Kink Resistance Research Articles

A Gelatin/Alginate Double Network Hydrogel Nerve Guidance Conduit Fabricated by a Chemical-Free Gamma Radiation for Peripheral Nerve Regeneration.

Nerve guidance conduits (NGCs) are widely developed using various materials for the functional repair of injured or diseased peripheral nerves. Especially, hydrogels are considered highly suitable for the fabrication of NGCs due to their beneficial tissue-mimicking characteristics (e.g., high water content, softness, and porosity). However, the practical applications of hydrogel-based NGCs are hindered due to their poor mechanical properties and complicated fabrication processes. To bridge this gap, a novel double-network (DN) hydrogel using alginate and gelatin by a two-step crosslinking process involving chemical-free gamma irradiation and ionic crosslinking, is developed. DN hydrogels (1% alginate and 15% gelatin), crosslinked with 30 kGy gamma irradiation and barium ions, exhibit substantially improved mechanical properties, including tensile strength, elastic modulus, and fracture stain, compared to single network (SN) gelatin hydrogels. Additionally, the DN hydrogel NGC exhibits excellent kink resistance, mechanical stability to successive compression, suture retention, and enzymatic degradability. In vivo studies with a sciatic defect rat model indicate substantially improved nerve function recovery with the DN hydrogel NGC compared to SN gelatin and commercial silicone NGCs, as confirm footprint analysis, electromyography, and muscle weight measurement. Histological examination reveals that, in the DN NGC group, the expression of Schwann cell and neuronal markers, myelin sheath, and exon diameter are superior to the other controls. Furthermore, the DN NGC group demonstrates increased muscle fiber formation and reduced fibrotic scarring. These findings suggest that the mechanically robust, degradable, and biocompatible DN hydrogel NGC can serve as a novel platform for peripheral nerve regeneration and other biomedical applications, such as implantable tissue constructs.

Reduction of cell surface attachment in experimental hydrocephalus using a novel ventricular catheter with modified tethered liquid perfluorocarbon.

Ventriculoperitoneal shunting, the most common treatment for the neurological disorder hydrocephalus, has a failure rate of up to 98% within 10 years of placement, mainly because of proximal obstruction of the ventricular catheter (VC). The authors developed a new VC design modified with tethered liquid perfluorocarbon (TLP) and tested it in a porcine model of hydrocephalus. In this study, they aimed to determine if their TLP VC design reduced cell surface attachment and consequent shunt obstruction in the pig model. TLP VCs were designed to reduce drainage hole obstruction using modified TLP and slightly enlarged draining holes, but their number and placement remained very similar to standard VCs. First, the authors tested the device in nonhydrocephalic rats to assess biocompatibility. After confirming safety, they implanted the VCs in hydrocephalic pigs. Hydrocephalus was induced by intracisternal kaolin injections in 30-day-old domestic juvenile pigs. Surgical implantation of the ventriculoperitoneal shunt (clinical control or TLP) was performed 10-14 days postinduction and maintained up to 30 days posttreatment. MRI was performed to measure ventricular volume before treatment and 10 and 30 days after treatment. Histological and immunohistochemical analyses of brain tissue and explanted VCs, intracranial pressure measurement, and clinical scoring were performed when the animals were euthanized. TLP VCs showed a similar surgical feel, kink resistance, and stiffness to control VCs. In rats (biocompatibility assessment), TLP VCs did not show brain inflammatory reactions after 30 or 60 days of implantation. In pigs, TLP VCs demonstrated increased survival time, improved clinical outcome scores, and significantly reduced total attached cells on the VCs compared with standard clinical control VCs. TLP VCs exhibited similar, but not worse, results related to ventriculomegaly, intracranial pressure, and the local tissue response around the cortical shunt track in pigs. TLP VCs may be a strong candidate to reduce proximal VC obstruction and improve hydrocephalus treatment.

