An Experimental Study of Laser in situ Fenestration of Current Aortic Endografts.

OBJECTIVE/BACKGROUND: Laser in situ fenestration (LISF) is emerging as an immediately available alternative in the endovascular treatment of complex aortic aneurysm. However, its biomechanical features remain poorly understood. The aim of this study was to experimentally evaluate textile damage secondary to LISF and to compare LISF with mechanical in situ fenestration (MISF). METHODS: An in vitro study evaluated the damage created by LISF on endograft fabrics versus MISF using a needle. Five different models of commercially available aortic endografts were used (32 samples of polyethylene terephthalate and expanded polytetrafluoroethylene fabrics). Tensile strength tests were performed on the fabrics before and after in situ fenestration, to determine the loss of mechanical strength. Integral water permeability tests at the stent-fenestration interface evaluated the watertightness of junctions. Stability of the connection was assessed with a fatigue bench test flexing the branch on the fenestration. In a second step, an in vivo study evaluating LISF in sheep was conducted. RESULTS: Resulting holes had circular and cauterised edges following LISF, whereas fabric filaments were pushed aside after MISF. Tensile tests demonstrated a 34% and a 27% mechanical resistance loss after LISF (p = .004) and MISF (p = .001) compared with non-fenestrated samples. A non-significant global decrease of 7% in mechanical resistance was found following LISF compared with MISF (p = .520). Water permeability tests highlighted that leak rates were higher following LISF than with MISF with regard to multifilament specimens (p < .05). Fatigue tests induced modification of the morphology of fenestrations. The surface area of the fenestration was increased for all samples after 170,000 cycles. Regarding the in vivo study, 14 LISF were performed in 12 sheep with a technical success rate of 88%. CONCLUSION: This study demonstrates that both LISF and MISF create substantial damage to all available endograft fabrics. Until comparisons with reinforced fenestrations are performed, LISF and MISF should not be used outside investigational studies.

Textile Aging Characterization on New Generations of Explanted Commercial Endoprostheses: A Preliminary Study.

OBJECTIVE/BACKGROUND: The goal of the present study was to assess the aging phenomena on second-generation textile endoprostheses (EPs) through explant analysis and to establish a preliminary classification of observed defects and material damages. METHODS: From January 2011 to June 2016 110 second- and recent-generation EPs were collected as a part of a European collaborative retrieval program. The analysis focused on the first 41 consecutive commercial EPs collected between 2011 and 2014 and made from polyethylene terephthalate. Explants were submitted to a standardized evaluation protocol, which included data recording, eye-naked evaluation, cleaning of organic remnants, and structural analysis under numerical optical microscopy. Observations were reported using a classification based on 15 features evaluating the fabric, the stitches between the fabric and the stents, and the stents. The total surface area of the holes within the fabric was measured. RESULTS: EPs were implanted for thoracic and abdominal procedures in 12 and 29 cases, respectively. The mean ± SD duration of implantation was 34 ± 26 months (range 2 days-8 years). Sixty-four percent of the samples demonstrated at least one defect caused by compression damage potentially related to the insertion of the EP within the delivery system, which promoted holes and tears. Ninety-five percent of all EPs demonstrated at least one type of abrasion on the stitches. The degradation of the stitches and the number of ruptures increased with duration of implantation. Stent degradation was rare and consisted of corrosion and rupture. Cumulated holed surface area increased with time and was measured up to 13.5 mm2. CONCLUSION: Various aging-related phenomena on commercial textile EPs were identified and classified. Main damaging mechanisms were related to compression and abrasion leading to tears and holes in the fabric and rupture of stitches.

A bridging bis-phosphanido-phosphinidene complex of lanthanum supported by a sterically encumbering PN ligand.

Synthesis of a bulky anilidophosphine ligand (short PNTerph) and its lanthanum complexes 1 and 3 is reported. When exposed to KPHMes, both complexes form the first example of a bis-phosphanido-phosphinidene complex 2. This complex undergoes Phospha-Wittig type reactions and its reactivity towards strong bases is further investigated.

A novel stent for percutaneous heart valve implantation: first in vitro results.

