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1
Kattach, Hassan. "Blood pressure control in aortic stenosis". Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526473.
Testo completo
2
Andresen, Jean M. "Aortic Baroreceptor Reflex Control of Blood Pressure: Effect of Fitness". Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc500922/.
Testo completoAbstract (sommario):
Aortic baroreflex (ABR) control of blood pressure was examined in 7 untrained (UT) and 8 endurance exercise trained (EET) young men. ABR control of blood pressure was determined during a steady state phenylephrine infusion to increase mean arterial pressure 10-15 mmHg, combined with positive neck pressure to counteract the increased carotid sinus transmural pressure, and low levels of lower body negative pressure to counteract the increased central venous pressure. Functioning alone, the ABR was functionally adequate to control blood pressure. However, ABR control of HR was significantly diminished in the EET subjects due solely to the decrease in the ABR sensitivity. The persistent strain from an increased stroke volume resulting from endurance exercise training could be the responsible mechanism.
3
Lantz, Jonas. "On Aortic Blood Flow Simulations : Scale-Resolved Image-Based CFD". Doctoral thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-85682.
Testo completoAbstract (sommario):
This thesis focuses on modeling and simulation of the blood flow in the aorta, the largest artery in the human body. It is an accepted fact that abnormal biological and mechanical interactions between the blood flow and the vessel wall are involved in the genesis and progression of cardiovascular diseases. The transport of low-density lipoprotein into the wall has been linked to the initiation of atherosclerosis. The mechanical forces acting on the wall can impede the endothelial cell layer function, which normally acts as a barrier to harmful substances. The wall shear stress (WSS) affects endothelial cell function, and is a direct consequence of the flow field; steady laminar flows are generally considered atheroprotective, while the unsteady turbulent flow could contribute to atherogenesis. Quantification of regions with abnormal wall shear stress is therefore vital in order to understand the initiation and progression of atherosclerosis.However, flow forces such as WSS cannot today be measured with significant accuracy using present clinical measurement techniques. Instead, researches rely on image-based computational modeling and simulation. With the aid of advanced mathematical models it is possible to simulate the blood flow, vessel dynamics, and even biochemical reactions, enabling information and insights that are currently unavailable through other techniques. During the cardiac cycle, the normally laminar aortic blood flow can become unstable and undergo transition to turbulence, at least in pathological cases such as coarctation of the aorta where the vessel is locally narrowed. The coarctation results in the formation of a jet with a high velocity, which will create the transition to turbulent flow. The high velocity will also increase the forces on the vessel wall. Turbulence is generally very difficult to model, requiring advanced mathematical models in order to resolve the flow features. As the flow is highly dependent on geometry, patient-specific representations of the in vivo arterial walls are needed, in order to perform an accurate and reliable simulation. Scale-resolving flow simulations were used to compute the WSS on the aortic wall and resolve the turbulent scales in the complex flow field. In addition to WSS, the turbulent flow before and after surgical intervention in an aortic coarctation was assessed. Numerical results were compared to state-of-the-art magnetic resonance imaging measurements. The results agreed very well, suggesting that that the measurement technique is reliable and could be used as a complement to standard clinical procedures when evaluating the outcome of an intervention.The work described in the thesis deals with patient-specific flows, and is, when possible, validated with experimental measurements. The results provide new insights to turbulent aortic flows, and show that image-based computational modeling and simulation are now ready for clinical practice.
4
Kordzadeh, Ali. "Blood and blood component transfusion on 30-day mortality and morbidity of infra-renal ruptured abdominal aortic aneurysm". Thesis, Anglia Ruskin University, 2017. http://arro.anglia.ac.uk/702581/.
Testo completoAbstract (sommario):
This thesis for the first time in the literature, through a single cohort (n=82), systematic review and meta-aggregation of the data, has identified that the majority (>85%) of ruptured abdominal aortic aneurysm (rAAA) do not present with coagulopathy. In addition, the thesis for the first time, through a retro and prospective cohort study, has demonstrated that the hemostatic resuscitation protocols derived from military and civilian trauma for the correction of coagulopathy with a blood product ratio of one unit of packed red blood cell to one unit of fresh frozen plasma to one pool of platelet (1:1:1), contributes to increased postoperative (30-day) morbidity and mortality, especially thrombotic complications. This was attributed to different baseline demographics, pathophysiology and coagulation status. Through a comparative study, the thesis then confirms that such transfusion practice not only contributes to adverse outcomes, but also has no impact on final coagulation status of rAAAs. In addition, through a retro and prospective cohort study, a novel hematological marker (neutrophil to lymphocyte ratio) (NLR) was identified as an independent predictor of morbidity in rAAAs. This thesis was set on the background of significant research into all factors that could contribute to pathogenesis, inhibition and progression of rAAAs. This thesis concludes that the use of additional blood products (fresh frozen plasma and platelet) in hemostatic resuscitation of ruptured abdominal aortic aneurysms alongside packed red blood cell is not evidence based and a single protocol derived from one cohort (military and civilian trauma) of patients does not apply to another. The use of additional products in ruptured abdominal aortic aneurysms should be tailored to the individual hematological and clinical requirements and not as a part of a set transfusion ratio (1:1:1). This thesis has resulted in a change of practice and has created a platform for further search of the optimal transfusion protocol in this cohort of patients.
5
Kordzadeh, Ali. "Blood and blood component transfusion on 30-day mortality and morbidity of infra-renal ruptured abdominal aortic aneurysm". Thesis, Anglia Ruskin University, 2017. https://arro.anglia.ac.uk/id/eprint/702581/1/Kordzadeh_2017.pdf.
Testo completoAbstract (sommario):
This thesis for the first time in the literature, through a single cohort (n=82),
systematic review and meta-aggregation of the data, has identified that the
majority (>85%) of ruptured abdominal aortic aneurysm (rAAA) do not present
with coagulopathy. In addition, the thesis for the first time, through a retro and
prospective cohort study, has demonstrated that the hemostatic resuscitation
protocols derived from military and civilian trauma for the correction of
coagulopathy with a blood product ratio of one unit of packed red blood cell to
one unit of fresh frozen plasma to one pool of platelet (1:1:1), contributes to
increased postoperative (30-day) morbidity and mortality, especially thrombotic
complications. This was attributed to different baseline demographics,
pathophysiology and coagulation status. Through a comparative study, the
thesis then confirms that such transfusion practice not only contributes to
adverse outcomes, but also has no impact on final coagulation status of rAAAs.
