Nonporous silicone polymer coating of expanded polytetrafluoroethylene grafts reduces graft neointimal hyperplasia in dog and baboon models

Purpose: Neointimal hyperplasia frequently develops after placement of prosthetic vascular grafts and is a major cause of graft failure. This study was an attempt to prevent vascular lesion formation by coating the graft luminal surface with a thin layer of nonporous silicone polymer, and subsequently with an ultrathin layer of vapor phase (plasma gas) deposited fluoropolymer, thereby providing a smooth and chemically uniform surface that was postulated to limit pannus tissue ingrowth across the graft anastomoses.Methods: Bilateral femoral arteriovenous (AV) conduits were constructed in four dogs using expanded polytetrafluoroethylene graft materials (ePTFE; 6-mm inside diameter, 2.5-cm long). In each animal, one femoral AV shunt was constructed from a graft whose luminal surface was entirely coated with polymer. On the contralateral side, an uncoated graft served as a control. Bilateral aortoiliac grafts were placed in three baboons using 5-cm segments of ePTFE (4-mm inside diameter). One end (1 cm) of each graft had been coated with polymer. In each animal, the coated end of one graft was placed proximally and the coated end of the second graft was placed distally in the contralateral vessels.Results: All grafts were patent at 30 days. In the dog model, there was a significant reduction in graft neointimal area at the venous anastomoses for the coated grafts compared with the uncoated grafts (0.03 ± 0.02 mm ² and 1.11 ± 0.54 mm ² , respectively; p < 0.05). In the baboon model, the silicone coating significantly reduced the graft neointimal thickness (0.003 ± 0.003 mm vs 0.21 ± 0.05 mm; p < 0.05) and neointimal area (0.05 ± 0.08 mm ² vs 0.82 ± 0.58 mm ² ; p < 0.05).Conclusions: These data demonstrate that healing of ePTFE grafts can be effectively modified by altering the physical properties of the graft surface. Neointimal hyperplasia within ePTFE grafts is significantly reduced by the local application of a fluorocarbon-coated, silicone-based polymer. The resulting graft flow surface effectively prevents tissue ingrowth from the adjacent native vessel, thereby preserving the anastomosis luminal area. This approach could represent a new strategy for limiting graft surface anastomotic neointimal hyperplasia. (J Vasc Surg 1996;24:825-33.)     

Bacterial adherence to vascular prostheses: A determinant of graft infectivity

An in vitro model was developed to quantitatively measure bacterial adherence to the surface of prosthetic vascular graft material. Four strains of bacteria (Staphylococcus aureus, nonmucin-producing S. epidermidis [SP-2], mucin-producing S. epidermidis [RP-12], and Escherichia coli) were used to inoculate expanded polytetrafluoroethylene (ePTFE), woven Dacron, and velour knitted Dacron graft material. After graft specimens were incubated in a 10⁷ suspension of bacteria, they were washed to remove nonadherent organisms and ultrasonically oscillated to dislodge adherent organisms. Quantitative culture of the sonication effluent was used to calculate bacterial adherence, expressed as the number of colony-forming units found in each square centimeter of graft material per 10⁷ inoculum. All bacterial strains had a greater affinity to velour knitted Dacron graft than to ePTFE (p < 0.025). E. coli and S. aureus adhered to velour knitted Dacron in greater numbers than to woven Dacron (p < 0.04). The production of extracellular polysaccharide (mucin) by the RP-12 strain significantly increased adherence to both ePTFE and Dacron grafts compared with the other three bacterial strains tested (p < 0.04). Although E. coli was less adherent to ePTFE than nonmucin-producing staphylococcal strains (S. aureus and SP-2), no difference in adherence to knitted or woven Dacron graft material was demonstrated. The differential adherence of bacteria to prosthetic vascular grafts pays an important role in the pathogenesis of graft sepsis and determines relative graft infectivity. The in vitro model developed is well suited for further study of the mechanisms by which bacteria adhere to and colonize vascular grafts. (J VASC SURG 1986;3:732-40.)     

