Science topic

Stents - Science topic

Devices that provide support for tubular structures that are being anastomosed or for body cavities during skin grafting.
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I have a disruptive question to ask those researching and practicing lower extremity biomechanics that reinforces the fact that hyperpronation is a biomechanical red herring:
If Subtalar Joint Stenting (SJS) is indicated to correct a "hyperpronated" subtalar joint, why is it that as talar declination does improve when stenting or dispensing a custom foot orthotic does the calcaneal inclination angle remain relatively or completely unchanged?
Perhaps the biomechanical correction of a STJ stent or custom foot orthotic actually is working to reverse biomechanical pathology in the ankle joint instead?
If so, what is the stent or orthotic correcting so effectively against gravity and grf?
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I know the answer as it for me, was rhetorical.
I have waited for more than a year for answers which only justify the question and a correct answer.
Hint: The calcaneus has not moved in the stenting case.
E mail me if your interest is piqued as I would enjoy debating others in this arena.
Dr Sha
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As per title, I'm interested in knowing whether any commercially available (not research based), medical devices are manufactured (even if partly) through the polymerisation of monomers using photoinitiators such as Irgacure, Eosin-Y, riboflavin etc. Specifically, polymerisation of the material outside of the body. Equivalent to the polymerisation of a polymeric coating on a stent within a manufacturing facility.
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Dental prosthesis devices like dentures or aligners are made with 3D printing by DLP process.
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Blockage of arteries is a common problem during theses days, which may lead to myocardial infraction or heart attack. Once the plaque is formed, it cant be removed. The problem can be overcome either through bye-pass surgery of heart or by putting a stent at blocked portion of the arteries. So my request is to know that is there any chemical individually or in combination in Allopathy / Ayurveda that can reverse the plaque formation.
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Thanks, dear Mahesh Golla for your kind suggestion.
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The widespread use of ureteral double J stents preventing renal damage do not take in sight the ureteral damage or the time resolving the obstrucción.
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Double J Stents or Double-Edged Sword in management for urinary obstruction?
You are right about the use of Double J stents.
One should clearly weigh the benefits and complications resulting from double J stents, as exemplified in the articles below:
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I am doing an analysis on the stent structure where
In Step 1: I am expanding the stent from its crimped state to expanded state using radial boundary Condition.
In step 2: I want to remove the stress generated during the previous step on the stent structure but I want to retain the expanded geometry of the stent.
In step 3: I want to crimp this structure again and calculate the stress generated during this step.
For step 2, I have tried using MODEL CHANGE from interaction module to deactivate elements in the step but I am not able to go see stress as 0,instead the model disappears.Can some one help me with this?
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In case of restenosis of blood vessel future heart surgery will be simplified as the approach to heart blood vessels will be from surface
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Stents are used to open the narrowed heart vessels (coronary arteries) without the need to open the chest.
For further knowledge about history, uses and types of stents, and their use in emergency or planned procedures to open diseased coronary arteries, please have a look at these articles (1-3):
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We usually administer dual antiplatelet therapy in various combinations to a post PCI patient. Some of them are on chronic anticoagulant therapy for stroke prevention. Some of them may have relatively higher bleeding risk. How do you plan your antiplatelet regime to such patients without compromising bleeding risk and risk of stent thrombosis?
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Calculate his bleeding risk/thrombotic risk
Ranging from triple therapy (ASA+Clopidogrel+warfraine) for one month then warfarine plus clopidogrel onwards for 6month/one year then warfraine alone after one year for high bleeding low thrombosis risk patients or
It will be triple for three months then dual (warfarine+clopidogrel) for 6 month/one year then warfarine one
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Hello,
I am trying to show if there is any relationship between the different variables (weight, age, risk score) and freedom of re-intervention after a stent placement. Freedom of reinterevntion is a time depending value, so the more I think about it I think I should use cox's regression model. But on the other hand I am thinking weight/age/risk score and freedom of re-intervention are both continuous values so if I want to show a correlation between the two I should use the pearson/spearman? What do you think? Also if I am reporting the cox model, should I just report the hazard values and the p-values or may be more?
Thank you in Advance
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You might find the attached google search to be of some interest should you wish to use Cox regression. Best wishes, David Booth
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According to Dawson and colleagues (2007), some surgical faculty identified some shortcoming of knowledge and skills. Example of these include the choice of catheter, balloon , and stent size. Adequate placing of the sheath was also identified as an issue in training residents.
What do vascular surgical residents struggle most with in their surgical education and training? Do vascular surgical residents and attendings believe that their medical education should be changed from the current standards?
Dawson and colleagues (2007)
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We have a projet about valvular stents
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do you mean valves used in open heart surgery or in TAVI ?
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One of the major drawbacks of cardiac stents is the placement of the clot inside the cardiac stent
How can these clots be removed?
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The first step should be the dissolution of the clot, so When the tip of the catheter reaches the clot, a clot-dissolving drug such as tissue plasminogen activator is infused into the clot through the catheter. Usually, it will dissolve in a day or two. Then, later, When a catheter containing a collapsed stent retriever reaches a clot blocking the artery, the stent moves out of the catheter, unfolds to form a 3D mesh tube, captures the blood clot, and retracts back into catheter with its catch.
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I successfully completed the simulation for stent. I'm able to find stresses, strain and displacement of an element/node. But how to find the values of elastic recoil, dog-boning and foreshortening for stent?
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I am performing the same type of simulation, did you end up finding an answer?
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In a study there are some animal species need to implement a coronary stent from (femoral artery) and to undergo a laparotomy in order to place a telemetric transponder.
What are the recommended anesthetic drugs that induct anesthesia without affecting the cardiovascular system at the time of procedures for equine?
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Ketamine ,thiopentone has good cardiovascular safety profile .If monitor and anesthetic machine present propofol can be used cautiously.