In addition, through a retro and prospective cohort study, a novel hematological
marker (neutrophil to lymphocyte ratio) (NLR) was identified as an independent
predictor of morbidity in rAAAs. This thesis was set on the background of
significant research into all factors that could contribute to pathogenesis,
inhibition and progression of rAAAs.
This thesis concludes that the use of additional blood products (fresh frozen
plasma and platelet) in hemostatic resuscitation of ruptured abdominal aortic
aneurysms alongside packed red blood cell is not evidence based and a single
protocol derived from one cohort (military and civilian trauma) of patients does
not apply to another. The use of additional products in ruptured abdominal aortic
aneurysms should be tailored to the individual hematological and clinical
requirements and not as a part of a set transfusion ratio (1:1:1). This thesis has
resulted in a change of practice and has created a platform for further search of
the optimal transfusion protocol in this cohort of patients.
6
McGregor, Brian. "The left ventricle, aortic valve, and arterial tree - a fresh engineering perspective". Thesis, University of Ulster, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339346.
Testo completo
7
Camacho, Fernando Graduate School of Biomedical Engineering Faculty of Engineering UNSW. "Statistical analysis of central aortic blood pressure parameters derived from the peripheral pulse". Awarded by:University of New South Wales. Graduate School of Biomedical Engineering, 2006. http://handle.unsw.edu.au/1959.4/26215.
Testo completoAbstract (sommario):
With the rise in prevalence of cardiovascular (CV) disease, risk stratification is becoming increasingly important. Accurate characterization of the CV system is required, for which central aortic blood pressure (BP) parameters form an integral part. However, invasive measurement of central aortic BP parameters (aP) is difficult. Therefore, non-invasive methods to estimate aP from the radial pressure pulse (rPulse) have been proposed. To analyze accuracy of estimated aP (aPhat) and applicability in risk stratification and diagnosis, this study presents: (1) a novel representation of the rPulse with minimal loss of information, (2) a framework for strict definition and statistical analysis of aPhat, and (3) a dynamic analysis of effects of mean BP (MP) and heart rate (HR) in the rPulse shape. Methods: (1) 2671 rPulse s measured by applanation tonometry were represented using the first eight principal components (PC) scores after standard PC transformation. rPulse shapes were compared in three subpopulations. (2) The concept of "estimation option" (EO) for aP estimation was presented. A framework for strict definition of aPhat and the comparison of EOs was proposed, and 7 different EOs compared. (3) A sequence of rPulse s was analyzed during soft exhalation maneuver (SEM) %, a mild Valsalva type maneuver, in eight healthy subjects. Radial BP and respiration pressure were continuously measured. The effects of MP and HR in the rPulse parameters were analyzed by standard linear regression for each subject. Results: (1) PC representation of the rPulse improves accuracy of the estimation of aPhat compared with the simple use of rPulse parameters. Subpopulations have distinctive rPulse shapes. (2) No single EO was better for the estimation of all aPhat. Inclusion of MP improves estimation accuracy. Despite further improvement when rPulse is included, the general transfer function EO is a biased estimator. (3) The dynamic analysis of the rPulse provides information of the effects of MP and HR in the rPulse not available in static analysis. The effects were specific for each individual and different from the results obtained from a general population. Conclusions: For accurate CV risk stratification, future studies should include a dynamic measurement of calibrated radial pressure pulse during SEM maneuver. Risk analysis and diagnosis should be based on representations of the rPulse with minimum loss of information. aPhat should be used for better understanding of the underlying physiological principles.
8
Cheng, Zhuo. "Analysis of blood flow in patient-specific models of type B aortic dissection". Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9178.
Testo completoAbstract (sommario):
Aortic dissection is the most common acute catastrophic event affecting the aorta. The majority of patients presenting with an uncomplicated type B dissection are treated medically, but 25% of these patients develop subsequent dilatation and aortic aneurysm formation. The reasons behind the long‐term outcomes of type B aortic dissection are poorly understood. As haemodynamic factors have been involved in the development and progression of a variety of cardiovascular diseases, the flow phenomena and environment in patient‐specific models of type B aortic dissection have been studied in this thesis by applying computational fluid dynamics (CFD) to in vivo data. The present study aims to gain more detailed knowledge of the links between morphology, flow characteristics and clinical outcomes in type B dissection patients. The thesis includes two parts of patient‐specific study: a multiple case cross‐sectional study and a single case longitudinal study. The multiple cases study involved a group of ten patients with classic type B aortic dissection with a focus on examining the flow characteristics as well as the role of morphological factors in determining the flow patterns and haemodynamic parameters. The single case study was based on a series of follow‐up scans of a patient who has a stable dissection, with an aim to identify the specified haemodynamic factors that are associated with the progression of aortic dissection. Both studies were carried out based on computed tomography images acquired from the patients. 4D Phase‐contrast magnetic resonance imaging was performed on a typical type B aortic dissection patient to provide detailed flow data for validation purpose. This was achieved by qualitative and quantitative comparisons of velocity‐encoded images with simulation results of the CFD model. The analysis of simulation results, including velocity, wall shear stress and turbulence intensity profiles, demonstrates certain correlations between the morphological features and haemodynamic factors, and also their effects on long‐term outcomes of type B aortic dissections. The simulation results were in good agreement with in vivo MR flow data in the patient‐specific validation case, giving credence to the application of the computational model to the study of flow conditions in aortic dissection. This study made an important contribution by identifying the role of certain morphological and haemodynamic factors in the development of type B aortic dissection, which may help provide a better guideline to assist surgeons in choosing optimal treatment protocol for individual patient.
9
Wolowczyk, Leszek. "Acute normovolaemic haemodilution in abdominal aortic aneurysm repair : the effect on systemic inflammatory response and clinical outcome". Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271910.
Testo completo
10
Kumar, Hemant, University of Western Sydney e of Science Technology and Environment College. "Software analytical tool for assessing cardiac blood flow parameters". THESIS_FSTA_XXX_Kumar_H.xml, 2001. http://handle.uws.edu.au:8081/1959.7/392.
