Search

Metallic stents have been largely used over the last decades to treat vascular diseases like coronary artery or peripheral vessel stenosis. Although they remain the gold standard for vascular treatment, they are subjected to in‐vivo complications such as corrosion, structural failure, fractures, and re‐stenosis due especially to the material which is used. Polymer material being less rigid than metallic material could be a potential solution and would help limiting these issues especially in peripheral vessels where flexibility is required. Among polymeric materials, polyethylene terephthalate (PET) has been used to develop stents of this study, since its biocompatibility has already been proven especially in the field of cardiovascular applications. Moreover, to guarantee flexibility, braiding technology has been used to manufacture the samples. The goal of this work was to evaluate PET‐braided stents behavior under accelerated fatigue up to 105 cycles. The effect of fatigue on the radial compression strength was then investigated and the material surface was examined by SEM to identify locations of structural failure. The effect of the different manufacturing parameters (braiding angle, braiding pattern, stent diameter, and wire diameter) on the fatigue behavior was also assessed. Results show that stents have a good elastic recovery of their diameters after fatigue despite the friction that occurred between the filaments. Moreover, fatigue loading induces radial strength loss in all stents. However, this loss varies according to the stent design. In addition, no wire fracture has been reported. It comes out from the study that PET‐braided stents show suitable mechanical behavior over accelerated fatigue loading up to 105 cycles and that their braiding parameters have a huge impact on their performances. [ABSTRACT FROM AUTHOR]

Transcatheter aortic valve replacement has become today a largely considered alternative technique to surgical valve replacement in patients with high risk for open chest surgery. Biological valve tissue used in the transcatheter devices has shown success over 5 years now, but the procedure remains expensive. Moreover, different studies point out potential degradations that the tissue can undergo when folded to lower diameter and released in calcified environment with irregular geometry, which may jeopardize the durability of the device. The use of synthetic materials, like textile in particular, to replace biological valve leaflets would help reducing the procedure costs, and limit the degradations when the valve is crimped. Textile polyester material has been extensively used in the vascular surgery and is characterized by outstanding folding and strength properties combined with proven biocompatibility. However, the friction effects that occur between filaments and between yarns within a fabric under flexure loading could be critical for the resistance of the material on the long term. The purpose of this study was to assess the early fatigue performances of textile valve prototypes under accelerated cyclic loading up to 200 Mio cycles. Durability tests show that the fibrous material undergoes rearrangements between fibrous elements within the textile construction and the mechanical properties are modified on the long term. But testing is not complete with 200 Mio cycles. The material should be tested up to a higher number of cycles in future work to test the effective long-term durability. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 986-992, 2016. [ABSTRACT FROM AUTHOR]

Old patients exhibit muscle impairments and increased perioperative risk during vascular surgery procedures. Although aging generally impairs protective mechanisms, data are lacking concerning skeletal muscle in elderly. We tested whether cyclosporine A (CsA), which protects skeletal muscle from ischemia-reperfusion ( IR) in young rats, might reduce skeletal muscle mitochondrial dysfunction and oxidative stress in aging rats submitted to hindlimb IR. Wistar rats aged 71-73 weeks were randomized to IR (3 h unilateral tourniquet application and 2 h reperfusion) or IR + CsA (10 mg/kg cyclosporine IV before reperfusion). Maximal oxidative capacity ( VMax), acceptor control ratio ( ACR), and relative contribution of the mitochondrial respiratory chain complexes II, III, IV ( VSucc), and IV ( VTMPD/Asc), together with calcium retention capacity ( CRC) a marker of apoptosis, and tissue reactive oxygen species ( ROS) production were determined in gastrocnemius muscles from both hindlimbs. Compared to the nonischemic hindlimb, IR significantly reduced mitochondrial coupling, VMax (from 7.34 ± 1.50 to 2.87 ± 1.22 μ MO2/min/g; P < 0.05; −70%), and VSucc (from 6.14 ± 1.07 to 3.82 ± 0.83 μ MO2/min/g; P < 0.05; −42%) but not VTMPD/Asc. IR also decreased the CRC from 15.58 ± 3.85 to 6.19 ± 0.86 μ MCa2+/min/g; P < 0.05; −42%). These alterations were not corrected by CsA (−77%, −49%, and −32% after IR for VMax, VSucc, and CRC, respectively). Further, CsA significantly increased ROS production in both hindlimbs ( P < 0.05; +73%). In old rats, hindlimb IR impairs skeletal muscle mitochondrial function and increases oxidative stress. Cyclosporine A did not show protective effects. [ABSTRACT FROM AUTHOR]