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We have a projet about TAVI
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VR simulation using 3D workstations like true 3D (Echo pixel) might help you simulate the procedure.
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Hello there, I am doing Explicit analysis of Three different materials and for one of the material Strain value is coming High as compare to remaining Then what it signifies to me? For best material, considering the elastic strain which one is best ? and how to choose it.
Please explain in details if you know.Thank you in advance
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Dear Ajinkya Ramesh Mane
The material strain is defined as the change in dimensions (based on the original dimensions) as results of applied stress. The material strain is not a material property. You cannot use the strain value to compare your three materials. I suggest that you compare the three materials using the Elastic modulus, Elastic limit, plastic limit, etc. However, the strain value is high because the specimen material exhibits the smallest Elastic modulus classified as soft material.
Thank you
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A 42-year-old patient with history of diabetes, hypertension and ischemic heart disease where coronary angiography with stent was done for him before presented to ED with chest pain and fatigue
What is your diagnosis ?
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Mobitz Type I (Wenckebach) second degree heart block with complete LBBB in the setting of recent STEMI.
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I am working on a project that involves predicting the cost estimate of an Angioplasty and Stent placement procedure. I need to know the variables to put into my model. Would highly appreciate if anybody could give me an idea of what all parameters affect the overall bill. Numbers aren't necessary. Just the categorical split-up will do. Numbers would be great if you have them.
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Md Rabiul Alam ....Good point...I always forget tax!
Probably because I wish I didnt have to pay it.
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Medical devices cover a wide range of products ranging from eyeglasses to active coronary stent, via wheelchairs. Medical devices are also characterized by a short life in the market, small patient populations and a high potential for innovation. Do you think it is necessary to distinguish different clinical study methods for the authorization of new medical devices to be marketed according to their level of risk?
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Risk management should take into account all sources of potential hazard to the health and safety of a patient, including user expertise (eg, education), training (eg, company device training) and environment (eg, is the clinical lab adequately equipped?). Normally this is required to qualify a user prior to participating in a clinical study, or as a condition for device purchase after market approval. Of course this hasn't been ideal as many adverse events occur due to user error. It should be noted here that another obvious source of risk is the state of disease itself. Devices and training might be optimal, yet the patient's anatomy and disease can present treatment challenges.
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Hello,
I am modelling a vascular tissue (intima) cut by a sharp instrument in Abaqus. The scheme of my model in on the picture. The instrument will be translated and simultaneously oscillated with ultrasonic frequency. The tissue is cut just below the metal stent struts.
I can figure out the nonlinear properties of my tissue (Mooney-Rivlin coefficients deduced from experimental data of simple tension) and the loading conditions but the problem is - how to define damage properties for soft tissue in Abaqus? More precisely, I want to find out what “material behaviours” in material definition should I introduce except for the "mechanical-elasticity-hyperelastic".
All the "cutting" models I've found use “Johnson-Cook formulation” or “Ductile damage” but I think they are only for metals. “Traction-separations laws” can’t be implemented because they require the predefined crack path and it is not possible because I can’t predict this path.
This problem is more similar with a “bullet impact in gelatin” – the material is damaged by an instrument but the instrument can be translated in course of the impact https://www.sciencedirect.com/science/article/pii/S175161611630412X
I tried to make the research by myself but I still have several questions:
1. As I have the complete test data maybe it is sufficient for damage modelling to indicate elastic and plastic behavior of the tissue?
2. What “material behaviours” would you recommend me to define in this case?
Thank you in advance,
Nikita.
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Thank you very much! It is indeed the method that I finally used.
Unfortunately, this type of model (with inserted cohesive elements) is not working for unhomogenoius materials so if you have any advice or solution - it would be very helpful!
The problem is the following: when I add another material inside the model with inserted cohesive elements it does not complete because of аn exessive deformation ratio or distortion of elements. I give two examples below:
1) the vascular tissue with holes calculates perfectly
2) the vascular tissue with a metallic stent in these holes gives deformation in the bottom of the model (wrong place) and the analysis ends with an error.
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A 54 year old Male underwent Non Anatomical resection for Cholangiocarcinoma involving Seg 5/6 in December 2018. He developed perihepatic collection for which he had undergone percutaneous catheter drainage 3 times. Last drainage was done about 2.5 months back in June 2019. ERCP and CBD stenting done in Feb/March 2019 failed to stop the leak which ranged about 20-25 ml a day. He has no abdominal pain or fever. He has undergone percutaneous transhepatic glue injection on 20th July 2019 as MRI showed a small collection communicating with ductal system on the right side (Segment 7). Post the procedure, the daily discharge has fallen to about 9-10 ml/day. (It has reduced but had not been arrested). What is the appropriate next step to take in this regard to stop the leak ?
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I agree with Dr Machado that this sounds like a segment that is disconnected from the downstream Biliary tree. Besides doing surgical re-resection of segment 7, you could do radiation segmentectomy using Y-90. This would require your interventional radiologist to superselectively cannulate the artery to segment 7 and infuse a relatively high dose of Y-90 which will subsequently induce radiation necrosis and atrophy with cessation of bile flow.
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I want to develop a material for a cardiovascular stent application. Therefore, I want to know about the pressure which a stent will bear in the artery.
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The pressure at which stent is deployed has nothing to do with blood pressure. The nominal pressure for most of the stents as has been pointed out is 8 to 12 bar. But most stents require post dilatation with non compliant balloon at 18 to 20 bar. Some lesions rarely require post dilatation at even higher pressures . If the lesion and vascular bed are properly prepared, very high pressure post dilatation can be avoided, as it carries risk of vascular rupture.
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We have many techniques for revascularization [angiplasties, new stents, vascular bypass], yet we are not doing early screening in patients with multiple vascular risk factors.
