En los últimos años el stenting carotídeo ha emergido como una potencial alternativa a la endarterectomía carotídea en téminos de seguridad y eficacia. El estudio SAPPHIRE probó que en los pacientes de alto riesgo con estenosis carotídea grave, el stenting carotídeo realizado con protección cerebral mediante filtro distal no es inferior a la endarterectomía. Aunque los sistemas de protección cerebral que utilizan los filtros distales reducen las complicaciones tromboembólicas durante el stenting carotídeo, la protección parece ser insuficiente. Por el contrario, cuando la protección cerebral implica la oclusión de la arteria carótida común y la creación de un flujo reverso en la arteria carótida interna se consigue una importante ventaja: la protección cerebral se realiza antes de atravesar la lesión, uno de los pasos más embolígenos durante el stenting carotídeo. En nuestra experiencia, el flujo reverso a través de un acceso transcervical es un método simple y seguro que elimina los inconvenientes de la instrumentación del arco aórtico y el hecho de atravesar la lesión sin protección. Es además más barato que los métodos que requieren un filtro distal y los resultados a corto y medio plazo son comparables a los reportados para la endarterectomía. Se ha sugerido que los pacientes de edad avanzada podrian constituir un subgrupo de alto riesgo para el stenting carotídeo. Distintas experiencias individuales y particularmente los resultados del estudio CREST, parecen confirmar esta idea. Tradicionalmente y fuera de experiencias individuales de endarterectomía carotídea en octogenarios, este subgrupo de pacientes fueron excluidos de los estudios multicéntricos que compararaban la endarterectomía con el mejor tratamiento médico, por lo que la incidencia de complicaciones de la endarterectomía en estos pacientes no es bien conocida haciendo más dificil establecer la mejor opción de tratamiento en esta población. La hipótesis que podría explicar la mayor tasa de complicaciones con el stenting carotídeo por vía transfemoral en pacientes añosos es la mayor dificultad técnica debido a la mayor complejidad del arco aórtico y a la tortuosidad de los troncos supraórticos en este grupo de edad. El stent carotídeo trancervical con flujo reverso evita ambos pasos: permite el despliegue del stent en la lesión estenótica sin instrumentación del arco aórtico. Los resultados de nuestro estudio confirman que la revascularización carotídea mediante stenting carotídeo transcervical con inversión de flujo para la protección cerebral es tan seguro como la endarterectomía en pacientes octogenarios, en contraste con las consideraciones de la mayoría de los autores que no recomiendan stenting carotídeo en este subgrupo de pacientes. Además, en la actualidad, los resultados del meta-análisis y revisiones sistemáticas ponen de manifieso altas tasas de ictus y muerte en pacientes de edad avanzada (mayores de 70 años) sometidos a stenting carotídeo por vía transfemoral y sugieren que el stent carotídeo se debe evitar en esta población. En esta tesis doctoral se ha podido demostrar que en pacientes octogenarios el stent carotídeo realizado con abordaje transcervical y flujo reverso es tan seguro como la endarterectomía carotídea a corto plazo. El acceso transcervical evita las limitaciones anatómicas antes mencionados y la inversión del flujo reduce el número de microembolias que ocurren durante el procedimiento. Hemos podido además confirmar los mismos resultados en pacientes mayores de 70 años. Creemos que lo que se debe evitar en esta población es la instrumentación del arco aórtico y de los troncos supraórtcicos, no el stenting carotídeo y por tanto el uso de la vía transcervical y la creación del flujo reverso es una técnica segura y eficaz en este grupo de pacientes. / In the last few years transfemoral carotid artey stenting has emerged as a potential alternative to endarterectomy in terms of both safety and efficacy. The SAPPHIRE trial proved that among high risk patients with severe carotid artery stenosis and coexisting conditions, carotid artey stenting with the use of an emboli-protection device is not inferior to carotid endarterectomy: Cerebral filtering devices reduce thromboembolic complications durins carotid artey stenting , however the degree of protection appears to be incomplete. Systems for cerebral protection that involve proximal common carotid artery occlusion and establishment of flow reversal in the internal carotid artery offer an important advantage: cerebral protection is established before crossing the lesion, which is one of the most emboligenic maneuvers in carotid stenting. The use of a transfemoral route to establish flow reversal presents the drawbacks related to femoral access. In our experience, flow reversal using a transcervical access route is a simple, safe method that eliminates the drawbacks of aortic arch instrumentation and crossing the target lesion without protection. In addition, it is less expensive than methods requiring a filter device, and the short- and long-term outcomes are comparable to the reported results for carotid vascularization by endarterectomy. It has been suggested that patients of advanced age may constitute a high-risk subgroup for carotid artery angioplasty and stenting .Various individual experiences, and particularly the preliminary results of the lead-in phase of the CREST study, seem to confirm this idea. Moreover, apart from individual experiences with carotid endarterectomy in octogenarians, this age group was historically excluded from multicenter trials comparing endarterectomy and the best medical therapy. Thus, the precise incidence of complications associated with carotid endarterectomy is not known, making even more difficult to establish the best treatment option in this population. The hypothesis that may explain the higher rate of complications with the use of transfemoral carotid artey stenting in elderly patients is the greater technical difficulty of the treatment due to frequent anatomical complexity of the aortic arch and tortuosity of the supraaortic trunks in this age group. Transcervical carotid stenting with flow reversal is a technique that allows stent deployment over the stenotic lesion without aortic arch instrumentation. The results of our study confirm that carotid revascularization by transcervical carotid artey stenting with flow reversal for cerebral protection is as safe as carotid endarterectomy in octogenarian patients in contrast to the considerations of most authors who do not recommend carotid artey stenting in this patient subgroup. Currently, the results of meta-analyses and systematic reviews have pointed to elevated rates of stroke/death in older patients ( over 70 years) undergoing transfemoral carotid artery angioplasty and stenting , and strongly suggest that carotid stenting should be avoided in this population. The hypotheses are the same as those discussed above. This thesis has been demonstrated that carotid stenting octogenarians performed with transcervical approach and reverse flow is as safe as carotid endarterectomy in the short term. Transcervical access anatomical avoids the limitations mentioned above and the reversal of the flow reduces the number of microemboli which occur during the procedure. We could also confirm the same results in patients over 70 years. We believe that what should be avoided in this population is the implementation of the aortic arch and supraórtcicos trunks, not carotid stenting and therefore the use of the transcervical and the creation of flow reversal is a safe and effective in this group patients.