Comparison of small-intestinal submucosa and expanded polytetrafluoroethylene as a vascular conduit in the presence of gram-positive contamination

OBJECTIVE: As a vascular conduit, expanded polytetrafluoroethylene (ePTFE) is susceptible to graft infection with Gram-positive organisms. Biomaterials, such as porcine small-intestinal submucosa (SIS), have been successfully used clinically as tissue substitutes outside the vascular arena. SUMMARY BACKGROUND DATA: In the present study, we compared a small-diameter conduit of SIS to ePTFE in the presence of Gram-positive contamination to evaluate infection resistance, incorporation and remodeling, morphometry, graft patency, and neointimal hyperplasia (NH) development. METHODS: Adult male mongrel pigs were randomized to receive either SIS or ePTFE (3-cm length, 6-mm diameter) and further randomized to 1 of 3 groups: Control (no graft inoculation), Staphylococcus aureus, or mucin-producing S epidermidis (each graft inoculation with 10 colonies/mL). Pressure measurements were obtained proximal and distal to the graft to create the iliac/aorta pressure ratio. Morphometric analysis of the neointima and histopathologic examinations was performed. Other outcomes included weekly WBC counts, graft incorporation, and quantitative culture of explanted grafts. RESULTS: Eighteen animals were randomized. All grafts were patent throughout the 6-week study period. Infected SIS grafts had less NH and little change in their iliac/aorta indices compared with infected ePTFE grafts. Quantitative cultures at euthanasia demonstrated no growth in either SIS group compared with 1.7 x 10(4) colonies for ePTFE S aureus and 6 x 10(2) for ePTFE S epi (each P < 0.001). All SIS grafts were incorporated. Histology demonstrated remodeling into host artery with smooth muscle and capillary ingrowth in all SIS groups. Scanning electron micrography illustrated smooth and complete endothelialization of all SIS grafts. CONCLUSIONS: Compared with ePTFE, SIS induces host tissue remodeling, exhibits a decreased neointimal response to infection, and is resistant to bacterial colonization. SIS may provide a superior alternative to ePTFE as a vascular conduit for peripheral vascular surgery.     

Experimental infection of dacron and bovine grafts.

This study compared the susceptibility of Dacron and ficin treated bovine grafts, implanted in dogs, to infection induced by a staphylococcal bacteremia. Forty mongrel dogs had a 2-cm segment of the infrarenal aorta replaced with either a 6-mm diameter Dacron or bovine graft. The dogs were divided into four groups: Control Groups I and II consisted of 5 dogs with Dacron grafts and 5 dogs with bovine grafts, respectively. In Group III, 16 dogs had Dacron grafts implanted and were given a S. aureus bacteremia. Group IV consisted of 15 dogs with bovine grafts subjected to S. aureus bacteremia. All dogs were sacrificed at 6 wk postoperatively, unless death occurred earlier. The grafts were cultured in beefbrain broth, plated, and bacterial growth identified by phage typing. Control Groups I and II showed no growth on cultures of the grafts. In Group III (Dacron grafts) 5 dogs died between the seventh and ninth postoperative days due to disruption of the infected anastomoses. Fifteen of the 16 Dacron grafts yielded growth of S. aureus phage type 29/52/81 on culture. All 15 bovine grafts in Group IV were infected with S. aureus and there were 14 deaths between days 5 and 8 due to hemorrhage from the disrupted grafts. It is concluded that Dacron and bovine grafts are equally susceptible to bacteremic infection, but disruption occurs more frequently and earlier in the infected bovine graft.     

Treatment of vascular graft infection by in situ replacement with a rifampin-bonded gelatin-sealed Dacron graft