Should we be more active in our early screening of the carotid and cerebral vessel circulations?
Are we missing the boat?
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We have new innovative patented moleculs who are able to treat Demencia vascular .
Look inside if its possible to participe ( preclinical and clinical developpement needed to dispose of new drug for neurodegenerescences )
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Clopidogrel is often used to keep coronary stents patent
Clopidogrel resistance can be up to 30% of African/Asian populations
Should we be doing more routine testing for the marker of resistance- CYP 19 in these populations? Otherwise we may be giving placebo to our stent patients...
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Clopidogrel resistance has been found in roughly 20% individuals. High risk cases of PCI should be recognised and those individuals should be subjected to genetic testing before prescribing clopidogrel. Anyway, we hardly prescribe clopidogrel to our ACS patients who recieve either Ticagrelor or Pradugrel instead. Clopidogrel is reserved for stable CAD patients who are anyway low risk individuals.
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Basically, biomechanical stent modeling can be divided into three areas. The first area belongs to the modeling related to the mechanical properties of the stent, the checking of the stress states of deformations, the arrangement of the voltage on the wall of the blood vessel, etc. and mainly these tests are based on the Finite Element Method (FEM). It is very important to carry out all the tests at this stage in order to find out all design defects in time, because any irregularity discovered later requires a return to this stage and a re-testing, and this can be a very "expensive" step both materially and temporally. In the second area, the influence of the stent design itself (for example, the shape and layout of the sticks) on the flow of fluid (blood) within the blood vessel is studied and is based on the computational fluid dynamics (CFD), an area belonging to the FEM. In the third area, it is also investigated and tested for the release of the drug in DES stents and its spreading through the bloodstream, penetration into the blood wall.
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I am not sure what is the question, but if you are interested in these topics, Simulia/Abaqus has quite a few stent examples you can take a look at. There is even a dedicated training.
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The objective of the position is to develop a PhD work on the subject “cardiovascular stent design and analysis”. The aim of the work will be to analyze the expansion of the stent and the contact with the artery to simulate thrombectomy technique. The developments will have to be carried out within the Kratos framework.
More info:
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Is this position still vacant? Please let me know email ekram.aust08@gmail.com....thanks in advance
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I need a reference for the "pre-clinical testing market for vascular implantable devices (including peripheral stents, angioplasty tools, aortic stents, synthetic surgical grafts, chronic total occlusion devices, embolic protection devices and inferior vena cava filters)"
In Dollars or Euros and for U.S.A, Europe, or worldwide.
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I follow the question.
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I'm working on stents. I simulated crimping process by using 8 rigid plates around the stent. The analysis was successful. Now I want to simulate the dilatation process. I want to remove the rigid plates using 'model change' tool in the interaction module but there's error saying this is not possible with R3D4 elements which is the element type of the rigid plate.
Now what should I do to simulate the analysis.
What is an alternative procedure to define rigid plates?
Young's mod? Value?
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attached file will answer your questions
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Recent developments in potential treatments for metastatic intrahepatic cholangiocarcinoma (both extra- & intra- hepatic metastases) after: Substantial liver resection; standard chemotherapies; multiple surgical removals of affected lymph nodes; maintenance of stent in common bile duct near/at Pancreas; FGFR inhibitor clinical trial; & stereotactic proton beam therapy directed at extrahepatic affected lymph nodes.
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cholangiocarcinoma is difficult to treat because it is usually diagnosed late.the only hope of good prognosis is the early diagnosis which happens when discovered accidentally
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I just collect materials of stent insertion for obstructive incurable esophageal cancer. It is retrospectively, so it is difficult to clarify if it's beneficial for relief of dysphagia and a better health-related quality of life. Do you have any good idea to make it useful?
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We have a positive experience of stenting for palliative cases, thanks largely to the expertise of our interventional radiologists who perform the majority of the procedures. High strictures are very challenging and this is the one group where stenting is often not possible. In cases where resection is still a possibility, we fund that stenting was an independent risk factor for loco-regional recurrence although its difficult to know whether this was because the tumour was advanced (hence needing a stent) or whether the stent may have expanded the tumour towards its radial margin. Chicken and egg difficult to differentiate in this scenario
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I want to design a 3 fold balloon for stent analysis. Can anyone provide me a step by step guide to it? I'm new to using Abaqus.
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Dear Shubham Jyoti Das,
if you are interested in designing the components inside the Abaqus environment I would suggest that you first create the CAD models in a software like CATIA, Solidworks or Inventor. Since you are dealing with a mechanism it would be extremely helpful if you design the parts/assembly in a CAD software and then decide which features you will use. By that I mean that for a tube you might need to use beam or truss elements (to both simplify the geometry and reduce the computational cost).
Unfortunately, there is no standard way to design geometries and create FE models. When you have a complex system you have to decide which components are crucial for the analysis and need more details and which can be simplified or even omitted.
Regards,
Anargyros
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I want to compare balloon-expandable stent simulation using elemen type between beam 188 and solid 187 ?
In the solution beam 188, there are option beam tool, and I use direct stress to know the stress in axial direction,
Thus, same for beam 188. I want to know the stress in axial direction in solid 187 element type, but in option stress, there is only stress in the following picture..
can me get the stress in axial direction for solid 187 element type ?
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Yes you can, but the stresses in the solid model (I assuming you have more than one element on the cross section) in any direction (assming you have a load case more than axial tension/compresion) would not be a single value, but follow some distribution. How to compare a value to an array of numbers? It highly depend on the nature of your objective.
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I'm starting to work on stent analysis. For crimping analysis I'm not sure what kind of boundaries will be preferable.(For both pressure controlled and displacement controlled). Also any efficient alternate method to carry out crimping?
Thank you.
