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Baker, Steven Gerald. "In vitro elution of analgesic medications from an absorbable gelatin sponge." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/8790.
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Master of ScienceDepartment of Clinical Sciences
Walter C. Renberg
Objective: To compare the in vitro elution characteristics of six common analgesic medications from a commercially available absorbable gelatin sponge. Study Design: Experimental study. Methods: Gelatin sponges were loaded with various analgesic medications, including two opioids, preservative-free morphine and fentanyl, two local anesthestics, bupivacaine and lidocaine, and two α2-adrenergic agonists, dexmedetomidine and xylazine. The loaded sponges were placed in dishes containing phosphate-buffered saline (PBS) and maintained at 37° C with constant agitation. Concentrations of each drug were determined at various time points up to 24 hours post-inoculation using high-pressure liquid chromatography. Two phases were conducted, utilizing undried loaded sponges (phase one) and dried loaded sponges (phase two). Results: In both phases, all analgesic medications eluted from the gelatin sponge and equilibrated rapidly with the PBS, achieving maximal concentration within 30 minutes. In phase two, the rapid nature of the release was captured by increasing sampling within the initial 30 minutes. Results were consistent for each medication with minimal variation. Steady state concentrations were significantly higher in phase two with four out of six medications. Conclusions: Analgesic medication elution from an absorbable gelatin sponge was rapid and consistent. Drying the loaded sponge prior to use will likely substantially increase the amount of medication eluted but not prolong release. Clinical Relevance: The rapid release of analgesic medications from the gelatin sponge makes a prolonged analgesic effect unlikely without further modification. Toxicity may be a concern. Further study is required to investigate efficacy in vivo, safe dosing regimens and prolongation of duration of action.
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Zhao, Yibei. "Phospholipid Transport in Silicon Hydrogel Contact Lenses." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3083.
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Dry eye syndrome has been associated with the lack of phospholipids in the tear film, leading to disruption of the tear film and subsequent irritation. Characterization of the transport and release of phospholipids from a silicone hydrogel contact lens is required to assess the possible use of these lenses for phospholipid delivery to increase patient comfort. This thesis examines the use of silicone hydrogel contact lenses as phospholipid delivery devices. Contact lenses of silicone hydrogel composition were loaded with varying amounts of radiolabeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) from a solution of n-propanol. These lenses were eluted at 35°C into artificial tear fluid (ATF) or ATFcontaining varying amounts of DMPC. The amount of DMPC loaded into a lens is a linear function of the time of exposure to the DMPC/propanol solution. The initial rate of elution into ATF appears to be diffusion controlled for at least 10 hrs and is proportional to the amount of DMPC loaded. The ease of loading and the controllable release of DMPC from silicone hydrogels present the possibility of using such lenses to counter eye discomfort caused by inherently low levels of phospholipid in tears. To reduce manufacturing steps and concern for residual n-propanol in the lens, it is beneficial to incorporate the DMPC into the monomer formulation and then photopolymerize the lens. Results showed that using this process, DMPC can be placed in the lens and then eluted at faster rates than when it was loaded from n-propanol.
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Safranski, David Lee. "Poly(beta-amino esters) for cardiovascular applications." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42825.
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Abdominal aortic aneurysms are a leading cause of death in the U.S. where 14,000 people die from aneurysm rupture and 178,000 are diagnosed each year. A novel alternative treatment for abdominal aortic aneurysms has been proposed, where a biodegradable polymer scaffold is photopolymerized in situ around the exterior of the aneurysm. This scaffold will mechanically constrain the aneurysm from further expansion, and will deliver a drug, doxycycline, to treat the underlying biological cause of the disease. In order for device development, a suitable polymer must be designed with appropriate mechanical properties, degradation rate, polymerization, and elution rate. Poly(β-amino ester) networks have been proposed as the material of choice; however, many of their structure-property relationships have yet to be determined.
Therefore, the overall goal of this work is to determine the structure-property relationships of the poly(β-amino ester) networks in order to advance the design of the treatment, and has been divided into three objectives: (1) understand the structure-property relationships of poly(β-amino ester) networks, specifically the polymerization, degradation rate, and thermo-mechanical properties, (2) determine the impact of doxycycline incorporation on degradation rate and mechanical properties, (3) evaluate the effect of simulated physiological conditions on degradation rate and mechanical properties.
In the initial chapters, the fundamental structure-property relationships are established between reactant chemical structure, step-growth polymerization, photopolymerization, thermo-mechanical properties, and degradation rate using a systematic approach of two homologous series of reactants. Further tailoring of degradation rate, water content, and modulus in vitro was performed by using a copolymer network. Doxycycline inhibited photopolymerization due to overlapping absorbance spectra with the photoinitiator, but full network formation occurred by increasing the photoinitiator concentration. Networks displayed varying controlled release rates, and the underlying release mechanism was determined for each network using established methods.
In order to increase mechanical properties, a co-monomer, methyl methacrylate, was added to the network to increase the glass transition temperature, toughness, and deformation capacity. These co-networks displayed temporal-control of mechanical properties in simulated physiological conditions, since degradation caused a shift in the glass transition temperature, which changed the mechanical behavior of the network. The temporal-control of mechanical properties was further investigated under degradation conditions in vitro and in vivo. Due to the mechanically active loading environment in vivo, networks displayed a decrease in toughness, yet maintained mechanical properties similar to native biological tissues. These networks establish a multifunctional biomaterials platform with materials that can be easily synthesized, photopolymerized into various geometries, and sustain mechanical properties while undergoing degradation and therapeutic agent release.
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Bozsak, Franz. "Optimization of Drug-Eluting Stents." Palaiseau, Ecole polytechnique, 2013. https://pastel.hal.science/pastel-00858100.
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L'utilisation de stents actifs (DES) a révolutionné le traitement de l'athérosclérose. Le relargage contrôlé de médicaments anti-prolifératifs dans la paroi artérielle (PA) a permis de réduire fortement le taux de resténose intra-stent. Mais le risque de thromboses intra-stents tardives demeure un enjeu majeur des DES en partie lié au retard de cicatrisation de la PA endommagée lors de l'implantation. Cette thèse présente une méthode d'optimisation du design des DES afin d'inhiber la resténose sans affecter la cicatrisation. Pour quantifier la performance des différents designs, un modèle numérique décrivant l'écoulement sanguin et le transport de médicaments dans les artères stentées a été développé. Il prend en compte la structure multi-couches de la PA et les interactions du médicament avec les cellules. Un algorithme d'optimisation est couplé au modèle afin d'identifier les DES optimaux. L'optimisation du temps de relargage ainsi que de la concentration initiale du médicament dans le revêtement du DES ont un effet significatif sur la performance. Lorsque le médicament utilisé est le paclitaxel, les solutions optimales consistent à relarguer le produit à des concentrations nettement inférieures à celles des DES actuels soit pendant quelques heures, soit pendant une durée d'un an. Pour le sirolimus, un relargage lent est nécessaire. Les formes optimales des spires du DES sont toujours allongées mais profilées seulement lorsque le relargage est rapide. Ces résultats permettent d'expliquer en partie les performances des différents DES récents et révèlent un fort potentiel d'amélioration dans la conception des DES par rapport aux dispositifs commerciaux actuelsDrug-eluting stents (DES), which release anti-proliferative drugs into the arterial wall in a controlled manner, have drastically reduced the rate of in-stent restenosis and revolutionized the treatment of atherosclerosis. However, late stent thrombosis remains a safety concern of DES, mainly due to delayed healing of the wound inflicted during DES implantation. We present a framework to optimize DES design such that restenosis is inhibited without affecting the healing process. To this end, we have developed a computational model of blood flow and drug transport in stented arteries which provides a metric for quantifying DES performance. The model takes into account the multi-layered structure of the arterial wall and incorporates a reversible binding model to describe drug interaction with the cells of the arterial wall. The model is coupled to a novel optimization algorithm that minimizes the DES performance metric to identify optimal DES designs. We show that optimizing the period of drug release from DES and the initial drug concentration within the coating has a drastic effect on DES performance. Optimal paclitaxel-eluting stents release the drug either within a few hours or slowly within a year at concentrations considerably lower than current DES. Optimal sirolimus-eluting stents require a slow drug release. Optimal strut shapes for DES are elongated and can be streamlined only if the drug release occurs quickly. The results offer explanations for the performance of recent DES designs, demonstrate the potential for large improvements in DES design relative to the current state of commercial devices, and define guidelines for implementing these improvements
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Suhardi, Vincentius Jeremy. "Drug eluting prosthetic joints through drug cluster morphology control." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111323.
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Thesis: Ph. D. in Medical Engineering and Medical Physics, Harvard-MIT Program in Health Sciences and Technology, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 299-330).
More than one million joint replacements are performed in the USA annually. However, around 10 % of patients require revision surgery within 10 years with prosthetic joint infections (PJI) as a common reason. PJI has a recurrence rate of 16 %, a mortality rate of 2.5 %, and end-stage treatments involving arthrodesis and amputation. Most drug eluting polymers that were in development to address this problem failed due to toxic degradation products, insufficient drug release, and insufficient mechanical strength. The gold standard of treatment uses antibiotic eluting bone cement which has a mechanical failure rate of 26-60 % within 49-54 months if used under load bearing conditions. Therefore, despite advances in orthopedic materials, development of drug-eluting devices with effective, sustained delivery with the necessary mechanical strength for a fully load bearing joint implant has been elusive. Here, we report the synthesis and application of a drug eluting, fully load bearing, and articulating joint prosthesis that has superior mechanical strength and drug elution profile compared to the clinical gold standard, antibiotic eluting bone cement. We modified the eccentricity of drug clusters and percolation threshold in the polymeric matrix of Ultra-High Molecular Weight Polyethylene (UHMWPE), which resulted in maximized drug elution and mechanical strength retention. The optimized antibiotic eluting UHMWPE elutes antibiotic at a higher concentration for a longer period of time than antibiotic eluting bone cement while retaining the mechanical and wear properties of clinically used UHMWPE joint prosthesis. After drug elution, the empty drug clusters in the polymer were filled with biological lubricants during articulation, which through a combination of weeping and elastohydrodynamic lubrication, reduced the overall wear rate of the UHMWPE. Treatment of Staphylococcus aureus infected lapine knee with the antibiotic eluting UHMWPE showed complete bacterial eradication without any detectable systemic side effect. Taken together, our study showed that the drug-eluting UHMWPE joint implants in this study are promising candidates for further clinical trial and as the next generation prosthetic joints.
by Vincentius Jeremy Suhardi.
