Beta Titanium Alloys with Very High Ductility Induced by Complex Deformation Mechanisms: a New Material Perspective for Coronary Stent Applications

2011 ◽  
Vol 172-174 ◽  
pp. 129-134 ◽  
Author(s):  
Fan Sun ◽  
Thierry Gloriant ◽  
Philippe Vermaut ◽  
Pascal Jacques ◽  
Frédéric Prima
Keyword(s):  
Stainless Steel ◽  
Titanium Alloys ◽  
Design Method ◽  
Bare Metal Stents ◽  
Mechanical Twinning ◽  
Metal Stents ◽  
High Ductility ◽  
Stent Deployment ◽  
Major Drawback ◽  
Complex Deformation

The increased use of metallic biomaterials in contact with blood e.g. for application as coronary stents is steadily resulting in the development of new biomaterials. Conventional bare-metal stents made by stainless steel were reported on adverse reactions against human body and are gradually replaced by coated stainless steel. The new generation of stent requires fundamental improvements at the materials point of view. Although titanium and classical Ti-alloys display superior biocompatibility compared to other metallic materials (stainless steels, Co-Cr), the major drawback of their relatively low ductility (typically 15%-25% of elongation) seriously limits their applications as cardiovascular stents, where large ductility is basically required during the stent deployment procedure and long-term service. In this paper, new titanium alloys with high ductility, a binary Ti-12Mo (wt%) and a ternary Ti-9Mo-6W (wt%) were designed by using a chemical formulation strategy based on the electronic design method called “the d-electron alloy design method”. Both alloys were synthesized and thermo-mechanically treated into beta-metastable state. In tensile tests, both alloys exhibited outstanding ductility of 43% and 46% in total elongation at room temperature, which is almost two times greater than the normal value shown with classical titanium alloys. Optical microscopy and detailed TEM observations on the deformed specimens revealed a complex deformation mechanism, involving {332}<113> mechanical twinning, stress induced plate shaped omega phase and stress induced martensitic (SIM) transformation β-α’’.

scholarly journals eG Coated Stents Exhibit Enhanced Endothelial Wound Healing Characteristics

2021 ◽  
Author(s):  
Belen Rodriguez-Garcia ◽  
Christophe Bureau ◽  
Abdul I. Barakat
Keyword(s):  
Wound Healing ◽  
Endothelial Cells ◽  
Bare Metal Stents ◽  
Automated Image Analysis ◽  
Butyl Methacrylate ◽  
Metal Stents ◽  
Cobalt Chromium ◽  
Endothelial Lining ◽  
Stent Deployment ◽  
Endothelial Wound Healing

Abstract Purpose Despite their widespread use, a significant fraction of coronary stents suffer from in-stent restenosis and stent thrombosis. Stent deployment induces extensive injury to the vascular endothelium. Rapid endothelial wound closure is essential for the success of a stenting procedure. A recent study has demonstrated that the BuMA Supreme® sirolimus-eluting stent exhibits particularly attractive strut coverage characteristics. A unique feature of this stent is the presence of a thin brush layer of poly-butyl methacrylate (PBMA), covalently bonded to the stent’s cobalt-chromium frame via electro-grafting (eG™). The present study aimed to determine whether the PBMA coating has an effect on endothelial cell wound healing and stent strut coverage. Methods We used an in vitro coronary artery model whose wall consisted of an annular collagen hydrogel and whose luminal surface was lined with a monolayer of endothelial cells. Mechanical wounding of the endothelial lining was preformed prior to deployment of a bare cobalt-chromium stent either with or without the PBMA layer. The migration of fluorescently labeled endothelial cells was monitored automatically over a period of 48 h to determine endothelial wound healing rates. Results Quantitative assessment of endothelial wound healing rates within the simulated arterial model is achievable using automated image analysis. Wound healing is significantly faster (44% faster at 48 h) for stents with the PBMA eG Coating™ compared to bare metal stents. Conclusion The PBMA eG Coating™ has the effect of promoting endothelial wound healing. Future studies will focus on elucidating the mechanistic basis of this observation.