Purpose: The purpose of this study was to treat an established prosthetic vascular graft infection by in situ replacement with a rifampin-bonded gelatin-sealed Dacron graft in an animal model.Methods: The infrarenal aorta of 18 dogs was replaced with a gelatin-sealed graft contaminated in vitro by soaking it in a solution with Staphylococcus epidermidis. One week later, animals were randomized into three groups. In group I (control, (n = 6), the dogs did not undergo repeat operations. The dogs in groups II and III underwent repeat operation. In these animals the infected grafts were removed for bacteriologic analysis and replaced in situ with one of two types of grafts: group II (n = 6) received an untreated, gelatin-sealed graft; group III (n = 6) received a rifampin-bonded, gelatin-sealed graft. Antibiotic bonding was obtained by soaking grafts for 15 minutes in a 60 mg/ml saline solution of rifampin at 37° C. All 18 dogs received no systemic adjunct antibiotic therapy. Control grafts and replacement grafts were removed 4 weeks after the initial implantation for bacteriologic analysis. When harvested, all the grafts were cut into two fragments, and quantitative bacterial cultures were obtained from all the fragments. Results were expressed as colony-forming units (CFU)/cm² of graft material.Results: All 18 initially implanted grafts and all the untreated replacement grafts were grossly infected at the time of removal, whereas all the rifampin-bonded replacement grafts had normal incorporation. None of the rifampin-bonded grafts grew bacteria, whereas all the initially implanted and all the untreated replacement grafts were infected (p < 0.01). Bacterial counts from the infected fragments were similar in control grafts (2.6 ± 1.9 × 10⁶ CFU/cm²), in initially implanted grafts of groups II (9 ± 1.1 × 10⁵ CFU/cm²) and III (1.3 ± 1.5 × 10⁶ CFU/cm²), and in untreated replacement grafts of group II (1.7 ± 2.5 × 10⁶ CFU/cm²). Blood culture results and culture results of liver, spleen, kidney, and lung specimens at the time of sacrifice were negative.Conclusion: This study demonstrates that rifampin-bonded gelatin-sealed Dacron grafts are resistant to infection when used for in situ replacement of an infected graft in the dog. (J VASC SURG 1994;19:739-44.)     

Synthetic vascular grafts seeded with genetically modified endothelium in the dog: Evaluation of the effect of seeding technique and retroviral vector on cell persistence in vivo

Unique characteristics of endothelium make it an attractive target cell for gene transfer. Genetically modified endothelial cells (ECs) seeded on synthetic vascular grafts offer the potential to control neointimal hyperplasia, decrease graft thrombogenicity and improve small diameter graft patency. This study addresses the issue of synthetic vascular graft colonization with endothelial cells transduced with noninducible retroviral marker genes in the dog. Autologous endothelial cells were enzymatically harvested and transduced with either the bacterial Neo^R gene or human growth hormone gene using retroviral vectors. All transduced cells were positive by polymerase chain reaction (PCR) amplification for the transduced gene sequence prior to graft seeding. Transduced ECs were seeded on Dacron grafts (n = 3) preclotted with autologous blood. These grafts exhibited complete endothelialization at times from 250 to 360 days. Recovered DNA, however, was negative for the transduced gene sequence when analyzed by PCR and Southern blotting. Expanded polytetrafluoroethylene (ePTFE) was evaluated (n = 8) using several different cell seeding protocols. Grafts were seeded at 3 densities (ranging from 6 × 10³ to 1.5 × 10⁵ cells/cm²) and 2 different adherence times. Seeding substrate was also evaluated. Grafts were either preclotted with whole blood or incubated with 20 or 120 μg/ml fibronectin for 60 min. Graft biopsies were evaluated from 2 to 52 wk. Limited endothelialization was present in 4 dogs as early as 2 wk, but never progressed to full luminal coverage. The remaining dogs failed to ever exhibit any luminal EC adherence. Two dogs with limited EC coverage had positive DNA by PCR for the Neo^R gene sequence at 2 and 3 wk. In contrast to transduced EC's, nontransduced EC colonization of ePTFE was complete at 2 wk when seeded under conditions that transduced cells had failed to persist. Neither seeding density, adherence time, seeding substrate or retroviral vector used influenced the uniformly poor graft coverage seen with transduced cells. Results of this study indicate that despite successful gene transfer using 4 different retroviral vectors, transduced endothelial cells seeded under varying conditions appear altered in their ability to stably adhere and colonize synthetic vascular grafts in vivo.     

Small intestinal submucosa as a large diameter vascular graft in the dog

Autogenous saphenous vein and synthetic materials, such as Dacron and expanded polytetrafluoroethylene, have been used extensively as vascular grafts with moderate success. Improved success rates for vascular graft surgery may be possible if superior graft material was available. We tested the use of autogenous small intestinal submucosa (SIS) as a large diameter (10 mm) vascular graft in the infrarenal aorta of 12 dogs. One dog died with graft thrombosis within 48 hr of surgery. Nine dogs were sacrificed at various times during a 52-week post-surgical period and showed patent grafts without infection, thrombosis, intimal hyperplasia, or adverse effects upon blood pressure. There was no ultrastructural evidence of endothelial cell growth on the luminal surface of the SIS graft which was composed of a dense, non-thrombogenic, organized collagenous connective tissue. The SIS material was approximately one order of magnitude less elastic than natural aorta and showed an immediate dilatation of approximately 18% after exposure to the systemic blood pressure. However, there was no progressive dilatation during the 52-week postsurgical period. Two dogs remain alive at 8 and 52 weeks post-surgery with patent grafts as determined by positive contrast radiography and Doppler studies. We conclude that autogenous small intestinal submucosa can be successfully used as a large diameter arterial graft in the dog and is worthy of further investigation.     