Ph. D. in Medical Engineering and Medical Physics
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Ahrenstedt, Lage. "Drug Eluting Hydrogels : Design, Synthesis and Evaluation." Doctoral thesis, University of Cape Town, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-36503.
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Hydrogels have successfully proved themselves useful for drug delivery applications and several delivery routes have been developed over the years. The particular interest in this work was to design, synthesise and evaluate in situ forming drug eluting hydrogels, which have the potential to ameliorate the healing of cardiovascular diseases. With this aim the anti-inflammatory and immunosuppressant drugs rapamycin (Ra) and dexamethasone (Dex) were made water soluble by conjugation with polyethylene glycol (PEG). Ra was attached pendant from the terminal of PEGs while Dex was incorporated into dendritic structures grown from PEGs. These conjugates were further crosslinked into hydrogels by either conjugate or thiol-ene addition. The gel degradation was tuned to take between 5 and 27 days by using gel building block combinations that induced either 2 or 4 hydrolytically labile bonds per crosslink or by varying the number of crosslinking sites of the building blocks. The use of thiol-ene addition prolonged the degradation time nearly seven folded compared to conjugate addition as a more stable crosslink was formed. Two different formulations for gelling via conjugate addition were used (acrylate-thiol or vinyl sulphone-thiol) to deliver Ra, which was carried by either a 4- or 2-armed PEG. The elution kinetic for the respective gel formulation was of zero order during 15 and 19 days of gel degradation. In addition, Ra was PEGylated via esters, with a distance of either one or two carbons to a nearby thio-ether functionality. The difference in ester conjugation resulted in a slight but significant change in drug-PEG conjugate stability, which was mirrored by the increased time to reach the half amount of total drug elution; from 9.3 to 10.2 days and from 5.1 to 9.7 days for the two gel formulations, respectively. Dexamethasone was incorporated via an ester into dendrons of first and second generation pending from 2- and 4-armed PEGs at loadings of 2, 4 or 6 Dex molecules per carrier molecule. The resulting elution kinetic was of zero order during degradation periods of 5-27 days. Released Dex still possessed biological activity as determined by an in vitro cell assay. The novelties in this thesis are: (A) slow release of rapamycin obtained by covalent incorporation into hydrogels, (B) the use of unique PEG-based dendrimers to incorporate dexamethasone into a hydrogel and (C) zero order sustained release of dexamethasone at physiological pH.Hydrogeler har framgångsrikt visat sig användbara för att leverera läkemedel och ett flertal metoder har utvecklats de senaste 20 åren. Fokuset i den här avhandlingen ligger på att designa, framställa och utvärdera läkemedelsutsöndrande hydrogeler som spontanhärdar in situ, vilka har potential att förbättra läkningen efter kardiovaskulär sjukdom. Med det syftet gjordes de anti-inflammatoriska och immunsänkande läkemedlen rapamycin (Ra) och dexametason (Dex) vattenlösliga genom att konjugeras med polyetylenglygol (PEG). Ra fästes kovalent längst ut på PEGar medans Dex inkluderades i dendritiska strukturer vilka byggdes från ändpunkten av PEGar. De här konjugaten tvärbands till hydrogeler via antingen konjugerad addition eller radikal polymerisation. Nedbrytningen av gelerna trimmades till att ta mellan 5 och 27 dagar genom att använda kombinationer av gelbyggstenar som bildar antingen 2 eller 4 hydrolyserbara estrar per tvärbindning eller genom att variera antalet tvärbindningspunkter hos byggstenarna. Användandet av radikal polymerisation i sig ledde till att nedbrytningen av geler tog nära sju gånger längre tid jämfört med geler gjorda via konjugerad addition eftersom stabilare tvärbindningar då formas. Två olika kombinationer för härdning via konjugerad addition (akryl-tiol eller vinylsulfon-tiol) användes för att leverera Ra som bars av antingen en 4- eller 2-armad PEG. Utsöndringskinetiken av Ra för de två kombinationerna var av nollte ordningen under de 15 och 19 dagar som gelerna degraderade. Dessutom, Ra PEGylerades via estrar med ett avstånd på antingen ett eller två kol till en närliggande tioeter. Skillnaden i avstånd ledde till en liten men signifikant skillnad i stabiliteten hos Ra-PEG konjugaten, vilket speglades i den förlängda tiden att nå halva mängden av den totala läkemedelsutsöndringen; från 9.3 till 10.2 dagar och från 5.1 till 9.7 dagar för de två respektive gelkombinationerna. Dex kopplades in via en esterbindning till dendroner av första och andra generationen byggda från PEGar med 2 eller 4 armar, vilket resulterade i att 2, 4 eller 6 Dex levererades per bärarmolekyl. Dex eluerade med nollte ordningens kinetik under degraderingsperioder på mellan 5 och 27 dagar. Vidbehålllen biologisk aktivitet av eluerad Dex bekräftades genom cellexperiment in vitro. Nyheterna i den här avhandlingen består av: (A) kontrollerad utsöndring av rapamycin uppnådd genom kovalent inbindning till hydrogeler, (B) användandet av unika PEGbaserade dendrimerer för kovalent inbindning av dexametason till hydrogeler och (C) nollte ordningens utsöndring av dexametason vid fysiologiskt pH.
QC 20130204
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Van, den Bergh Willem Johannes Wian. "Drug eluting electrospun scaffolds for tissue regeneration." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29581.
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The desired healing response to electrospun scaffolds in tissue engineering is often limited by poor ingrowth due to insufficient porosity, thrombogenicity, lack of vascularisation and/or excessive inflammation. This study aimed at increasing structural porosity and incorporating/delivering anti-thrombotic/angiogenic (heparin) and anti-inflammatory (dexamethasone) agents. Porosity enhancement techniques were explored using two different approaches i) electrospinning of biostable polymer (Pellethane® , Pel) with concomitant electrospraying of soluble microparticles, which were subsequently removed to increase scaffold interconnectivity and ii) electrospinning of biodegradable polymer (DegraPol® , DP) at low collecting temperatures. Dexamethasone (Dex) was incorporated by simple admixture, while heparin (Hep) required chemical modification (heparin tributylammonium, HepTBA) to achieve solubility. Release rates were determined in vitro, followed by thrombogenicity (thromboelastography) and cytotoxicity (cell viability) assessments of modified/unmodified heparin prior to incorporation and after elution. Finally, in vivo responses were evaluated in a subcutaneous model (24 rats) for up to 12 weeks. Porosity was enhanced (P0.1). At 12 weeks of implantation, high-porosity Pel scaffolds allowed for full tissue ingrowth (>98%) while conventional scaffolds were limited (0.3). High-porosity scaffolds produced by combined electrospinning/spraying have the potential to enhance healing. Dex or HepTBA can be incorporated and eluted from degradable electrospun scaffolds, and localised delivery of HepTBA improves implant vascularisation. This study may contribute towards tissue engineered vascular graft development where anti-thrombogenicity and increased vascularisation are desired.
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Dolla, William Jacob Spenner Becker Bryan R. "Drug diffusion and structural design criteria for conventional and auxetic drug-eluting stents." Diss., UMK access, 2006.
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Thesis (Ph. D.)--School of Computing and Engineering and Dept. of Chemistry. University of Missouri--Kansas City, 2006."A dissertation in engineering and chemistry." Advisor: Bryan R. Becker. Typescript. Vita. Description based on contents viewed Jan. 26, 2007; title from "catalog record" of the print edition. Includes bibliographical references (leaves 127-130). Online version of the print edition.
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Ashrafi, Koorosh. "Novel bioresponsive drug eluting microspheres to enhance chemoembolisation therapy." Thesis, University of Brighton, 2014. https://research.brighton.ac.uk/en/studentTheses/d72e0cce-8b99-4659-9b8d-c0e5a48da701.
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Drug eluting beads (DEB) are employed in the treatment of solid hypervascularised malignant tumours by a method called trans-arterial chemoembolisation (TACE). When the microcirculation to a tumour is blocked, oxygen levels decrease to critically low levels causing the tumour to become hypoxic. Hypoxic tumours are known to be chemoresistant and send out growth factor signals leading to angiogenesis and metastasis of tumour cells to other parts of the body. Commercially available DEB are unable to respond to the conditions of hypoxia and will continue to release drug at a constant rate via ionic exchange through the hydrogel. It is therefore recognised that an avenue for improvement would be the development of novel bioresponsive DEB that are able to react to the conditions of hypoxia to overcome chemoresistance associated with the tumour cells.
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Frahnow, Andreas [Verfasser]. "Lebensqualitätsentwicklung nach Implantation von drug eluting stents im Vergleich zu bare metal stents : eine Analyse des Deutschen Drug Eluting Stent-Registers (DES.DE) / Andreas Frahnow." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2019. http://d-nb.info/1202042147/34.
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Wu, Ming. "The micro and nano scale characterization of drug eluting stents." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493323.
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Aggarwal, Rajesh Kumar. "The antithrombotic properties of polymer-coated, drug eluting coronary stents." Thesis, University of Leicester, 1996. http://hdl.handle.net/2381/34296.
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Champeau, Mathilde. "Supercritical CO2 Assisted Impregnation to prepare Drug-eluting Polymer Implants." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0205/document.
