Stainless Steel Stents Research Articles

Deformation mechanics of self-expanding venous stents: Modelling and experiments

Deformation properties of venous stents based on braided design, chevron design, Z design, and diamond design are compared using in vitro experiments coupled with analytical and finite element modelling. Their suitability for deployment in different clinical contexts is assessed based on their deformation characteristics. Self-expanding stainless steel stents possess superior collapse resistance compared to Nitinol stents. Consequently, they may be more reliable to treat diseases like May-Thurner syndrome in which resistance against a concentrated (pinching) force applied on the stent is needed to prevent collapse. Braided design applies a larger radial pressure particularly for vessels of diameter smaller than 75% of its nominal diameter, making it suitable for a long lesion with high recoil. Z design has the least foreshortening, which aids in accurate deployment. Nitinol stents are more compliant than their stainless steel counterparts, which indicates their suitability in veins. The semi-analytical method presented can aid in rapid assessment of topology governed deformation characteristics of stents and their design optimization.

A thermosensitive material coated resonant stent for drug delivery on demand.

An electromagnetic energy source in the radio-frequency range delivers power to a stent circuit via resonant inductive coupling, allowing a thermally triggered release of gel via Joule heating. A gold-electroplated, medical-grade stainless steel stent, serving as the base of the prototype device, melts a coating made from an emulsion composed mainly of dodecanoic acid. These coated devices produce wirelessly controllable releases of a gel into thermally regulated, stirred water that is near body temperature. The gel is made from salt, water, and gelatine from porcine skin and used to simulate drug release in this study. Thus, this system serves as a proof of concept to show the viability of controlling local drug delivery using this prototype device. Dodecanoic acid, a fatty acid, has a phase transition from solid to liquid near 43[Formula: see text]C and has relatively good biocompatibility. The average melting temperature of two different emulsions was 40.8±0.7[Formula: see text]C, a suitable value for the targeted application. Demonstration of controllable releases used electromagnetic pulses of approximately 180 seconds in duration, illustrating reproducibility of a controllable release phase while remaining relatively inert in the absence of stimuli. Releases were observable through measuring the conductivity of the water, the water temperature, and the stent temperature. This electrothermally active stent device enables wirelessly controlled local delivery with controlled dosage and timing, a concept with a wide range of potential applications. Some relevant examples include inhibiting restenosis or cancer treatment via targeted chemotherapy.

Aortic dissection assessment by 4D phase-contrast MRI with hemodynamic parameters: the impact of stent type.

To explore the diagnostic performance of 4-dimensional phase-contrast magnetic resonance imaging (4D PC-MRI) in evaluating aortic dissection in different clinical scenarios. The study group comprised 32 patients with a known aortic dissection who each underwent computed tomography angiography (CTA), and then 4D PC-MRI with a 1.5-T MR scanner. The 4D PC-MRI images were compared with the CTA images to evaluate the aortic size, branch identification, and iliac and femoral arterial access. The patients were divided into three groups: (I) patients diagnosed with Type B aortic dissection but did not undergo intervention (n=8); (II) patients with residual aortic dissection after open repair of Type A dissection (n=7); (III) patients who underwent endovascular aortic repair with or without open surgery (n=17). Without radiation or contrast media injection, 4D PC-MRI provided similar aortic images for patients in Group 1 and most of those in Group 2. In Group 3, stainless steel stents affected image quality in three patients. High-quality 4D PC-MRI images were obtained for the remaining 14 patients in Group 3, who had non-stainless steel stents, and provided major aortic information comparable to that provided by CTA with contrast media. The hemodynamic parameters of true and false lumens were evaluated between three patients with Type B aortic dissections and three patients who underwent thoracic endovascular aortic repair for their aortic dissection. The stroke volume was higher in the true lumen of the patients with stent-grafts than in the patients with Type B aortic dissection without intervention. The regurgitant fraction, an indicator of nonlaminar flow, was higher in the false lumens than in the true lumens. All 32 patients in this study tolerated 4D PC-MRI without adverse events. 4D PC-MRI is radiation- and contrast media-free option for imaging aortic dissection. It not only provided images comparable in quality to those obtained with CTA but also provided information on hemodynamic parameters, including endoleak detection after thoracic endovascular aortic repair. 4D PC-MRI was safe and accurate in evaluating chronic Type B aortic dissection and residual aortic dissection after surgery for acute Type A aortic dissection. Therefore, it could be a potential tool in treating pathology in aortic dissection, especially for patients with malperfusion syndrome of visceral vessels and in young patients with renal function impairment. However, certain endograft materials, especially stainless steel, may prevent the further application of 4D PC-MRI and should be avoided.