Individual functionalization of textiles by powder coating using laser fixation

Sensors and actuators in textile structures are increasingly in demand across various textile markets. They find applications in the smart system sector for communication using RFID chips, energy transmission, wearable humidity, and pressure sensors. However, current conductive textile structures, achieved by integrating conductive yarns, wires, and strands, lack kink resistance and reliable contact points. The proposed process combines the principles of electrostatic powder coating and the additive manufacturing process of selective laser sintering. The project aims to develop a technology for digitally reproducible functional textile surfaces through laser-sintered powder coating. A coating comprising a blend of TPU powder, and silver particles is applied to the textile using a CO2 laser radiation for fixation, creating flexible electronic circuit structures on textiles. The resulting structures are evaluated using analytical and microscopic methods.

Boosted Mechanical Properties of Polyamide 11 Tube Originated from the Hierarchical Architecture Manipulation by Helical Flow Field

Polyamide 11 (PA11) is a biobased polymer originated from the renewable plant-based resources and thus holds promising potential in reducing the consumption of limited fossil resources and protecting the environment. Compared to the commonly investigated polyolefin, the flow manipulation strategy for improving the mechanical properties of PA11 still remained a huge challenge because the strong intermolecular interactions elevated the difficulty of stretching the polar polymer chains. Herein, a helical flow was introduced in the PA11 tube extrusion by superposing a hoop flow from mandrel rotation onto an axial flow. Then, the helical flow-induced hierarchical architecture was investigated to reveal the effect of intermolecular interactions on the orientation and crystalline structure. Limited by strong hydrogen bonds between the amide groups, the PA11 chains were not stretched sufficiently to form anisotropic shish-kebab crystals but assembled into a helically aligned configuration in amorphous regions, similar to that in natural materials, endowing the as-prepared tube with enhanced hoop kink resistance and axial compression properties which were favorable to the practical application of the thin-wall tube. This study not only can provide a feasible way to tailor the mechanical properties of the PA11 tube by constructing a special multidimensional flow but also is beneficial to the fundamental understanding on the flow-induced crystallization mechanism of polar polymers with strong intermolecular interactions.

Fabrication and Mechanical Property Evaluation of Peripheral Stent Made from Shape Memory Alloys

This study proposes to design and fabricate the peripheral stent using NiTi shape memory alloy wires by braiding technique. The 0.2 mm diameter NiTi wire was attached to the automatic braiding machine and fabricated the braided stent under the different height of circular rod holder. Heat-treatment was carried out at 450°C, 500°C, 550°C and 600°C for 10 and 20 minutes, respectively. Then transformation temperature, the shape of cell area, and mechanical properties were evaluated. The results show that complete superelasticity can be confirmed under body temperature in stent prototypes with heat-treatment temperature over 500°C irrespective of heat-treatment time. The prototype with the height of circular mold of 70 mm shown a good braiding pattern with high kink resistance. The radial force shown no significant difference at any section along the length profile. It is noted that stent with the height of circular mold at 70 mm, carrier speed of 30 rad/sec and take-up speed of 4.86 mm/s which shown radial resistive force (ROF) of 2.44 ± 0.05 N/mm, and chronic outward force (COF) of 0.533 ± 0.03 N/mm which is sufficient for vessel expansion.

784-P: An Insulin Infusion Set with Novel Kink-Free Flexible Cannula: In-Vitro/In-Vivo Studies