scholarly journals In Vitro Behavior and Surface Morphology of Modified 316L Stainless Steel Stents

2008 ◽  
Vol 14 (S3) ◽  
pp. 35-36 ◽  
Author(s):  
J. Nunes ◽  
A.P. Piedade ◽  
C.B. Duarte ◽  
M.T. Vieira
Keyword(s):  
Stainless Steel ◽  
316L Stainless Steel ◽  
Cardiovascular Surgery ◽  
Research Work ◽  
Bare Metal Stents ◽  
Metal Stents ◽  
Metallic Stent ◽  
Stent Restenosis ◽  
Drug Eluting

When compared with conventional bare metal stents, such as 316L stainless steel, the introduction of drug-eluting stents can promote reduction in the incidence of in-stent restenosis. However, the chemical discrepancy between the metallic stent and the polymeric material that acts as the reservoir for the drug is responsible for some problems during the cardiovascular surgery. Besides the research work aiming at the development of new bulk alloys for stent production, focus as been also directed to the surface modification of these devices. However, the use of functional graded coatings (FGC), i.e., coatings with a gradient of chemical composition between the substrate and the outmost layer, has never been reported in devices for cardiovascular surgery.

Treatment of central venous in-stent restenosis with repeat stent deployment in hemodialysis patients

2017 ◽  
Vol 18 (3) ◽  
pp. 214-219 ◽  
Author(s):  
James Ronald ◽  
Bradley Davis ◽  
Carlos J. Guevara ◽  
Waleska M. Pabon-Ramos ◽  
Tony P. Smith ◽  
...  
Keyword(s):  
Bare Metal Stents ◽  
Hemodialysis Patients ◽  
Transluminal Angioplasty ◽  
Primary Patency ◽  
Metal Stents ◽  
Central Vein ◽  
Secondary Patency ◽  
Stent Deployment ◽  
Percutaneous Transluminal ◽  
Stent Stenosis

Purpose To report patency rates for stent deployment for treatment of in-stent stenosis of the central veins of the chest in hemodialysis patients. Materials and Methods A retrospective analysis was performed on 29 patients who underwent 35 secondary percutaneous transluminal stent (PTS) deployments for in-stent stenosis within the central veins that were refractory to angioplasty and ipsilateral to a functioning hemodialysis access (in-stent PTS group). For comparison, patency data were acquired for 47 patients who underwent 78 successful percutaneous transluminal angioplasty (PTA) procedures for in-stent stenosis (in-stent PTA group) and 55 patients who underwent 55 stent deployments within native central vein stenosis refractory to angioplasty (native vein PTS group). Results The 3-, 6-, and 12-month primary lesion patency for the in-stent PTS group was 73%, 57%, and 32%, respectively. The 3-, 6-, and 12-month primary patency for the in-stent PTA group was 70%, 38%, and 17% and for the native vein PTS group was 78%, 57%, and 26%, which were similar to the in-stent PTS group (p = 0.20 and 0.41, respectively). The 3-, 6-, and 12-month secondary access patency was 91%, 73%, and 65% for the in-stent PTS group. Sub-analysis of the in-stent PTS group revealed no difference in primary (p = 0.93) or secondary patency rates (p = 0.27) of bare metal stents (n = 23) compared with stent grafts (n = 12). Conclusions Stent deployment for central vein in-stent stenosis refractory to angioplasty was associated with reasonable patency rates, which were similar to in-stent PTA and native vein PTS.