Evaluation of in Vitro Corrosion Behavior of Titanium Oxynitride Coated Stainless Steel Stents

Coronary artery disease (CAD) affects every fifth person in the world. The gold-standard treatment for CAD is stent implantation, however, the existing therapy is not sufficient. In recent years, titanium oxynitride (TiOxNy) coatings on bare metal stents (BMSs) attracted the attention of many researchers around the world due to their promising results and improved surface properties. However, good coating adhesion and coverage of the inner surface in stent applications is still a challenging task. Moreover, enhanced corrosion resistance and durability over a longer period under the influence of an aggressive biological environment is one of the main requirements while developing novel coatings for bare-metal stents. In this work, the titanium oxynitride (TiOxNy) coated stainless steel stents were fabricated by magnetron sputtering and the corrosion behavior of coated and uncoated stents has been studied using immersion, fluid dynamic, and electrochemical corrosion tests. For the first time, the entire stent surface has been used for quantitative corrosion tests on stents. We discuss and compare the in vitro biostability and corrosion behavior of bare stainless steel (316L) and titanium oxynitride films (TiOxNy) coated stents.TiOxNy coatings provide valuable stability to the BMS against harsh environments or conditions. The coated stents are remarkably more stable when compared with the reference uncoated stents (316L BMS), regardless of the ratio of O2 and N2. The variation of stent coating parameters is still possible to get more anticorrosive and biostable behavior; therefore, the results could provide the basis for further research.

Microstructural and Mechanical Characterization of Thin-Walled Tube Manufactured with Selective Laser Melting for Stent Application

This paper focuses on microstructural and mechanical characterization of metallic thin-walled tube produced with additive manufacturing (AM), as a promising alternative technique for the manufacturing of tubes as a feedstock for stents micromachining. Tubes, with a wall thickness of 500 μm, were made of 316L stainless steel using selective laser melting. Its surface roughness, constituting phases, underlying microstructures and chemical composition were analyzed. The dependence of hardness and elastic modulus on the crystallographic orientation were investigated using electron backscatter diffraction and nanoindentation. Spherical nanoindentation was performed to extract the indentation stress–strain curve from the load–displacement data. The obtained results were compared with those for a commercial 316L stainless steel stent. Both tube and commercial stent samples were fully austenitic, and the as-fabricated surface finish for the tube was much rougher than the stent. Microstructural characterization revealed that the tube had a columnar and coarse grain microstructure, compared to equiaxed grains in the commercial stent. Berkovich nanoindentation suggested an effect for the grain orientation on the hardness and Young’s modulus. The stress–strain curves and the indentation yield strength for the tube and stent were similar. The work is an important step toward AM of patient-specific stents.