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Le procédé d’imprégnation par voie CO2 supercritique est une solution prometteuse pour préparer des implants polymère à libération contrôlée de médicaments.Ce travail a permis de comprendre l’influence des paramètres gouvernant ce procédé et de préciser dans quelle mesure ce procédé peut être utilisé pour préparer des implants polymères chargés en médicament. Pour ce faire, nous avons combiné les informations obtenues grâce aux techniques classiques de caractérisation de polymères et à un dispositif que nous avons développé basé sur la micro-spectroscopie FTIR haute pression in situ.Dans cette étude, des fils de suture de PLLA, PP and PET ont été imprégné avec deux anti-inflammatoires (aspirine et kétoprofène).Tout d’abord, l’évolution du comportement des systèmes binaires médicament/CO2 (solubilité et spéciation) et polymère/CO2 (quantité de CO2 adsorbé, gonflement de la matrice, évolution de la microstructure et des propriétés de tension du polymère) a été déterminé en fonction de la pression et de la température. Ensuite, le procédé d’imprégnation a été étudié. L’influence des conditions expérimentales sur le taux d’imprégnation a été déterminée et expliquée par la quantité de CO2 adsorbé, le gonflement de la matrice, la solubilité du médicament, l’évolution de la microstructure du polymère et aussi l’affinité médicament/polymère. La matrice de PLLA a pu être plus largement imprégnée (jusqu’à 32%) que celles de PP et PET (5% max). Enfin, l’influence des conditions d’imprégnation et de dépressurisation sur le relargage a été démontrée sur le système PLLA/Kétoprofène, la durée de relargage variant de 3jours à 3moisThe scCO2 impregnation process is a promising alternative to other manufacturing process to prepare drug-eluting polymer implants.This work enabled to rationalize the influence of the key parameters governing this process and to determine in which extent this process can be used to prepare drug-eluting implants. We have combined the information obtained with traditional polymer characterization techniques and a newly characterization set-up we have developed that is based on in situ FTIR micro-spectroscopy. We have worked on the impregnation of sutures made of PLLA, PP and PET with two anti-inflammatory drugs namely ketoprofen and aspirin.Firstly, the thermodynamic behaviors of the systems drug/CO2 (solubility and speciation of the drug) and polymer/CO2 (CO2 sorption, polymer swelling, evolution of the polymer microstructure and of the tensile properties) were studied as a function of pressure and temperature. Then, the scCO2 impregnation process was investigated. The impact of the operational conditions on the drug loading (contact time, pressure, temperature and depressurization conditions) was explored and accounted regarding to the CO2 sorption, the2swelling, the drug solubility as well as the changes in the polymer microstructure with the experimental conditions and the presence of the drug. The drug/polymer affinity was also explored. The tensile properties of the impregnated fibers were also evaluated. PLLA was more impregnated (up to 32%) than PP and PET (up to 5%) in the investigated conditions. Finally, we have shown that the drug release can be tuned from 3 days to 3 months by varying the impregnation and depressurization conditions on the system PLLA/Ketoprofen
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Zhu, Xiaoxiang Ph D. Massachusetts Institute of Technology. "Mathematical modeling and simulation of intravascular drug delivery from drug-eluting stents with biodegradable PLGA coating." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/98152.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 178-190).
Drug-eluting stents (DES) are commonly used in coronary angioplasty procedures. A DES elutes drug compounds from a thin polymeric coating into the surrounding coronary artery tissue to reduce in-stent restenosis (a significant lumen loss due to growth of vascular tissue). Biodurable (non-erodible) polymers are often used in the current DES coatings, which stay permanently in the patients. While promising treatment results were obtained, in-stent restenosis remains an issue and late in-stent thrombosis, which is associated with hypersensitivities to the polymer coatings, is also reported. Increasing interests have been raised towards the design of a more biocompatible coating, in particular a poly(lactic acid-co-glycolic acid) (PLGA) coating, for DES applications to improve the drug delivery and reduce adverse outcomes in patients. This dissertation aims to develop a mathematical model for describing the process of drug release from a biodegradable PLGA stent coating, and subsequent drug transport, pharmacokinetics, and distribution in the arterial wall. A model framework is developed in the first part of the dissertation, where a biodurable stent coating is considered, and the intravascular delivery of a hydrophobic drug from an implanted DES in a coronary artery is mathematically modeled. The model integrates drug diffusion in the coating with drug diffusion and reversible drug binding in the arterial wall. The model was solved by the finite volume method. The drug diffusivities in the coating and in the arterial wall were investigated for the impact on the drug release and arterial drug uptake. In particular, anisotropic vascular drug diffusivities result in slightly different average arterial drug levels but can lead to very different spatial drug distributions, and is likely related to the reported non-uniform restenosis thickness distribution in the artery cross-section. The second part of the dissertation focuses on modeling drug transport in a biodegradable poly(D,L-lactic-co-glycolic acid) (PLGA) coating. A mathematical model for the PLGA degradation, erosion, and coupled drug release from PLGA stent coating is developed and validated. An analytical expression is derived for PLGA mass loss. The drug transport model incorporates simultaneous drug diffusion through both the polymer solid and the liquid-filled pores in the coating, where an effective drug diffusivity model is derived taking into account factors including polymer molecular weight change, stent coating porosity change, and drug partitioning between solid and aqueous phases. The model predicted in vitro sirolimus release from PLGA stent coating, and demonstrated the significance of the developed model by comparing with existing drug transport models. An integrated model for intravascular drug delivery from a PLGA-coated DES is developed in the last part of the dissertation. The integrated model describes the processes of drug release in a PLGA coating and subsequent drug delivery, distribution, and drug pharmacokinetics in the arterial wall. Model simulations first compared a biodegradable PLGA coating with a biodurable coating for stent-based drug delivery. The simulations further investigated drug internalization, interstitial fluid flow in the arterial wall, and stent embedment for impact on the drug release and arterial drug distribution of a PLGA-coated stent. These three factors greatly change the average drug concentrations in the arterial wall. Each factor leads to significant and distinguished alterations in the arterial drug distribution that can potentially influence the treatment outcomes. The developed model here provides the basis of a design tool for evaluating and studying a PLGA coating for stent applications. Simulations using the model helped to provide insights into the potential impacts of various factors that can affect the efficacy of drug delivery. With the developed model, optimization of the model parameters can also be performed for future exploration on the design of PLGA-coated drug-eluting stents.
by Xiaoxiang Zhu.
Ph. D.
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Austin, David. "Drug-eluting stents : a study of appropriateness and variations in practice." Thesis, University of Glasgow, 2010. http://theses.gla.ac.uk/2186/.
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Summary 1) Background Drug-eluting stents (DES) reduce in-stent restenosis, hitherto a frequent complication of percutaneous coronary intervention (PCI). Despite the reduction in recurrent symptoms and the need for repeat procedures, only highly selected patient groups with simple coronary lesions were studied in the initial trials, and long-term outcome or safety data were initially limited. The lack of long term data was compounded by reports of late stent thrombosis, potentially threatening the safety of the device. DES are more expensive than bare metal stents (BMS), so there is a significant increase the procedural cost of PCI. The uptake of DES in clinical practice created pressure on healthcare budgets leading to explicit rationing in some countries. This thesis comprises a programme of original work addressing three related aspects of DES use: DES use in clinical practice (Scotland and internationally), “off-label” use of DES and appropriate use of DES (a modified Delphi consensus study). 2) Drug-eluting stent use in clinical practice Relatively little was known about the actual application of DES in clinical practice. Anecdotal accounts suggested there were geographical practice variations within Scotland and internationally. Scottish practice was analysed with the aim of determining whether DES use varied between hospitals and operators within the Scottish NHS beyond the influence of clinical factors. In examining international practice the aim was to show whether the adoption and use of DES varied between countries and to determine whether practice changed after the stent thrombosis controversy. a. Clinical practice variation within Scotland - methods and results Using data from the Scottish Coronary Revascularisation Registry, multi-level logistic regression analysis was performed, analysing for variations in DES use at hospital, operator and patient level. Overall, DES were used in 47.6% of lesions, but varied between hospitals (range 30.6%-61.8%, χ2=341.6, p<0.0001). There was significant between-operator variation in the null model. This was attenuated by the addition of hospital as a fixed effect. Nonetheless, the final model demonstrated significant between-operator variability and between-hospital variation, after case-mix adjustment. b. Drug-eluting stent use internationally - methods and results This study involved collaboration between centres from four countries with established PCI registries: APPROACH Registry (Alberta, Canada), BWGIC (Belgium), Mayo Clinic PCI Registry (USA) and the Scottish Coronary Revascularisation Registry. Customised graphics software was employed to perform trend analysis examining variations in DES use over time, and by clinical sub-group. 178,504 lesions treated between January 2003 and September 2007 were included. In the Mayo Clinic Registry rapid adoption to a peak of 91% DES use for all lesions by late 2004 was observed. Alberta and Scotland showed delayed adoption with lower peak DES use, respectively 56 and 58% of lesions by early 2006. Adoption of DES in Belgium was more gradual and peak use of 35% lower than other registries. Reductions in DES use were seen in all datasets during 2006, though this varied in absolute and relative terms and by clinical sub-group. c. Conclusions Practice variations were found at operator and hospital level within Scotland and between countries internationally. Influences on stent choice in the “real world” are likely to be multi-factorial; on an international level, macro-economic forces exerting their influence through healthcare system regulation, payment systems, level of funding and central control are particularly important. It was also clear from the multilevel study of Scottish practice, however, that a clinical consensus does not exist. 3) “Off-label” use of drug-eluting stents DES are often used for “off-label” indications, untested in RCTs, where observational studies demonstrate complications are higher when compared to “on-label” use. The aim was to determine whether clinical outcomes differ following DES and BMS implantation in a patient cohort defined by DES “off-label” indications. a. Methods and results Patients who underwent coronary stenting for an “off-label” indication between January 2003 and September 2005 in Scotland were included. Clinical outcomes were determined using linkage to national admission and death databases. Propensity scores were calculated using important baseline variables and DES were matched to BMS on a one-to-one basis to provide a fair comparison. The final study population comprised 1,642 well matched patients. Event-free survival was calculated over 24 months using the Kaplan-Meier method. All-cause death was more common following BMS during follow-up. No difference in the rates of MI was noted. Target vessel revascularisation was reduced in patients treated with DES. b. Conclusions The largely reassuring findings of this study should be seen in the context of a subsequent growing body of literature also suggesting similar risks for DES and BMS when compared for both on-label and off-label use. Although the benefits of DES were evident, the absolute reduction in TVR was lower than previously demonstrated in RCTs. 4) Appropriate use of drug-eluting stents - a modified Delphi consensus study Best practice with respect to stent selection during PCI was poorly defined, as evidenced by the lack of detailed clinical guidance on the use of DES and wide practice variation demonstrated. It was not clear whether in any given setting there had been either underuse - potentially forfeiting the benefits of DES, or overuse - where benefits may be outweighed by risks. The aim was to use an expert panel to develop criteria for the appropriate use of DES using the modified Delphi method, to determine the extent to which current practice in Scotland met the appropriateness criteria and to validate the criteria by analysing clinical outcomes a. Methods, results, conclusions Consensus criteria for appropriate DES use were defined using a modified Delphi questionnaire. Expert panelists were used to define levels of appropriate use and were compared to clinical practice. The results suggested that current overall rates of DES use are acceptable. Better targeting of DES to the most appropriate lesions may be possible with the aims of reducing the known geographical inequities and maximising clinical benefit. Finally, using similar methods to chapter 4, it was shown that underuse of DES in appropriate patients was associated with higher levels of target vessel revascularisation without any difference in MI or death.
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Lützner, Michael [Verfasser]. "Drug Eluting Stents in der Therapie von chronischen Koronarverschlüssen / Michael Lützner." Ulm : Universität Ulm, 2018. http://d-nb.info/1166756890/34.
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Sua, Andy. "Using Metal-Organic Framework Film as a Drug-Eluting Stent Coating." Thesis, California State University, Long Beach, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10975741.