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The techniques used for oesophagectomy can vary greatly amongst countries, units and surgeons. This is also true for outcomes and historically oesophagectomy has been associated with significant morbidity and mortality. Operative access, anastomostic technique and the treatment of leaks (conservative, stent, endoVac or reoperative) have been continued areas of disagreement amongst oesophago-gastric surgeons and their influence on mortality and morbidity has long been disputed. This audit seeks to provide up to date information in the international variances in practice.
Please complete this Google Form:  https://goo.gl/LzvECw 
Please see attached invitation letter for some further details. 
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Study is underway! 120 oesophagectomy patients have been entered in to the online database in the 5 weeks of opening. We are accepting new centre registrations until July 2018 - so if your centre wants to be involved please get in touch. All the best, Ewen.
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Can you recommend some material , paper, articles, abput Nitinol Laser cutting for stents fabrication?
I have some doubts about fatigue behavior and the resulting surface.
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I don´t think it is common, however there are some companies that use this technology.
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Hi everyone!
I need to write the history if the stent.
Is there someone who can just give me some papers or research about the stent, its technology and history (from its introduction to evolution/changes and new technologies/applications)?
I would be glad to get in touch, too with some specialists that can give some added value.
Thank you in advance.
Stefania
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If dead cells of microorganisms forming a biofilm on a stent, accumulate due to actions of antimicrobials, could they provoke inflamation?
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I think you are asking whether these cells could provoke inflammation and the authors precisely missed the point and tried to explain infection. Well, let me ask you whether you have observed that a sterile needle of an injection system can also provoke inflammation inspite of taking all precaution regarding disinfection. Just like this, dead or live bacterial cells are foreign to the body and hence it is the inherent duty of the immune system to get rid of them and one of the method is by inflammation.
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I'm working on a research for the university so i'm wondering does the artery return back the same if we didn't use a stent after inflate a balloon ? and why it's better to udse a stent that made from auxetic material? I know the properties for auxetic materials but what does it have to do with the blood?
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Hi, Maryam.
stent is used for preventing artery elastic recoil, not avoiding it completely, but decreasing its impact on final result after balloon inflation.
So the initial loosing of diameter at the stenosis level after balloon inflation can be minimized by using stents. However, the first use of stents in PTCA was as a device for treating arterial wall dissection, and later was discovered that stenting helped to increase immediate final lumen diameter, and also decreasing the rate of restenosis.
i hope this coloquial comment would help you to better understanding of stents, best regards
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Stent Can be coated with drug embedded in a surface polymer. Drug-eluting coronary stents can help prevent plaque buildup, promote good blood flow to your heart, and relieve chest pain. They may also lower your chances of having a heart attack.
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Everolimus, Biolimus A9 and Zotarolimus , recentily Sirolimus are large used. Sirolimus was the first antiproliferative drug used on the first generation of DES (Cordis Cypher). Recently it has been widely reused on new generation stents being the most effective among the limus family and no longer having the exclusivity patent. SIrolimus is combined with polymers, often abluminal, with more homogeneous and short kinetics release that guarantee antiproliferative safety and efficacy. Sirolimus is also used on DRUG COATED BALLON and cardiac and PERIPHERALSTENT. Paclitaxel was extensively used in the Taxus stent but it is no longer used in the latest generation stents due to the lower therapeutic effect and the higher risk of thrombosis.
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I have done the simulation such as:
"The simulative model about the living arteries by stent for various diseases: from expanding to blood flowing to possible fracture "
Key words: Artery stenosis, Stent, Nonlinear Finite Element Method, Bidirectional Fluid-Structure-Interaction, Fracture
BUT I want to an idea for biomechanics or clinical medicine !
Would you give me some advice or cooperation?
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Hi Zhao,
I have advice but I am not capable to create a cooperation between your project and mine, mine is finished now.
It depends on how you want to tackle the problem, it depends on your previous knowledge on models for the stent behaviour, and models for the movement of the artery.
Doctors that are linked to the University are keen to discuss some past cases of stenting and what happened to the patient in time. If you don't have approval to collect clinical data then only the knowledge obtained from the clinicians, correlated with the literature, can give you ideas on simulation scenarios.
The only thing left is for you decide what geometries to use and then prove the hypothesis your supervisors want from your work.
I hope it helps.
Cristina
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drug eluting stents are the second generation of stent that deliver the drugs on the vesseles wall. many research has been done on these stents.
I want to know are these stents available for all of countries or not.
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In our country, the price of stents also dropped significantly. On the one hand, thanks to the centralized procurement of the state. On the other hand, thanks to the launch of new companies on the market.
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Dear Experts,
Am aware, 400 series of steel possess high strength, high wear and acceptable corrosion resistance. Also, it has been extensively used as Cutting tools for Medical surgeries but why not as an Implant (orthopaedic or stents).
I looked for papers which relates the Bio-response of the cell or platelet adhesion over Martensitic steel ( ex. 420 or 440 ) but i couldn't see any published work explaining the same.
It would be great if someone could help me to understand better or to suggest some more research articles ?
Thank you in advance.
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Actually, austenitic SSs have become less used. A certain % of people react badly to the Ni in grades like 316.  Ti alloys, nitinol and Co-based alloys (hip implants) have become more popular. MSSs have too high a modulus of elasticity, likewise the ASSs. The Ti alloys have a lower modulus of elasticity and weigh less, which is a better balance to bone. They have good corrosion resistance in the body.
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i have used a quasi-linear visco-elastic model. now , i want to test a single cube with one element with a pressure load in tension in different time periods in abaqus explicit .
1-why are the  stress results different in different time periods?
2- why is kinetic energy  so big compared to total energy(50 % of total energy or even more) while i'm not using a dynamic model?
3- why the results change when i use mass scaling?
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You should read basics....abaqus/explicit is dynamic procedure
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After performing endoscopic dacrocstorhinostomy (DCR), some surgeons  prefer to put sialastic tubes as stents in the lacrimal system to prevent recurrence an to keep patent nasoacrimal system.