Computational analysis of the effects of geometric irregularities and post-processing steps on the mechanical behavior of additively manufactured 316L stainless steel stents

Advances in additive manufacturing enable the production of tailored lattice structures and thus, in principle, coronary stents. This study investigates the effects of process-related irregularities, heat and surface treatment on the morphology, mechanical response, and expansion behavior of 316L stainless steel stents produced by laser powder bed fusion and provides a methodological approach for their numerical evaluation. A combined experimental and computational framework is used, based on both actual and computationally reconstructed laser powder bed fused stents. Process-related morphological deviations between the as-designed and actual laser powder bed fused stents were observed, resulting in a diameter increase by a factor of 2-2.6 for the stents without surface treatment and 1.3-2 for the electropolished stent compared to the as-designed stent. Thus, due to the increased geometrically induced stiffness, the laser powder bed fused stents in the as-built (7.11 ± 0.63 N) or the heat treated condition (5.87 ± 0.49 N) showed increased radial forces when compressed between two plates. After electropolishing, the heat treated stents exhibited radial forces (2.38 ± 0.23 N) comparable to conventional metallic stents. The laser powder bed fused stents were further affected by the size effect, resulting in a reduced yield strength by 41% in the as-built and by 59% in the heat treated condition compared to the bulk material obtained from tensile tests. The presented numerical approach was successful in predicting the macroscopic mechanical response of the stents under compression. During deformation, increased stiffness and local stress concentration were observed within the laser powder bed fused stents. Subsequent numerical expansion analysis of the derived stent models within a previously verified numerical model of stent expansion showed that electropolished and heat treated laser powder bed fused stents can exhibit comparable expansion behavior to conventional stents. The findings from this work motivate future experimental/numerical studies to quantify threshold values of critical geometric irregularities, which could be used to establish design guidelines for laser powder bed fused stents/lattice structures.

Ultrashort echo time time-spatial labeling inversion pulse magnetic resonance angiography with denoising deep learning reconstruction for the assessment of abdominal visceral arteries.

Current contrast-enhanced magnetic resonance angiography (MRA) and non-contrast-enhanced balanced steady-state free precession (bSSFP) MRA cause susceptibility artifacts from metallic devices in assessing endovascular visceral-artery interventions. The aims of this study are to investigate and compare image quality (IQ) and susceptibility artifacts of three-dimensional (3D) ultrashort echo time (UTE) time-spatial labeling inversion pulse (Time-SLIP) with those of 3D bSSFP Time-SLIP and to assess denoising deep learning reconstruction (dDLR) for the improvement of the signal-to-noise ratio (SNR) in 3D UTE with sparse sampling in phantoms and human subjects. This is a prospective type of study. Pulsatile glycerin-water flow phantom with platinum-tungsten-alloy coil, stainless-steel, nitinol, and cobalt-alloy stents were used. Ten healthy volunteers (seven males) and three patients (two males) were included in this study. 3D UTE Time-SLIP and 3D bSSFP Time-SLIP at 3T were used. The phantom-based study compared the signal-intensity ratio of the device levels (SRdevice ) and distal segments (SRdistal ) to the proximal segments. The volunteer-based study measured SNR, contrast ratio (CR), and IQ. The patient study evaluated local artifacts from metallic devices. Statistical tests included paired t-tests, Wilcoxon-signed rank tests, and Kruskal-Wallis tests. In the phantom-based study, SRdevice was small with UTE Time-SLIP, except the stainless-steel stent. SRdistal was greater (49.1%-90.4%) on bSSFP images than UTE images (-11.1% to 9.6%). Among volunteers, dDLR in UTE images improved SNR (p < 0.05) and IQ (p < 0.05), but CR was unaffected. UTE Time-SLIP showed inferior SNR and IQ than bSSFP Time-SLIP in images with and without dDLR (p < 0.05 for each). However, among patients, UTE Time-SLIP showed reduced metal artifacts compared to bSSFP Time-SLIP. Irrespective of the lower SNR and IQ of 3D UTE Time-SLIP than those of 3D bSSFP Time-SLIP, the former appeared to better depict flow after stenting or coiling. This indicates the potential of 3D UTE Time-SLIP to provide suitable diagnostic images of target vessels. dDLR improved SNR with reducing artifacts related to radial sampling, while maintaining the contrast. LEVEL OF EVIDENCE: 2. TECHNICAL EFFICACY STAGE: 2.

Endograft platform does not influence aortic neck dilatation after infrarenal endovascular aneurysm repair with primary endostapling.