High-porosity expanded polytetrafluoroethylene grafts for thoracic vena cava replacement with or without an omentum wrap

We previously reported that, in a short-term thoracic inferior vena cava (IVC) replacement, a high-porosity expanded polytetrafluoroethylene (ePTFE) graft (fibril length 60 μm) performed well without altering the short-term patency, and that the healing of the high-porosity ePTFE graft was accelerated by an omentum wrap. The purpose of this study was to examine the long-term performance of the high-porosity ePTFE graft with or without an omentum wrap. Eighteen grafts were placed as a thoracic IVC replacement in dogs. Nine of the grafts were wrapped in an omental pedicle flap while the other 9 were not. At 1 month and 6 months, the grafts were harvested and examined for a pathological analysis. During the observation period, one dog died of a viral infection, while the other 17 dogs survived. At 1 month and 6 months, the patency rates of the 17 grafts were 100% regardless of the presence or absence of an omentum wrap. The healing of the grafts without omentum wrap was incomplete 6 months after implantation; granulation tissue was present in the center of the pseudointima. The grafts healed completely by the addition of an omentum wrap. Our data suggest that, with an omentum wrap, the high-porosity ePTFE graft is fully expected to show a good long-term function. Received: January 5, 1999 / Accepted: November 11, 1999     

The effect of pancreatopeptidase E (elastase) on anastomotic intimal thickness in two types of vascular prosthesis

To determine the effects of pancreatopeptidase E (elastase) on anastomotic intimal thickness in vascular prostheses, expanded polytetrafluoroethylene (ePTFE) and Dacron grafts were implanted in the infrarenal aortas of 28 adult mongrel dogs, divided into four groups of seven dogs each according to the type of graft used and whether or not elastase was given. Thus, group E received ePTFE grafts without elastase; group D received Dacron grafts without elastase; group E + Ela received ePTFE grafts with concomitant oral elastase, 8 mg/kg per day; and group D + Ela received Dacron grafts with elastase given at the same dosage as in group E + Ela. Each graft was harvested 4 months following surgery for histologic examination. It was clearly observed that elastase suppressed intimal growth at the proximal and distal anastomoses in the ePTFE grafts (P<0.05), but not in the Dacron grafts. Furthermore, when we measured the smooth muscle cell percent extinction (%E) on microspectrophotometry in the intima within 2 mm of the proximal and distal anastomoses, it was found that elastase reduced intimal smooth muscle proliferation at the anastomosis of the ePTFE grafts, but not the Dacron grafts (P<0.05). These data suggest that elastase suppresses intimal growth by inhibiting smooth muscle cell migration and proliferation in the vascular prostheses of low but not of high porosity.     

Viability of engineered vessels as arterial substitutes.

The search for vessel substitutes to replace small-/medium-caliber vessels is an ongoing concern for vascular surgeons. Engineered vessels were designed for use as arterial equivalents and assessed in an in vivo model in dog. Three study groups were established: clinical expanded polytetrafluoroethylene (ePTFE; control, n = 24), ePTFE seeding with endothelial cells (EC graft, n = 12), and ePTFE with a fibroblast matrix seeded with EC (FM+EC graft, n = 12). Grafts were subjected to a custom-designed femoral ex vivo circuit and implanted in the carotid artery for 60 days. The viability of the prosthetic grafts was evaluated. The ex vivo circuit revealed that the presence of a fibroblast matrix induced over double the cell retention compared to EC grafts. A significant reduction in platelet adhesion in EC grafts was observed. After their in vivo implantation, the engineered vessels were more efficient at avoiding occlusion than the prosthetic grafts. The FM+EC grafts induced more endothelialization than those seeded with ECs alone. Intimal hyperplasia response was reduced in the EC substitutes. Significant differences in apoptotic cells emerged between the EC and control ePTFE grafts. In conclusion, engineered vessels showed improved initial patency over ePTFE grafts. The EC graft was best at combating restenosis, a good indicator of the long-term efficiency of the graft.     