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Metal-organic frameworks have a wide range of applications including gas separation, gas capture, catalysis and drug delivery. Due to the in-stent thrombosis of the current drug-eluting stents we propose replacing the toxic polymer with a more biodegradable MOF thin film consisting of MIL-88b. The MIL-88b thin film was formed on functionalized gold through a direct crystallization method and was confirmed using x-ray diffraction (XRD) and Fourier- transform infrared spectroscopy (FTIR). Possible ibuprofen encapsulation and elution was confirmed through FTIR and UV-VIS spectroscopy. The MIL-88b thin film was also formed on medical grade stainless steel to mimic conditions of the current DES. The surface area, using N2 gas isotherm at 770K, of MIL-88b and MIL-53 was compared to validate the favorable porosity for drug delivery application.
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Daemen, Joost. ""The caveats of drug-eluting stents" a critical appraisal of the safety concerns /." [S.l.] : Rotterdam : [The Author] ; Erasmus University [Host], 2008. http://hdl.handle.net/1765/14039.
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Kröhne, Lutz. "Untersuchungen zur Anwendbarkeit von Polyelektrolytmultischichten für Drug-Eluting Stents zur lokalen Freisetzung von Paclitaxel." kostenfrei, 2009. http://www.opus-bayern.de/uni-regensburg/volltexte/2009/1289/.
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Brandon, Pochatila Raymond. "TECHNOLOGY AND MARKET EVALUATION OF A RESVERAROL AND QUERCETIN ENDOVASCULAR DELIVERY PLATFORM FOR THE DRUG-ELUTING STENT AND DRUG COATED BALLOON MARKET." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1370527620.
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Swanson, N. M. G. "Drug-eluting polymer-coated coronary stents : an in vitro and in vivo evaluation of antirestenotic potential." Thesis, University of Edinburgh, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.662654.
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Percutaneous intervention (PCI) is complicated by restenosis, stent thrombosis and delayed endothelial recovery at the PCI site. One approach to reduce these complications is to deliver potent agents directly to the PCI site. This local drug delivery can be achieved by absorbing drugs into a polymer coating applied to the stent itself. In this thesis three such agents have been examined as potential anti-restenosis agents. Vascular Endothelial Growth Factor (VEGF) has been shown to accelerate the recovery of endothelium over a stent, reducing intimal hyperplasia and thrombosis. It has not previously been delivered bound onto the stent itself. VEGF-eluting stents were tested in vitro and in a rabbit model. Paclitaxel-eluting stents prevent restenosis in animal and clinical studies. This effectiveness was use to develop a new organ culture model of in-stent restenosis. Abciximab, which blocks the smooth muscle cell (SMC) vitronectin integrin, was tested in vitro as a stent-based therapy. Results: 21.7μg of VEGF was absorbed. This was released with a biexponential release curve with 20% remaining at 9 days. In arterial tissue, 11% of the VEGF was detectable in the tissue at 24hr. 125μg of paclitaxel and 2.85μg of Abciximab were absorbed after very short absorption times, with biexponential release kinetics. VEGF-eluting stents stimulated endothelial cell growth by 11% over 5 days, with effects that were sustained beyond the initial rapid VEGF release. Organ culture showed that the SMC response to stent implantation could be reproduced in vitro and that the effects of drug-eluting stents could be measured using this new model. Paclitaxel-eluting stents reduced SMC proliferation. The animal studies showed a trend (p=0.07) towards reduced platelet deposition early after PCI, with reduced thrombus formation at 7 days (12.5mg in VEGF stents vs. 0mg in controls). No benefit of VEGF stents was seen on the re-endothelialisation process or on intimal hyperplasia.
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Radic, Katarina. "Der Einfluss von Drug-Eluting-Stents und Bare-Metal-Stents auf die Ergebnisse nach notfallmäßiger Bypassoperation." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-166326.
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Youssefian, Sina. "Nanomechanics and Nanoscale Adhesion in Biomaterials and Biocomposites: Elucidation of the Underlying Mechanism." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-dissertations/490.
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"Cellulose nanocrystals, one of the most abundant materials in nature, have attracted great attention in the biomedical community due to qualities such as supreme mechanical properties, biodegradability, biocompatibility and low density. In this research, we are interested in developing a bio-inspired material-by-design approach for cellulose-based composites with tailored interfaces and programmed microstructures that could provide an outstanding strength-to-weight ratio. After a preliminary study on some of the existing biomaterials, we have focused our research on studying the nanostructure and nanomechanics of the bamboo fiber, a cellulose-based biocomposite, designed by nature with remarkable strength-to-weight ratio (higher than steel and concrete). We have utilized atomistic simulations to investigate the mechanical properties and mechanisms of interactions between cellulose nanofibrils and the bamboo fiber matrix which is an intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Our results suggest that the molecular origin of the rigidity of bamboo fibers comes from the carbon-carbon or carbon-oxygen covalent bonds in the main chain of cellulose. In the matrix of bamboo fiber, hemicellulose exhibits larger elastic modulus and glass transition temperature than lignin whereas lignin shows greater tendency to adhere to cellulose nanofibrils. Consequently, the role of hemicellulose is found to enhance the thermodynamic properties and transverse rigidity of the matrix by forming dense hydrogen bond networks, and lignin is found to provide the strength of bamboo fibers by creating strong van der Waals forces between nanofibrils and the matrix. Our results show that the amorphous region of cellulose nanofibrils is the weakest interface in bamboo microfibrils. We also found out that water molecules enhance the mechanical properties of lignin (up to 10%) by filling voids in the system and creating hydrogen bond bridges between polymer chains. For hemicellulose, however, the effect is always regressive due to the destructive effect of water molecules on the hydrogen bond in hemicellulose dense structure. Therefore, the porous structure of lignin supports the matrix to have higher rigidity in the presence of water molecules. "
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Evans, J. Stewart (James Stewart). "Comparing long-term antiplatelet strategies to prevent morbidity and mortality in patients with drug-eluting coronary stents." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/63226.
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Thesis (S.M.)--Harvard-MIT Division of Health Sciences and Technology, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 35-38).
Background: The optimal long-term antiplatelet therapy (APT) that balances the benefit of preventing myocardial infarction (MI) with the risk of severe bleeding is unknown in patients greater than one year after drug-eluting stent (DES) placement. Methods: We modeled life expectancy (LE) using published data by building a Markov model to compare several APT strategies composed of aspirin and clopidogrel, both as monotherapy and in various clinically plausible combinations. The base case examined a 65-year old person treated with a DES then continuous aspirin plus clopidogrel (Dual-Rx) for one year without complications. We considered risk of mortality from myocardial infarction and severe bleeding. We used a lifetime horizon and projected LE without quality-adjustment. Results: In the base-case analysis, APT yielding greatest LE was a toss-up between Dual-Rx indefinitely (LE of 13.48 years), clopidogrel indefinitely (LE of 13.45 years), and aspirin indefinitely (LE of 13.42 years); of the strategies considered, no APT was least preferred (LE of 13.36 years). All parameters were varied over plausible ranges in sensitivity analyses, including the duration of future treatment with clopidogrel (base-case, life long). The choice of APT remained a toss-up unless: the annual probability of MI fell below 0.0087 (base-case, 0.013) or the relative risk of systemic bleeding exceeded 1.52 (base case, 1.00), in which case clopidogrel indefinitely was preferred; or the efficacy of clopidogrel to prevent MI fell below 0.09 (base case, 0.20) or the relative risk of clopidogrel for severe gastrointestinal hemorrhage exceeded 3.33 (base case, 2.01), in which case aspirin indefinitely was preferred. Conclusions: For patients with a drug-eluting stent placed greater than one year ago, the antiplatelet therapy which yields the greatest life expectancy is a toss-up between dual antiplatelet therapy (clopidogrel plus aspirin indefinitely), clopidogrel indefinitely, and aspirin indefinitely. However, additional research (including a clinical trial, subgroup analysis, and modeling) is needed.
by J. Stewart Evans.
S.M.
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Gorodetski, Boris [Verfasser]. "Konventionelle versus Drug-Eluting Beads transarterielle Chemoembolisation (cTACE vs. DEB-TACE) beim hepatozellulärem Karzinom mit Pfortaderthrombose / Boris Gorodetski." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2017. http://d-nb.info/1126503770/34.
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Loughran, Michael John. "The degradation and drug-eluting properties of biodegradable polymers and their potential use as coatings for coronary stents." Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511045.
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Martinez, Adam W. "Design and development of an elastin mimetic stent with therapeutic delivery potential." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45926.
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Stenting remains a common treatment option for atherosclerotic arteries. The main drawback of early stent platforms was restenosis, which has been combated by drug eluting stents; however, these stents have suffered from a higher incidence of late stage thrombosis. To address current stenting limitations, the major research focuses have been the development of the next generation of drug eluting stents and first generation bioabsorbable stents. The main objective of this dissertation was the design and development of a new class of bioabsorbable stent composed of elastin mimetic protein polymers. The first phase explored different stent design schemes and fabrication strategies. Successfully fabricated stents were then mechanically tested to ensure they possessed sufficient mechanical strength. Additionally, described herein is the potential to modulate the properties of the elastin mimetics through different crosslinking strategies. We have demonstrated that chemical crosslinking allows for the tailoring of the physical, mechanical, drug delivery, and endothelialization properties of these materials. The potential for drug delivery from this elastin mimetic stent was benchmarked as was the potential to endothelialize these stents. Furthermore, we developed the necessary delivery systems to allow for deployment in the rat aorta model.
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Ponce, Arrones Alberto. "Design and elaboration of novel drug eluting stents to produce tailored releases aiming for the reduction of restenosis after implantation." Doctoral thesis, Universitat Ramon Llull, 2020. http://hdl.handle.net/10803/669571.
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Les malalties d'artèria coronària són el tipus més comú de malaltia cardíaca, matant a més de 385,000 persones anualment. Fins a la data, s'han provat moltes estratègies diferents a l'hora de plantejar tractaments que mantinguin les respostes inflamatòries al mínim. Entre aquests, l'ús de nanopartícules, recobriments multicapa i teràpia gènica destaquen com algunes de les estratègies terapèutiques noves més prometedores. L'ús de stents cardíacs s'ha mantingut al llarg dels anys amb diferents dissenys i recobriments, aconseguint millors resultats amb cada nova generació. Encara que el seu ús està justificat, els seus resultats no són òptims, creant la necessitat de desenvolupar millors estratègies per tractar aquest tipus de malalties.