Percutaneous aortic valve implantation has become an alternative technique to surgical valve replacement in patients with high risk for surgery. This technique is at its beginning and stents used for valve prostheses remain standard vascular stents. These stents are, however, not designed to undergo heart valve stress. They do not match the aortic environment geometry, and induce exaggerated tissue traumatism. Reduced implant lifetime may therefore be expected. The purpose of the present work is to evaluate in vitro the technical feasibility of noninvasive aortic valve replacement with a novel more specific stent. This stent is especially adapted to its implantation environment with a design that matches the shape of the aortic root while respecting the valve functions. We present a design, a manufacturing process and in vitro performances for the stent under static pressure loading and pulsatile flow. The stent shows good dynamic behavior in keeping position imposed at implantation time and in matching the aortic root dimensions changes. Prosthesis static and dynamic regurgitation are evaluated and show values close to those obtained with other commercially available prostheses.

Surface modification of polymer textile biomaterials by N2 supercritical jet: Preliminary mechanical and biological performance assessment.

Foreign Body Reaction (FBR) is a critical issue to be addressed when polyethylene terephthalate (PET) textile implants are considered in the medical field to treat pathologies involving hernia repair, revascularization strategies in arterial disease, and aneurysm or heart valve replacement. The natural porosity of textile materials tends to induce exaggerated tissue ingrowth which may prevent the implants from remaining flexible. One hypothesized way to limit the FBR process is to increase the material surface roughness at the yarn level. Supercritical N2 (ScN2) jet particle projection is a technique that provides enough velocity to particles in order to induce plastic deformation on the impacted surface. This work investigates the influence of ScN2 jet projection parameters like standoff distance or particle size on the roughness that can be obtained on medical polymer yarns of various diameters (100 and 400 µm) and woven textile surfaces obtained from a 100 µm yarn. Moreover, the mechanical and biological performances of the obtained modified textile material are assessed. Results bring out that with appropriate testing conditions (500 bars jet/500 mm distance between nozzle and PET textile) and particle size around 50 µm, it is possible to generate 20 µm large and 4 µm deep craters on a 100 µm monofilament PET yarn and fabric. Regarding the strength of the textile material, it is only slightly modified with the treatment process, as the tenacity of the yarns decreases by only 10%. Moreover, It is shown that the obtained structures tend to limit the adhesion and slow down the proliferation of human fibroblasts.

[Contribution of mathematical models and biomechanical properties in predicting the risk of abdominal aortic aneurysm rupture]. / Apport des modèles mathématiques et des études biomécaniques dans la prédiction du risque de rupture des anévrysmes de l'aorte abdominale.

INTRODUCTION: Rupture is the worst outcome of abdominal aortic aneurysm (AAA). The decision to operate should include counterbalancing the risk of aneurysm rupture against the risk of aneurysm repair, within the context of a patient's overall life expectancy. Current surgical guidelines are based on population studies, and important variables are missed in predicting individual risk of rupture. METHODS: In this literature review, we focused on the contribution of biomechanical and mathematical models in predicting risk of AAA rupture. RESULTS: Anatomical features as diameter asymmetry and lack of tortuosity are shown to be anatomical risk factors of rupture. Wall stiffness (due to modifications of elastin and collagen composition) and increased inflammatory response are also factors that affect the structural integrity of the AAA wall. Biomechanical studies showed that wall strength is lower in ruptured than non-ruptured AAA. Intra-luminal thrombus also has a big role to play in the occurrence of rupture. Current mathematical models allow more variables to be included in predicting individual risk of rupture. CONCLUSION: Moving away from using maximal transverse diameter of the AAA as a unique predictive factor and instead including biological, structural and biomechanical variables in predicting individual risk of rupture will be essential in the future and will help gain precision and accuracy in surgical indications.

Aging of retrieved gel breast implants: a comparison between two product generations.

In order to get a marketing authorization, breast implants (BI) must meet a number of standard requirements. French and European standards ISO 14607 list a number of official tests to be performed before an implant can be used clinically. However, the BI material characteristics evolution over implantation time remains a research field which is unexplored. The goal of the present study is to compare the mechanical ageing of two breast implant generations and assess if the use of one generation rather than the other is advantageous in terms of durability. For that purpose, 21 explanted BI were analyzed in terms of biomechanical characteristics and compared. Twelve BI were textured anatomic specimens of 5th generation and 10 BI were round textured specimens of 4th generation. All the specimens were produced by the same manufacturer. Implantation time ranged from 3 to 130 months. Both the shell and the gel of every specimen were analyzed. Results show that the mechanical properties go down with the implantation time for all the implants. Moreover, the shell of round implants appear to be less resistant than the shell of anatomic specimens with 25% lower rupture forces. With regard to the gel, whatever the specimen, results show that the properties change with implantation time. The color changes from transparent to milky to finally become yellow, while the cohesion goes down especially for the round specimens. Globally, the study brings out that BI get degraded with implantation time and provides information which could help predicting the durability of the implant.

