded Hemodialysis e-PTFE Grafts Result in 20% Clot Free Survival Benefit

Luminal surface heparin bonded hemodialysis e-PTFE grafts (N=83) with prolonged bioactivity retention (CBAS technology) were compared to 67 control e-PTFE grafts using Kaplan-Meier survival curve estimates. Log-rank tests were used for statistical comparisons between groups. Heparin bonded graft recipients were on average 3.5 years older (NS), and had upper arm grafts in 66% vs. 43% (p=0.003) compared to controls. There was no clot-free survival (CFS) difference between groups for upper arm vs. forearm placed grafts (p=0.792). Patient mortality at one year was 15%, with no group difference. The overall combined clot-free survival for all 150 e-PTFE grafts was 69% at 12 months. At 6 and 12 months, CFS for the heparin bonded graft group was 88% and 78%, which is significantly higher than that of 69% and 58% for the control group, respectively, (p=0.007). It is concluded that heparin binding technology to artificial surfaces has evolved to a clinically powerful technique for the hemodialysis patient resulting in a 20% improved primary graft patency of about 80% at one year.

Citric acid‐based elastomers provide a biocompatible interface for vascular grafts

Prosthetic vascular bypass grafting is associated with poor long-term patency rates. Herein, we report on the mid-term performance of expanded polytetrafluoroethylene (ePTFE) vascular grafts modified with a citric acid-based biodegradable elastomer. Through a spin-shearing method, ePTFE grafts were modified by mechanically coating a layer of poly(1,8 octanediol citrate) (POC) onto the luminal nodes and fibrils of the ePTFE. Control and POC-ePTFE grafts were implanted into the porcine carotid artery circulation as end-to-side bypass grafts. Grafts were assessed by duplex ultrasonography, magnetic resonance angiography, and digital subtraction contrast angiography and were all found to be patent with no hemodynamically significant stenoses. At 4 weeks, POC-ePTFE grafts were found to be biocompatible and resulted in a similar extent of neointimal hyperplasia as well as leukocyte and monocyte/macrophage infiltration as control ePTFE grafts. Furthermore, POC supported endothelial cell growth. Lastly, scanning electron microscopy confirmed the presence of POC on the ePTFE grafts at 4 weeks. Thus, these data reveal that surface modification of blood-contacting surfaces with POC results in a biocompatible surface that does not induce any untoward effects or inflammation in the vasculature. These findings are important as they will serve as the foundation for the development of a drug-eluting vascular graft.

Biodegradable nitric oxide‐releasing poly(diol citrate) elastomers

We have developed novel poly(diol citrate) elastomers, which are capable of providing localized and sustained release of nitric oxide (NO). The elastomer prepolymer was obtained by condensation of citric acid, 1,8-octanediol, and N,N'-bis(2-hydroxyethyl)ethylenediamine at 130 degrees C for 40 min. Films were prepared by solvent casting followed by crosslinking at 80 degrees C for 4 days. Mechanical properties were tested. NO-releasing expanded poly(tetrafluoroethylene) (ePTFE) vascular grafts were fabricated by coating the graft's lumen with the prepolymer and crosslinking it at 80 degrees C for 4 days prior to diazeniumdiolation. Samples were diazeniumdiolated via exposure to pressurized NO. Cell compatibility was assessed by monitoring the proliferation of porcine aortic smooth muscle cells (PASMC) on the elastomers. Degradation in phosphate buffer saline (PBS) (pH = 7) at 37 degrees C was evaluated for up to 6 weeks. The secondary amine-containing poly(diol citrate) films had a Young's modulus that ranged from 5.91 to 32.64 MPa, an ultimate tensile stress that ranged from 1.47 to 10.71 MPa, and an elongation at break from 200 to 260%, depending on the content of secondary amine in the feed monomer. These elastomers were degradable and compatible with PASMC. Furthermore, degradation rate was found to be independent of the content of secondary amines in the prepolymer. The NO release from diazeniumdiolated films and ePTFE grafts was sustained for two days. In conclusion, these novel diazeniumdiolated polyester elastomers may be useful in medical devices that require blood contact or control of cell proliferation.

