Estudio comparativo de diferentes técnicas de implantación de stents en bifurcaciones coronarias

ResumenEl objetivo de este trabajo es el análisis comparativo de los cambios hemodinámicos locales producidos en una bifurcación coronaria por el implante de stents mediante 3 técnicas diferentes: stent simple en la arteria principal, stent simple en la arteria principal con orificio de comunicación con la arteria secundaria para el paso de un balón de inflado («kissing») y «culotte». Para ello se ha utilizado la geometría ideal de una bifurcación coronaria a 45 y 90°.En primer lugar se simularon los modelos en régimen estacionario mediante el código comercial ANSYS Fluent, y a continuación se validaron con las medidas experimentales tomadas en el laboratorio mediante velocimetría de imagen de partículas (particle image velocimetry [PIV]). Una vez obtenida una buena concordancia de resultados entre ambos estudios en régimen permanente, se abordó el flujo pulsátil. Los parámetros que se consideraron para comparar las diferentes técnicas en este régimen fueron los esfuerzos cortantes y la caída de presión promediados en el tiempo, así como el índice de esfuerzos cortantes oscilatorios (oscillatory shear index [OSI]). Las conclusiones finales fueron que el stent simple presenta los peores resultados, en términos de caída de presión, y la técnica «kissing», los mejores. Esto sería aplicable a los stents liberadores de fármacos, donde la reestenosis no es tan crucial como el restablecimiento del flujo sanguíneo. En cuanto al criterio basado en el valor menor de los esfuerzos cortantes (<0,4Pa) y un OSI elevado (>0,1), la técnica «culotte» presenta el peor comportamiento. Esto sería aplicable a los stents sin recubrimiento, en que la mejor opción sería el stent simple.AbstractThe objective of this work is to analyze the local hemodynamic changes caused in a coronary bifurcation by three different stenting techniques: simple stenting of the main vessel, simple stenting of the main vessel with kissing balloon in the side branch and culotte. To carry out this study an idealized geometry of a coronary bifurcation is used, and two bifurcation angles, 45° and 90°, are chosen as representative of the wide variety of real configurations. Both numerical simulations and experimental measurements are performed. First, steady simulations are carried out with the commercial code ANSYS Fluent, then, experimental measurements with PIV (Particle Image Velocimetry), obtained in the laboratory, are used to validate the numerical simulations. The steady computational simulations show a good overall agreement with the experimental data. Second, pulsatile flow is considered to take into account the transient effects. The time averaged wall shear stress, oscillatory shear index (OSI) and pressure drop obtained numerically are used to compare the behavior of the stenting techniques. As conclusions obtained, simple stenting technique shows the worst results in terms of pressure drop, and kissing the best ones. This criterion could be applied for DES (Drug Eluting Stents) where the restenosis is not as critical as the reestablishment of the blood flow. But considering the regions of low wall shear stress (<0.4Pa) and elevated OSI (>0.1), the culotte procedure shows the worst performance and the simple stent, the best. This could be applied to BMS (Bare Metal Stents)

A gradient-enhanced continuum damage model with application to fibre-reinforced tissues at finite strains

A non-local gradient-based damage formulation within a geometrically non-linear set- ting is presented. The hyperelastic constitutive response at local material point level is governed by a strain energy function which is additively composed by an isotropic neo-Hookean matrix and by an anisotropic fibre-reinforced material based on the model proposed by T. Gasser, R. Ogden, and G. Holzapfel

A gradient-enhanced continuum damage model for fibre-reinforced materials

Modelo de daño no local definido a materiales fibrados. Este modelo se aplica al estudio de problemas típicos en la biomecánica de los tejidos blandos, como las paredes arteriales

Economic crisis, immigrant women and changing availability of intimate partner violence services: a qualitative study of professionals&apos; perceptions in Spain

Economic crisis, immigrant women and changing availability of intimate partner violence services: a qualitative study of professionals¿ perceptions in Spain.. Abstract Introduction: Since 2008, Spain has been in the throes of an economic crisis. This recession particularly affects the living conditions of vulnerable populations, and has also led to a reversal in social policies and a reduction in resources. In this context, the aim of this study was to explore intimate partner violence (IPV) service providers&apos; perceptions of the impact of the current economic crisis on these resources in Spain and on their capacity to respond to immigrant women&apos;s needs experiencing IPV. Methods: A qualitative study was performed based on 43 semi-structured in-depth interviews to social workers, psychologists, intercultural mediators, judges, lawyers, police officers and health professionals from different services dealing with IPV (both, public and NGO&apos;s) and cities in Spain (Barcelona, Madrid, Valencia and Alicante) in 2011. Transcripts were imported into qualitative analysis software (Atlas.ti), and analysed using qualitative content analysis. Results: We identified four categories related to the perceived impact of the current economic crisis: a) &quot;Immigrant women have it harder now&quot;, b) &quot;IPV and immigration resources are the first in line for cuts&quot;, c) &quot; Fewer staff means a less effective service&quot; and d) &quot;Equality and IPV policies are no longer a government priority&quot;. A cross-cutting theme emerged from these categories: immigrant women are triply affected; by IPV, by the crisis, and by structural violence. International journal for equity in health, Conclusion: The professionals interviewed felt that present resources in Spain are insufficient to meet the needs of immigrant women, and that the situation might worsen in the future