Multicenter evaluation of a polyurethaneurea vascular access graft as compared with the expanded polytetrafluoroethylene vascular access graft in hemodialysis applications

Objectives: The purpose of this study was to compare in a randomized, prospective, and controlled study, the performance of a multilayered, self-sealing polyurethane vascular access graft (PVAG) and expanded polytetrafluoroethylene (ePTFE) vascular access grafts in hemodialysis applications. Performance measures included graft survival, complications, time to early cannulation, and hemostasis times after cannulation. Study Design: A total of 142 patients were randomized equally to receive one of the two grafts after meeting all eligibility requirements. All patients were followed up prospectively to 12 months or to the end of secondary patency. Specifically, this study documented the performance of the PVAG and ePTFE grafts by determining the patencies and complications for both grafts. Results: Patient characteristics between the two groups were similar with respect to risk factors and demographic characteristics (P >.05). Life-table patencies from the date of first dialysis were primary patency: PVAG 55% versus ePTFE 47% (6 months) and PVAG 44% versus ePTFE 36% (12 months) and secondary patency: PVAG 87% versus ePTFE 90% (6 months) and PVAG 78% versus ePTFE 80% (12 months). None of these differences were significant (P >.05). Both primary and secondary patencies were also not significantly different when the date of implantation was the starting point. Adverse events and complications were similar for the two groups, except the PVAG group had a higher incidence of technical complications manifested by graft kinking when compared with the control cohort (P <.05). Additionally, there was no significant difference in complication rates between these two groups with regard to infection and bleeding. When the time to hemostasis after cannulation was compared at 5 minutes or less, there were more PVAG cannulation sites that achieved hemostasis compared with ePTFE sites, and this difference was significant (P <.0001). When time to first dialysis access was compared between the two grafts, 53.9% of all PVAG grafts were cannulated before 9 days versus none with the ePTFE grafts (P <.001). However, long-term graft survival was not significantly different when PVAG patients were stratified into early (< 9 days) and the late access (9 ≥ days) groups (P =.29). Conclusions: The PVAG graft allows for early access without compromising long-term performance. Both PVAG and standard ePTFE grafts have similar long-term outcomes, despite early access with the PVAG vascular access grafts. (J Vasc Surg 2001;34:465-73.)     

Small Intestinal Submucosa as a Vascular Graft: A Review

Continuing investigations of vascular graft materials suggest that unacceptable graft complications continue and that the ideal graft material has not yet been found. We have developed and tested a biologic vascular graft material, small intestine submucosa (SIS), in normal dogs. This material, when used as an autograft, allograft, or xenograft has demonstrated biocompatibility and high patency rates in aorta, carotid and femoral arteries, and superior vena cava locations. The grafts are completely endothelialized at 28 days post-implantation. At 90 days, the grafts are histologically similar to normal arteries and veins and contain a smooth muscle media and a dense fibrous connective tissue adventita. Follow-up periods of up to 5 years found no evidence of infection, intimal hyperplasia, or aneurysmal dilation. One infection-challenge study suggested that SIS may be infection resistant, possibly because of early capillary penetration of the SIS (2 to 4 days after implantation) and delivery of body defenses to the local site. We conclude that SIS is a suitable blood interface material and is worthy of continued investigation. It may serve as a structural framework for the application of tissue engineering technologies in the development of the elusive ideal vascular graft material.     

ePTFE人工血管材料内衬自体骨髓内皮细胞的实验研究

目的:探讨自体骨髓内皮细胞衬里对ePTFE人工血管材料通畅性的影响。方法:24只犬随机分入实验组(12只)和对照组(12只)。实验组取犬自体骨髓,提取单核细胞种植ePTFE人工血管,行左髂动脉人工血管置换术;对照组采用普通ePTFE人工血管。分别于术后1月、3月行彩色多普勒超声观察其通畅率,并行组织染色及扫描电镜观察,比较人工血管表面内皮化情况。结果:术后1月时实验组人工血管通畅率及内膜厚度同对照组均无明显差别;但术后3月时实验组通畅率高于对照组,内膜厚度明显小于对照组(P0.05)。结论:自体骨髓内皮细胞衬里技术可明显提高ePTFE人工血管的短期通畅率,但其对远期通畅率的影响尚有待进一步观察。     