Transcatheter aortic valve implantation (TAVI) has become a popular alternative technique to surgical valve replacement. However, the biological valve tissue used in these devices appears to be fragile material in the long term particularly due being folded for low diameter catheter insertion purposes and when released in a calcified environment with irregular geometry. Textile polyester material is characterized by outstanding folding and strength properties combined with proven biocompatibility. It could therefore be considered as a replacement for biological valve leaflets in the TAVI procedure. The folding process associated with crimping, however, may degrade the filaments involved in the fibrous assembly and limit the durability of the device. The purpose of the present work is to study the effect of different crimping conditions on the mechanical performances of textile valve prototypes made from various fabric constructions. Results show that crimping generates some creases in the fabrics, which surface topography varies with fabric construction and crimping configuration. The mechanical properties of the crimped materials are globally slightly reduced. To determine how critical the modifications due to crimping are for prosthesis durability, more detailed long term in vitro and in vivo trials with crimped textile prototypes are needed in addition to this preliminary work. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 1488-1497, 2015. [ABSTRACT FROM AUTHOR]

Impaired skeletal muscle energetic participates in peripheral arterial disease (PAD) patient’s morbidity and mortality. Angiotensin converting enzyme inhibition (ACEi), cornerstone for pharmacologic risk factor management in PAD patients, might also be interesting by protecting skeletal muscle energetic. We therefore determined whether chronic ACEi might reduce ischemia-induced mitochondrial respiratory chain dysfunction in the frequent setting of hindlimb ischemia–reperfusion. Ischemic legs of rats submitted to 5 h ischemia induced by a rubber band tourniquet applied on the root of the hindlimb followed by reperfusion without (IR, n = 11) or after ACEi ( n = 14; captopril 40 mg/kg per day during 28 days before surgery) were studied and compared to that of sham-operated animals ( n = 11). The effect of ACEi on the non-ischemic contralateral leg was also determined in the ACEi group. Maximal oxidative capacities ( Vmax) and complexes I, II and IV activities of the mitochondrial respiratory chain of the gastrocnemius muscle were determined using glutamate–malate, succinate and TMPD–ascorbate substrates. Arterial blood pressure was significantly decreased after ACEi (124 ± 2.8 vs. 108 ± 4.19 mmHg; P = 0.01). Ischemia–reperfusion reduced Vmax (4.4 ± 0.4 vs. 8.7 ± 0.5 μmol O2/min/g dry weight, −49%, P < 0.001), affecting mitochondrial complexes I, II and IV activities. ACEi failed to modulate ischemia-induced dysfunction ( Vmax 5.1 ± 0.7 μmol O2/min/g dry weight) or the non-ischemic contralateral muscle respiratory rate. Ischemia–reperfusion significantly impaired the mitochondrial respiratory chain I, II and IV complexes of skeletal muscle. Pharmacologic pre-treatment with ACEi did not prevent or increase such alterations. Further studies might be useful to improve the pharmacologic conditioning of PAD patients needing arterial revascularization. [ABSTRACT FROM AUTHOR]

The rapid developments and success in percutaneous vascular surgery over the last two decades with the now common stent grafts implantation, make the noninvasive surgery technique today attractive even for heart valve replacement. Less traumatic for the patient and also less time consuming, percutaneous heart valve replacement is however at its beginning and restricted to end of life patients. The noninvasive procedure expects from the heart valve prosthesis material to be resistant and adapted to folding requirements of the implantation process (catheter). Polyester fabric could be a suited material for heart valve implanted percutaneously. Highly flexible and resistant, polyester fabric proved to be well adapted to the dynamic behavior of a valve and polyester (Dacron) is also widely used for vascular grafts implantation and shows good biocompatibility and durability. However, today there's no data available on long‐term durability of fabric used as heart valve material. The purpose of this work is to study the long term behavior of a microdenier polyester fabric construction under combined in vitro flexure and tension fatigue stress. In the novel in vitro testing technique presented, a fabric specimen was subjected to combined flexural and tensile fatigue generated by fluid flow under physiological pressure conditions. The results obtained show how flexural properties change with fatigue time, which reflects directly on the suitability of a fabric in such devices. It was also observed that these fabric structural changes directly influence the in vitro behavior of the textile heart valve prosthesis. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010 [ABSTRACT FROM AUTHOR]