Entenem que un control total de l'alliberament de la càrrega farmacològica d'un dispositiu mèdic pot canviar profundament els resultats d'un pacient, convertint-se així en una prioritat del nostre treball. Presentem una forma de produir recobriments, a escala industrial i de laboratori, orientats per a dispositius mèdics i que s'utilitzen per produir recobriments multicapa a mida per stents amb alliberament de fàrmac. A més d'això, també es presenta un enfocament per tractar malalties d'artèria coronària a través de la teràpia gènica amb nanoportadors, el que obre noves possibilitats per a tractaments localitzats emprant stents amb alliberament de fàrmac. Començant amb l'elaboració de metodologies i instruments necessaris per a produir recobriments a mida, es creen i estudien nous dissenys de stent al llarg d'aquest treball. Això permet la producció de nous recobriments i sistemes d’alliberació els quals són provats in-vitro i in-vivo per demostrar la seva efectivitat.
En conclusió, aquesta tesi demostra que es pot aconseguir un alliberament de fàrmacs a mida mitjançant dissenys multicapa i alliberament amb nanoportadors, aplicable a stents amb alliberament de fàrmac per obtenir una reducció en les taxes de reestenosi amb resultats prometedors.Las enfermedades de arteria coronaria son el tipo más común de enfermedad cardíaca, matando a más de 385,000 personas anualmente. Hasta la fecha, se han probado muchos enfoques distintos a la hora de plantear tratamientos que mantengan las respuestas inflamatorias al mínimo. Entre estos, el uso de nanoparticulas, recubrimientos multicapa y terapia génica destacan como algunas de las estrategias terapéuticas novedosas más prometedoras. El uso de stents cardíacos se ha mantenido a lo largo de los años con diferentes diseños y recubrimientos, logrando mejores resultados con cada nueva generación. Aunque su uso está justificado, sus resultados no son óptimos, creando la necesidad de desarrollar mejores estrategias para tratar este tipo de enfermedades. Entendemos que un control total de la liberación de la carga farmacológica de un dispositivo médico puede cambiar profundamente los resultados de un paciente, convirtiéndose así en una prioridad de nuestro trabajo. Presentamos una forma de producir recubrimientos, a escala industrial y de laboratorio, orientados para dispositivos médicos y que se utilizan para producir recubrimientos multicapa a medida para stents con liberación de fármaco. Además de esto, también se presenta un enfoque para tratar enfermedades de arteria coronaria a través de la terapia génica con nanoportadores, lo que abre nuevas posibilidades para tratamientos localizados empleando stents con liberación de fármaco. Comenzando con la elaboración de metodologías e instrumentos necesarios para producir recubrimientos a medida, se crean y estudian nuevos diseños de stent a lo largo de este trabajo. Esto permite la producción de nuevos recubrimientos y sistemas de liberación los cuales son probados in-vitro e in-vivo para demostrar su efectividad. En conclusión, esta tesis demuestra que se puede lograr una liberación de fármacos a medida mediante diseños multicapa y liberación con nanoportadores, aplicable a stents con liberación de fármaco para obtener una reducción en las tasas de reestenosis con resultados prometedores.
Coronary artery disease is the most typical type of heart disease, killing more than 385,000 people annually. Up to date, many different approaches have been tested in order to treat patients while trying to keep inflammatory responses to a minimum. Among these, the use of nanocarriers, multilayered coatings and gene therapy stand out as some of the most promising novel therapeutic strategies tested lately. Stents have been used throughout the years with different designs and coatings, achieving enhanced healing results with every new generation. Although their use is justified their results are not optimal, creating a need to develop better strategies to treat coronary artery diseases. We understand that a total liberation control of the pharmacological drug load from a medical device can profoundly change a patient’s outcome, therefore, becoming a priority of our work. Here, we present a way of producing in-lab and industrial scaled coatings for medical devices which are used to produce tailored multilayered coatings for drug eluting stents. Apart from this, an approach to treat coronary artery disease through gene therapy with nanocarriers is also introduced, opening new possibilities for localized treatments with drug eluting stents. Starting with the elaboration of methodologies and instrumentation required to produce tailored coatings, novel stent designs are created and studied in this work. This enables the production of new coatings and delivery systems which are tested in-vitro and in-vivo in order to prove their effectiveness. In conclusion, this thesis demonstrated that a tailored drug release can be achieved through multilayered designs and nanoparticle liberations, which can be applied to drug eluting stents to obtain a reduction in restenosis rates with promising results.
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Barnikel, Michaela [Verfasser], and Maximilian [Akademischer Betreuer] Reiser. "Experimentelle in vitro Analyse physikalischer Charakteristika von Drug-Eluting Beads sowie deren Beladungs- und Elutionskinetik / Michaela Barnikel ; Betreuer: Maximilian Reiser." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/1163948942/34.
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Borchardt, Annette. "Behandlung der koronaren Herzerkrankung mit Ballondilatation und Implantation von Sirolimus-Drug-Eluting-Stents : klinische und angiographische Ergebnisse eines nicht selektionierten Krankengutes /." Regensburg, 2007. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000253168.
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Sternberg, Katrin [Verfasser]. "Funktionalisierte, degradierbare Polymerbeschichtungen zur lokalen Freisetzung von Wirkstoffen : Entwicklung und Charakterisierung von Drug-Eluting-Stents für verschiedene medizinische Indikationen / Katrin Sternberg." Rostock : Universitätsbibliothek Rostock, 2010. http://d-nb.info/1007321385/34.
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Radic, Katarina [Verfasser], and Bruno [Akademischer Betreuer] Reichart. "Der Einfluss von Drug-Eluting-Stents und Bare-Metal-Stents auf die Ergebnisse nach notfallmäßiger Bypassoperation / Katarina Radic. Betreuer: Bruno Reichart." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1049890876/34.
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Hessian, Renee. "Drug eluting stents versus bare metal stents for the treatment of coronary artery disease: A review of the benefits and harms." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28149.
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Drug eluting stents (DES) have been found to reduce restenosis and the rate of repeat angiographic procedures related to restenosis. However, an increase in harms with their use has been suspected. Therefore, there may be an important trade-off of efficacy for harms with the use of DES, especially over the long term.
We conducted asystematic review and meta-analysis of RCT, examining the efficacy of DES versus bare metal stents (BMS). A separate review was then conducted which included non randomized studies, as well as RCT to evaluate long term harms of DES when compared to BMS. Analysis demonstrated that there was significant efficacy noted for DES over BMS, especially for the sirolimus coated stents. The long-term data demonstrated preserved efficacy of DES with no significant increase in the harms of death, myocardial infarction, stent thrombosis or revascularization for a follow-up extending out to four years.
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Baylatry, Minh-Tâm. "Microsphères de chimioembolisation appliquées au poumon : étude de la libération in vivo d'anticancéreux." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA114819/document.
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La chimioembolisation est une thérapie loco-régionale qui consiste à injecter, au moyend’un microcathéter, un principe actif et un agent d’occlusion vasculaire de manière la plussélective possible dans les artères nourricières du processus pathologique. Les microsphèresde chimioembolisation sont des microsphères calibrées et chargeables en principe actif,développées ces dernières années afin d’optimiser la chimioembolisation et permettre unelibération ciblée et contrôlée du principe actif au sein du territoire pathologique. L’utilisationde ces microsphères n’a encore jamais été appliquée à la chimioembolisation du poumon. Ellepourrait être intéressante dans le traitement des tumeurs pulmonaires malignes en permettantune imprégnation de la tumeur par un anticancéreux, tout en évitant une toxicité systémiquede ce dernier et dans le traitement des hémoptysies massives en évitant les récidives, dues àune recanalisation des vaisseaux après embolisation, par l’utilisation d’un inhibiteur duremodelage vasculaire.Notre travail a consisté à évaluer les performances de libération de l’irinotécan et dusirolimus à partir des microsphères de chimioembolisation au niveau systémique et au niveautissulaire, sur des modèles de chimioembolisation pulmonaire chez la brebis. Nos résultats ontmontré que les microsphères de chimioembolisation ne permettaient pas une délivrancetissulaire prolongée de l’irinotécan pour espérer obtenir une imprégnation efficace d’un lobepulmonaire. Les microsphères chargées en sirolimus semblent permettre une libérationcontrôlée du principe actif et paraissent intéressantes pour prévenir la recanalisation.Les microsphères de chimioembolisation doivent être améliorées pour permettre unelibération prolongée du principe actif. Des études complémentaires notamment en termesd’efficacité (modèle tumoral) doivent être réalisées pour montrer l’intérêt d’utiliser lachimioembolisation pulmonaire par microsphères en pratique cliniqueChemoembolization is a loco-regional therapy, which consists of delivering selectively and directly to the pathologic area, by means of catheters through the vasculature, a drug and an embolic agent. The purpose is to achieve nutrient and oxygen starvation of the tumor, to minimize chemotherapy wash-out with prolonged contact with tumor tissue and therefore to increase the local drug concentration and reduce systemic toxicity. Drug eluting beads are a new generation of calibrated embolization beads, which behave as a drug delivery system. They have been developed in order to optimize chemoembolization and to control precisely the release and the dose of drug into the treatment site. Drug eluting beads have never been used for lung chemoembolization. It may be interesting to evaluate them in the treatment of lung tumors in order to impregnate the tumor with an anticancer drug while avoiding systemic toxicity of this drug and in the treatment of massive hemoptysis to avoid recurrences, induced by a recanalization of vessels after embolization, by using an inhibitor on vascular remodeling. Our purpose was to evaluate the release performances of irinotecan and sirolimus from drug eluting beads, in systemic circulation and in lung tissue, in sheep lung chemoembolization models. Our results showed that drug eluting beads did not allow a sufficient sustained delivery of irinotecan to expect to obtain an effective impregnation of a pulmonary lobe. Sirolimus eluting beads seem to allow a drug controlled release and appear interesting to prevent recanalization. Drug eluting beads have to be improved in order to allow sustained and controlled release of the drug. Complementary studies especially efficacy studies have to be investigated for showing the interest to use lung chemoembolization with drug eluting beads in clinical practice
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Remak, Edit. "A real options game approach to health technology assessment." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/12565.