Aortic endografts used for endovascular aneurysm repair (EVAR) are based on varying skeletal platforms such as stainless steel or nitinol stents, using radial force applied to seal at the aneurysm neck, and varying proximal fixation methods, applying either suprarenal or infrarenal fixation. This study assesses whether varying skeleton/fixation platforms affect neck-related outcomes after primary endostapling with Heli-FX EndoAnchors at EVAR. Retrospective analysis of a prospective database of infrarenal EVAR undertaken at a single centre. Chimney-EVAR, secondary cases were excluded. Primary outcomes analysed included neck diameter evolution from pre-EVAR to latest imaging follow-up, including a comparison of stent platforms to see if there was any outcome difference between those using stainless steel or nitinol, as also freedom from type I endoleakage and migration. Secondary outcomes assessed included average number of EndoAnchors, and sac size patterns before and after EVAR. A total of 101 patients underwent endostapled infrarenal EVAR between September 2013 and March 2020. After exclusion of ineligible patients, 84 patients (76 male, 8 female, age 73.7 ± 7.8 years) were available for analysis. 57/27 endografts used suprarenal/infrarenal fixation, whilst 16/68 devices were based on stainless steel/nitinol platforms, respectively. Mean oversizing was higher for stainless steel/suprarenal fixation endografts (p = 0.02). A total of 582 EndoAnchors were deployed, averaging 7 ± 2 per patient. Median neck diameter was 25 mm (IQR 22-31) with 22 necks having non-parallel morphology (conical, tapered or bubble). Median follow-up period was 28.5 (IQR 12-43) months. Neck evolution studies suggested aortic neck dilatation of 5 ± 4 mm (p <0.001, paired T-test), independent of platforms employed (p = NS, ANOVA). There was no endograft migration; one immediate post-EVAR endoleak settled by eight weeks. There was a mean 5.7 ± 8.2 mm sac size reduction (p < 0.001, paired T-test). Aortic neck dilatation occurs after EVAR with primary endostapling, but the process may be independent of stainless steel/nitinol platforms, possibly due to the attenuating effect of EndoAnchors. Adjunct aneurysm neck fixation by primary endostapling prevents migration regardless of whether suprarenal/infrarenal fixation is the primary fixative method. Device platform choice therefore may be left to the operator discretion if primary endostapling is applied at EVAR. Freedom from complications such as migration and endoleakage in the intermediate term suggests a higher level of 'tolerance' to aortic neck dilatation with primary endostapling. We would therefore suggest routine usage of EndoAnchors at EVAR when not otherwise contraindicated.

In vivo biological safety evaluation of an iron-based bioresorbable drug-eluting stent.

Bioresorbable stents (BRS) are investigated and designed to revascularize occluded arteries. The iron-based bioresorbable stent is a promising device in interventional therapies, although it's corrosion and bioresorption rate remain challenging. In this work, we introduced a novel nitrided iron coronary stent (IBS) with enhanced degradation rate compared with pure iron stent. To evaluate the biosafety of this device, a sub-chronic systemic toxicity study was conducted and a stainless steel stent (Supporter™) served as a control. Here, the bioresorbable stent was first evaluated in rat abdominal aortic implantation model. When subjected to exaggerated exposure dose, no clinical signs of toxicity or mortality were observed in either, the IBS group or the control group. Histopathological examinations showed the corrosion particles of iron were encapsulated by fibrocytes and engulfed by macrophages, indicating that the degradation of iron was in the early stage. Our results demonstrated that the nitrided iron stent did not induce systemic toxicity under the experimental conditions.

Successful Reduction of Neointimal Hyperplasia on Stainless Steel Coronary Stents by Titania Nanotexturing.