Thesis (doctoral)--Technische Universität, Berlin, 2000.

The prevalence of cardiovascular disease (CVD) has increased dramatically due in part to the increased rates of obesity in North America. Atherosclerosis, the most prevalent type of CVD, is a progressive disease characterized by the build-up of plaque within the arteries. The plaque development leads to the narrowing of arteries, referred to as stenosis, and restricts crucial blood flow to the organs of the body. This condition is often treated by the implantation of a stent, a wire mesh scaffold device placed in the region of an atherosclerotic plaque after balloon angioplasty. The stent was developed to improve the clinical outcome of angioplasty procedures by mitigating the effects of elastic recoil by the vessel wall and maintaining vessel patency after angioplasty. Since the introduction of stents as a treatment option over a decade ago, in-stent restenosis (ISR) has been an iatrogenic outcome and remains an unsolved limitation of the interventional treatment device, resulting in stent failure and additional surgical procedures to restore blood flow. Many improvements have been made in stent design in order to reduce the likelihood of ISR, but none have eliminated the problem. Endothelial cells lining vessel walls transduce local hemodynamic loading in the stent vicinity, such as wall shear stress magnitude (WSS), into biochemical signals that lead to the progression of ISR. Hence, resolving the hemodynamics in the vicinity of the stent is crucial to reducing the rates of stent failure. The objective of the study is to address the problem of ISR by clearly elucidating the flow physics induced by stent implantation, accounting in particular for vessel curvature, by first considering idealized stent models, then progressing to an actual stent model. Stent designs are typically based upon data originating solely from studies of flow in straight vessels, which, once optimized for this configuration, may lead to suboptimal performance when placed in tortuous vessels. Previous stent studies have almost categorically neglected the effects of curvature on the flow physics, despite the fact that even extremely mild curvature changes the axial WSSM distribution within the vessel and induces the development of secondary flows, which alters the advection of chemicals released into the lumen. Using computational fluid dynamics (CFD) techniques, this study seeks to (i) determine the impact of stent strut amplitude and frequency on primary and secondary flow structures; (ii) determine the significance of the stent strut shape in the size of the stagnation zone; (iii) evaluate flow behavior in the transition region from smooth walled to stented vessel; and (iv) examine the collection of these effects in a full stent model geometry in a curved tube. This study takes a systematic approach, dissecting the impact of the stent first into simplified foundational components, then investigating each component and finally synthesizing the components into a full stent model with the long-term goal of optimizing stent design to reduce the rate of restenosis. As well, the study findings can aid in understanding the signal transduction mechanisms of the endothelial cells, which play a role in the development of ISR, and reduce the cardiovascular disease mortality rate by improving the clinical outcome of treatment procedures. Further, the study findings contribute to the fundamental understanding of flow in curved pipes with wall protrusions, the impact of the choice of the constitutive model of the fluid, and the hemodynamic environment in the vicinity of the stent.

Regensburg, Univ., Diss., 2009.

München, Techn. Univ., Diss., 2004.

München, Techn. Univ., Diss., 2004.

München, Techn. Univ., Diss., 2004.