Objective: The wear duration of insulin infusion sets (IIS) is impacted by initial local trauma caused by cannula insertion and sustained inflammation due mostly to insulin infusion, both of which affect insulin absorption. Efforts have been made to mitigate cannula kinking at insertion and during use, and other site reactions that contribute to IIS failures. This Medtronic preclinical study investigated performance of a novel flexible and kink-free soft cannula. Method: In-vitro tests (included buckling kink test, inflammatory macrophage cell culture, and insulin compatibility test by USP insulin monographic methods) were conducted on the Flexible cannula and commercial Teflon cannulas. In-vivo study of 3-day sets with both cannulas were conducted on diabetic swine by having animals wear one set multiple times (on the abdomen) while receiving Novolog™ insulin subcutaneously via a pump for 7 days or until set failure, determined by (1) blood glucose (BG) value not decreasing by ≥50 mg/dL an hour after a correction bolus for a BG level >350 mg/dL, or (2) evidence of infection at the infusion site. Result: Compared to the control Teflon cannula, kink resistance of the Flexible cannula was significantly improved (Kinked: Teflon 6/6, Flexible 0/6) . In the inflammatory in-vitro cell culture model, the pro-inflammatory cytokines generated by the Flexible cannula trended less (mean MCP-1: Teflon -9.7 ng/mL, Flexible - 7.7 ng/mL; mean MIP-1α: Teflon -24.1 ng/mL, Flexible - 24.0 ng/mL) . Tested by the USP methods, both cannulas were insulin compatible. In the swine diabetes model, the 3-day IIS with the Flexible cannula had a greater 7-day survival rate (50%, n=10) than the corresponding control (36%, n=56) , although not statistically different. No significant increase in total daily dose of insulin was observed. Conclusion: Preliminary in-vitro and in-vivo test results indicate that the novel Flexible cannula is ideally suited for IIS device performance. Further product development is ongoing. Disclosure C.Chiu: Employee; Medtronic. G.Zhang: Employee; Medtronic. S.Chattaraj: Employee; Medtronic. R.Gottlieb: Employee; Medtronic.

Silk Vascular Grafts with Optimized Mechanical Properties for the Repair and Regeneration of Small Caliber Blood Vessels.

As the incidence of cardiovascular diseases has been growing in recent years, the need for small-diameter vascular grafts is increasing. Considering the limited success of synthetic grafts, vascular tissue engineering/repair/regeneration aim to find novel solutions. Silk fibroin (SF) has been widely investigated for the development of vascular grafts, due to its good biocompatibility, tailorable biodegradability, excellent mechanical properties, and minimal inflammatory reactions. In this study, a new generation of three-layered SF vascular scaffolds has been produced and optimized. Four designs of the SILKGraft vascular prosthesis have been developed with the aim of improving kink resistance and mechanical strength, without compromising the compliance with native vessels and the proven biocompatibility. A more compact arrangement of the textile layer allowed for the increase in the mechanical properties along the longitudinal and circumferential directions and the improvement of the compliance value, which approached that reported for the saphenous and umbilical veins. The higher braid density slightly affected the grafts’ morphology, increasing surface roughness, but the novel design mimicked the corrugation approach used for synthetic grafts, causing significant improvements in kink resistance.

Tri-Layered Vascular Grafts Guide Vascular Cells' Native-like Arrangement.

Bionic grafts hold great promise for directing tissue regeneration. In vascular tissue engineering, although a large number of synthetic grafts have been constructed, these substitutes only partially recapitulated the tri-layered structure of native arteries. Synthetic polymers such as poly(l-lactide-co-ε-caprolactone) (PLCL) possess good biocompatibility, controllable degradation, remarkable processability, and sufficient mechanical strength. These properties of PLCL show great promise for fabricating synthetic vascular substitutes. Here, tri-layered PLCL vascular grafts (TVGs) composed of a smooth inner layer, circumferentially aligned fibrous middle layer, and randomly distributed fibrous outer layer were prepared by sequentially using ink printing, wet spinning, and electrospinning techniques. TVGs possessed kink resistance and sufficient mechanical properties (tensile strength, elastic modulus, suture retention strength, and burst pressure) equivalent to the gold standard conduits of clinical application, i.e., human saphenous veins and human internal mammary arteries. The stratified structure of TVGs exhibited a visible guiding effect on specific vascular cells including enhancing endothelial cell (EC) monolayer formation, favoring vascular smooth muscle cells’ (VSMCs) arrangement and elongation, and facilitating fibroblasts’ proliferation and junction establishment. Our research provides a new avenue for designing synthetic vascular grafts with polymers.

Development and in-vitro characterization of a novel fetal vesicoamniotic shunt - The Vortex shunt.