Testo completoAbstract (sommario):
Introduction of Doppler ultrasound techniques into the Intensive Care setting has revolutionised the way haemodynamic status is monitored in the critically ill. However, in order to increase the usefulness of these techniques, the Doppler signal and its spectrum need to be further analysed in ways to facilitate a better clinical response. Extensive processing of the Doppler spectrum on Diagnostic ultrasound machines is limited by the real time performance considerations. It was therefore proposed that the spectral information from these systems be extracted off-line and full set of analytical tools be made available to evaluate this information. This was achieved by creating an integrated and modular software tool called Spectron, which was intended as an aid in the overall management of the patients. The modular nature of Spectron was intended to ensure that new analytical tools and techniques could be easily added and tested. The software provides its users with considerable latitude in choosing various data acquisition and analysis parameters to suit various clinical situations and patient requirements. Spectron was developed under the Windows environment to provide a user friendly interface and to address a range of programming problems such as memory management and the size of the colour palettes. Spectron is able to detect the maximal velocities and compute the mean and median velocities. Relative increases in maximal velocities in cardiac blood flows after the administration of inotropic drugs have been shown in the pilot studies that were conducted. Spectron is able to help in obtaining estimates of the aortic blood flows and in other applications such measuring vascular impedance. Stenotic blood flows can be detected by using the spectral broadening index and blood flow characteristics can be studied by using various blood flow indices. Thus, this project attempted to help in patient management by providing clinicians with a range of blood flow parameters and has succeeded in meeting its objective to a large extentMaster of Engineering (Hons)
11
da, Cunha Daise Nunes Queiroz. "Properties of flow through the ascending aorta in boxer dogs with mild aortic stenosis momentum, energy, Reynolds number, Womersley's, unsteadiness parameter, vortex shedding, and transfer function of oscillations from aorta to thoracic wall /". Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1243910694.
Testo completo
12
TORRES, DIEGO FERNANDO CELIS. "NUMERICAL STUDY OF THE INFLUENCE OF TILT VALVE ANGLE ON BLOOD FLOW IN AN AORTIC MODEL". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=32320@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
A substituição de válvula aórtica por cateter (Transcatheter Aortic Valve Replacement, TAVR) tornou-se uma poderosa alternativa para pacientes com estenose aórtica e com alto risco de serem submetidos à cirurgia tradicional de peito aberto. O conhecimento da distribuição da pressão, bem como a tensão cisalhante na superfície da aorta podem ajudar a identificar regiões críticas, onde o processo de remodelamento da aorta pode ocorrer. O objetivo do presente trabalho é avaliar numericamente a influência do posicionamento do orifício da válvula protética no campo de escoamento. O estudo foi realizado com base em um paciente submetido a TAVR. Um modelo 3D foi gerado a partir de angiotomografia e de segmentação de imagens da aorta. Dados experimentais obtidos anteriormente na mesma geometria indicaram que o fluxo do jato através da válvula de entrada é de natureza turbulenta. O escoamento foi determinado numericamente com o software comercial FLUENT. A turbulência foi modelada com o modelo de dois equações k-omega SST. Para representar um fluxo pulsátil, foram impostos diferentes fluxo de massa na entrada da válvula. Para todas as vazões investigadas, obteve-se um padrão de escoamento semelhante. Mostrou-se que uma pequena variação dos ângulos de inclinação pode modificar a natureza do fluxo, deslocando a posição dos vórtices e alterando a localização das regiões de alta tensão de cisalhamento, assim como de alta pressão, na superfície interna da aorta. Mostrou-se também que um aumento da intensidade da turbulência na entrada diminui os valores de tensão cisalhante e de pressão nas paredes da aorta. Essas características hemodinâmicas podem ser relevantes no processo de remodelação aórtica e os estresses mecânicos podem influenciar na durabilidade da prótese valvular.
Transcatheter Aortic Valve Replacement (TAVR) has become a powerful alternative for patients with aortic stenosis and a high surgical risk to face a traditional open chest surgery. The knowledge of the pressure distribution as well as shear stress at the aortic surface may help identify critical regions, where aortic remodeling process may occur. The purpose of the present work is to evaluate numerically the influence of the positioning of the prosthetic valve orifice in the flow field. The study was carried out on the basis of a particular patient who had undergone a TAVR. A 3D model was generated from computed tomography angiography and image segmentation of the aorta. Experimental data previously obtained in the same geometry indicated that the jet flow through the inlet valve is turbulent flow. The flow field was numerically determined with the commercial software Fluent. The turbulence was modeled with the two-equation k-omega SST model. To represent a pulsatile flow, different mass flow rates were imposed at the inlet valve. Similar flow pattern was observed for all flow rates investigated. It was shown that small variations of the tilt angle can modify the nature of the flow, displacing the position of the vortices and altering the location of high shear stress, as well as high pressure, at the aortic inner wall. It was also shown that an increase of the turbulent intensity at the entrance decreases the values of shear stress and pressure on the walls. These hemodynamic features may be relevant in the aortic remodeling process and the mechanical stresses may influence the durability of the valve prosthesis.
13
Hazer, Dilana [Verfasser]. "Automated Patient-Specific Modeling of Blood Flow and Vessel Wall Mechanics in Aortic Pathology / Dilana Hazer". München : Verlag Dr. Hut, 2010. http://d-nb.info/100948530X/34.
Testo completo
14
Burbridge, Michael Frank. "The rat aortic ring model of angiogenesis in vitro as an assay for angiogenic modulators, the role of the matrix metalloproteinases in vessel formation". Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367795.
Testo completo
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Li, Longchuan. "Numerical and experimental study of three imaging advancements in phase contrast magnetic resonance imaging". Birmingham, Ala. : University of Alabama at Birmingham, 2007. http://www.mhsl.uab.edu/dt/2007p/li.pdf.
Testo completo
16
Lacroix-Desmazes, Sebastien. "Influence of flow environment on the production and secretion of metalloproteinases and urokinase-type plasminogen activator by cultured bovine aortic endothelial cells". Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15826.
Testo completo
17
Celestin, Carey Jr. "Computational Fluid Dynamics Applied to the Analysis of Blood Flow Through Central Aortic to Pulmonary Artery Shunts". ScholarWorks@UNO, 2015. http://scholarworks.uno.edu/td/1972.