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Current economic evaluations do not explicitly acknowledge that there are multiple decision points throughout the lifecycle of new health technologies which, in the presence of uncertainty and irreversible consequences of those decisions, influence value. Real options analysis (ROA) has been proposed to overcome these limitations. However, applications to date all assumed that decisions influencing the arrival of information are made by the same actors making the decisions on adoption. The aim of this thesis is to explicitly incorporate into health technology assessment (HTA) the impact of uncertainty on decision making about new health technologies in the presence of irreversibilities. I present a series of analyses comparing “traditional” economic evaluation methods to applications of ROA using the case study of drug-eluting stents (DES). The conventional application of ROA allowed for flexibility in decisions incorporating all economic consequences of changing decisions. Over and above uncertainty surrounding the current estimate of value, three major components contributing to the economic value of the new technology were assumed to also change over time. This type of analysis can be used to determine the optimal initial decision allowing for changes in decisions and the optimal timing for review. However, it assumes that new information will always be revealed, regardless of the original decision on adoption. To reflect the combined impact of coverage, pricing and research decisions in HTA and therefore to make information arrival endogenous, a more complex approach is suggested: a Real Options Game (ROG) combining ROA with a game theoretical approach. In the ROG the HTA body and the manufacturer are assumed to play a sequential, incomplete information game, where the manufacturer has control over the arrival of information. The manufacturer decides whether to submit evidence, reduce price and conduct more research, while the HTA body decides on adoption. The DES analysis modelled a series of decision points between 2005 and 2010, with decisions not depending on hindsight, but allowing for predicted changes in value, incorporating a drift in information and responses by the other party. Payoffs were estimated for both players using a probabilistic Markov model. Optimal strategies incorporating the impact of earlier decisions on research were determined. HTA is a dynamic and interactive process, therefore results of the ROA analyses sometimes suggested a different course of action compared to traditional analyses. The best decision may depend on predictions of how other parties will react, as well as likely evolution of the evidence base and the costs of decision reversal.
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Furdella, Kenneth J., Russell S. Witte, and Geest Jonathan P. Vande. "Tracking delivery of a drug surrogate in the porcine heart using photoacoustic imaging and spectroscopy." SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2017. http://hdl.handle.net/10150/624370.
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Although the drug-eluting stent (DES) has dramatically reduced the rate of coronary restenosis, it still occurs in up to 20% of patients with a DES. Monitoring drug delivery could be one way to decrease restenosis rates. We demonstrate real-time photoacoustic imaging and spectroscopy (PAIS) using a wavelength-tunable visible laser and clinical ultrasound scanner to track cardiac drug delivery. The photoacoustic signal was initially calibrated using porcine myocardial samples soaked with a known concentration of a drug surrogate (Dil). Next, an in situ coronary artery was perfused with DiI for 20 min and imaged to monitor dye transport in the tissue. Finally, a partially DiI-coated stent was inserted into the porcine brachiocephalic trunk for imaging. The photoacoustic signal was proportional to the DiI concentration between 2.4 and 120 mu g/ml, and the dye was detected over 1.5 mm from the targeted coronary vessel. Photoacoustic imaging was also able to differentiate the DiI-coated portion of the stent from the uncoated region. These results suggest that PAIS can track drug delivery to cardiac tissue and detect drugs loaded onto a stent with sub-mm precision. Future work using PAIS may help improve DES design and reduce the probability of restenosis. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
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Sambola, Antonia, Pau Rello, Toni Soriano, Deepak L. Bhatt, Vinay Pasupuleti, Christopher P. Cannon, C. Michael Gibson, et al. "Safety and efficacy of drug eluting stents vs bare metal stents in patients with atrial fibrillation: A systematic review and meta-analysis." Elsevier Ltd, 2020. http://hdl.handle.net/10757/655507.
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Objective: A systematic review and meta-analysis was performed to evaluate the safety and efficacy of drug-eluting stents (DES) vs bare-metal stents (BMS) in atrial fibrillation (AF) patients. Methods: We systematically searched 5 engines until May 2019 for cohort studies and randomized controlled trials (RCTs). Primary outcomes were major bleeding and major adverse cardiac events (MACE) including cardiac death, myocardial infarction, target vessel revascularization (TVR) or stent thrombosis. Effects of inverse variance random meta-analyses were described with relative risks (RR) and their 95% confidence intervals (CI). We also stratified analyses by type (triple [TAT] vs dual [DAT]) and duration (short-vs long-term) of antithrombotic therapy. Results: Ten studies (3 RCTs; 7 cohorts) including 10,353 patients (DES: 59.6%) were identified. DES did not show higher risk of major bleeding than BMS (5.6% vs 6.9%, RR 1.07; 95%CI, 0.89–1.28, p = 0.47; I2 = 0%) or MACE (12% vs 13.6%; RR 0.96; 95%CI 0.81–1.13, p = 0.60; I2 = 44%). Although, DES almost decreased TVR risk (6.4% vs 8.4%, RR 0.78; 95%CI, 0.61–1.01, p = 0.06; I2 = 15%). Stratified analyses by type and duration of antithrombotic therapy showed no differences in major bleeding or MACE between both types of stents. In DES, long-term TAT showed higher major bleeding risk than long-term DAT (7.7% vs 4.7%, RR 1.48, 95%CI 1.08–2.03, p = 0.01; I2 = 12%). For both types of stents, MACE risk was similar between TAT and DAT. Conclusions: In patients with AF undergoing PCI, DES had similar rate of major bleeding and MACE than BMS. DAT seems to be a safer antithrombotic therapy compared with TAT.Janssen Pharmaceuticals
Revisión por pares
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Rüther, Charlotte [Verfasser], and Gunnar [Akademischer Betreuer] Tepe. "Prädiktoren des Outcomes nach Drug-Eluting-Angioplastie nach peripheren Interventionen unter besonderer Berücksichtigung der vaskulären Kalzifikation / Charlotte Anna Rüther ; Betreuer: Gunnar Tepe." Tübingen : Universitätsbibliothek Tübingen, 2017. http://d-nb.info/1199462721/34.
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Simunovic, Iva [Verfasser], Adnan [Akademischer Betreuer] Kastrati, and Tareq [Akademischer Betreuer] Ibrahim. "Inzidenz und Prädiktoren der Stentthrombose in Bare-Metal-Stents und Drug-Eluting-Stents / Iva Simunovic. Gutachter: Tareq Ibrahim ; Adnan Kastrati. Betreuer: Adnan Kastrati." München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1059238063/34.
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Guo, Qiongyu. "POSS-Based Biodegradable Polymers for Stent Applications: Electroprocessing, Characterization and Controlled Drug Release." Cleveland, Ohio : Case Western Reserve University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1259706279.
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Thesis(Ph.D.)--Case Western Reserve University, 2010Title from PDF (viewed on 2009-12-22) Department of Macromolecular Science and Engineering Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
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Nanda, Hitesh. "APPLICATION OF IN VIVO FLOW PROFILING TO STENTED HUMAN CORONARY ARTERI." Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2600.
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The study applies in vivo technique for profiling hemodynamics and wall shear stress (WSS) distribution in human coronary arteries. The methodology involves fusion of 2D Intra Vascular Ultra Sound and Bi-plane angiograms to reproduce the 3D arterial geometry. This geometry is then used in a Computational Fluid Dynamics (CFD) module for flow modeling. The Walburn and Schneck constitutive relation was used to represent the non-Newtonian blood rheology. The methodology is applied to study the relationship between WSS and Neointimal Hyperplasia (NIH) in two groups of diabetic patients after being treated separately with bare metal stents (BMS) and Sirolimus Eluting Stents (SES). The stent assignments were blinded until the end of the study. The study was repeated for the patients after 9 months. The predicted WSS ranged from (0.1- 8 N/m2) and was categorized into five classes: low (< 1 N/m2); low-normal (1-2 N/m2); normal (2-3 N/m2); high-normal (3-4 N/m2); high (>4 N/m2). The results indicate NIH in 5 of the patients treated with BMS and none in SES cases. These results correlate with our predicted WSS distribution.M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering
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Watanabe, Hirotoshi. "Antiplatelet Therapy Discontinuation and the Risk of Serious Cardiovascular Events after Coronary Stenting: Observations from the CREDO-Kyoto Registry Cohort-2." Kyoto University, 2016. http://hdl.handle.net/2433/215212.
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Byrne, Robert A. [Verfasser], Adnan [Akademischer Betreuer] Kastrati, Steffen [Akademischer Betreuer] Massberg, and Kieran [Akademischer Betreuer] Daly. "Coronary Restenosis and Arterial Healing Following Drug-Eluting Stent Implantation – Time Course, Angiographic Metrics and Impact of Modifications in Polymer and Drug Coatings / Robert Byrne. Gutachter: Steffen Massberg ; Adnan Kastrati ; Kieran Daly. Betreuer: Adnan Kastrati." München : Universitätsbibliothek der TU München, 2011. http://d-nb.info/1016742010/34.
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Rossbach, Cornelius. "Randomisierter Vergleich von Medikamenten freisetzenden Stents mit minimal-invasiver Bypasschirurgie für isolierte proximale LAD-Stenosen – Ein 7-Jahres-Follow-Up." Doctoral thesis, Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-221662.
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OBJECTIVES The aim of this analysis was to assess the 7-year long-term safety and effectiveness of a randomized comparison of percutaneous coronary intervention (PCI) with sirolimus-eluting stents (SES) versus minimally invasive direct coronary artery bypass (MIDCAB) surgery for the treatment of isolated proximal left anterior descending lesions.
BACKGROUND Long-term follow-up data comparing PCI by SES and MIDCAB surgery for isolated proximal left anterior descending lesions are sparse.
METHODS Patients were randomized either to PCI with SES (n ¼ 65) or MIDCAB (n ¼ 65). Follow-up data were obtained after 7 years with respect to the primary composite endpoint of death, myocardial infarction, and target vessel revas-
cularization. Angina was assessed by the Canadian Cardiovascular Society classification and quality of life with Short Form 36 and MacNew quality of life questionnaires.
RESULTS Follow-up was conducted in 129 patients at a median time of 7.3 years (interquartile range: 5.7, 8.3). There were no significant differences in the incidence of the primary composite endpoint between groups (22% PCI vs. 12%
MIDCAB; p ¼ 0.17) or the endpoints death (14% vs. 17%; p ¼ 0.81) and myocardial infarction (6% vs. 9%, p ¼ 0.74). However, the target vessel revascularization rate was higher in the PCI group (20% vs. 1.5%; p < 0.001). Clinical symptoms and quality of life improved significantly from baseline with both interventions and were similar in magnitude between groups.
CONCLUSIONS At 7-year follow-up, PCI by SES and MIDCAB in isolated proximal left anterior descending lesions yielded similar long-term outcomes regarding the primary composite clinical endpoint and quality of life. Target vessel revascularization was more frequent in the PCI group. (Randomied Comparison of Minimally Invasive Direct Coronary Artery Bypass Grafting and Percutaneous Coronary Intervention With Drug-Eluting Stents in Patients With Proximal Stenosis of the Left Anterior Descending Coronary Artery; NCT00299429) (J Am Coll Cardiol Intv 2014;-:-–-) © 2014 by the American College of Cardiology Foundation.