To develop and test a novel vesicoamniotic shunt (VAS) to treat fetal lower urinary tract obstruction (LUTO), decrease dislodgement and optimize shunt deployment in-vitro. Vesicoamniotic shunt design objectives included: (1) robust and atraumatic fixation elements, (2) kink resistant conduit to adjust to fetal movement and growth, (3) one-way pressure valve to facilitate bladder cycling, and (4) echogenic deployment visualization aids. The force to dislodge the novel Vortex shunt was compared with existing commercially available shunts in a bench-top porcine bladder model. Sonographic echogenicity was evaluated with ultrasound-guided deployment, and the shunt valve pressure measured. A prototype novel Vortex shunt was developed using braided nitinol "umbrella-type" ends with a kink-resistant stem incorporating an internal one-way valve. The peak force required to dislodge the Vortex shunt was significantly higher than commercially available shunts (p<0.01). Shunt deployment in the bench-top model was easily confirmed with ultrasound guidance and the brisk decompression of the inflated porcine bladder thereafter. In-vitro valve gauge pressure testing mirrored bladder pressures in human LUTO cases. In-vitro testing shows that the Vortex shunt may improve deployment, sonographic visualization, kink resistance, and dynamic size adjustment. Validation in preclinical animal models are warranted and currently underway.

Transradial quadraxial system for coil embolization of distal anterior cerebral artery aneurysms: A radial-first center case series and literature review

PurposeEndovascular treatment is technically challenging as distal anterior cerebral artery (DACA) aneurysms have distal location, small-caliber parent artery, and small size/wide neck. This study evaluated the feasibility and safety of the transradial approach (TRA) with a radial-specific neurointerventional guiding sheath as the first-line technique for DACA aneurysms. MethodsWe retrospectively analyzed an institutional database of consecutive patients with DACA aneurysm who underwent coil embolization using TRA. Ten consecutive patients were included in this study. After the radial-specific 6F Simmons guiding sheath (0.088″ inner diameter) was completely engaged into the target common carotid artery, a quadraxial system (6F Simmons guiding sheath/6F intermediate catheter/3.2F intermediate catheter/single microcatheter) was used for embolization. Then, we assessed for procedural success, angiographic outcomes, and procedure-related or vascular access site complications. ResultsEmbolization procedures were conducted using simple coiling in eight and stent-assisted coiling with the trans-cell approach in two patients. The embolization procedure was successful in all patients (n = 10). Moreover, none presented with catheter kinking, parent artery flow stagnation, or system instability during the procedure. Immediate postprocedural angiography revealed complete obliteration in six and residual neck in four patients. Then, eight patients underwent follow-up angiography at a mean of 7.1 months, and none developed recanalization or required retreatment. The postprocedural course was uneventful, and there were no complications. ConclusionThe transradial quadraxial system had the ability to achieve sufficient stability and kink resistance in DACA aneurysm embolization. Thus, this method was feasible and safe and had a high success rate.

Artificial vascular implants with unidirectional drug release and mechanical properties imitating natural blood vessels

Small-diameter artificial vessels require a combination of a range of material properties, including high strength, compliance, sutureability, and kink resistance in specific situations. We combined electrospinning technology with thermally induced separation technology to prepare composite three-layer artificial vessels using a PCL/gelatin co-blended material and a hybrid hydrogel enhanced gel structure to achieve high strength, flexibility and kink resistance, as well as excellent water tightness. The electrospun fibers in the artificial vessel provide mechanical stability, while the gelatin blended material enhances hydrophilicity. The results show that the three-layer composite structure is well bonded together, provides sufficient rupture strength and sutureability, and exhibits arterial-like compliance and resistance to kinking. The hydrogel layer drug release rate can also be adjusted by adjusting the PCL/gelatin co-blended layer ratio. This composite vascular scaffold is expected to play an important role in tissue engineering.

Analytical methods for braided stents design and comparison with FEA

Braiding technology is nowadays commonly adopted to build stent-like devices. Indeed, these endoprostheses, thanks to their typical great flexibility and kinking resistance, find several applications in mini-invasive treatments, involving but not limiting to the cardiovascular field. The design process usually involves many efforts and long trial and error processes before identifying the best combination of manufacturing parameters. This paper aims to provide analytical tools to support the design and optimization phases: the developed equations, based on few geometrical parameters commonly used for describing braided stents and material stiffness, are easily implementable in a worksheet and allow predicting the radial rigidity of braided stents, also involving complex features such as multiple twists and looped ends, and the diameter variation range. Finite element simulations, previously validated with respect to experimental tests, were used as a comparator to prove the reliability of the analytical results. The illustrated tools can assess the impact of each selected parameter modification and are intended to guide the optimal selection of geometrical and mechanical stent proprieties to obtain the desired radial rigidity, deliverability (minimum diameter), and, if forming processes are planned to modify the shape of the stent, the required diameter variations (maximum and minimum diameters).