Alcohol Pretreatment of Small‐diameter Expanded Polytetrafluoroethylene Grafts: Quantitative Analysis of Graft Healing Characteristics in the Rat Abdominal Aorta Interposition Model

Long-term patency rates of small-diameter expanded polytetrafluoroethylene (ePTFE) vascular prostheses are unsatisfactory. Treatment of ePTFE grafts by alcohol before implantation was reported to increase hydrophilic properties, yielding better endothelialization and cellular in-growth, thus improving graft healing. The effect of alcohol pretreatment on ePTFE grafts and postoperative healing characteristics of wet ePTFE grafts were evaluated in this study. Ten sterile ePTFE grafts (2 mm ID, 30 micro thru-pore, 12 mm long) were implanted in the infrarenal aorta of male Sprague-Dawley rats (324-380 g). Five grafts were treated with ethanol 70% and soaked with saline solution before implantation (wet); five nontreated grafts served as control. All rats were sacrificed after digital subtraction angiography and sampling of the graft for histological investigation after 3 weeks. Histomorphometric analysis was performed for endothelial coverage, cellular in-growth, and intimal hyperplasia. All grafts were patent at the end of 3 weeks in both groups. Histological evaluation revealed significantly better endothelial coverage and prominent infiltration by fibroblasts and lymphocytes in the wet group. Endothelial coverage (31.03 +/- 10.61% vs. 13.03 +/- 9.46%, P = 0.03) and cellular infiltration of grafts (50.91 +/- 8.55% vs. 39.29 +/- 10.70%, P = 0.11) were higher in the wet group. Area of intimal hyperplasia per graft length was also higher in the wet group (5.32 +/- 4.75 microm(2)/microm vs. 2.69 +/- 3.41 microm(2)/microm, P = 0.36). Wetting of ePTFE grafts with ethanol 70% pretreatment before implantation might have a beneficial effect on long-term patency of small-diameter vascular grafts due to facilitated graft healing.

Aortobifemoral Bypass Grafting Using Expanded Polytetrafluoroethylene Stretch Grafts in Patients with Occlusive Atherosclerotic Disease

The aim of this retrospective study was to evaluate the performance of bifurcated, longitudinally extensible (stretch), expanded polytetrafluoroethylene (ePTFE) grafts implanted in patients with aortoiliac or aortofemoral occlusive atherosclerotic disease. Between October 1991 and December 2005, 822 consecutive patients (708 men, 114 women; mean age 63.8 years) underwent aortoiliac or aortofemoral reconstruction using a bifurcated ePTFE stretch graft. Preoperatively, all patients had ultrasonographic and arteriographic evaluations and were divided into groups according to the TASC II morphological stratification of iliac lesions. Seventy-seven patients (9.4%) had type B lesions, 314 (38.2%) had type C lesions, and 431 (52.4%) were classified as type D lesions. Endarterectomy of the aorta was required in 172 patients (21%); femoral arteries were endarterectomized in 222 (27%). Femoropopliteal bypass grafting was performed in 18 patients, aortorenal bypass in 12, and mesenteric artery grafting in one. One patient died perioperatively of a myocardial infarction. Perioperative morbidity included cardiac (2.2% of patients), respiratory (0.9%), and gastrointestinal (1.2%) complications, as well as acute renal insufficiency (1.3%). Seven patients had bleeding requiring surgical revision within the first 24hr after surgery. There were four cases (0.5%) of immediate graft thrombosis and five (0.6%) of single-limb graft thrombosis. During a mean follow-up time of 72 months (range 28-170), 58 patients (7.1%) were lost to follow-up and 205 patients (24.9%) died. The primary and secondary graft-patency rates during the observation period were 90.6% and 97.9%, respectively. Twelve late graft occlusions resolved after thrombectomy alone. Eleven cases of single-limb late thrombosis resolved after thrombectomy and profundoplasty. The limb-salvage rate during the observation period in patients who underwent operation for critical limb ischemia was 84.5%. There were nine postoperative graft infections (1.1% infection rate) in the series. Our long-term experience with ePTFE stretch grafts in aortoiliac and aortofemoral reconstruction shows that these prostheses have a high rate of patency and a low rate of graft-related complications.

Dilatation of Aortic Grafts Over Time: What to Expect and When to be Concerned

Dilatation of aortic prosthetic grafts is commonly reported, but most reports are anecdotal, with little objective data in the literature. We performed a prospective trial of 303 patients who underwent prosthetic graft repair for aortic aneurysm or occlusive disease, randomizing patients between insertion of a woven polyester or expanded polytetrafluoroethylene (ePTFE) graft. Patients were followed with computed tomography and ultrasonography for up to 5 years in order to assess the frequency and magnitude of postoperative dilatation. Graft dilatation was documented in patients with polyester grafts at 12 months. Thereafter and up to 60 months, polyester grafts did not dilate further. After 5 years, polyester prostheses had dilated by 25% and ePTFE by 12.5%, as determined by computed tomography imaging. These observations suggest that dilatation of prosthetic grafts is more frequent with knitted polyester grafts compared with ePTFE. Dilatation occurs within the first year after implantation and can be, in part, explained by a discrepancy between the initial nominal graft diameter and its diameter after clamp release, probably due to an in vivo adaptation of the textile structure. Interestingly, graft dilatation did not appear to be associated with an increased frequency of graft-related complications.