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Oliveira, Flavio Roberto Azevedo de. "Avaliação da eficácia tardia após o implante de um stent miniaturizado, farmacológico versus não-farmacológico, em artérias coronárias de pequeno calibre." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/98/98131/tde-03082012-070905/.
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Os vasos de fino calibre apresentam maior risco para reestenose e revascularização da lesão alvo. Limitações relacionadas com a navegabilidade dos sistemas de dilatação por balão e menor capacidade de acomodação da neoíntima podem contribuir para isto. O stent autoexpansível de nitinol Sparrow® dedicado a vaso de calibre < 2,75 mm, resultou num conjunto com perfil de um fio-guia 0,014\". Testado na forma de stent de metal puro no estudo CARE I, revelou-se seguro e eficaz em vasos de fino calibre. Este estudo avaliou, de forma pioneira, o despenho de um stent autoexpansível farmacológico neste cenário. O objetivo primário foi comparar a perda luminal tardia no vaso-alvo pela angiografia coronária quantitativa ao final de oito meses, entre os stents Sparrow® farmacológico e não farmacológico, em coronárias com diâmetro de referência < 2,75 mm. Casuística e métodos: Os pacientes foram randomizados de forma prospectiva em dois grupos para procedimento de angioplastia: um grupo com o emprego o stent Sparrow® farmacológico (sirolimus), e ou outro grupo com o stent Sparrow® na versão não farmacológica. Análise pela angiografia coronária quantitativa foi realizada imediatamente antes e após o procedimento e aos oito meses, com seguimento clínico de 24 meses. Foi utilizado o programa IBM SPSS Statistics® para análise estatística e foi considerado nível de significância de 5% e poder de 80% para o cálculo do tamanho da amostra. Resultados: 24 pacientes foram randomizados, 12 no grupo com stent farmacológico Sparrow® e 12 no grupo com a versão não farmacológica. Na avaliação angiográfica aos oito meses verificou-se significativa redução de perda luminal tardia no grupo com o stent farmacológico Sparrow® em comparação com grupo com a versão não farmacológica (0,25 + 0,16 mm versus 0,97 + 0,76 mm, p = 0,008, IC 95% de -1,19 ; -0,22). No seguimento clínico de 12 meses, não foram observados eventos cardíacos adversos maiores (morte, infarto ou necessidade de revascularização do vaso alvo) no grupo com stent farmacológico. Não ocorreu trombose intrastent. Conclusão: Em pacientes submetidos à angioplastia transluminal percutânea em artérias coronárias com diâmetro de referência < 2,75 mm, o emprego do stent farmacológico autoexpansível Sparrow®, em comparação com a versão não farmacológica do mesmo stent, resultou em significativa redução de perda luminal tardia, sem ocorrência de eventos clínicos que deponham contra a segurança do dispositivo pesquisado.Small vessels represent a group with high risk for restenosis and target lesion revascularization. Limitations associated with navigability of balloon dilation systems and less accommodating of the neointima may contribute to this. The self-expanding Sparrow® stent system dedicated to the vessel size <2.75 mm resulted in a profile similar to a 0.014\" guide wire angioplasty. Tested as bare metal stent in the CARE trial I, the Sparrow® stent system has proved to be safe and effective in small vessels. This study evaluated, for the first time, the performance of a self-expanding drug eluting stent in this scenario. The primary objective was to compare the in-stent late lumen loss by quantitative coronary angiography at the end of eight months between the Sparrow® drug-elutig stent and Sparrow® bare metal stent in coronary arteries with reference diameter <=2.75 mm. Materials and methods: Patients were prospectively randomized (1:1) Analysis by quantitative coronary angiography was performed immediately before and after the procedure and at eight months with clinical follow-up to 12 months. We used the IBM® SPSS for statistical analysis and was considered a significance level of 5% and 80% power for the calculation of sample size. Results: 24 patients were randomized, 12 in each group. At Eight months follow-up there was significant reduction in late lumen loss in the Sparrow® drug-eluting stent group compared to the Sparrow® bare metal stent group (0.25 ± 0.16 mm vs. 0.97 + 0.76 mm, p = 0.008, 95% CI -1.19 to -0.22). Up to 12 months of clinical follow-up there no cases of death, myocardial infarction and target vessel revascularization Of note, there was no stent thrombosis. Conclusion: In patients undergoing percutaneous transluminal angioplasty in coronary arteries with reference diameter <= 2.75 mm, the use of Sparrow® drug-eluting stent, compared to the Sparrow® bare metal stent, resulted in significant less late loss without occurrence of clinical events that weigh against the security of device.
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Almeida, Breno Oliveira. "Avaliação da função endotelial após o implante de stents com revestimento cerâmico e baixas doses de sirolimus: estudo prospectivo, duplo-cego e randomizado." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/98/98131/tde-11062013-085036/.
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A disfunção endotelial é uma das possíveis causas relacionadas à taxa mais elevada de trombose após o implante da primeira geração de stents farmacológicos. Se a presença do polímero durável ou elevada dose de fármacos antiproliferativos, ou ambos, são responsáveis por este fenômeno não está definido. O Estudo VESTASYNC II comparou um novo stent farmacológico, com superfície revestida por uma camada porosa de hidroxiapatita e impregnado com baixa dose de sirolimus. (55?g - stent VestaSync®) com seu equivalente não farmacológico (Stent VestaCor® ). O Vestasync II é um estudo prospectivo, randomizado (2:1) e duplo-cego, que incluiu pacientes com lesões de novo em artérias nativas com extensão menor que 14mm, com diâmetro entre 3,0 e 3,5mm. Um subgrupo composto por 20 pacientes (10 em cada grupo) submeteu-se à avaliação da função endotelial, no seguimento angiográfico de oito meses. O objetivo primário foi a comparação da vasomotricidade após o implante de stents com a mesma plataforma, com e sem eluição de sirolimus, a fim de determinar o real impacto de baixa dose do sirolimus na função endotelial. O desfecho de eficácia foi a perda luminal tardia e o porcentual de obstrução intra-stent. A avaliação da função endothelial foi realizada através da estimulação atrial com marcapasso (20ppm acima da frequência cardiaca basal até alcançar 150ppm) e o diâmetro luminal foi mensurado nas extremidades proximal e distal do stent e em um segmento controle, em estágios diferentes (repouso, sucessivas fases do estímulo e após a infusão intracoronária de nitroglicerina). A eficácia deste novo dispositivo foi confirmada por angiografia coronária quantitativa (perda luminal tardia VestaSync = 0,39 mm vs. 0,78 mm, p=0,005) e ultrassom intravascular (% obstrução VestaSync 9,3% vs. 17,6%, p= 0,005). Houve variação negativa no diâmetro luminal, entre o repouso e o estímulo máximo, nas bordas proximal (10%) e distal (8%). Entre os segmentos controles esta variação não alcançou 3%. A eluição de dose baixa do sirolimus não parece interferir na função endotelial, oito meses após o implante do stent sem polímero revestido com hidroxiapatita.Endothelium dysfunction is among the possible causes related to higher thrombosis rates after first generation drug-eluting stents implant. Whether the presence of durable polymer or high anti-proliferative drug dose, or both, can be responsible for this phenomenon is not clear. The VESTASYNC II trial compared a novel polymer-free drug-eluting stent with a nanothinmicroporous hydroxyapatite surface coating impregnated with a low-dose of sirolimus (55?g-VestaSyncTM stent) to a bare-metal equivalent also coated with a nanothin-microporous hydroxyapatite surface (VestaCorTM stent). This is a randomized (2:1), double-blinded trial which enrolled patients with single de novo lesions in native coronary arteries from 3.0 to 3.5mm diameter and less than 14mm in length. A subset of 20 patients (10 from each group) underwent to endothelial function assessment at eight-month angiographic follow-up. The primary objective was to compare the vasomotricity after implantation of stents with the same platform, with and without drug elution, to determine the real impact of low-dose sirolimus release in endothelial function. Efficacy endpoint was in-stent late loss and % of stent obstruction. Endothelial function was assessed with atrial pacemaker stimulation (20 ppm over basal cardiac frequency until reach 150 ppm) and the lumen diameter was measured at 5 mm of proximal and distal stent edges and in a control segment, in different stages (at rest, at successive phases of stimulli and after nitroglycerin intracoronary infusion). The efficacy of this new device was confirmed by means of quantitative coronary angiography (late loss VestaSync = 0.39 mm vs. 0.78 mm, p=0.005) and intravascular ultrasound (% obstruction VestaSync 9.3% vs. 17.6%, p= 0.005). There was a negative variation in luminal diameter between basal and maximum stimulli in proximal (10%) and distal (8%) edges of both groups. Among control segments this variation did not reach 3%. The elution of low-dose of sirolimus does not seem to interfere in endothelial function 8 months after polymer-free hydroxyapatite coating stent implantation.
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Maria, Adriana Del Monaco De. "Estudo do revestimento de modelos de stents coronários biorreabsorvíveis de PLLA com PLDLA/PLGA e ácido hialurônico." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/98/98131/tde-04102017-140345/.
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A doença arterial coronariana vem sendo a maior causa de mortalidade no mundo, a angioplastia com implante de stent é uma estratégia importante nestes casos. Estudos apontam a biodegradabilidade, imobilização de antiproliferativos e moléculas bioativas nos stents, como características das futuras gerações destes dispositivos. Dentre estas, o ácido hialurônico contribui para a diminuição da agregação e proliferação de células entre as camadas da artéria e o dispositivo implantado. Foram desenvolvidos modelos de stents coronários biorreabsorvíveis de poli(-L-ácido láctico) (PLLA) com enxertia de ácido hialurônico (HA) em poli(-ácido lático co-ácido glicólico) (PLGA) e poli(L-D-ácido lático) (PLDLA). Os modelos foram caracterizados quanto suas propriedades térmicas, mecânicas e de superfície. O PLDLA e PLGA com enxertia de HA modificado com dihidrazida adípica (ADH) apresentaram características de superfície mais hidrofílicas, ideais para material de revestimento dos dispositivos. Desta forma, este trabalho possibilitou o desenvolvimento dos modelos físicos biorreabsorvíveis, com dimensões semelhantes aos stents coronários, feitos de PLLA, revestidos com PLGA e PLDLA com enxertia de HA e HAADH, e estáveis aos processos de esterilização por radiação ultravioleta e plasma de peróxido de hidrogênio.Coronary artery disease has been world´s leading cause of death and angioplasty stent implantation is an important strategy in these cases. Studies indicate that the biodegradability, immobilization of antiproliferatives and bioactive molecules in stents are characteristics of future generations of these medical devices. Amongst them, hyaluronic acid (HA) contributes to the decrease of the aggregation and proliferation of cells between artery layers and implanted device. For this purpose, poly (L-lactic acid) (PLLA) bioresorbable coronary stents with HA grafting in poly (lactic acid-co-glycolic acid) (PLGA) and poly (LD- (PLDLA) were developed. The models were characterized as their thermal, mechanical and surface properties. PLDLA and PLGA with adipic dihydrazide (ADH) modified HA grafting presented more hydrophilic surface characteristics, ideal as coating material of this devices. This project allowed the development of bioresorbable physical models with similar dimensions to coronary stents, made of PLLA, coated with PLGA and PLDLA with hyaluronic acid grafting, stable to ultraviolet radiation and plasma sterilization with hydrogen peroxide processes.