Разработка методики испытаний гибких шлангов на основе пластифицированного ПВХ, армированного спиралью из жесткого ПВХ

In this work, we develop laboratory techniques for evaluating service properties of flexible polymer hoses. The main parameters limiting the application of flexible polymer hoses are low-temperature flex-ibility and kink resistance at positive temperatures. To study the flexibility of hoses at low tempera-tures, a setup measuring deformability of a hose under cantilever loading was built. Cooling of hoses was carried out in a special refrigerating chamber. A standard three-point loading configuration was used to measure the hose kink resistance on an Instron 5980 testing machine. The measurements were performed at a temperature of 20C. Flexibility measurements performed on polymer hoses at negative temperatures showed that hoses from plasticised PVC remain flexible at –30C. Kink re-sistance depends on the pitch of spiral reinforcement and the wall thickness of the hose. Thus, two laboratory procedures for measuring the flexibility and kink resistance of PVC hoses were tested. It was shown that these techniques are capable of predicting the service temperature range and physical and mechanical characteristics of commercial polymer flexible hoses.

Feasibility and Safety of Radial-First Approach with a Radial-Specific Neurointerventional Guiding Sheath for Intracranial Aneurysm Coiling in the Anterior Circulation

In cardiac intervention, the transradial approach (TRA) is increasingly used as the first-line approach owing to numerous advantages over the transfemoral approach. Neurointerventional TRA, especially in intracranial interventions, is predominantly restricted to an alternative approach, as transradial carotid cannulation using a conventional transfemoral system can be technically challenging for patients with unfavorable acute takeoff of the target common carotid artery. This study evaluated the feasibility and safety of first-line TRA with a radial-specific neurointerventional guiding sheath for a large series of consecutive intracranial anterior circulation aneurysm embolizations. We retrospectively analyzed our institutional database of first-line TRA for consecutive coil embolizations of anterior circulation aneurysms conducted between June 2018 and March 2020. A radial-specific 6-F Simmons guiding sheath (0.088-inch inner diameter) was engaged into the target common carotid artery, and subsequently a triaxial or quadraxial system was created for the embolization procedure. We assessed procedural success and procedure-related or vascular access site complications. A total of 119 patients with intracranial anterior circulation aneurysms underwent 121 coil embolization procedures. Of these, 101 patients who underwent 103 (85.1%) embolization procedures treated with first-line TRA were included. After the triaxial or quadraxial system was constructed, the embolization procedure was successful for all 103 cases without catheter kinking, system instability, or complications. A transradial 0.088-inch triaxial or quadraxial system provided sufficient stability and kink resistance for intracranial aneurysm embolization. This method is feasible, highly successful, and safe for intracranial anterior circulation aneurysm embolization.

Sulfonation and Characterization of Tert-Butyl Styrene/Styrene/Isoprene Copolymer and Polypropylene Blends for Blood Compatibility Applications.