Testo completoAbstract (sommario):
This research utilizes CFD to analyze blood flow through pathways representative of central shunts, commonly used as part of the Fontan procedure to treat cyanotic heart disease. In the first part of this research, a parametric study of steady, Newtonian blood flow through parabolic pathways was performed to demonstrate the effect that flow pathway curvature has on wall shear stress distribution and flow energy losses. In the second part, blood flow through two shunts obtained via biplane angiograms is simulated. Pressure boundary conditions were obtained via catheterization. Results showed that wall shear stresses were of sufficient magnitude to initiate platelet activation, a precursor for thrombus formation. Steady results utilizing time-averaged boundary conditions showed excellent agreement with the time-averaged results obtained from pulsatile simulations. For the points of interest in this research, namely wall shear stress distribution and flow energy loss, the Newtonian viscosity model was found to yield acceptable results.
18
Morris, Ray William. "Changes in CW-Doppler aortic blood flow responses with passive tilting in normo- and borderline hypertensive men". Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/44126.
Testo completoAbstract (sommario):
Continuous-wave (CW) Doppler echocardiographic responses to passive tilting were measured in 39 men using the following protocol: standing; supine; +20° head-up; supine; â 20° head-down. Twenty of the subjects were normotensive (NTN) and the rest were borderline hypertensive (B-HTN) according to prior medical diagnosis. Doppler recordings of blood flow for aortic peak velocity (Pkv), peak acceleration (PkA), and stroke velocity integral (SVI) were taken after 15 minutes in each posture. A skilled technician, using the measurement procedures recommended by the instrument manufacturer, positioned the handâ he1d probe at the supra-sternal notch during recording. For both NTN and Bâ HTN groups, Pkv and PkA were unaffected by the imposed postural changes. The SVI was significantly altered (P<0.05) by postural stress, with the NTN group generally showing greater changes than the Bâ HTNs. The standing-to-supine postural change was associated with the largest change in SVI: NTN = 8.0 to 10.7 cm (+34%) and B-HTN = 7.6 to 8.8 cm (+15%). These results were interpreted as follows (1) SVI appears to be sensitive to changes in ventricular pre-load, while PkA and Pkv are not; (2) SVI changes with passive tilting follow the patterns expected for change in ventricular stroke volume and; (3) attenuated SVI responses to postural tilting may suggest impairment in cardiovascular regulation peculiar to individuals at risk for hypertension.Master of Science
19
Mercer, Kevin Graham. "Surgery for abdominal aortic aneurysm : the systemic inflammatory response and the relationship of blood transfusion to inflammatory complications". Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403029.
Testo completo
20
Staughton, Tracey Jane. "Transport properties of the rabbit aortic wall near branches : possible influences of nitric oxide synthesis and blood flow". Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326753.
Testo completo
21
Grytsan, Andrii. "Abdominal aortic aneurysm inception and evolution - A computational model". Doctoral thesis, KTH, Biomekanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-197289.
Testo completoAbstract (sommario):
Abdominal aortic aneurysm (AAA) is characterized by a bulge in the abdominal aorta. AAA development is mostly asymptomatic, but such a bulge may suddenly rupture, which is associated with a high mortality rate. Unfortunately, there is no medication that can prevent AAA from expanding or rupturing. Therefore, patients with detected AAA are monitored until treatment indication, such as maximum AAA diameter of 55 mm or expansion rate of 1 cm/year. Models of AAA development may help to understand the disease progression and to inform decision-making on a patient-specific basis. AAA growth and remodeling (G&R) models are rather complex, and before the challenge is undertaken, sound clinical validation is required. In Paper A, an existing thick-walled model of growth and remodeling of one layer of an AAA slice has been extended to a two-layered model, which better reflects the layered structure of the vessel wall. A parameter study was performed to investigate the influence of mechanical properties and G&R parameters of such a model on the aneurysm growth. In Paper B, the model from Paper A was extended to an organ level model of AAA growth. Furthermore, the model was incorporated into a Fluid-Solid-Growth (FSG) framework. A patient-specific geometry of the abdominal aorta is used to illustrate the model capabilities. In Paper C, the evolution of the patient-specific biomechanical characteristics of the AAA was investigated. Four patients with five to eight Computed Tomography-Angiography (CT-A) scans at different time points were analyzed. Several non-trivial statistical correlations were found between the analyzed parameters. In Paper D, the effect of different growth kinematics on AAA growth was investigated. The transverse isotropic in-thickness growth was the most suitable AAA growth assumption, while fully isotropic growth and transverse isotropic in-plane growth produced unrealistic results. In addition, modeling of the tissue volume change improved the wall thickness prediction, but still overestimated thinning of the wall during aneurysm expansion.Bukaortaaneurysm (AAA) kännetecknas av en utbuktning hos aortaväggen i buken. Tillväxt av en AAA är oftast asymtomatisk, men en sådan utbuktning kan plö̈tsligt brista, vilket har hög dödlighet. Tyvärr finns det inga mediciner som kan förhindra AAA från att expandera eller brista. Patienter med upptä̈ckt AAA hålls därför under uppsikt tills operationskrav är uppnådda, såsom maximal AAA-diameter på 55 mm eller expansionstakt på 1 cm/år. Modeller för AAA-tillväxt kan bidra till att öka förståelsen för sjukdomsförloppet och till att förbättra beslutsunderlaget på en patientspecifik basis. AAA modeller för tillväxt och strukturförändring (G&R) är ganska komplicerade och innan man tar sig an denna utmaning krävs de god klinisk validering. I Artikel A har en befintlig tjockväggig modell för tillväxt av ett skikt av en AAA-skiva utö̈kats till en två-skiktsmodell. Denna modell återspeglar bättre den skiktade strukturen hos kärlväggen. Genom en parameterstudie undersö̈ktes påverkan av mekaniska egenskaper och G&R-parametrar hos en sådan modell för AAA-tillväxt. I Artikel B utvidgades modellen från Artikel A till en organnivå-modell för AAA-tillväxt. Vidare inkorporerades modellen i ett “Fluid–Solid–Growth” (FSG) ramverk. En patientspecifik geometri hos bukaortan användes för att illustrera möjligheterna med modellen. I Artikel C undersöktes utvecklingen av patientspecifika biomekaniska egenskaper hos AAA. Fyra patienter som skannats fem till åtta gånger med “Computed Tomography-Angiography” (CT-A) vid olika tillfällen analyserades. Flera icke triviala statistiska samband konstaterades mellan de analyserade parametrarna. I Artikel D undersöktes effekten av olika tillväxt-kinematik för AAA tillväxt. En modell med transversellt-isotrop-i-tjockleken-tillväxt var den bäst lämpade för AAA tillväxt, medans antagandet om fullt-isotrop-tillväxt och transversellt-isotrop-i-planet-tillväxt producerade orimliga resultat. Dessutom gav modellering av vävnadsvolymsförändring ett förbättrat väggtjockleks resultat men en fortsatt överskattning av väggförtunningen under AAA-expansionen.