Submitted by Edileide Reis (leyde-landy@hotmail.com) on 2015-04-11T01:22:27Z No. of bitstreams: 1 Hugo Fabiano Fernandes de Novaes.pdf: 538652 bytes, checksum: 783adecb7d1066d3ec1f2807d7abe6d5 (MD5) / Made available in DSpace on 2015-04-11T01:22:27Z (GMT). No. of bitstreams: 1 Hugo Fabiano Fernandes de Novaes.pdf: 538652 bytes, checksum: 783adecb7d1066d3ec1f2807d7abe6d5 (MD5) Previous issue date: 2012 / Em algumas situações, correlações entre diferentes estruturas do corpo humano poderiam auxiliar no planejamento de cirurgias intra-abdominais. O conhecimento do comprimento do ureter permitiria um planejamento cirúrgico pré-operatório, reduzindo gastos com exames; auxiliaria também na escolha do cateter duplo-J, reduzindo sintomatologia e morbidade, aumentando a aderência ao tratamento. Objetivo: Avaliar o comprimento ureteral em cadáveres adultos e analisar suas correlações com determinadas medidas antropométricas. Desenho do estudo: estudo transversal, descritivo e analítico. Materiais e métodos: realizamos mensuração do comprimento ureteral de cadáveres adultos, encaminhados para necropsia entre abril de 2009 e janeiro de 2012. Adicionalmente, coletamos as seguintes medidas: altura, distância ombro-punho, cotovelo-punho, xifo-umbilical, distância umbigo-púbis, distância xifo-púbica e distância entre espinhas ilíacas. Analisamos as correlações entre o comprimento ureteral e as demais medidas antropométricas. Resultados: Foram dissecados os ureteres de 115 cadáveres adultos no período entre abril/2009 e janeiro/2012. O comprimento ureteral médio não variou o gênero, nem com a estatura. Não foi encontrada correlação entre o comprimento ureteral e as medidas antropométricas pesquisadas na população geral analisada, bem como nos subgrupos analisados. Não se evidenciou diferenças significantes entre as medidas dos ureteres direito e esquerdo. Conclusões: Não há diferença no comprimento ureteral médio entre as diferentes faixas de altura e entre os gêneros masculino e feminino. Não há correlação significante entre o comprimento ureteral e as demais medidas antropométricas.

Angioplasty, or the use of rapidly deploying stents, is a common treatment for reopening narrowed vasculature often caused by atherosclerotic plaque. However, in-stent restenosis (ISR) induced by intimal hyperplasia is a common challenge to angioplasty. High impact stresses from current stent deployment processes have been linked to intimal hyperplasia; thus a stent that is gradually deployed over a longer period of time holds potential to mitigate these stresses. This work hypothesizes that resorbable polymeric links can be used as a triggering mechanism to enable repeatably controlled deployment of a compliant nitinol stent design with the eventual goal of reducing intimal hyperplasia. The aims of this work include the structured design process and design validation of a stent intended to meet this challenge. A structured design process was used to develop a multi-stage, gradually deploying nitinol stent in which PDLG (DL-lactide/Glycolide copolymer) bioresorbable links constrained specific mechanical cells within the stent geometry, thus limiting initial deployment to an intermediate diameter and allowing for secondary gradual deployment as the PDLG degraded via a combination of bioresorption and creep. A finite element analysis was carried out to design the link geometry to hold the stent at an intermediate stage (90% of final diameter) upon initial deployment, and enable a gradual secondary deployment phase lasting several minutes. Prototypes were then manufactured and the design was validated in a flow chamber mimicking the conditions of human blood flow and temperature. Using a camera and image processing methods, the diameter increase of the stents was tracked over time to characterize the secondary gradual deployment process of the stents. Results showed the links constrained the stents to an initial ~90% diameter upon initial deployment, followed by a gradual, secondary deployment with an average 63.2% rise time of 16.2 minutes. Creep was observed to be the primary driver of the gradual deployment, followed by subsequent bioresorption of the material. All prototypes exhibited gradual secondary deployment without any visible delamination of the bioresorbable links from the stent struts. Based on these findings it can be concluded our hypothesis has been demonstrated, and that a feasible gradually deploying stent design has been mechanically validated, preparatory to pre-clinical studies of its efficacy. Prior to clinical application, future in vivo work is needed to compare actual ISR rates with this stent design to other commonly used stent designs in preclinical trials. In addition, further preclinical work is needed to compare ISR rates through several stent design parameters such as initial deployment diameter, gradual deployment rate, final deployment diameter, and stent sizes to give insights into the optimal stent design. We anticipate that this gradually expanding stent design could reduce in-stent restenosis and improve clinical outcomes.

Endovascular repair of popliteal artery aneurysms has been used with increasing frequency in recent years. Advocates of the procedure claim a lower rate of complications, early return to work, no change in the quality of life, and long-term patency rates that are as favorable as those following open surgical repair. Unfortunately, data of only 1 prospective randomized study are available, and a recent meta-analysis showed a higher rate of early graft thromboses and more early reinterventions after endograft repair of popliteal artery aneurysms. Open, elective surgical repair with the vein graft has patency rates more than 90% in contemporary series. Current evidence only supports the use of stent grafts in those with high surgical risks and in the elderly.