Comparison of endovascular and conventional vascular prostheses in an experimental infection model

Introduction: The causes and management of prosthetic graft infections have been extensively studied for conventional bypass grafts; however, the infectivity and therapy for endovascular graft infections are completely unknown. The aim of this study was to compare the biologic properties of infected aortic grafts when inserted by endoluminal or standard transabdominal techniques.Methods: Eighteen dogs underwent placement of polytetrafluoroethylene grafts in their infrarenal aortas either by an endovascular technique (8) or a standard interposition technique (10). Endovascular grafts were constructed from polytetrafluoroethylene (3 cm) and two balloon-expandable stents coaxially mounted onto a balloon catheter delivery system. The grafts were inserted through a left carotid arteriotomy under fluoroscopic control. Initially, seven grafts were infected with decreasing inocula of Staphylococcus aureus, starting at 10⁷ organisms per ml for 30 minutes and then rinsed briefly (10 seconds) in normal saline solution, until a 50% infective dose for the standard grafts was determined to be 10² organisms per ml. After this initial experiment, a second group of 11 dogs were compared at a concentration of 10² S. aureus per ml. Five dogs underwent endovascular repair, and six dogs had standard graft interpositions after an identical period of bacterial exposure. All grafts were removed at 2 weeks under sterile conditions and were submitted for quantitative culture analysis.Results: Three of the six dogs (50%) with standard grafts appeared to clear their infections, whereas only one of the five dogs (20%) with an endovascular graft was free of organisms at 14 days. This result was further manifested by statistically significant lower postmortem colony counts in the standard grafts (p < 0.01).Conclusions: The endoluminal position of the graft and its proximity to the arterial wall do not appear to provide protection against infection. These data suggest that if endovascular grafts become infected, they may be in a disadvantaged position for host defense mechanisms to be effective. (J Vasc Surg 1996;24;920-6.)     

Small intestinal submucosa as a superior vena cava graft in the dog.

Autogenous spiral vein grafts and ePTFE have been used for reconstruction of the superior vena cava with moderate success. We tested autogenous small intestine submucosa as a superior vena cava interpositional graft in nine dogs. All dogs received aspirin and warfarin sodium for the first 8 weeks after surgery. Graft patency was evaluated by serial venography. One dog died from excessive anticoagulation. Eight dogs were sacrificed at periodic intervals until 72 weeks after surgery. Patent grafts had no evidence of thrombosis, aneurysm, or stenosis. The grafts consisted of dense, organized collagenous connective tissue with a complete endothelial cell layer on the luminal surface. Two dogs are alive at 28 and 34 months after surgery. Graft patency was 89% (eight of nine grafts). We conclude that autogenous small intestine submucosa can be used as a superior vena cava graft in the dog and is worthy of further investigations.     

Antibacterial activity,antibiotic retention,and infection resistance of a rifampin-impregnated gelatin-sealed Dacron graft

Purpose: A gelatin-sealed porous Dacron graft impregnated with rifampin was evaluated in a two-part study of its use in preventing prosthetic infection.Methods: The graft was impregnated by soaking it for 15 minutes in rifampin (1 mg/ml). In part 1 its antibacterial activity and rifampin retention over time were determined. Infrarenal aortic replacement was performed in pigs, and the rifampin concentration of the graft, serum, and perigraft space was assayed up to 96 hours after surgery. In part 2, infection resistance was tested in pigs in which the retroperitoneum was contaminated with Staphylococcus aureus after graft replacement. The postoperative infection rate was compared in three groups: pigs given gelatin-sealed grafts without rifampin (controls), pigs receiving nonimpregnated grafts and intravenous rifampin (15 mg/kg) for 3 days after surgery, and those given the rifampin grafts.Results: Rifampin was present in the grafts for up to 72 hours after surgery and in the perigraft fluid for 24 hours but was never detected in the serum. The grafts had inhibitory activity in vitro against S. aureus and the biofilm phase of Staphylococcus epidermidis for up to 3 days and against Escherichia coli for 2 days. Pigs given intravenous rifampin had a significantly lower infection rate than had control pigs (7/12 vs 13/13; p = 0.02); those receiving the rifampin graft had a lower rate (2/13) than had either the control pigs (p < 0.001) or those given intravenous rifampin (p < 0.04).Conclusions: This simple method of graft impregnation resulted in antibiotic retention for 3 days and appeared to be superior to intravenous antibiotic administration in preventing perioperative graft infection. (J VASC SURG 1994;19:675-82.)     