QC 20161201
22
Kekatpure, Avantika. "Gender differences in aortic endothelial function in a rat model of streptozotocin-induced diabetes : possible role of superoxide and cyclooxygenase". Scholarly Commons, 2009. https://scholarlycommons.pacific.edu/uop_etds/737.
Testo completoAbstract (sommario):
Objectives: To date little is known of the interaction between diabetes and sex hormones in the vasculature. A number of studies suggest that premenopausal diabetic women loose their gender based cardiovascular protection. However, there is insufficient evidence to explain the mechanism underlying the loss of this gender based cardioprotection in premenopausal diabetic women. The objectives of this study were to investigate whether there is a gender difference in the aortic endothelial function in · streptozotocin (STZ, 58 mg/kg, iv)-induced diabetic rats, and the potential role of superoxide and cyclooxygenase (COX) metabolites in diabetes-induced vascular dysfunction.
23
Schurtz-Bouissou, Camille. "Relations entre la variabilité tensionnelle et la rigidité des gros troncs artériels chez le rat : Etudes dans trois modèles expérimentaux". Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST0070.
Testo completoAbstract (sommario):
La rigidité artérielle ayant une valeur prédictive forte et indépendante d'évènements cardiovasculaires, nous émettons l'hypothèse que l'accumulation de variations de contraintes hémodynamiques altère la fonction et la structure des gros troncs artériels, indépendamment du niveau de pression artérielle. Nous avons donc mesuré l'impact de la variabilité tensionnelle sur la rigidité et la structure artérielles dans différents modèles de variabilité tensionnelle chez le rat.Chez le rat barodénervé et le rat sympathectomisé par la guanéthidine, 2 modèles de variabilité tensionnelle à court terme, une augmentation de la rigidité artérielle est associée à des altérations tissulaires différentes. En effet chez les rats barodénervés, une hypertrophie aortique est couplée à une augmentation du collagène et des attachements cellule-matrice (fibronectine et intégrine α5). Au contraire, chez les rats sympathectomisés, une hypotrophie vasculaire est associée à une diminution de l'élastine et une augmentation des attachements via l'intégrine αv.Nous avons ensuite créé, caractérisé et validé un modèle de variabilité tensionnelle à long terme, le rat spontanément hypertendu traité de façon discontinue par un antihypertenseur. Le traitement discontinu réduit la pression artérielle systolique tout en augmentant isolément la variabilité tensionnelle à long terme. La rigidité artérielle, élevée sous traitement discontinu, est associée à une hypertrophie vasculaire avec augmentation des attachements (fibronectine et intégrine αv) et sans modification du rapport élastine/collagène.En conclusion, l'élevation de variabilité tensionnelle engendre de la rigidité artérielle, et ce à pression artérielle constante. Les altérations structurales dans les modèles de variabilité tensionnelle étudiés impliquent des mécanismes différents reposant sur des modifications des relations cellule-matrice, mettant en jeu la fibronectine et les intégrines α5 et αvArterial stiffness is nowadays accepted as a strong and independent predictor of cardiovascular disease. We hypothesized that increased blood pressure variability (BPV) may lead to arterial damage, independently of the blood pressure level. We thus aimed investigating the relationship between BPV and arterial stiffness and composition of the aorta in different rat models of increased BPV.In a first study performed in two models of increased short term BPV, sinoaortic denervated and chemically sympathectomized rats, an increase in wall stiffness was associated with different modifications of cell-extracellular matrix adhesion. Indeed in sinoaortic denervated rats, increased media cross-sectional area was coupled with an increased collagen content and muscle cell attachments to its cell-extracellular matrix (fibronectin and its α5β1 integrin). In contrast, chemically sympathectomized rats were characterized by a reduced media cross-sectional area associated to a reduction of elastin content and upregulation of αvβ3 integrin.In a second study, we created, characterized and validated a new experimental model of long term BPV by discontinuously treating spontaneously hypertensive rats with valsartan. Discontinuous treatment reduced systolic blood pressure level but increased long term BPV. In addition, this treatment regimen failed to reduce arterial stiffness and induced a vascular hypertrophy without modification of elastin/collagen ratio. Discontinuous treatment also highly increased vascular fibronectin in parallel to αv integrin.In conclusion, a rise of both short- and long-term BPV leads to an increase in arterial stiffness, independently of blood pressure level. The structural changes at the origin of this increase in arterial rigidity involve different mechanisms, in which fibronectin and integrin α5 and αv play a key role
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Wetherill, Lindsay D. "Reproducibility of a continuous-wave Doppler ultrasound system for assessment of ascending aortic blood flow responses during graded exercise testing with healthy individuals". Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/80102.
Testo completoAbstract (sommario):
Continuous-wave (CW) Doppler recordings of ascending aortic maximal blood flow acceleration (PkA), maximal velocity (PkV) and systolic velocity integral (SVI) were taken at each stage of a graded exercise treadmill test on two separate days with 30 physically active adult males. Signals were measured (Quinton Exerdop) for all cardiac cycles in the 3rd minute of each stage using a hand-held probe positioned at the suprasternal notch. A dedicated microcomputer, programmed to select "valid" beats on the basis of value consistency in the sample set, determined the acceptability of signals. No significant differences were found between the three trial means within each stage on either day for PkA, PkV or SVI. Significant (p <.01) intraclass reliability estimates ranged from r = 0.89 to 0.97 (Pk.A), r = 0.90 to 0.98 (PkV) and r = 0.85 to 0.95 (SVI) . Coefficients of variation were calculated at each stage to estimate the relative consistency of each measure. A gradual reduction of the coefficient of variation was observed for each blood flow measure between stages one and four. The test-retest (between days) reliability coefficients for PkA, PkV and SVI for stages one to four ranged between r = 0.51 to 0.78 (P <.004), but correlations for the pre-exercise baseline and stages five and six were lower. These results indicate that (1) PkA, PkV and SVI demonstrate greater measurement stability within each stage of a graded exercise test than is the case between separate days of measurement at the same stage; and (2) there is modest day-to-day response stability for clinical testing with the Doppler parameter of PkV. Reliability/stability was best in exercise stages which encompass the speed and grade range of 45.0 m•min⁻¹/10%. - 111.7 m•min⁻¹/14%, i.e., those in which all subjects can walk.Master of Science
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Wilson, Timothy Dale. "The effects of prior heavy intensity exercise on oxygen uptake kinetics and aortic mean blood velocity during moderate intensity exercise in older adults". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0004/MQ42225.pdf.
