Platelet and coagulation factor variations induced in vitro by polyethylene terephthalate (Dacron) coated with pyrolytic carbon.

The haemocompatibility of polyethylene terephthalate (Dacron) coated with pyrolytic carbon was examined in vitro, evaluating its capability of inducing adhesion and platelet activation, and of modifying the intrinsic coagulation pathway. Platelet adhesion was evaluated by counting platelets before and after in vitro contact of human plasma with the material under examination. Platelet activation was evaluated by determining platelet factor 4 (PF4) and thromboxane B2. Intrinsic coagulation pathway alterations were studied by determining activated partial thromboplastin time (APTT) and the activity of single factors. The results obtained show that pyrolytic carbon-coated Dacron induces platelet adhesion, reduction in platelet volume and lower increase in thromboxane production than that obtained after contact with uncoated Dacron. Pyrolytic carbon-coated Dacron does not induce PF4 release, contrary to uncoated Dacron induces a significant release. Moreover, pyrolytic carbon-coated Dacron, induces a significant extension of APTT by reducing the activity of intrinsic pathway factors, particularly factor XI.

Iatrogenic vascular lesions. Pathogenesis and treatment: an 18 year review.

The records of 304 patients operated on for vascular injuries were reviewed; 76 (25%) of these presented an iatrogenic vascular injury: 13 involved the upper limbs, 49 the lower limbs and 14 the neck and trunk. The lesions were due to a vascular catheterism in 40 patients, to orthopaedic treatment in 27 patients, to general surgery procedure in 3 patients, to urologic surgery in 3 and to otorhinolaryngologic surgery in 3. In vascular catheterism the prevalent complications were thromboses and embolisms; 3 patients needed an amputation after the surgical repair. In orthopaedic surgery, vascular complications were linked prevalently to hip surgery, exchange arthroplasty and upper tibial osteotomy. In urologic, otorhinolaryngologic and general surgery, vascular lesions were prevalently related to haemorrhagic complications, followed by incorrect haemostatic manoeuvres. Retroperitoneal fibrosis or previous surgery increased the risk of vascular injuries. Delay in treatment was responsible for post-operative death or incomplete recovery.

Indobufen vs acetylsalicylic acid plus dipyridamole in long-term patency after femoropopliteal bypass.

To compare the effects of indobufen (INB) with those of ASA+dipyridamole (DP) on graft patency, 113 patients undergoing femoropopliteal bypass surgery were randomly and blindly assigned to treatment with INB 400 mg daily or with ASA 900 mg daily plus DP 225 mg daily. Treatment started 2 days before surgery and lasted for 12 months. All patients underwent two angiographic examinations: the first early after surgery (mean 6 days) and the second at the end of the study (mean 368 days). The 1 year cumulative patency rate for INB was 60% higher but not statistically different from the ASA-DP group (53.2%). The relative risk (INB/ASA+DP) calculated by the Mantel-Haenszel test was 0.86 (confidence limits 0.54-1.35). Only the site of operation (above-knee or below-knee) has a significant prognostic value on the fate of the graft.

Interaction between vascular prostheses and rifampicin in the prevention of the grafts infection. An experimental study.

Infections caused by synthetic prostheses are relatively rare (1.5-6%) but serious complication in vascular surgery. There is no doubt that during and immediately after surgery bacterial contamination may occur. An in vitro study was carried out in the Vascutek laboratories, which revealed a high affinity between prostheses in Dacron gel and Rifampicin. This affinity, the result of an ionic bond, was demonstrated by the fact that after 5 days Rifampicin was still present on the prostheses. Encouraged by this result, an experimental study was carried out in sheep. Five sheep were operated on making a prosthetic graft in both of the common carotid arteries: on one side a Gelseal Dacron prosthesis was implanted after being soaked for 15 minutes in a solution containing 1 mg/ml Rifampicin. A Knitted Dacron prosthesis was implanted in the contralateral carotid artery, again after pretreatment with Rifampicin. Explants were made after 2, 24, 48, 72 and 96 hours, and the concentration of Rifampicin on the prostheses was assessed on the basis of the diameter of the inhibition area on Staphylococcus aureus cultures. The results showed that the Gelseal Dacron prostheses maintained Rifampicin concentrations with an antibacterial activity up to 72 hours; this property disappears with the Knitted Dacron prostheses after only 24 hours. These results confirm the high affinity of Gelseal Dacron and Rifampicin also in in vivo experimental models.

Prophylaxis of graft infection with rifampicin-bonded Gelseal graft: 2-year follow-up of a prospective clinical trial. Italian Investigators Group.