In situ replacement of arterial prosthesis infected by bacterial biofilms: Long-term follow-up

Purpose: Bacterial biofilm infections of vascular prostheses are characterized by an absence of systemic sepsis, a fluid-filled cavity surrounding the graft, a draining sinus tract, and microorganisms that must be removed from the fabric prosthesis for bacterial culture.Methods: Since 1987 we have treated 20 infected grafts with prosthetic excision and in situ replacement in 14 men and 6 women. The time from initial graft implantation to diagnosis of graft infection ranged from 3 months to 14 years (mean 4.5 years). The original graft (Dacron-17, polytetrafluoroethylene-3) was an aortobifemoral in 14, axillofemoral femorofemoral in 3, iliofemoral in 2, and femoropopliteal in 1 patient. Presenting symptoms were groin false aneurysm with perigraft fluid in 10, inflammatory mass in 6, and sinus tract in 4. At surgery all unincorporated graft material and the perigraft capsule were excised from a point where the proximal graft was incorporated, including debridement of vessels at the distal anastomosis. Of the 14 aortobifemoral grafts, only the femoral limbs were excised at the initial presentation of biofilm infection. The conduit was replaced with an in situ polytetrafluoroethylene interposition graft, which was covered with a gracilis or sartorius muscle flap when possible.Results: All surgical sites healed, all grafts remained patent, and there was no limb loss. After ultrasonic oscillation of the explanted graft, bacterial cultures recovered coagulase-negative Staphylococcus species in 14, coagulase-positive Staphylococcus species in one, both species in three, with no growth from two specimens. During follow-up, two patients have had clinical involvement in the proximal intraabdominal portion of the graft that had not been previously resected. In all grafts, the in situ replacement graft remained well incorporated.Conclusion: In situ graft replacement is effective treatment for biofilm infections of vascular prostheses. Because of the indolent nature of these infections, subsequent infection of previously uninvolved graft segments may be expected. (J VASC SURG 1994;19:226-35.)     

Prevention of vascular graft infection by rifampin bonding to a gelatin-sealed dacron graft

This study examines the efficacy of rifampin bonding to a gelatin-sealed knitted Dacron graft to prevent perioperative bacteremic vascular graft infection. Antibiotic bonding was obtained by soaking grafts for 15 minutes in a 1 mg/ml saline solution of rifampin at 37°C. Nineteen dogs had thoracoabdominal aortic bypass: seven (group I) received a rifampin treated graft; six (group II) received an untreated gelatin-coated graft; and six (group III) received an uncoated Dacron graft. Two days later bacteremic challenge was produced by rapid intravenous injection of 5×10 ⁵ colony forming units of methicillin resistantStaphylococcus aureus.Grafts were harvested five days after this challenge and cut into 10 fragments, each submitted to bacterial counts. Results were expressed as CFU/cm ² of graft material. In group I, no graft was infected, whereas all grafts in groups II and III were infected (p<0.05). Median bacterial counts from the infected fragments (median±SD) were similar in groups II (2.5×10⁵ CFU/cm²) and III (4×10⁴ CFU/cm²). Blood cultures at time of sacrifice were negative in all dogs in group I and positive in five of six dogs in groups II and III. Cultures of liver, spleen, kidney, and lung specimens were always negative in group I and positive in 22 of 24 specimens in group II and 23 of 24 specimens in group III. Soaking a gelatin-sealed Dacron graft in rifampin solution evidently prevents early bacteremic graft infection and secondary foci of infection in this model.Presented at the Annual Meeting of the French Vascular Surgery Society, Nancy, France, May 18–19, 1990.     