Testo completo
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Nevala, T. (Terhi). "Endovascular treatment of an abdominal aortic aneurysm:mid-term results and management of a type II endoleak". Doctoral thesis, University of Oulu, 2010. http://urn.fi/urn:isbn:9789514261343.
Testo completoAbstract (sommario):
Abstract
Endovascular aneurysm repair (EVAR) is a minimally invasive alternative to open surgery to exclude an abdominal aortic aneurysm from the circulation to avert a rupture. The aim of this thesis was to evaluate the early and mid-term results of EVAR using the Zenith® stent-graft (Cook Inc, Bloomington, IN, USA) in asymptomatic and symptomatic abdominal aortic aneurysm (AAA) patients in three Finnish university hospitals. Furthermore, the aim was to study whether preoperative embolization of the inferior mesenteric artery (IMA) before EVAR decreases the incidence of a type II endoleak or has an effect on the aneurysm sac shrinkage. Finally, the results after secondary interventions for a type II endoleak were evaluated.
Two hundred six patients underwent elective endovascular repair of an intact AAA. The use of the Zenith® stent-graft was associated with good early and mid-term results. The thirty-day mortality rate (2.9%) was in accordance with other EVAR studies. Only one late aneurysm-related death occurred in this series, whilst no patients died of a late aneurysm rupture. No stent-graft migrations or fractures were observed. Endoleak, defined as persistent blood flow outside the graft and within the aneurysm sac, remains a long-term problem with EVAR. The overall endoleak incidence was 34.6%. A type II endoleak (retrograde perfusion via aortic side branches) occurred in 52 patients (25.4%).
EVAR was performed for 14 patients with a symptomatic, unruptured AAA. The median delay from admission to intervention was 4 days. EVAR of a symptomatic, unruptured AAA was associated with a favourable outcome even in patients with a very high operative risk. There were no perioperative deaths.
Altogether forty patients treated at Kuopio University Hospital had a patent IMA on preoperative computed tomography (CT) and were treated successfully with coil embolization before EVAR. Thirty-nine patients who underwent EVAR at Oulu University Hospital without preoperative embolization of a patent IMA served as a control group. Preoperative coil embolization of the IMA significantly reduced the incidence of type II endoleaks after EVAR, but the present study failed to show any influence on late postoperative aneurysm sac shrinkage.
Overall, 14 patients underwent a secondary intervention to repair the type II endoleak. Ten patients had transarterial embolization and four patients had translumbar embolization. The results were unsatisfactory; clinical success after the first secondary intervention was achieved in only two patients in the transarterial embolization group and three patients in the translumbar embolization group. These results seem to favour direct translumbar embolization rather than transarterial embolization.
In conclusion, EVAR with the Zenith® stent-graft is effective in excluding AAAs from the circulation and is associated with good mid-term results.
27
Kumar, Hemant. "Software analytical tool for assessing cardiac blood flow parameters". Thesis, View thesis, 2001. http://handle.uws.edu.au:8081/1959.7/392.
Testo completoAbstract (sommario):
Introduction of Doppler ultrasound techniques into the Intensive Care setting has revolutionised the way haemodynamic status is monitored in the critically ill. However, in order to increase the usefulness of these techniques, the Doppler signal and its spectrum need to be further analysed in ways to facilitate a better clinical response. Extensive processing of the Doppler spectrum on Diagnostic ultrasound machines is limited by the real time performance considerations. It was therefore proposed that the spectral information from these systems be extracted off-line and full set of analytical tools be made available to evaluate this information. This was achieved by creating an integrated and modular software tool called Spectron, which was intended as an aid in the overall management of the patients. The modular nature of Spectron was intended to ensure that new analytical tools and techniques could be easily added and tested. The software provides its users with considerable latitude in choosing various data acquisition and analysis parameters to suit various clinical situations and patient requirements. Spectron was developed under the Windows environment to provide a user friendly interface and to address a range of programming problems such as memory management and the size of the colour palettes. Spectron is able to detect the maximal velocities and compute the mean and median velocities. Relative increases in maximal velocities in cardiac blood flows after the administration of inotropic drugs have been shown in the pilot studies that were conducted. Spectron is able to help in obtaining estimates of the aortic blood flows and in other applications such measuring vascular impedance. Stenotic blood flows can be detected by using the spectral broadening index and blood flow characteristics can be studied by using various blood flow indices. Thus, this project attempted to help in patient management by providing clinicians with a range of blood flow parameters and has succeeded in meeting its objective to a large extent
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Brandi, Antonio Carlos. "Tratamento endovascular de pacientes com doenças da aorta torácica: avaliação de resultados em longo prazo". Faculdade de Medicina de São José do Rio Preto, 2015. http://hdl.handle.net/tede/365.