Evaluación de acciones explosivas sobre estructuras de hormigón armado mediante elementos finitos

Explosive phenomena on concrete structures have catastrophic effects in many instances despite its reduced occurrence. The civil buildings are usually not designed to withstand this type of dynamic load, so a methodology to analyze the structural response on blast loads is recommended. This paper studies the behavior of reinforced concrete frame structures against these actions by lagrangian finite elements method with explicit time integration. Finite element models of segregated concrete and rebar are used to make possible the study of structure parts as columns and slabs, but is not possible to use these detailed models in complete structures because of excessive computational costs. Shell and beam elements models properly calibrated are needed to obtain a similar response. Conclusions and practical recommendations are provided for the use and calibration of models and realistic simulations.El fenómeno de explosión sobre estructuras de hormigón tiene efectos en muchos casos catastróficos a pesar de su reducida frecuencia. Las edificaciones civiles no suelen estar diseñadas para resistir este tipo de solicitación dinámica, por lo que conviene disponer de una metodología que permita analizar los efectos de las explosiones sobre las mismas. Este trabajo estudia el comportamiento de las estructuras reticuladas de hormigón armado frente a estas acciones, mediante métodos numéricos de elementos finitos lagrangianos con integración explícita en el tiempo. Se analizan de forma realista partes de la estructura como columnas y forjados usando modelos con hormigón y armaduras de forma segregada, pero las limitaciones computacionales los hacen inviables para estructuras completas. Se proponen modelos de elementos lámina y viga debidamente calibrados para obtener una respuesta similar. Se obtienen conclusiones para el uso y calibración de modelos y simulaciones realistas de edificios completos para estudios de seguridad

Mechanical characterization of the human thoracic descending aorta Experiments and modelling

This work presents experiments and modelling aimed at characterising the passive mechanical behaviour of the human thoracic descending aorta. To this end, uniaxial tension and pressurisation tests on healthy samples corresponding to newborn, young and adult arteries are performed. Then, the tensile measurements are used to calibrate the material parameters of the Holzapfel constitutive model. This model is found to adequately adjust the material behaviour in a wide deformation range; in particular, it captures the progressive stiffness increase and the anisotropy due to the stretching of the collagen fibres. Finally, the assessment of these material parameters in the modelling of the pressurisation test is addressed. The implication of this study is the possibility to predict the mechanical response of the human thoracic descending aorta under generalised loading states like those that can occur in physiological conditions and/or in medical device application

Hemodynamic performance of different stent strategies for coronary bifurcations. Evaluation with a mathematical model

Purpose: Best percutaneous treatment strategy for lesions in coronary bifurcations is an ongoing subject of debate. There is limited data that analyses the effect of the different bifurcation strategies on coronary flow. Our aim is to evaluate the influence of different bifurcation stenting strategies on hemodynamic parameters, both in the main vessel (MV) and side branch (SB)

Adolescent pregnancies and girls' sexual and reproductive rights in the amazon basin of Ecuador: an analysis of providers' and policy makers' discourses

<p>Abstract</p> <p>Background</p> <p>Adolescent pregnancies are a common phenomenon that can have both positive and negative consequences. The rights framework allows us to explore adolescent pregnancies not just as isolated events, but in relation to girls' sexual and reproductive freedom and their entitlement to a system of health protection that includes both health services and the so called social determinants of health. The aim of this study was to explore policy makers' and service providers' discourses concerning adolescent pregnancies, and discuss the consequences that those discourses have for the exercise of girls' sexual and reproductive rights' in the province of Orellana, located in the amazon basin of Ecuador.</p> <p>Methods</p> <p>We held six focus-group discussions and eleven in-depth interviews with 41 Orellana's service providers and policy makers. Interviews were transcribed and analyzed using discourse analysis, specifically looking for interpretative repertoires.</p> <p>Results</p> <p>Four interpretative repertoires emerged from the interviews. The first repertoire identified was "sex is not for fun" and reflected a moralistic construction of girls' sexual and reproductive health that emphasized abstinence, and sent contradictory messages regarding contraceptive use. The second repertoire -"gendered sexuality and parenthood"-constructed women as sexually uninterested and responsible mothers, while men were constructed as sexually driven and unreliable. The third repertoire was "professionalizing adolescent pregnancies" and lead to patronizing attitudes towards adolescents and disregard of the importance of non-medical expertise. The final repertoire -"idealization of traditional family"-constructed family as the proper space for the raising of adolescents while at the same time acknowledging that sexual abuse and violence within families was common.</p> <p>Conclusions</p> <p>Providers' and policy makers' repertoires determined the areas that the array of sexual and reproductive health services should include, leaving out the ones more prone to cause conflict and opposition, such as gender equality, abortion provision and welfare services for pregnant adolescents. Moralistic attitudes and sexism were present - even if divergences were also found-, limiting services' capability to promote girls' sexual and reproductive health and rights.</p