What is the value of using stents after performing endoscopic dacrocstorhinostomy (DCR)?
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Stents increase incidence of infection and granulation tissue formation. So it is better avoided except in traumatic caese to keep patency of the NLD.
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Some children with post corrosive esophageal stricture are refractory to esophageal dilatation, at which time esophageal stenting many be indicated. 
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Thanks Dr. Deppisch, I will check.
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Please discuss the design and requirement of Mg alloy based stents? Are short stents made of Mg alloys are preferable?
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Short Stents are preferred since the stent thrombosis and restenosis rates are directly proportionate to stent length.  Additionally short stents are easier to deliver into the coronary arteries.  However, recent papers do suggest that site of overlapping stents (as compared to a single long stent) does not show adequate endothelialization and therefore can be a source of restenosis.   
Regarding Bioasbsorbable stents, magnesium alloys are used as a stent scaffold which is absorbed in about three years.  However, these are still in trial phase and not available for commercial use. The initial problem that earlier generation magnesium stents faced was early absorption.  The only approved bioabsorbable stent is composed of  poly L lactic acid, poly D,L lactic acid and everolimus from Abbot.
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Within the last few years, I experienced three cases of pneumoperitoneum with and without pneumomediastinum developed immediately after the colonic stent implantation in patients with severe malignant colonic stenosis. Despite the presence of pneumoperitoneum, no patients complained about abdominal pain and presented peritoneal irritation. Moreover, there was no evidence of panperitonitis and elevated inflammatory reactions. Oral intake became possible after the deployment of colonic stents. All these patients underwent surgical resection of colon cancers. Operative findings revealed no evidence of colonic perforation. Postoperative course was uneventful. Does anybody have concerns about pneumoperitoneum that develops after the colonic stent implantation in patients with severe malignant colonic stenosis?
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I must say, I agree with Dr Wong. Close monitoring is indicated, but, even if the incidence of an asymptomatic pneumoperitoneum were 10%, I would find routine post-procedure CT difficult to justify, considering management is based on the clinical findings. The scenario in oesophageal stenting is much different, where spontaneous resolution is not the norm and one has to look for pneumomediastinum proactively. 
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Aman of 70 years DM, Hypertension and CAD had CBD partial injury(3/4 of circumference) during a difficult lap chole with frozen callots.No energy source was used.Corners were secured with 4o prolene and an antigrade stenting was attemted with 10 f Amsterdam stent.It was not successful as the division was on the CHD as the flaps were coming out through the defect despite several attepmts to place it.Hence a 12 f T-tube was placed and the CBD was repaired well.No leak of bile post operatively.The recovery of the of the patient was uneventful.Tube drain in the sub hepatic space was removed on 4th post op day and pt was discharged.T-tube out put is around 300mls in 24 hours.
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Sir , follow the classical approach, wait for 4 weeks atleast before considering ERCP
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I have been working as a member of a research group in the field of cardiovascular stent. We prepared our 3D-printing stent with a reasonable mesh-like structure. But before any further surface modification, we need to investigate its mechanical properties, and conduct the mechanical testing on our model stent.
I need to know what type of analysis testings we need to be run.
I would be happy to hear your answers.
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Dear Setareh
I think you can go for these tests:
- Volume Fraction
-  weight fraction
- Elasticity test 
- Destructive Test which include( Tensile Test, Compression Test, Torsion Test , Bending Test, and Hardness Test)
- Non Destructive Test(NDT) which include :( Visual Technique, Liquid Penetrant, Ultrasonic Test ,  Impact Resonance, Pulse Velocity, and vibration dampingtechnique).
 Regard
 Raid
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Your experience of optimum duration for ureteral stenting post augmentation cystoplasty, in the following cinarios, 1) augment without ureter reimplantation, 2) with reimplantation 3) redo augmentation ?
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Try to avoid stenting whenever possible
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Is there a role for esophageal stenting in late presenter 31 years old female with stable iatrogenic tracheoesophageal fistula prior to ercp 45 days ago. it is 25 cm from the central incisor with a good communication between the esophagus and the bronchus intermedius
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WE HAD A NEW CT WITH ORAL CONTRAST. ATTACHED BELOW THE IMAGES. She is ALmost totally obstructed clinically. OGD done but failed to pass this obstruction. What is your diagnosis and advice of management knowing that she is now > 6 months post truma, well built, good chest, refusing surgery
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This 18 year old girl was detected to have Takayasu arteritis with hypertension during evaluation for polyarthralgias. MR angiography revealed her to have severe renal artery stenosis left and left subclavian artery stenosis. Recent literature seems to suggest a higher failure rate and restenosis with stenting rather than with plain angioplasty. This goes contrary to what we see in atherosclerotic coronary artery disease stents have a higher success rates. 
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I suggest angioplasty followed by drug coated balloon therapy.  I recently treated a young patient with a variant of pseudoxanthma elastica who developed sma stenosis and  mesenteric ischemia .  Plain balloon therapy lasted 6 months with recurrence.  I initially approached the patient as if it were fibromuscular dysplasia.  But the patient recurred and I did cutting balloon therapy followed by DCB.  She is now nearly 1 year out without recurrence.
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The choice of the more appropriate method of SFA recanalizazion represents a very interesting and actual topic. This is particularly relevant in claudicant patients. It is reasonable the use  in these cases of a covered Stent  ?
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I think that the risk is very small, and should not affect your decision to technically optimize your procedure.  However as I said in CLI pts with diffuse SFA disease and probably poor tibial runoff I would avoid implanting a covered stent.
 
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Hello everyone
I want to start my thesis on biodegradable stent modeling. What do you think, would it be useful? Which material do you suggest, magnesium or PLA?