Hemagglutinating virus of Japan-liposome–mediated gene transfer of endothelial cell nitric oxide synthase inhibits intimal hyperplasia of canine vein grafts under conditions of poor runoff

Purpose: Late graft failure is a critical problem, particularly in the presence of poor runoff vessels. Intimal hyperplasia is considered to be the main cause of graft failure. We have already reported that intimal thickening of experimental vein grafts in dogs with poor runoff vessels is more pronounced than that in dogs with normal vessels. We and others also have reported that production of nitric oxide (NO) in the endothelium of canine vein grafts is impaired. In the present study, we asked whether in vivo gene transfer of endothelial cell NO synthase (ecNOS) would inhibit intimal hyperplasia of autogenous vein grafts implanted in limbs with poor distal runoff in dogs. Methods: After exposing femoral veins, the nuclear-targeted lac Z gene, bovine ecNOS cDNA, or control vector plasmid encapsulated in the hemagglutinating virus of Japan-liposomes was infused intraluminally, followed by incubation for 10 minutes at room temperature under a distending pressure of 100 mm Hg. Twenty reversed vein grafts were implanted under normal runoff conditions, and 4 days later these were used to confirm gene transfer to the vein grafts. Twelve reversed vein grafts were implanted under conditions of poor runoff, and 4 weeks after the operation intimal thickening was evident. Results: In vein grafts under normal runoff conditions, lac Z gene transfer exhibited diffuse and frequent X-Gal-positive signals in both medial and adventitial layers 4 days after implantation (n = 3). In case of the ecNOS gene–transferred vein grafts, bovine ecNOS protein was mainly detected in medial smooth muscle cells and adventitial cells 4 days after implantation, determined using immunohistochemical techniques and bovine ecNOS specific antibody (n = 3). In addition, ecNOS-transferred vessels showed intense purple signals by reduced nicotinamide adenine dinucleotide phosphate diaphorase and nitroblue tetrazolium reaction, in both medial and adventitial layers, whereas weak NOS activity was recognized at the adventitial vasa vasorum of the untreated veins or control vector transferred veins (n = 3, respectively). In vein grafts under poor runoff conditions, the intimal thickness at 4 weeks after implantation was significantly reduced by ecNOS gene transfer (n = 4; 90.0 ± 7.6 μm and 1.18 ± 0.07 mm²) in comparison with buffer-treated vessels (n = 4; 195.8 ± 25.7 μm and 2.62 ± 0.48 mm²) or vector vehicle–treated vessels (n = 4; 193.0 ± 15.8 μm and 2.65 ± 0.22 mm²). Conclusions: Our findings show that gene transfer of ecNOS inhibited intimal hyperplasia of canine vein grafts caused by poor runoff conditions, as a result of an increased local production of NO. Thus ecNOS gene transfer warrants further study as a possible approach to prevent late graft failure. (J Vasc Surg 1998;27:135-44.)     

Differential effects of a gram-negative and a gram-positive infection on autogenous and prosthetic grafts

A canine model was developed to study the differential response of a gram-negative and a gram-positive bacterial infection on autogenous and prosthetic grafts. After replacing segments of the femoral arteries of 15 dogs with autogenous vein in one groin and polytetrafluoroethylene in the contralateral groin, 10(8) colony-forming units of nonmucin-producing Staphylococcus epidermidis (five dogs), Pseudomonas aeruginosa (five dogs), or sterile saline solution (five dogs) were directly inoculated onto the grafts. The grafts were examined 7 to 10 days after implantation. None of the control dogs exhibited inflammatory signs, and no grafts or anastomoses disrupted. S. epidermidis was unrecoverable from either graft material in any of the animals, although histologic evaluation confirmed neutrophils and bacteria in four of five animals in the vein and polytetrafluoroethylene groups. No dog inoculated with S. epidermidis had graft or anastomotic disruption. By contrast, P. aeruginosa was recovered from both types of grafts in all inoculated animals. Neutrophils, bacteria, and microabscesses were observed in all of these animals. In addition, three of five polytetrafluoroethylene grafts and all five vein grafts disrupted either at the anastomoses or in the body of the vein graft. Therefore S. epidermidis is a less virulent organism that may persist in graft walls despite negative cultures, whereas P. aeruginosa is a highly virulent organism that can disrupt native artery, vein grafts, and anastomoses. The graft material appears to be less important than the bacteria in determining the outcome of infection.