Between March 1991 and June 1992, 600 patients were treated with mono-, bifemoral or iliofemoral arterial graft revascularization for occlusions and/or aneurysms. The patients were divided into two groups: group A (n = 296) received a Gelseal Vascutek graft immersed for 15 min before implant in a solution containing 1 mg/ml rifampicin; group B (n = 304) received an untreated Gelseal Vascutek graft. Both groups received perioperative antibiotic treatment with cephalosporins. Clinical follow-up was performed at 1, 6, 12 and 24 months after surgery to exclude signs of graft infection. Statistical analysis (X(2)) of pre-, intra- and postoperative risk factors showed both groups to be well matched. Among 600 patients treated, the 2-year follow-up showed 12 cases of graft infection (2.0%): five in group A (1.7%) and seven in group B (2.3%) (P = n.s.). All cases of graft infection originated in the groin and Staphylococcus aureus was isolated in 50% of cases. Statistical analysis (Mann-Whitney U test) showed a significant prevalence of lymphatic complications and immediate redo surgery in patients with graft infection. Of the 12 cases with infection, one was lost to follow-up, three were treated with total graft removal, six with partial graft removal and two with conservative therapy: there were no deaths. In spite of the relatively limited series and follow-up, no statistically significant difference emerged from the clinical use of vascular grafts pretreated with antibiotics.

[Anomalies of the subrenal inferior vena cava in the surgery of non-specific and inflammatory abdominal aortic aneurysms]. / Les anomalies de la veine cave inférieure sous-rénale dans la chirurgie des anévrismes non spécifiques et inflammatoires de l'aorte abdominale.

The sub-renal abnormalities of the lower vena cava (LVC) (left LVC, double LVC) are determined by a deterioration of the alteration process of supra-cardinal veins. Though they are rare, it is necessary to look for them during surgery of abdominal aorta in order to lower the risk of iatrogenic venous injuries. You will find below the description of six cases of sub-renal lower vena cava abnormality (3 double LVC, 3 left LVC) associated with an abdominal aorta aneurism (4 non specific aneurisms, 2 inflammations ones) as well as the diagnostic aspects and the technical issues they cause during the reconstruction of a non specific and inflammation aneurism of the abdominal aorta.

Endothelialization of a new Dacron graft in an experimental model: light microscopy, electron microscopy and immunocytochemistry.

Two types of synthetic vascular grafts, Dacron Triaxial and Dacron Gelseal Triaxial, were implanted into both the common carotids of sheep. The animals were sacrificed 1, 2, 8, and 16 weeks after surgery. Multiple specimens, obtained from grafts and anastomoses, were studied by light microscopy, transmission and scanning electron microscopy. A parallel immunocytochemical analysis was performed on some specimens. Dacron Triaxial grafts failed to develop a complete neointimal coverage. Myofibroblasts and fibroblasts were the dominant cells in such synthetic graft. Moreover, focal areas of stripping, platelet deposition, and thrombosis were observed at 8 and 16 weeks. In contrast, a stable endothelial coverage developed on the Gelseal Triaxial grafts after 16 weeks.

Healing of prosthetic arterial grafts.

Numerous synthetic biomaterials have been developed as vascular substitutes. In vitro, ex vivo and in vivo studies have demonstrated that in animals, selected materials, i.e., Dacron and ePTFE (expanded polytetrafluoroethylene) grafts, are successfully incorporated in both the large and the small caliber host arteries through a process which is generally referred to as graft healing. Morphologically, this process consists of a series of complex events including fibrin deposition and degradation, monocyte-macrophage recruitment and flow-oriented cell-layer generation, this last event being the complete endothelialization of the arterial substitute. In contrast to experimental animals, the flow surface of synthetic vascular grafts remains unhealed in humans, particularly in the small caliber conduits. Healing in man consists of graft incorporation by the perigraft fibrous tissue response with a surface covered by more or less compacted, cross-linked fibrin. It is therefore obvious that: i) marked differences in graft healing exist between animals and man; and ii) the usual mechanisms of graft endothelialization are partially ineffective in man. In order to guarantee the patency of synthetic vascular grafts for human small artery bypass, new strategies and approaches have recently been attempted. In particular, the endothelial cell seeding approach has been successfully accomplished in animals and is being experimented in human clinical studies. The problems and results of this biological approach are outlined in this paper.

An ultrastructural and immunocytochemical analysis of human endothelial cell adhesion on coated vascular grafts.

Human adult endothelial cells were enzymatically harvested from adipose tissue. Cell viability was established by Trypan blue exclusion and transmission and scanning electron microscopy. Endothelial cells were identified by immunocytochemical investigation at light microscopy, transmission electron microscopy, and scanning electron microscopy. Isolated cells were positive for actin and vimentin, negative for desmin. Factor VIII RA was mainly expressed at cell surface and occasionally disclosed in the cytoplasm. Reactivity for UEA I and J15 was weak or undetectable. Human endothelial cells were seeded and left to adhere for one hour onto different nonvascular substrates (glass, poly-l-lysine, formvar-carbon, fibronectin, Teflon). Scanning electron microscopy defined surface features, suggesting tenacious cell adhesion on the substrate. Different vascular substrates were tested (preclotted Dacron, albumin Dacron, Hemashield Dacron, Gelseal Dacron, ePTFE, fibronectin-ePTFE). Commercially available coated grafts showed qualitative and quantitative differences in cell adhesion. In particular, Gelseal Dacron provided the best quantitative results, even though a wide variability was observed. In contrast, fibronectin-coated ePTFE gave more reliable results and high spreading efficiency. In the short term, coated grafts do not seem to offer greater advantages than fibronectin-coated ePTFE. However, specific incubation times for each coated graft should be selected and the long-term approach (graft culture) should also be attempted.