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What type of vessel is it going to be used,? It should be considered that the stent must have adaptive propertives regarding the patient may develope such multivessel diseases, diabetis and of course aging. I believe a drug eluting biodegradable stent  of material  which allows its mechanical and chemical properties managable by taking some medication or special type of radiation would be of high efficacy.
You can have a look at the following articles, 
  1. Martin, D., Boyle, F.: 'Drug-eluting stents for coronary artery disease: a review, Medical Engineering & Physics (2011) Volume: 33, Issue: 2, Pages: 148-163. PubMed 21075668. 
  2. Fully bioresorbable drug-eluting coronary scaffolds: A review, Emmanuel Charpentiera,∗, Alexandre Barnaa,Loïc Guillevin , Jean-Michel Juliard           http://dx.doi.org/10.1016/j.acvd.2015.03.009
  3. Clinical Outcomes With BioabsorbablePolymer- Versus Durable Polymer-BasedDrug-Eluting and Bare-Metal StentsEvidence From a Comprehensive Network Meta-Analysis, http://dx.doi.org/10.1016/j.jacc.2013.09.061
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Hi,
Is there any way to know how much radial stiffness the stent should have in order to open the occluded vessel.
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I am not sure, if you are eluding to the pressure used to deploy the stent. If this is what you are looking for, as an example for Xience stent we use more commonly between the nominal pressure to burst pressure that is listed as 10 to 18 atmospheres. The nominal and burst pressureso are listed on the packet insert. Hope this helps
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Or do you have any other thecnique to share?
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Dear Alexandre Campos Moraes Amato ,
It Depends . We use both tecniques .
Generally when the carotid body tumor is small i prefer to treat with surgery .When we have large tumors  or they are around the internal carotid artery we try to do embolization before surgery
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Which force is needed to make an implant move/grow through soft tissue? There seems to be a threshold to be overcome by stents (or other implants) to make them grow through tissue. Too low means no growing through. Too high would create lesions. The only reported force I know is from bracelets on the teeth (nearly constant 1-2 N for extraction).
Is there anything known for soft tissue? Ideally for stents in atrial walls? Which biological processes enable this kind of "growing through"? How could i foster it?
I'd be thrilled to hear about your input!
Johannes
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Conventional arterial stents are designed not to grow into the intimal, medial or the adventitial layers. The stent is designed to distribute a uniform radial force sufficient to hold it in place reliably. Restenosis is and undesirable consequence that presents as a growth around the stent. If you want a stent to 'migrate' through the artery wall then it must be designed for that purpose. The form factor and profile for each strut should be reconsidered. Other considerations would be the edge effect of outward radial forces and perhaps other means of constricting the artery to provide a reactive force. These can be mechanically or pharmaceuticaly induced.
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Despite of notable results of decreasing restenosis in patients who have used Drug-eluting stents, There are doubts about impact of DESs on thrombosis and death after one year. Is this been proven as a serious issue or it's ignorable?
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Dear Zahra, there is a major Special Issue in Biomedical Engineering being published in February. You will find this very useful as it presents state of the art and future directions. I am one of the guest editors along with Peter McHugh (Galway, Ireland) and Abdul Barakat (Ecole Polytechnique, Paris)
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if a stent Is implanted  into a narrowed part of a vein the question Is if there will be blond coagulation preferable? Is it dependent on the blood system of the individual? What are the duration times for coagulation? 
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Yes, mentioned above biophysical and biochemical methods of implant surface modification are seemed an effective enough. To prevent thrombus formation, new attempts of formation of bioactive coatings with mosaic surface structure have been undertaken lately.  Also, some references (not very new) may be useful:  
Tanzi M.C., Petrini P., Fare S. Advanced polyurethanes for blood contacting applications containing prime as “smart” heparin-adsorbing moieties // Journal of Biomechanics. – 2001. – Vol. 34. – P. 51-66.
Rasche, H. Haemostasis and thrombosis: an overview / H. Rasche // European Heart Journal Supplements. – 2001. – Vol. 3. – P. 3–7.
 Bluestein D., Li Y.M., Krukenkamp I.B. Free emboli formation in the wake of bi-leaflet mechanical heart valves and the effects of implantation techniques // J. Biomechanics.– 2002.– Vol. 35, P. 1533-1540.
Best regards, Serge
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I prepared chitosan nanoparticles some have got 0.2 and others are in the range of 0.4 - 0.5.
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Polydispersity Index is dimensionless and scaled such that values smaller than 0.05 are rarely seen other than with highly monodisperse standards. Values greater than 0.7 indicate that the sample has a very broad size distribution and is probably not suitable for the DLS technique. The various size distribution algorithms work with data that falls between these tow extremes. The calculations for these parameters are defined in the ISO standard document 13321:1996 E and ISO 22412:2008
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We know that,we use stents to splint or keep the coronary artery open.
There is several types of stent procedure.
So,when we use nitinol stents,and what are its advantages over others?
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Dear All,
I agree with Josef Veselka , self expandeble stents are used in peripheral arterial interventions and their use could be obrigatory or alleatory , it will depends of the localization of the critical aterosclerotic plaque or the arteriografic findings after balloon angioplasty.
Stents are useful after angioplasty complications as dissection, obstruction or arterial rupture with covered stents.
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Bile duct stones: recent studies and meta-analyses demonstrated that there is no advantage in biliary stent positioning after LCBDE with choledochotomy when compared to primary duct closure in elective surgery. Is there any indication for biliary stent positioning in emergency scenarios?
Thank you very much for your contribution.
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I would recommend following the same indications we use with ERCP-based CBD interventions.  This would generally include strictures, retained stones, cholangitis, casts, retained blood clot, leaks or perforations, and/or significant edema at the sphincter after sphincterotomy/balloon dilation. Some of this would depend on the location of the lesion or problem of course, and might require collaboration with an ERCP provider or PTC provider. 