Testo completoAbstract (sommario):
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Introduction: Thoracic aortic diseases, including dissections, aneurysms, pseudoaneurysms among other, are serious conditions that bring serious risks of morbidity and mortality. Its incidence is low, but has been growing gradually due to the increase in life expectancy of the population, that in most cases, is associated with hypertension, smoking and diabetes mellitus. Advances in diagnostic techniques have also contributed to the identification of an increasing number of cases. The development of minimally invasive endovascular procedures has been used successfully in the treatment of these diseases, including patients with no indication for conventional surgical treatment. Objective: Evaluate the long-term results of endovascular treatment of patients with diseases of the thoracic aorta underwent implantation of self-expandable stent-grafts. Methods: This prospective study evaluated 112 patients who underwent percutaneous implantation of endoprosthesis of the thoracic aorta, from October 1998 to August 2013. Self-expandable endoprosthesis stent-graft Braile Biomédica ®, made of stainless steel and nitinol were employed. The occurrence of intraoperative and postoperative primary success, endoleaks, mortality, late evolution of the endoprosthesis and survival were evaluated in long term follow-up. Results: The mean time of the procedures was 72.66 ± 43.36 minutes (range 30-240 minutes). A total of 150 self-expandable stents were implanted in 112 patients, 61 (40.66%) of stainless steel and 89 (59.33%) of nitinol. The diameter and length of the stents of stainless steel and nitinol ranged from 24-45 mm (median 33) and 70-130 mm (median 90) 22-46 mm (median 35) and between 40 and 230 mm (median 110) respectively. The number of stents implanted per patient ranged from 1 to 4 (median 1). Primary success was observed in 100 (82.14%) of 112 patients treated. Immediate mortality occurred in seven (6.25%) patients, five (4.46%) from cardiovascular causes and two (1.78%) for non-cardiovascular causes. Late mortality occurred in 31 (27.68%) patients, 10 (8.93%) from cardiovascular causes, 12 (10.71%) for non-cardiovascular causes, two (1.78%) from natural causes-seven (6.25%) with no diagnosis. There hospital type I endoleaks occurred in four patients (3.57%), type II in five (4.46%) and three type IV (2.68%). Late endoleaks type I occurred in five (4.46%) patients and type IV in three (2.68%). Twenty-two patients (19.64%) had clinical complications in the immediate postoperative period, including nine (8.03%) pulmonary complications, four (3.57%) neurological abnormalities, three (2.67%) acute renal failure, two (1.78%) infections in the surgical incision, two (1.78%) with progression to post-implantation syndrome and one (0.89%) with laceration of the arterial access. Follow-up time ranged from 1 to 179 months (median 46). The acturial survival curve was 79,3% (IC95% 67,0-91,7) at 132 months free of death from cardiovascular causes. The logistic regression analysis showed that renal failure was the only risk factor that showed a statistically significant difference. Conclusions: The low levels of intra and postoperative complications demonstrate that the treatment is safe and effective. The high rate of survival after 132 months of follow-up for these critically ill patients show the benefits of endovascular technique to treatment of thoracic aorta diseases.
Introdução: Doenças da aorta torácica, incluindo as dissecções, aneurismas, pseudoaneurismas entre outras, são condições graves que trazem sérios riscos de morbimortalidade. Sua incidência é baixa, porém, vem crescendo gradativamente em virtude do aumento da expectativa de vida da população que, na maioria dos casos, está associada à hipertensão arterial, tabagismo e diabetes. Os avanços nas técnicas diagnósticas também têm contribuído para a identificação de um número cada vez maior de casos. O desenvolvimento de procedimentos endovasculares minimamente invasivos vem sendo utilizado com sucesso no tratamento destas doenças, inclusive em pacientes sem indicação para tratamento cirúrgico convencional. Objetivo: Avaliar os resultados em longo prazo do tratamento endovascular de pacientes portadores de doenças da aorta torácica submetidos ao implante de endopróteses autoexpansíveis stent-grafts. Casuística e Métodos: Estudo prospectivo que avaliou 112 pacientes submetidos ao implante percutâneo de endoprótese na aorta torácica, no período de outubro de 1998 a agosto de 2013. Foram empregadas endopróteses autoexpansíveis stent-grafts da Braile Biomédica®, confeccionadas em aço inox e nitinol. Foram avaliadas a ocorrência de complicações intra e pós-operatórias, sucesso primário, endoleak, mortalidade, evolução tardia da endoprótese e a sobrevivência em seguimento de longo prazo. Resultados. O tempo médio dos procedimentos foi de 72,66±43,36 minutos (variação 30-240 minutos). Foram implantadas um total de 150 endopróteses autoexpansíveis em 112 pacientes, sendo 61 (40,66%) de aço inox e 89 (59,33%) de nitinol. O diâmetro e comprimento dos stents de aço inox e de nitinol variaram de 24-45 mm (mediana 33) e 70-130 mm (mediana 90), 22-46 mm (mediana 35) e 40 a 230 mm (mediana 110), respectivamente. O número de endopróteses implantadas por paciente variou de 1 a 4 (mediana 1). Sucesso primário foi observado em 100 (82,14%) dos 112 pacientes tratados. A mortalidade hospitalar ocorreu em sete (6,25%) pacientes, cinco (4,46%) por causas cardiovasculares e dois (1,78%) por causas não cardiovasculares. A mortalidade tardia ocorreu em 31 (27,68%) pacientes, 10 (8,93%) por causas cardiovasculares, 12 (10,71%) por causas não cardiovasculares, dois (1,78%) por causas naturais e sete (6,25%) sem diagnóstico. No período hospitalar, ocorreu endoleak do tipo I em quatro pacientes (3,57%), tipo II em cinco (4,46%) e tipo IV em três (2,68%). Endoleak tardio do tipo I ocorreu em cinco (4,46%) pacientes e do tipo IV em três (2,68%). Vinte e dois pacientes (19,64%) apresentaram complicações clínicas no pós-operatório imediato, incluindo nove (8,03%) complicações pulmonares, quatro (3,57%) alterações neurológicas, três (2,67%) pacientes com insuficiência renal aguda, duas (1,78%) incisões cirúrgicas com infecção, duas (1,78%) síndromes pós-implante e uma (0,89%) laceração do acesso arterial. O tempo de seguimento variou de 1 a 179 meses (mediana 46). A curva atuarial de sobrevivência foi de 79,3% (IC95% 67,0-91,7) aos 132 meses livre de mortalidade por causas cardiovasculares. A análise de regressão logística mostrou que a insuficiência renal foi o único fator de risco para mortalidade que apresentou diferença estatisticamente significante. Conclusões. Os baixos índices de complicações intra e pós-operatórias demonstram que o tratamento é seguro e eficaz. O alto índice de sobrevivência após 132 meses de seguimento para estes pacientes graves mostram os benefícios da técnica endovascular no tratamento das doenças da aorta torácica.
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Pfluecke, C., M. Christoph, S. Kolschmann, D. Tarnowski, M. Forkmann, S. Jellinghaus, D. M. Poitz et al. "Intra-aortic balloon pump (IABP) counterpulsation improves cerebral perfusion in patients with decreased left ventricular function". Sage, 2014. https://tud.qucosa.de/id/qucosa%3A35364.