Hydrogenated styrenic block copolymers (HSBCs) have been used in medical tubing for many years due to their high clarity, flexibility, kink resistance, and toughness. However, when it comes to blood storage applications, HSBC compounds’ market has been limited because of their high hydrophobicity, which may trigger platelet adhesion when contacting with blood. HSBC needs to be physically or chemically modified in advance to make it blood compatible; however, HSBC has strong UV/ozone resistance, thermooxidative stability, and excellent processing capability, which increases the difficulty of the chemical modification process as unsaturated dienes has been converted to saturated stable midblocks. Moreover, medical HSBC-containing compounds primarily make up with the non-polar, hydrophobic nature and benign characteristics of other common ingredients (U.S. Pharmacopeia (USP) grades of mineral oil and polypropylene), which complicates the realization of using HSBC-containing compounds in blood-contacting applications, and this explains why few studies had disclosed chemical modification for biocompatibility improvement on HSBC-containing compounds. Sulfonation has been reported as an effective way to improve the material’s blood/platelet compatibility. In this study, hydrogenated tert-butyl styrene (tBS)-styrene-isoprene block copolymers were synthesized and its blends with polypropylene and USP grades of mineral oil were selectively sulfonated by reaction with acetyl sulfate. By controlling the ratio of the hydrogenated tBS-styrene-isoprene block copolymer in the blend, sulfonated films were optimized to demonstrate sufficient physical integrity in water as well as thermal stability, hydrophilicity, and platelet compatibility.

In vivo performance analysis of silanized and coated nitinol wires in biological environment

Abstract

Final results from a postmarket registry of an iliac leg graft with a continuous, spiral nitinol stent

ObjectiveTo evaluate clinical outcomes from a postmarket registry of the Zenith Spiral-Z abdominal aortic aneurysm iliac leg graft with a continuous, spiral nitinol stent that was designed for improved conformability, kink, and migration resistance. MethodsThis prospective, multicenter registry was designed to evaluate physician-reported outcomes of the Spiral-Z leg graft in up to 600 patients who underwent endovascular repair of abdominal aortic or aortoiliac aneurysms at up to 30 investigative sites in the United States and Canada. Study outcomes were focused on iliac limb occlusion, limb-related reintervention, limb-related endoleak, component separation, and device integrity. Short-term data were collected during an interval of 1 to 6 months, with longer term data collected at 12 months. ResultsBetween March 2012 and March 2015, 599 patients (mean age 74 ± 8 years; 87% male; 26% with aortoiliac aneurysm) were treated, with Spiral-Z iliac leg grafts placed in 564 left iliac arteries and 559 right iliac arteries. The mean iliac inner diameters (both left and right) were 9 ± 3 mm; moderate/severe occlusive disease, calcification, and vessel tortuosity were present in 14%, 25%, and 36% and 15%, 25%, and 34% of the left and right iliac arteries, respectively. Iliac artery adjunctive procedures (iliac artery angioplasty and/or stent placement) were performed intraoperatively in 112 patients (19%; bilateral in 52 patients). Mortality within 30 days was 1.7% (10/599); cumulative mortality at 1 year was 6.2% (37/599). There were no aortic ruptures and only one open conversion (0.2%). Limb occlusions occurred in 11 of 599 patients (2%; 3 within 30 days and 8 after 30 days, all unilateral, none had received procedural iliac artery adjuncts at implantation); of these, 7 patients underwent reinterventions. Other limb-related reinterventions were performed on eight patients for nonocclusive kink, compression, or thrombus (six within 30 days and three after 30 days). In total, 13 patients (2%) underwent 15 limb-related reinterventions (7 for occlusions and 8 for nonocclusive causes). In one patient, a distal type I endoleak and device migration (>10 mm) involving a right iliac leg was noted at the 12-month follow-up visit. No other limb-related endoleak, migration, component separation, or stent fracture was reported during a mean follow-up of 11 ± 6 months. ConclusionsThe Spiral-Z leg graft demonstrated excellent patency and required infrequent limb-related reinterventions in routine clinical care in a postmarket registry.

Small caliber heparin loaded ultrafine microfiber woven graft achieved high patency rate in a preliminary study of canine carotid artery implantation