Bare metal stents (BMSs) of stainless steel (SS) were surface engineered to develop nanoscale titania topography using a combination of physical vapor deposition and thermochemical processing. The nanoleafy architecture formed on the stent surface remained stable and adherent upon repeated crimping and expansion, as well as under flow. This titania nanoengineered stent showed a preferential proliferation of endothelial cells over smooth muscle cells in vitro, which is an essential requirement for improving the in vivo endothelialization, with concurrent reduction of intimal hyperplasia. The efficacy of this surface-modified stent was assessed after implantation in rabbit iliac arteries for 8 weeks. Significant reduction in neointimal thickening and thereby in-stent restenosis with complete endothelial coverage was observed for the nanotextured stents, compared to BMSs, even without the use of any antiproliferative agents or polymers as in drug-eluting stents. Nanotexturing of stents did not induce any inflammatory response, akin to BMSs. This study thus indicates the effectiveness of a facile titania nanotopography on SS stents for coronary applications and the possibility of bringing this low-priced material back to clinics.

1-Year Clinical Outcomes of All Comers Treated With 2 Bioresorbable Polymer-Coated Sirolimus-Eluting Stents: Propensity Score–Matched Comparison of the COMBO and Ultrathin-Strut Orsiro Stents

ObjectivesThe aim of this study was to determine 1-year safety and efficacy after treatment with the COMBO and Orsiro stents. BackgroundThe COMBO stainless-steel stent has an anti-CD34+ antibody coating to capture endothelial progenitor cells, thereby promoting faster endothelialization. The Orsiro is an ultrathin-strut cobalt-chromium stent, covered by an extremely thin layer of amorphous silicon carbide to minimize ion leakage. Both devices elute sirolimus from biodegradable polymers. MethodsFor this analysis we included European patients from the COMBO collaboration, a patient-level pooling of 2 prospective all-comers registries of COMBO stent implantation (n = 2,775), and all patients randomized to the Orsiro stent (n = 1,169) from the Dutch BIO-RESORT (Comparison of Biodegradable Polymer and Durable Polymer Drug-Eluting Stents in an All Comers Population) randomized trial. The main outcome of interest was 1-year target lesion failure, a composite of cardiac death, target vessel myocardial infarction, and clinically driven target lesion revascularization evaluated using propensity score–matched analysis. ResultsAt baseline, COMBO patients were older and had more insulin-treated diabetes, renal insufficiency, and other comorbidities. However, Orsiro patients included more current smokers and more acute coronary syndrome presentations. Orsiro patients also received longer stents and had more complex target lesions. After propensity score–matched analysis (n = 862/arm), 1-year target lesion failure occurred in 4.1% of COMBO-treated and 2.7% of Orsiro-treated patients (hazard ratio: 1.55; 95% confidence interval: 0.92 to 2.62; p = 0.10). Definite stent thrombosis occurred in 0.5% of COMBO-treated and 0.5% of Orsiro-treated patients (p = 0.99). ConclusionsA propensity score–matched comparison of all comers treated with the COMBO or Orsiro stent showed no statistically significant differences. Stent thrombosis risk was low and similar between the stents. (Comparison of Biodegradable Polymer and Durable Polymer Drug-Eluting Stents in an All Comers Population [BIO-RESORT], NCT01674803; MASCOT–Post Marketing Registry [MASCOT], NCT02183454; Prospective Registry to Assess the Long-term Safety and Performance of the Combo Stent [REMEDEE Reg], NCT01874002)

Prosthetics provide room to grow

Cardiology Children with congenital heart disease who require heart valve replacement often must undergo multiple high-risk surgeries because the replacement valve cannot grow as their heart grows. Inspired by this problem, Hofferberth et al. developed a prosthetic valve that mimics the geometry of the human venous valve, which maintains function despite large fluctuations in blood volume. The prosthesis, composed of polymeric leaflets attached to a stainless-steel stent, can be mechanically expanded using transcatheter balloon dilation to adapt to larger fluid volumes. Size-adaptable valves maintained function when implanted into growing lambs and could be mechanically expanded over 10 weeks. Sci. Transl. Med. 12 , eaay4006 (2020).

First in man study of a new semi-open cell design Zephyr cobalt-chromium stent in large vessels and conduits.