High Performance Beta Titanium Alloys as a New Material Perspective for Cardiovascular Applications

2012 ◽  
Vol 706-709 ◽  
pp. 578-583 ◽  
Author(s):  
Frédéric Prima ◽  
F. Sun ◽  
Philippe Vermaut ◽  
Thierry Gloriant ◽  
D. Mantovani ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Titanium Alloys ◽  
Metal Ion ◽  
High Performance ◽  
Mechanical Twinning ◽  
High Yield ◽  
Dislocation Slip ◽  
Beta Titanium ◽  
Beta Titanium Alloys

During the last few decades, titanium alloys are more and more popular and developed as biomedical devices because of their excellent biocompatibility, very good combination of mechanical properties and prominent corrosion resistance [1-3]. Recently, a new generation of beta titanium alloys dedicated to biomedical applications has been developed. Based on biocompatible alloying elements such as Ta, Nb, Zr and Mo, these alloys were designed as low modulus alloys [4] or nickel-free superelastic materials [5, 6] mainly for orthopedic or dental applications as osseointegrated implants. Beta type titanium alloys take great advantages from their capacity to display several deformation mechanisms as a function of beta phase stability. Therefore, from low to high beta stability, stress assisted martensitic phase transformation (β-α’’), mechanical twinning or simple dislocation slip can alternatively be observed [7]. As a consequence, a very large range of mechanical properties can be reached, including low apparent modulus, large reversible elastic deformation or high yield stress. Although titanium alloys display now a long history of successful applications in orthopedic and dental devices, none of them have been commercially exploited in the area of coronary stents, despite their superior long term haemocopatibility compared to the 316L stainless steel. However, according to previous researches on the biocompatibility of various metals, the corrosion behavior of stainless steel is dominated by its nickel and chromium components, which may induce redox reaction, hydrolysis and complex metal ion–organic molecule binding reactions, whereas none are observed with titanium [8, 9].

Role of stents in hemodialysis vascular access

2018 ◽  
Vol 19 (4) ◽  
pp. 341-345 ◽  
Author(s):  
Kenneth Abreo ◽  
Adrian Sequeira
Keyword(s):  
Bare Metal Stents ◽  
Arterial Disease ◽  
Current Evidence ◽  
Metal Stents ◽  
Bare Metal ◽  
Stent Deployment ◽  
Hemodialysis Vascular Access ◽  
Nitinol Stents ◽  
Arteriovenous Access ◽  
Peripheral Arterial

Stents are ubiquitously utilized in coronary and peripheral arterial disease. Interventional nephrologists, however, place stents in the venous outflow of the arteriovenous access. Stenosis is the predominant pathology that causes access dysfunction and will ultimately lead to thrombosis if uncorrected. Angioplasty and stent deployment are the current techniques available to combat stenosis. From initial bare metal stainless steel stents, the current generations of stents used are predominately covered nitinol stents. The latest randomized control trials reveal that stents decrease the number of interventions required to maintain patency but do not improve the overall access survival. Furthermore, bare metal stents have been shown to be inferior to stent grafts. This review discusses indications for stent deployment in the hemodialysis access, the current evidence for their use, and briefly touches on their complications.

Bare metal stents can maintain arterial patency in traumatic occlusion

2018 ◽  
Vol 2 (1) ◽  
Author(s):  
Viktor A Reva ◽  
Jonathan J Morrison ◽  
Alexey V Denisov ◽  
Alexey B Seleznev ◽  
Gennady G Rodionov ◽  
...  
Keyword(s):  
Bare Metal Stents ◽  
Bare Metal Stent ◽  
Metal Stents ◽  
Control Group ◽  
Bare Metal ◽  
Metal Stent ◽  
Ovine Model ◽  
Stent Group ◽  
Stent Deployment ◽  
Arterial Patency