The Effect of Locally Administered Anti-Growth Factor Antibodies on Neointimal Hyperplasia Formation in Expanded Polytetrafluoroethylene Grafts

The selective blockage of platelet-derived growth factor BB (PDGF-BB), basic fibroblast growth factor (bFGF), and transforming growth factor beta1 (TGF-beta1) by specific antibodies coated into expanded polytetrafluoroethylene (ePTFE) grafts may diminish neointimal hyperplasia. Sixty pigs were divided into two groups (n = 30 each) and then further divided into five subgroups. Group 1 had a bilateral iliac artery ePTFE interposition graft precoated with Matrigel. Three subgroups (A, B, and C) received a specific monoclonal antibody against PDGF-BB, bFGF, or TGF-beta1. One (D) received all antibodies, and one served as control (nonimmune immunoglobulin G [IgG] isotypes) (E). Group 2 had a bilateral iliac artery endothelial cell (EC)-seeded ePTFE interposition graft precoated with Matrigel. Three subgroups (A, B, and C) received a specific antibody against PDGF-BB, bFGF, or TGF-beta1. One (D) received all antibodies, and one served as control (nonimmune IgG isotypes) (E). Light microscopy and immunohistochemical stain showed that neointimal hyperplasia formation was significantly reduced in subgroups D compared to the others (p < 0.05). In subgroups D, the different precoating influenced neointimal hyperplasia formation. It was more pronounced in the prosthesis precoated with EC and Matrigel (p < 0.05). In organ culture, the amount of PDGF-BB, bFGF, and TGF-beta1 release was reduced in subgroup D animals compared to the others (p < 0.05). In subgroups D, the release of PDGF-BB, bFGF, and TGF-beta1 depended on ePTFE seeding. A higher amount of these growth factors was released in the prostheses precoated with EC and Matrigel (p < 0.05), and the bromodeoxyuridine labeling index confirmed higher incorporation in this subgroup (p < 0.001). The combined use of locally administered anti-PDGF-BB, bFGF, and TGF-beta1 monoclonal antibodies reduces neointimal hyperplasia formation.

RR21. Treatment of Infrainguinal Critical Limb Ischemia Using a Heparin-bonded ePTFE Graft: Mid-term Results from a Multicenter Registry

RR21. Treatment of Infrainguinal Critical Limb Ischemia Using a Heparin-bonded ePTFE Graft: Mid-term Results from a Multicenter Registry

Heparin-bonded ePTFE grafts compared with vein grafts in femoropopliteal and femorocrural bypasses: 1- and 2-year results

Many patients with peripheral arterial occlusive disease who require a lower-limb bypass have no available autologous saphenous vein (ASV) for the procedure and thus require a prosthetic graft. Expanded polytetrafluoroethylene (ePTFE) grafts are commonly used, but results with these prostheses have varied, especially when the distal anastomosis is below the knee. However, there is increasing evidence that ePTFE grafts to which heparin has been bound with use of covalent endpoint linkage provide better results. This nonrandomized study compared the performance of these grafts with that of ASV conduits in the largest clinical series of heparin-bonded ePTFE graft implantations reported so far. The records of 350 patients who underwent a lower-limb bypass procedure that used either a heparin-bonded ePTFE graft (n = 240) or an ASV graft (n = 110) were reviewed, and preoperative, operative, and follow-up data were recorded. Kaplan-Meier analyses were used to calculate primary patency and limb salvage rates in the two graft groups; results were compared by using log-rank testing. The primary patency rates at 1 year for the heparin-bonded ePTFE grafts were 92% for above-knee femoropopliteal (AK FP) bypasses, 92% for below-knee femoropopliteal (BK FP) bypasses, and 79% for femorocrural (FC) applications. The corresponding 2-year rates were 83%, 83%, and 69%, respectively. In the ASV group, the 1-year primary patency rates for AK FP, BK FP, and FC bypasses were 91%, 72%, and 69%, respectively; the 2-year rates were 80%, 72%, and 64%, respectively. There were no significant differences in patency when AK FP, BK FP, or FC procedures were considered separately. Two-year limb salvage rates in the heparin-bonded ePTFE graft group were 92%, 98%, and 87%, respectively, for AK FP, BK FP, and FC bypasses; in the ASV group, the rates were 100%, 91%, and 96%, respectively. Two infections occurred in patients given a heparin-bonded ePTFE graft. In this large retrospective study, heparin-bonded ePTFE grafts had 1- and 2-year primary patency results that were not significantly different from those for ASV grafts. Results in BK FP and FC applications were especially promising. Randomized studies comparing the use of heparin-bonded ePTFE and ASV grafts in the treatment of peripheral arterial disease are needed to substantiate our results.