We present a first-in-man clinical use of a new hybrid design stent in stenosed large vessels. Its unique C and S polylinks prevent foreshortening without compromising its strength. Its thin profile permits use of smaller introducer sheaths. Stent angioplasty is widely employed in large vessel and conduit stenosis. These procedures are associated with difficulties due to large stent profiles, stent fractures, foreshortening and recoil. Cobalt chromium stents have high tensile strengths compared to stainless steel stents. A retrospective analysis of feasibility and safety of a new Cobalt chromium stent in large vessels namely aorta, pulmonary arteries and outflow conduits was done from two institutions. Demographic patient details, procedural results, complications and medium term follow-up were analyzed. Stent recoil, foreshortening, fractures were assessed. Twenty patients including three with aortic coarctations, seven with stenosed conduits and 10 with pulmonary artery stenosis underwent stent angioplasty using 23 stents. Three stents were deployed to expand further a previously implanted stent. Procedure was successful in all patients, lumen increased by 150-300%, gradients reduced in all patients. There was no stent recoil, foreshortening or fractures. There were no complications. At a follow up of 3-27 months, there were no stent related complications and the gradients remained stable. The new Zephyr stent was useful in a wide variety of stenotic lesions involving large vessels including those that were previously stented. Lack of stent recoil and foreshortening seems to be an advantage for this new stent that needs validation in larger multicenter studies.

New tracheal stainless steel stent pilot study: twelve month follow-up in a rabbit model.

BackgroundCanine tracheal collapse is a complex airway pathology without promising treatment results. Currently nitinol stents are the best surgical option; however, some professionals are doubting if stent placement is the best option due to the associated complications.ObjectiveDetermine the technical feasibility, safety, and long-term follow-up after the implantation of a new tracheal stent designed for canine tracheal collapse.MethodsThirteen healthy, adult female New Zealander rabbits were involved in this pilot study.A new intra-tracheal device (Reference number 902711 patent registered as CasMin-Twine) was implanted in ten animals. Deployment was performed under general anesthesia, making a puncture incision via a 21 Gauge needle in the intra-tracheal space where the stent was introduced with a screwing process. The device was fixed to the tracheal wall with a non-absorbable suture. Computerized Tomography (CT) and an endoscopy to study structural abnormalities were performed after 30, 90 and 365 days after stent placement.ResultsTechnical and clinical success was 100%. There was no significant change in behavior or respiratory disorders. CT studies showed no significant alterations. After the 30 days, 60% of the animals showed partial endothelization in the endoscopy study, and only one animal still presented partial endothelization after 12 months. Mucus accumulation was only present in 40% of cases and classified as low, without respiratory consequences. Only one animal presented a single granuloma at caudal stent tip.ConclusionsThis new tracheal stent (CasMin-Twine) is an effective and safe procedure with promising results, and also shows the possibility of removing the device after endothelization has been produced. New studies should be carried out to evaluate the effectiveness in patients with tracheomalacia.Clinical Significance/ImpactThis new product can give veterinarians a new option of treatment for this complicated pathology. Minimizing specific equipment for its deployment, CasMin-Twine will be more accessible for all professionals.

A computational study on vascular damage caused by shape memory alloy self-expandable and balloon-expandable stents in a stenosed artery

Atherosclerosis is one of the major types of cardiovascular diseases. Stent deployment into the stenosed artery is the most common treatment for atherosclerosis. Two common stent models based on two different expansion principles are balloon-expandable and self-expandable stents. Depending on the modality of the expansion, the material used for these two stents varies. Despite the extensive progress made in the field of stent construction, plaque fragmentation and in-stent restenosis are two of the problems that still cause complications in stenting. Computational modeling and finite element method help us predict the damage effects to the artery and plaque in the stenting process. In this article, we simulate the insertion of two stents (the stainless steel stent and the shape memory alloy stent) in a diseased artery with real geometry. Results are compared to account for the effects of these stents on the artery, especially, the maximum stress in the plaque and arterial layers and surgically induced damage as the main cause of plaque fracture during the stent deployment and in-stent restenosis. It is found that arising from superelasticity, the shape memory alloy stent induces less damage to the artery. In addition, the stress created in the artery by the shape memory alloy stent is smaller. Therefore, the risk of plaque fragmentation and in-stent restenosis is reduced in shape memory alloy stents.