ObjectiveIn the past five decades, many small caliber vascular grafts have been developed as bypasses for infrapopliteal or coronary arteries. However, reliable grafts have not been obtained owing to poor patency, mainly caused by early thrombosis or neointimal hyperplasia in the intermediate period after implantation. We developed a novel small caliber heparin-loaded polyethylene terephthalate ultrafine microfiber (HL-PET) graft and evaluated the feasibility to overcome those main causes of graft failure in canine carotid artery implantation. MethodsThe HL-PET graft with a diameter of 3 mm and length of 30 mm was made with combination of three key technologies: (1) weaving with PET ultrafine microfiber with a high biological porosity allowing for cell ingrowth, (2) heparin loading on microfiber surfaces, and (3) an outer coating with a flexible bioabsorbable polymer for prevention of blood leakage and graft kinking. Kink resistance, water permeability, and loaded heparin were assessed. One HL-PET graft each was implanted into a carotid artery of six animals. Graft patency rate and healing were assessed 24 weeks after implantation. ResultsAmong the six grafts, five were deemed patent (patency rate of >83%), with one occluded 20 weeks after implantation. Histopathology of the patent grafts showed neointima formation with confluent endothelial cell lining (estimated mean endothelial cell coverage area, 89 ± 18%). Intimal hyperplasia at the anastomotic sites and severe chronic inflammatory responses were not observed. Immunohistochemistry with antibodies to endothelial nitric oxide synthase, alpha 2 smooth muscle actin and calponin 1 revealed luminal surface endothelial cell layer with expression of endothelial nitric oxide synthase and vascular smooth muscle cells with contractile phenotype in the subintimal layer. ConclusionsThe HL-PET graft showed no early postoperative thrombosis and was able to demonstrate a high patency rate with no severe biological response observed after 24 weeks. These results strongly suggest the potential of the HL-PET graft to be used for distal bypasses.

Endovascular Treatment of Superficial Femoral and Proximal Popliteal Arteries Lesions

Abstract Mechanical stress due to flexion-extension in the femoropopliteal space may cause stent failure via stent fracture and thrombosis. Wire-Interwoven self-expanding Nitinol Stents design partially mimics the reticular structure of native vessels, emphasizing radial strength, flexibility and kink resistance; these stent features can offer more chances for short and long term patency. We have evaluated 5 patients with peripheral artery disease with significant superficial femoral artery or proximal popliteal artery lesions. All patients underwent endovascular therapy with Wire-Interwoven self-expanding Nitinol Stents, with primary focus on stent patency at follow-up visits (1, 6, 12 months). The endovascular initial success was achieved in all 5 patients. Stent patency at 1-year follow-up was achieved in 3 patients (60%). 2 patients (40%) had stent thrombosis within 30 days after procedure secondary to arterial dissection at distal stent extremity and self-withdrawal dual antiplatelet therapy; subsequently target lesion revascularization with endovascular therapy and ilio-femoral bypass was performed.

A cardiovascular magnetic resonance (CMR) safe metal braided catheter design for interventional CMR at 1.5\u2009T: freedom from radiofrequency induced heating and preserved mechanical performance

BackgroundCatheter designs incorporating metallic braiding have high torque control and kink resistance compared with unbraided alternatives. However, metallic segments longer than a quarter wavelength (~ 12 cm for 1.5 T scanner) are prone to radiofrequency (RF) induced heating during cardiovascular magnetic resonance (CMR) catheterization. We designed a braid-reinforced catheter with interrupted metallic segments to mitigate RF-induced heating yet retain expected mechanical properties for CMR catheterization.MethodsWe constructed metal wire braided 6 Fr catheter shaft subassemblies using electrically insulated stainless-steel wires and off-the-shelf biocompatible polymers. The braiding was segmented, in-situ, using lasers to create non-resonant wire lengths. We compared the heating and mechanical performance of segmented- with un-segmented- metal braided catheter shaft subassemblies.ResultsThe braiding segmentation procedure did not significantly alter the structural integrity of catheter subassemblies, torque response, push-ability, or kink resistance compared with non-segmented controls. Segmentation shortened the electrical length of individually insulated metallic braids, and therefore inhibited resonance during CMR RF excitation. RF-induced heating was reduced below 2 °C under expected use conditions in vitro.ConclusionWe describe a simple modification to the manufacture of metallic braided catheters that will allow CMR catheterization without RF-induced heating under contemporary scanning conditions at 1.5 T. The proposed segmentation pattern largely preserves braid structure and mechanical integrity while interrupting electrical resonance. This inexpensive design may be applicable to both diagnostic and interventional catheters and will help to enable a range of interventional procedures using real time CMR.