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Ohya, Masanobu. "Long-Term Outcomes After Stent Implantation for Left Main Coronary Artery (from the Multicenter Assessing Optimal Percutaneous Coronary Intervention for Left Main Coronary Artery Stenting Registry)." Kyoto University, 2018. http://hdl.handle.net/2433/235034.
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Hurley, Nicole Elizabeth. "Modulating the Functional Contributions of c-Myc to the Human Endothelial Cell Cyclic Strain Response." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19822.
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With each heartbeat, major arteries experience circumferential expansion due to internal pressure changes. This pulsatile force is called cyclic strain and has been implicated in playing a pivotal role in the genetic regulation of vascular physiology and pathology. This dissertation investigates the hypothesis that in human umbilical vein endothelial cells (HUVEC), pathological levels of cyclic strain activate the c-Myc promoter, leading to c-Myc transcription and downstream gene induction. To determine expression and time-dependency of c-Myc in HUVEC, mRNA and protein expression of c-Myc under physiological (6-10% cyclic strain) and pathological conditions (20% cyclic strain) were studied. Both c-Myc mRNA and protein expression increased more than three-fold in HUVEC (P4-P5) cyclically-strained at 20%. This expression occurred in a time-dependent manner, peaking in the 1.5-2 hour range and falling to basal levels by 3 hours. Subsequently, the mechanism of c-Myc transcription was investigated by using specific inhibitors to modulate c-Myc transcriptional activation. These compounds, obtained from the University of Arizona Cancer Center, attenuated cyclic-strain-induced c-Myc transcription by about 50%. Having established this reduction in expression, it was investigated how these effects modulate downstream genes that are regulated by c-Myc. The results indicate that direct targeting of the c-Myc promoter may decrease stretch-induced gene expression of vascular endothelial growth factor (VEGF), proliferating cell nuclear antigen (PCNA) and heat shock protein 60 (HSP60). These findings may help in the development of a novel therapeutic opportunity in vascular diseases.
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Ferreira, Esmeralci. "Análise do custo-efetividade dos stents farmacológicos versus stents convencionais: resultados clínicos e de custos a médio e longo prazo." Universidade do Estado do Rio de Janeiro, 2009. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=1505.
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Os resultados tardios com os stents farmacológicos são melhores do que com stents convencionais, principalmente no que se refere à reestenose. Entretanto, no mundo real, os stents farmacológicos são implantados em pacientes de maior complexidade, o que teoricamente já diminui a diferença dos resultados. Comparar resultados da utilização de stents com paclitaxel (Grupo I) em pacientes complexos com stents convencionais (Grupo II) implantados em pacientes menos graves. A partir dos resultados realizar análise para estimar a razão de custo-efetividade nos dois grupos. Foram analisados 220 pacientes prospectivamente durante aproximadamente dois anos (média de 17 meses): 111 do Grupo 1 (GI) e 109 do Grupo II (GII). Foram avaliadas a sobrevida e a sobrevida livre de eventos através do método de Kaplan-Meier. Usando-se os critérios da Organização Mundial de Saúde, calculou-se a razão custo-efetividade incremental (RCEI) para cada reestenose evitada. O escore de propensão foi usado para reduzir diferenças entre os dois grupos. Foi observado predomínio do sexo masculino nos dois grupos (n=174 66,8%), mas sem diferenças entre eles. Também não houve diferenças em relação à idade, que variou de 42 anos a 91 anos (65,9 anos). As diferenças que ocorreram, com maior incidência no GI foram: diabetes: GI=60 (50,4%) e GII=19 (17,4%), p=0,0001; história familiar para doença arterial coronariana (DAC): GI=43 (38,7%) e GII=24 (22,1%), p=0,007; infarto prévio: GI=54 (48,6%) e GII=31 (28,4%), p=0,002; cirurgia de revascularização prévia: GI=24 (21,7%) e GII=6 (5,5%), p=0,0005; angioplastia prévia: GI=28 (25,2%) e GII=17 (15,5%), p=0,077; síndromes coronarianas agudas: GI=48 (43,3%) e GII=35 (32,0%), p=0,088. Os pacientes triarteriais foram mais presentes no GI=21 (18,9%) do que no GII=11 (10,1%), p=0,029. No entanto, os pacientes do GII apresentaram mais frequentemente função normal do VE: GI=51 (45,9%) e GII=85 (77,9%), p=0,0001. Não houve diferença no número de lesões tratadas e entre o número de artérias por paciente, entre os dois grupos. O grupo dos stents convencionais abordou lesões mais simples: Tipo A GI=43 (25,6%); GII=65 (45,5%), p=0,0002; Tipo B: B1 GI=50 (29,7%) e GII=35 (24,5%), p=0,30; e B2 GI=51 (30,4%) GII=26 (18,1%), p=0,53; e Tipo C: GI=24 (14,3%) e GII=17 (11,9%), p=0,53. O número de reestenoses por paciente foi menor no GI=7 (6,3%) vs GII=14 (12,8%), mas sem significância estatística (p=0,099). Entretanto, a reestenose por lesão foi menor no GI=7 (4,1%) vs GII=14 (9,8%) p=0,0489. A sobrevida geral em dois anos foi 96,2% no GI e 89,3% no GII (p=0,76) e as sobrevidas livres de eventos foram similares: eventos maiores (p=0,35) e livre de reestenose (p=0,82). O escore de propensão demonstrou que pacientes com idade >72 anos, os diabéticos, as lesões com diâmetro <3,2mm e com o comprimento >18mm foram as variáveis que melhor classificaram pacientes para receber SF. Avaliando-se todos os fatores clínicos, angiográficos e técnicos através da curva de regressão logística, o único item de destaque foi o tamanho dos stents (OR=6,75 e RR=4,37). Com valor corrigido o GII tem 4,3 vezes maior chance de reestenose do que o GI. No que se refere aos custos, a árvore de decisão foi modelada na reestenose dos dois grupos GI=6,3% vs GII=12,8% em 17 meses (média). O benefício líquido do implante do stent com paclitaxel foi 6,3% de redução de reestenose, com incremento de custo de R$9.590,00. A razão custo-efetividade incremental (RCEI) foi R$147.538,00 por reestenose evitada, cujo valor incremental encontra-se acima do limiar sugerido pela OMS. Conclusões: Os resultados foram similares no GI e GII, mesmo o GI atendendo uma população mais grave, com mais diabéticos e outras comorbidades. A reestenose por lesão foi maior no GII. O tamanho do stent foi a única variável importante para a reestenose. O implante dos stents farmacológicos, em pacientes do mundo real, revelou-se uma estratégia não custo-efetiva.Long term outcomes for drug eluting stents are better than those for bare metal stents, especially for restenosis. However, drug eluting stents are usually implanted in more complex patients, theoretically lessening the difference in the outcomes. To compare the outcomes of paclitaxel stents (GI) in complex patients and bare metal stents (GII), in less complex patients. For some two years (mean: 17 months), 220 patients were analyzed prospectively: 111 in GI and 109 in GII. Their general survival and cardiovascular event-free survival rates were assessed through the Kaplan-Meier method. Using the criteria of the World Health Organization (WHO), the incremental cost-effectiveness ratio (ICER) was calculated for each restenosis avoided. Propensity scores was used to reduce selection bias by equating both groups based on these covariates. Men predominated in both groups (n=174 66.8%), with no differences between them, including age, ranging from 42 to 91 years (65.9 years). The main differences, with higher rates in GI, were diabetes: GI=60 (50.4%) and GII=19 (17.4%), p=0.0001; family history: GI=43 (38.7%) and GII=24 (22.1%), p=0.007; previous acute myocardial infarction: GI=54 (48.6%) and GII=31 (28.4%), p=0.002; previous coronary artery bypass graft: GI=24 (21.7%) and GII=6 (5.5%), p=0.0005; previous angioplasty: GI=28 (25.2%) and GII=17 (15.5%), p=0.077; acute coronary syndrome: GI=48 (43.3%) and GII=35 (32.0%), p=0.088. Multivessel patients were more frequent in GI=21 (18.9%) than in GII=11 (10.1%), p=0.029. However, the GII patients presented normal left ventricle functions more frequently: GI=51 (45.9%) and GII=85 (77.9%), p=0.0001. There were no differences between the groups for the number of lesions treated and number of arteries per patient. The bare metal stent group presented simpler lesions: Type A GI=43 (25.6%); GII=65 (45.5%), p=0.0002; Type B: B1 GI=50 (29.7%) and GII=35 (24.5%), p=0.30; and B2 GI=51 (30.4%) GII=26 (18.1%), p=0.53; and Type C: GI=24 (14.3%) and GII=17 (11.9%), p=0.53. The restenosis per patient was lower in GI=7 (6.3%) than in GII=14 (12.8%), but without statistical significance (p=0.099). However, restenosis by lesion was lower in GI=7 (4.1%) than in GII=14 (9.8%) p=0.0489. The general two-year survival rate was 96.2% in GI and 89.3% in GII (p=0.76) with similar event-free survival rates: major events (p=0.35) and restenosis (p=0.82). The propensity score showed that it was better to receive SF in patients: age >72, diabetics and lesions with diameter <3,2mm and length >18mm. Assessing all the clinical, angiographic and technical factors through the logistic regression curve, the only the major predictor was stent size. With the value corrected, GII has 4.3 times more chances of restenosis than GI. In terms of costs, the decision tree was modeled on the restenosis in the two groups: GI=6.3% versus GII=12.8% in 17 months (mean). The net benefit of implanting of paclitaxel stents was a 6.3% reduction in restenosis, with a cost increase of R$ 9,590.00. The incremental cost-effectiveness ratio (ICER) was R$ 147,538.00 for avoided restenosis, whose incremental value exceeds the threshold suggested by the WHO (World Health Organization). The results were similar in GI and GII, despite more diabetes and other co-morbidities in GI. Restenosis by lesion was higher in GII. The size of the stent was the only important variable for restenosis. The use of drug eluting stents in patients is not a cost-effective strategy in actual practice.