There is no well-documented indication for 'preventive' stenting in ERC. T-tube placement after LCBDE in the absence of these problems would likely only increase post-op complication risks.  We found this to be the case over a long history of routinely using t-tubes in duct-to-duct anastamosis in OLT.
However, there is opinion that bleeding risk, from GDA injury (via CBD manipulations and pseudoaneurysm) or portal hypertension - associated intraductal varices, can be reduced by fully covered metal stent or a 'tight-fitting' plastic stent. 
best regards
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I want to know which polymers except PLGA, PLA and PEG are used in DES and which drugs help to have lower restenosis. 
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Most polymers used are based on lactic acid. D-lactic polylactic acid (DLPLA). A combination of Glycolide (GA), lactide (LA), ϵ-caprolactone (CL), and polyethylene glycol (PEG). And a combination of Poly L-Lactide, 50/50 Poly DL-Lactide-co-Glycolide and Polyvinyl Pyrrolidone. There are also some new ones based on salicylates, 
Talking about the drugs, they are either rapalogs (sirolimus, everolimus, temsirolimus, novolimus etc etc) or the less used paclitaxel. Both classes of drugs are proliferation/migration inhibitors, rapalogs inhibit mTOR while paclitaxel inhibit tubulin. 
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In our hospital, we use plastic stents for malignant biliary obstruction, usually it needs to be replaced due to its obstruction.
Due to the nature of the disease, the short life span of the patient, the possible obstruction and the need for replacement and the much more expensive metallic stent... I ask if malignant biliary stricture is worth this very expensive self expanding metallic stent?
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I would tend to agree with Georgios, from a strict viewpoint of stent obstruction only. It is certainly possible that the placement of multiple simultaneous plastic stents can be sufficient if this is a short life expectancy and for palliation only. Having said that, if there is any possibility of any salvage therapy that could prolong the life of the patient, then the SEMS are always a better choice. One important consideration is that we should not only look at the cost of the stents alone. One additional ER visit for cholangitis or hospitalization or return for replacement due to obstructed plastic stents, even within the 3 months, will cost far more than having placed the SEM in the first place.  That is why we are tending to just opt for the SEM immediately.
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I found the the anticoagulation therapy strategy varies with ePTFE material implants in human vessels, such as artificial vascular graft, stent, etc. What are the factors that influence the anticoagulation therapy?
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Never used anticoagulation.  Never had a problem.  Veins are pretty large caliber and don't typically thrombose.
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I am researching into hyperperfusion syndrome and prevention, specially in carotid stenting. 
Is there any evidence that a staged procedure is more beneficial than a single stage procedure in severe ICA stenosis (80% or higher)
Have you experienced cases with hyperperfusion syndrome following carotid stenting ?
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Due to the laws of hemodynamic, the ICA stenosis is the most frequent place for stenosis according the laws of various diameter of bifurcation branches. The phenomenon of postoperative hyperperfusion is closely connected with deep and longtime status of arteriovenous disbalance. Such patients need the preoperative course of vascular correction of the abnormal disproportion in total arterial-capillary-venous tube system for the prophylactic of arterial hydraulic stroke. More- http://angio-veritas.com/technologies/vascular-innovations/?lang=en
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38 year old non alcoholic diagnosed to have recurrent pain due to chronic tropical pancreatitis underwent PJ(longitudinal) 8 months ago.Relapse of his symptoms in 3to4 months after surgery.Investigations about a month ago showed elevated Amylase and Lipase,CT reported to show dilated distal PD and non visualized duct at the level of PJ.Options mentioned were Endotherapy(pd sphincterotomy,stenting),Revision surgery and coeliac ganglion block.Prior to these a good MRCP,
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It seems as if you did all the right things. However, some patients do not respond or develop differently. The longitudinal opening of the MPD might not sufficient. This patient might need a full pancreatic head resection. 
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I'm a doctor in training and and I would like to explore this new type of stent understanding how it works in detail.
Thank you
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Hello. You should check this article.: Sfyroeras GS, Dalainas I, Giannakopoulos TG, Antonopoulos K, Kakisis JD, Liapis CD. Flow-diverting stents for the treatment of arterial aneurysms. J Vasc Surg. 2012 Sep;56(3):839–46.
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When a stent is placed in a STEMI patient, and a pre-dilation balloon is used to facilitate crossing the lesion, what is regarded as balloon time in the door to balloon time profile? I have had 2 indicators suggested. For me I see it as pre-dilation balloon catheter withdrawal time, as this now facilitates flow through the lesion, but others have said its the device deployed time, as a result, stent balloon catheter withdrawal time. I need to be uniform in my research variable, so would like to ask what is generally accepted as balloon time?
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For me Time AT obtention TIMI 3 whatever the tool!!!
philippe BRUNELBRUNEL
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67 year old woman with a recent H/O Rectal tenesmus, no blood or mucous.Otherwise no other GI findings clinically.Had CAG and stenting 7 years ago. Now upper GI and colonoscopy and biopsy from sigmoid are normal. CECT with contrast showed mild thickening of sigmoid with few diverticula. Uterus and ovaries are atrophic.
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Clinical evaluation plus pelvic MRI and rectal manometry
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Good day, I am reaching out to the research community in an effort to find information/guidelines for segmental pressure testing s/p bypass graft and stenting. If there are articles that you may know of on this subject I would appreciate your help.
Jay Shafer
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Dear James Shafer ,
I hope this attached can help you!
Best Regards,
Paulo
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In case of a  patient non-responder to clopidogrel do you shift to triple therapy (ASA+clopidogrel+ warfarin) or do you switch to a new p2y12 inhibitor + warfarin?