Background: The standard approach to an occlusive vascular injury is open arterial reconstruction, although endovascular stenting is becoming more common, despite limited evidence. The aim of this study is to examine the performance of bare-metal stents in an ovine model of occlusive arterial trauma. Methods: Through a groin incision, a 2 cm segment of the left superficial femoral artery (SFA) was bluntly injured using a hemostat and injection of air to achieve thrombosis. Animals then underwent a stent deployment (Stent group, n=5) or no-treatment (Control group, n=5). In the Stent group, recanalization of the thrombotic lesion, thromboaspiration and bare-metal stent deployment were performed. Enoxaparin 1.5 mg/kg was given to all animals. The stent group animals were fed Clopidogrel 75 mg and Aspirin 125 mg daily. Angiography and doppler ultrasound were used to evaluate arterial patency during the 7-day observation period. Results: A thrombosis was obtained in all cases. After the fall in the systolic velocity (SV, cm/sec) in both the Control (43 (36–56) to 6 (0–16); p<0.001) and Stent Groups (45 (32–53) to 8 (0–12); p<0.001), stent implantation resulted in a significant permanent increase of the SV. Day 7 angiography confirmed SFA patency in all (5/5) stented animals, with persisting occlusions in the Control group (p=0.008). There was no evidence of distal emboli in the run-off arteries. Conclusions: Bare-metal stent implantation restores arterial patency of a traumatic occlusive lesion in a standardized ovine model with a short follow-up period.

scholarly journals Thin Strut CoCr Biodegradable Polymer Biolimus A9-Eluting Stents versus Thicker Strut Stainless Steel Biodegradable Polymer Biolimus A9-Eluting Stents: Two-Year Clinical Outcomes

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Ian B. A. Menown ◽  
Mamas A. Mamas ◽  
James M. Cotton ◽  
David Hildick-Smith ◽  
Franz R. Eberli ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Clinical Outcomes ◽  
Biodegradable Polymer ◽  
Bare Metal Stents ◽  
Metal Stents ◽  
Target Vessel ◽  
Cobalt Chromium ◽  
Landmark Analysis ◽  
Propensity Analysis ◽  
Biolimus A9

Background. While thinner struts are associated with improved clinical outcomes in bare-metal stents (BMS), reducing strut thickness may affect drug delivery from drug-eluting stents (DES) and there are limited data comparing otherwise similar thin and thick strut DES. We assessed 2-year outcomes of patients treated with a thin strut (84–88um) cobalt-chromium, biodegradable polymer, Biolimus A9-eluting stent (CoCr-BP-BES) and compared these to patients treated with a stainless steel, biodegradable polymer, Biolimus A9-eluting stent (SS-BP-BES). Methods. In total, 1257 patients were studied: 400 patients from 12 centres receiving ≥1 CoCr-BP-BES in the prospective Biomatrix Alpha registry underwent prespecified comparison with 857 patients who received ≥1 Biomatrix Flex SS-BP-BES in the LEADERS study (historical control). The primary outcome was major adverse cardiac events (MACE)—cardiac death, myocardial infarction (MI), or clinically driven target vessel revascularization (cd-TVR). Propensity analysis was used to adjust for differences in baseline variables and a landmark analysis at day-3 to account for differences in periprocedural MI definitions. Results. MACE at 2 years occurred in 6.65% CoCr-BP-BES versus 13.23% SS-BP-BES groups (unadjusted HR 0.48 [0.31–0.73]; P = 0.0005 ). Following propensity analysis, 2-year adjusted MACE rates were 7.4% versus 13.3% (HR 0.53 [0.35–0.79]; P = 0.004 ). Definite or probable stent thrombosis, adjudicated using identical criteria in both studies, occurred less frequently with CoCr-BP-BES (1.12% vs. 3.22%; adjusted HR 0.32 [0.11–0.9]; P = 0.034 ). In day-3 landmark analysis, the difference in 2-year MACE was no longer significant but there was a lower patient-orientated composite endpoint (11.7% vs. 18.4%; HR 0.6 [0.43–0.83]; P = 0.006 ) and a trend to lower target vessel failure (5.8% vs. 9.1%; HR 0.63 [0.4–1.00]; P = 0.078 ). Conclusion. At 2-year follow-up, propensity-adjusted analysis showed the thin strut (84–88um) Biomatrix Alpha CoCr-BP-BES was associated with improved clinical outcomes compared with the thicker strut (114–120um) Biomatrix Flex SS-BP-BES.

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