Community-acquired pneumonia. A prospective outpatient study.

We initiated a prospective study with a group of practitioners to assess the etiology, clinical presentation, and outcome of community-acquired pneumonia in patients diagnosed in the outpatient setting. All patients with signs and symptoms suggestive of pneumonia and an infiltrate on chest X-ray underwent an extensive standard workup and were followed over 4 weeks. Over a 4-year period, 184 patients were eligible, of whom 170 (age range, 15-96 yr; median, 43 yr) were included and analyzed. In 78 (46%), no etiologic agent could be demonstrated. In the remaining 92 patients, 107 etiologic agents were implicated: 43 were due to "pyogenic" bacteria (39 Streptococcus pneumoniae, 3 Haemophilus spp., 1 Streptococcus spp.), 39 were due to "atypical" bacteria (24 Mycoplasma pneumoniae, 9 Chlamydia pneumoniae, 4 Coxiella burnetii, 2 Legionella spp.), and 25 were due to viruses (20 influenza viruses and 5 other respiratory viruses). There were only a few statistically significant clinical differences between the different etiologic categories (higher age and comorbidities in viral or in episodes of undetermined etiology, higher neutrophil counts in "pyogenic" episodes, more frequent bilateral and interstitial infiltrates in viral episodes). There were 2 deaths, both in patients with advanced age (83 and 86 years old), and several comorbidities. Only 14 patients (8.2%) required hospitalization. In 6 patients (3.4%), the pneumonia episode uncovered a local neoplasia. This study shows that most cases of community-acquired pneumonia have a favorable outcome and can be successfully managed in an outpatient setting. Moreover, in the absence of rapid and reliable clinical or laboratory tests to establish a definite etiologic diagnosis at presentation, the spectrum of the etiologic agents suggest that initial antibiotic therapy should cover both S. pneumoniae and atypical bacteria, as well as possible influenza viruses during the epidemic season.

Double-blind report on the efficacy of lactic acid-producing Enterococcus SF68 in the prevention of antibiotic-associated diarrhoea and in the treatment of acute diarrhoea.

A multicentre double-blind, placebo-controlled clinical trial, involving 123 patients at 10 centres, was carried out to assess the efficacy of a preparation of lactic acid-producing Enterococcus SF 68 in the prevention of antibiotic-associated diarrhoea and in the treatment of acute diarrhoea. In the prevention study, 45 patients being treated with antibiotics were given, concurrently, one capsule twice daily of either Enterococcus SF68 or placebo. Acute diarrhoea was present in 78 patients who were given the same treatment but three times daily. All treatments were continued for 7 days. Enterococcus SF 68 was shown to be effective in reducing the incidence of antibiotic-associated diarrhoea in comparison with placebo (8.7% compared with 27.2%, respectively). Patients with acute enteritis showed a significantly faster resolution of bowel abnormalities during treatment with Enterococcus SF68 compared with placebo.

Properties and challenges in materials used as vascular and endovascular devices.

In the last decades, main evolutions in the field of vascular surgery have been correlated to the development of devices allowing more reliable and safe sustainable treatment. First devices that have been proposed were vascular prostheses made of polymeric materials. The second generation of devices was stents made of metals and alloys. The third generation, endografts, associated these both materials. Materials used as vascular and endovascular devices must meet a number of requirements based on dimensional, physical and mechanical criteria. Ideally, they should demonstrate a behavior as close as possible as that of human arteries in terms of mechanical properties such as compliance, long-term durability, and in terms of biological properties such as biocompatibility, luminal surface healing and thrombogenicity. We propose in the present manuscript a review of properties of materials currently used for the construction of vascular and endovascular devices, future challenges in the fields of new materials and scientific approaches and tests to understand and predict the behavior of the next generations of devices.

Stent evolution for peripheral arterial disease.

Endovascular treatment and stent implantation for peripheral arterial disease have been proposed for over 20 years. However, the first experiments with stainless stents were relatively disappointing. The first improvement consisted in the introduction of nitinol self-expanding stents. This technology allowed an initial improvement of clinical performances, but the first generation of nitinol stents demonstrated a relatively high rate of fractures. Better knowledge of arterial biomechanics and advances in technology allowed to propose a second generation of nitinol stents with improved flexibility, which decreased the rates of fracture. In-stent restenosis related to neointimal hyperplasia has also led to the development of new concepts to improve patency rates after stenting: drug-eluting stents (coated-stents), biodegradable stents, and covered stents. These technologies will help to treat more complex lesions in the future, but we are still waiting for results of ongoing studies.