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It is a very interesting question. In our institution we routinely test for predischarge antiplatelet efficacy of prescribed drugs with the Multiplate test. In cases such a WOEST strategy I think that the evidence of a good response to clopidogrel could reassure the treating physician thus helping to avoid unnecessary long triple therapy and consequently bleeding complications. The problem is if the test shows poor clopidogrel response, because there are concerns about switching to prasugrel or ticagrelor in association with Warfarin and continuing with Warfarin plus aspirin could leave doubt in tackling the late thrombosis risk in high risk patients with DES deployed with complex interventions and in critical positions. In such cases OCT could "enlighten" the problem, but at present the latter is a matter of faith...
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I have a patient in follow-up after thrombolytic treatment (EKOS) after DVT. His CT venography revelaed left common iliac vein stenosis (subocclusion). The venous stents are not imbursed in Turkey as far as I know. Do you think Supera stent may be a feasible choice? Does anybody has any experience of Supera stent in venous stenting? 
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Dear All,
I`ve a good experience  with sinus venous and wall-stent also . We never stent the contralateral side in MAy-Thurner Syndrome except if the right side have venous obstruction. Generally we try to deploy the stent in the left iliac vein but with 1 cm inside the vena cava as showed in the attached publication.
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As in ansys workbench 14.5 or higher version, in material library Shape memory alloy is inbuilt as you can refer in ansys workbench .
Somehow, I am unable to show the shape memory effect and superelastic in workbench even in simple problem definition.
As for your convenience here I am sending link for papers In first paper problem is discussed for eyeglass frame and modeling was also done by using SMA property.
In second paper from page 8-11, SMA application is done for Stent design,
For convenience Here i have attached stent model in STP file.
Kindly give any solution or suggestion or way to proceed this in workbench.
Paper1-
Paper 2-
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Dear Awani,
I am using ANSYS 14.5 (APDL) inbuilt material models for modelling shape memory effect of SMA materials. If you have experience with APDL you can use the Verification Manual examples (VM273 & VM221) to see an example. As far as I know you can use/link ANSYS APDL to ANSYS workbench. The VM examples that I am telling you can be found in the ANSYS help files and they cover both Shape memory effect and superelastic behavior.
Please contact me again if you need any further clariification, I am working along the same lines to these kind of issues. I ll be glad to help if I can!
Regard,
Dimitris
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Is it only because of ease of removal and rigid/flexible endoscopy variation?
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The reason for this might really be that in Europe more rigid bronchoscopies are done compared to the States and silicone stents can't be placed thorugh the flexible bronchoscope. Recomendation is to use only silicone stents for benign stenoses, while for malignant both metallic and silicone can be used. We use silicone stents in postintubational stenoses, and sometimes in malignant stenosis when the patient is expected to stard differential therapy so we expect that after the therapy he might not need the stent any more. But in majority of malignant stenoses we still use metallic ones.
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Subarachnoid hemorrhage in a post-PCI patient on antiplates is a double jeopardy. Antiplatelet drug(s) is essential in a patient undergoing PTCA with stenting. On the other hand, intracranial hemorrhage is a contraindication to use of such drugs. Commonly antiplatelet drugs are stopped, and restarted 6 weeks or more after stabilization. Clipping of the culprit vessel may have an important role.
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If I understand well, you are talking about a patient who already had PCI+ stenting, and then SAH. This is one of the greatest unanswered clinical problems, which doesn't have just one solution. In my opinion, as Dr Oteh M said, it depends on how serious the SAH was, on how has it been resolved (if possible), and on how much time ago the patient had PCI and stenting. The second anti-platelet drug (tyeno) must be stopped. About Aspirin I have no data in patient at intermediate or high thrombotic risk, whereas I usually decide about withdrawal in low thrombotic risk (e.g. 12 months after DES or 6 months after BMS).
Regards
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I am new to Abaqus and experience some difficulties with performing a high cycle fatigue analysis on a stent strut. We would like to apply an internal displacement caused by the pulsation of the blood. We've tried to implement this by creating a uniform boundary condition, with periodic amplitude. However, we don't know how to proceed with Edit Amplitude window.
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Dear Maureen,
the magnitude of your boundary condition will be multiplied by the amplitude that you prescribe. In the windows, you have to set, at a specific time step, what is the value of the amplitude. You can create periodic amplitude, or general amplitude.
If, for example, you want to simulate a cyclic loading on a bar in a static step you can apply a displacement at the end of the bar of the maximum amplitude that you want to consider (for example, 0.02 if your bar has length equal to 1 and you want to consider cycles with maximum strain equal to 0.02). Then, you have to create the amplitude. For example, if your time step is equal to 1 (the default), and you want to consider four loading traction-compression cycles, you will have something similar to
Time Amp
0 0
0.25 1
0.5 -1
0.75 1
1 .-1
This table means that, at the time step 0.25, your BC magnitude will be multiplied for 1.
Note that, you have to prescribe in the BC windows, you that your loading follows you Amplitude.
Moreover, in the step module, you have to prescribe a "small" initial increment, something like 0.01. In a different case, ABAQUS will try to solve your problem directly for a time step equal to 1.
I hope this will help you.
Andrea
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Tandem ICA and MCA lesions have always caused concern in the minds of managing specialists. If treated by CAS and ICAS then is it better to stage the procedures or to perform them in a single go? If performed in a single procedure would you stent distal to proximal or proximal to distal?
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Difficult question, since the symptom status is very important. If, however, neither stenosis was currently symptomatic, but both appeared sufficiently severe (say 70%) on imaging, then the evidence for doing both at one 'sitting' is lacking.
It is very difficult to organise an RCT to investigate this.
From past papers, there has been some information suggesting that dealing with the Carotid lesion alone may be sufficient, and certainly the SAMMPRIS results wouldn't encourage intervention on the intracranial stenosis. Following Carotid surgery, the more distal stenosis may appear less severe....