Research on elastic recoil and restoration of vessel pulsatility of Zn-Cu biodegradable coronary stents.

Coronary stents made of zinc (Zn)-0.8 copper (Cu) (in wt%) alloy were developed as biodegradable metal stents (Zn-Cu stents) in this study. The mechanical properties of the Zn-Cu stents and the possible gain effects were characterized by in vitro and in vivo experiments compared with 316L stainless steel stents (316L stents). Young's modulus of the as-extruded Zn-0.8Cu alloy and properties of the stents, including their intrinsic elastic recoil, stent trackability were evaluated compared with 316L stents. In vivo study was also conducted to evaluate restoration of pulsatility of vessel segment implanted stents. Both Zn-Cu stents and 316L stents have good acute lumen gain. By comparison, the advantages of Zn-Cu stents are as follows: (I) Zn-Cu stents have less intrinsic elastic recoil than 316L stents; (II) stent trackability indicates that Zn-Cu stents have a smaller push force when passing through curved blood vessels, which may cause less mechanical stimulation to blood vessels; (III) in vivo study suggests that Zn-Cu stents implantation better facilitates the recovery of vascular pulsatility.

Covalent immobilization of biomolecules on stent materials through mussel adhesive protein coating to form biofunctional films.

It is widely accepted that surface biofunctional modification may be an effective approach to improve biocompatibility and confer new bioactive properties on biomaterials. In this work, mussel adhesive protein (MAP) was applied as a coating on 316 L stainless steel substrates (316 L SS) and stents, and then either immobilized VEGF or CD34 antibody were added to create biofunctional films. The properties of the MAP coating were characterized by scanning electron microscope (SEM), atomic force microscope (AFM) and a water contact angle test. Universal tensile testing showed that the MAP coating has adequate adhesion strength on a 316 L stainless steel material surface. Subsequent cytotoxicity and hemolysis rate tests showed that the MAP coatings have good biocompatibility. Moreover, using N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysulfosussinimide (EDC/NHS) chemistry, VEGF and CD34 antibody were immobilized on the MAP coatings. The amount and immobilized yield of VEGF on the MAP coatings were analyzed by enzyme-linked immuno-assays (ELISA). Finally, an endothelial cells culture showed that the VEGF biofunctional film can promote the viability and proliferation of endothelial cells. An in vitro CD34+ cells capturing test also verified the bioactive properties of the CD34 antibody coated stents. These results showed that the MAP coatings allowed effective biomolecule immobilization, providing a promising platform for vascular device modification.

In vivo research on Cu-bearing ureteral stent.

Infection and encrustation limit the use of ureteral stent and to data no device can completely solve these complications. The Cu-bearing stainless steel is a novel material with properties of inhibiting infection and decreasing encrustation in vitro. In this work, ureteral stents were fabricated and implanted into the bladder of New Zealand rabbits, aiming to further investigate the effects of material on bacterial survival and growth as well as the implant related encrustation. Less adherent microbes and deposited crystals on Cu-bearing stainless steel stents were found, with significant differences in comparison with stainless steel stents, which further support the development of biofunctional ureteral stents.