Prevention of early graft infection with rifampicin-bonded Gelseal grafts: a multicentre experimental study.

The possibility of increasing the resistance of a synthetic vascular graft to intraoperative or immediate postoperative bacterial contamination justifies the interest in methods such as antibiotic bonding or antibiotic soaking. On the basis of this experience and with the aim of testing the efficacy of such a graft, a multicentre experimental study on sheep to compare the susceptibility to infection of Dacron Gelseal grafts (control) versus rifampicin-bonded Dacron Gelseal grafts (treated) following the intravenous infusion of 10(7)-10(8) cells Staphylococcus aureus was conducted. The grafts were implanted in both common carotid arteries of sheep. In a group of 11 animals (group A), a treated and a control graft were implanted in the same animal. In a group of four sheep (group B), only treated or control grafts were implanted in each animal. In group A, 36% of (four of 11) the treated grafts became infected versus 54% (six of 11) of the control prostheses. In group B, none of the treated grafts was infected by the inoculated pathogen, which, by contrast, infected 75% (three of four) of the controls. These observations confirm the recent interest aroused by the possibility of pretreating gelatin-coated Dacron grafts with rifampicin in the prevention of early graft infection.

Electron microscopic and immunocytochemical profiles of human subcutaneous fat tissue microvascular endothelial cells.

The ultrastructural and immunocytochemical characteristics of microvascular cells from human subcutaneous fat tissue were studied after the addition of collagenase and Percoll density gradient, respectively. Monoclonal and polyclonal antibodies directed against antigens specific for endothelial cells (factor VIII, Ulex europaeus, CD31, and CD34), pericytes (muscle-specific actin and desmin), adipocytes (S-100 protein), and monocytes-macrophages (MAC 387 and 150.95 protein) were demonstrated by alkaline phosphatase monoclonal anti-alkaline phosphatase and protein A-gold techniques. In addition, to determine whether the harvesting method interfered with microvascular cell function, DOT immunoassays of factor VIII and CD34 were conducted on solutions recovered at collagenase incubation as well as after nylon filtration and Percoll administration, respectively. After the collagenase step, the vast majority of microvascular cells had the typical ultrastructural and immunophenotypical features of endothelial cells. In sharp contrast, following the Percoll step, only 1% to 18% of microvascular cells stained with factor VIII, Ulex europeaus, and CD31, whereas 90% of them expressed the CD34 antigen. Surprisingly, DOT immunoassay revealed the presence of factor VIII in the washing buffer recovered after the Percoll step only. Consequently the decreased expression of common endothelial cell markers (factor VIII, Ulex europaeus, and CD31) observed at the end of the cell isolation procedure was related to the adverse effects of Percoll on endothelial cell function. The CD34 surface molecule, being highly resistant, is particularly well suited for unequivocal characterization of microvascular cells as true endothelium.

Traumatic dissection in an inflammatory aneurysm.

Primary dissections of the abdominal aorta are rare (0.4-4% of aortic dissections) and in most cases are traumatic (accidental or iatrogenic) in origin. The authors describe a case of iatrogenic dissection of the abdominal aorta following arteriography. The macroscopic and histological appearance of the aortic wall was compatible with an inflammatory aneurysm. In this type of aneurysm and in the presence of aortoiliac atherosclerosis, aortic catheterization carries a risk of aortic wall dissection.

Endovascular repair as first-choice treatment for anastomotic and true iliac aneurysms.

PURPOSE: To report our experience with the endovascular repair of iliac aneurysms secondary to aortoiliac bypass grafting. METHODS: Thirteen patients (12 men; age range 62-86 years) with histories of aortoiliac reconstructions were treated with endovascular stent-grafts for 11 false and 2 true iliac aneurysms that averaged 5.2 cm in diameter (range 3.0-7.0). Via a percutaneous access and 9-F or 12-F sheaths, Passager or Wallgraft stent-grafts were delivered to exclude the aneurysms. RESULTS: Twelve (92%) of 13 interventions were completed satisfactorily; 1 procedure for a true iliac aneurysm was converted to traditional bypass grafting. Two patients underwent additional surgical procedures. The average hospital stay for the patients with endovascular repairs only was 3 days (range 2-5). After a mean follow-up of 28 months (range 17-40), no complication or endoleak has been detected in any patient, and all endografts are patent. CONCLUSIONS: Endovascular repair is an effective treatment for secondary aneurysms arising after aortoiliac surgery. It is less invasive and involves a shorter hospital stay. Endovascular repair should be the first choice treatment for iliac aneurysms.