Five-year results from the Study of Thoracic Aortic Type B Dissection Using Endoluminal Repair (STABLE I) study of endovascular treatment of complicated type B aortic dissection using a composite device design

ObjectiveWe report the final 5-year results from the Study of Thoracic Aortic Type B Dissection Using Endoluminal Repair (STABLE I) study, a prospective, single-arm, multicenter study of the Zenith Dissection Endovascular System (William Cook Europe, Aps, Bjaeverskov, Denmark), a pathology-specific device comprising a proximal stent graft with barbs and a distal bare stainless steel stent for the treatment of patients with complicated type B aortic dissection. MethodsThe study prospectively enrolled 86 patients (mean age, 59 years; 73% male) at sites in the United States, Europe, and Australia from 2007 to 2012. Treatment occurred during the acute phase (≤14 days after symptom onset) in 55 patients and during the nonacute phase (>14 days; all treated ≤90 days) in 31 patients. Five-year clinical and imaging follow-up was available for 88.5% of eligible patients. ResultsThe 30-day all-cause mortality rate was 5.5% (3 of 55) for acute and 3.2% (1 of 31) for nonacute patients (P > .99). The 5-year freedom from all-cause mortality was 79.9% ± 6.2% for acute and 70.1% ± 8.4% for nonacute patients (log-rank test, P = .40). The 5-year freedom from dissection-related mortality (including deaths of indeterminate relatedness to dissection repair) was 83.9% ± 5.9% for acute and 90.1% ± 5.9% for nonacute patients (log-rank test, P = .55). Complete false lumen thrombosis in the thoracic aorta increased over time and was observed in 74.1% of acute and in 58.8% of nonacute patients at 5 years. From preprocedure through 5 years, there was an overall increase in true lumen diameter and a concomitant decrease in false lumen diameter in both acute and nonacute patients at the level of the largest diameter in both the thoracic and abdominal aortas. At 5 years, 65.5% of acute and 81.3% of nonacute patients exhibited a stable or shrinking transaortic diameter in the thoracic aorta, and 48.3% of acute and 76.5% of nonacute patients had a stable or shrinking transaortic diameter in the abdominal aorta. Freedom from secondary intervention at 5 years was 65.5% ± 7.5% for acute and 71.2% ± 9.0% for nonacute patients (log-rank test, P = .71). ConclusionsEndovascular repair of complicated type B aortic dissection with a composite device design demonstrated low all-cause mortality at 30 days, as well as low dissection-related mortality throughout follow-up. Overall, the acute and nonacute cohorts appeared to respond similarly to treatment involving use of the stent-graft and bare metal stent, demonstrating similar clinical outcomes and favorable improvement in aortic remodeling in the thoracic and abdominal aortas.

Development of Dual Drug Eluting Cardiovascular Stent with Ultrathin Flexible Poly(l-lactide-co-caprolactone) Coating.

The pleiotropic effects of the atorvastatin-fenofibrate combination can be effectively harnessed for site-specific therapy to minimize stent-related complications. The present study aims to utilize the pleiotropic effects of these two drugs entrapped in a uniform and defect-free coating of poly(l-lactide-co-caprolactone) (PLCL) on a stainless steel stent to overcome stent-associated limitations. The stent coating parameters were optimized using ultrasonic spray coating technique to achieve a thin, smooth, and defect-free dual drug-loaded polymer coating on the stent. The dual drug-loaded polymer coated stent was characterized for surface morphology, thickness and coating integrity. In vitro drug release kinetics of the fabricated stent reveals a sustained release of both drugs for more than 60 days. Significant reduction of thrombus formation and adhesion of lipopolysaccharide-stimulated macrophages on the dual drug containing polymer-coated stent indicates that the drug combination possesses antithrombotic and anti-inflammatory effects. The combination did not adversely influence endothelialization but significantly retarded smooth muscle cell proliferation indicating its potential to overcome restenosis. No bacterial biofilm formation was observed on the stent due to the antibacterial activity of atorvastatin. A rat subcutaneous model was used to evaluate the biocompatibility of the coated stent and compared with the commercial stent. MicroCT, scanning electron microscopy, and morphometric analyses revealed that the coated stents exhibited excellent histocompatibility with no inflammatory response as evidenced from the cytokine levels measured 28 days postimplantation. Our data demonstrates for the first time that the combination of atorvastatin and fenofibrate can be successfully employed in cardiovascular stents to overcome the current limitations of conventional drug-eluting stents.