Testo completoAbstract (sommario):
Background: The current goal of treatment after acute ischemic stroke is the increase of cerebral blood flow (CBF) in ischemic brain tissue. Intra-aortic balloon pump (IABP) counterpulsation in the setting of cardiogenic shock is able to reduce left ventricular afterload and increase coronary blood flow. The effects of an IABP on CBF have not been sufficiently examined. We hypothesize that the use of an IABP especially enhances cerebral blood flow in patients with pre-existing heart failure.
Methods: In this pilot study, 36 subjects were examined to investigate the effect of an IABP on middle cerebral artery (MCA) transcranial Doppler (TCD) flow velocity change and relative CBF augmentation by determining velocity time integral changes (ΔVTI) in a constant caliber of the MCA compared to a baseline measurement without an IABP. Subjects were divided into two groups according to their left ventricular ejection fraction (LVEF): Group 1 LVEF >30% and Group 2 LVEF ≤30%.
Results: Both groups showed an increase in CBF using an IABP. Patients with a LVEF ≤30% showed a significantly higher increase of ΔVTI in the MCA under IABP augmentation compared to patients with a LVEF >30% (20.9% ± 3.9% Group 2 vs.10.5% ± 2.2% Group 1, p<0,05). The mean arterial pressure (MAP) increased only marginally in both groups under IABP augmentation.
Conclusions: IABP improves cerebral blood flow, particularly in patients with pre-existing heart failure and highly impaired LVEF. Hence, an IABP might be a treatment option to improve cerebral perfusion in selected patients with cerebral misperfusion and simultaneously existing severe heart failure.
30
Spühler, Jeannette Hiromi. "Patient-Specific Finite Element Modeling of the Blood Flow in the Left Ventricle of a Human Heart". Doctoral thesis, KTH, Beräkningsvetenskap och beräkningsteknik (CST), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215277.
Testo completoAbstract (sommario):
Heart disease is the leading cause of death in the world. Therefore, numerous studies are undertaken to identify indicators which can be applied to discover cardiac dysfunctions at an early age. Among others, the fluid dynamics of the blood flow (hemodymanics) is considered to contain relevant information related to abnormal performance of the heart.This thesis presents a robust framework for numerical simulation of the fluid dynamics of the blood flow in the left ventricle of a human heart and the fluid-structure interaction of the blood and the aortic leaflets.We first describe a patient-specific model for simulating the intraventricular blood flow. The motion of the endocardial wall is extracted from data acquired with medical imaging and we use the incompressible Navier-Stokes equations to model the hemodynamics within the chamber. We set boundary conditions to model the opening and closing of the mitral and aortic valves respectively, and we apply a stabilized Arbitrary Lagrangian-Eulerian (ALE) space-time finite element method to simulate the blood flow. Even though it is difficult to collect in-vivo data for validation, the available data and results from other simulation models indicate that our approach possesses the potential and capability to provide relevant information about the intraventricular blood flow.To further demonstrate the robustness and clinical feasibility of our model, a semi-automatic pathway from 4D cardiac ultrasound imaging to patient-specific simulation of the blood flow in the left ventricle is developed. The outcome is promising and further simulations and analysis of large data sets are planned.In order to enhance our solver by introducing additional features, the fluid solver is extended by embedding different geometrical prototypes of both a native and a mechanical aortic valve in the outflow area of the left ventricle.Both, the contact as well as the fluid-structure interaction, are modeled as a unified continuum problem using conservation laws for mass and momentum. To use this ansatz for simulating the valvular dynamics is unique and has the expedient properties that the whole problem can be described with partial different equations and the same numerical methods for discretization are applicable.All algorithms are implemented in the high performance computing branch of Unicorn, which is part of the open source software framework FEniCS-HPC. The strong advantage of implementing the solvers in an open source software is the accessibility and reproducibility of the results which enhance the prospects of developing a method with clinical relevance.QC 20171006
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Sigüenza, Julien. "Fluid-structure interaction problems involving deformable membranes : application to blood flows at macroscopic and microscopic scales". Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT301/document.
Testo completoAbstract (sommario):
Cette thèse traite plusieurs aspects scientifiques inhérents à la simulation numérique de problèmes d'interaction fluide-structure impliquant de fines membranes déformables. Deux cas spécifiques relatifs à la biomécanique cardiovasculaire sont considérés : l'interaction de l'écoulement sanguin avec la valve aortique (qui se produit à l'échelle macroscopique), et l'interaction de la membrane des globules rouges avec ses fluides interne et externe (qui se produit à l'échelle microscopique). Dans les deux cas, le couplage fluide-structure est géré par l'intermédiaire d'un formalisme de frontières immergées, en représentant la membrane par un maillage Lagrangien se mouvant au travers d'un maillage fluide Eulérien. Lorsque l'on traite la dynamique des globules rouges, la membrane est considérée comme étant une structure sans masse et infiniment fine. La première question à laquelle on s'intéresse dans cette thèse est la manière de modéliser la microstructure complexe de la membrane des globules rouges. Un moyen possible pour caractériser un modèle de membrane adapté est de simuler l'expérience des pinces optiques, qui consiste en une configuration expérimentale bien contrôlée qui permet d'étudier la mécanique individuelle d'un globule rouge isolé dans une large gamme de déformations. Plusieurs modèles pertinents sont identifiés, mais les caractéristiques de déformation mesurées durant l'expérience des pinces optiques se révèlent n'être pas assez sélectives pour être utilisées dans un contexte de validation. Des mesures de déformation additionnelles sont proposées, qui pourraient permettre une meilleure caractérisation de la mécanique de la membrane des globules rouges. En ce qui concerne les configurations macroscopiques, une méthode numérique innovante est proposée afin de gérer des simulations numériques de membranes 3D continues, en conservant le formalisme de frontières immergées. Dans cette méthode, appelée méthode des frontières immergées épaisses, la membrane a une épaisseur finie. La précision et la robustesse de la méthode sont démontrées par l'intermédiaire d'une variété de cas tests bien choisis. La méthode proposée est ensuite appliquée à un problème d'interaction fluide-structure réaliste, à savoir l'interaction d'un écoulement (sanguin) pulsé avec une valve aortique biomimétique. Une étude combinée expérimentale et numérique est menée, montrant que la méthode est capable de capturer la dynamique globale de la valve, ainsi que les principales caractéristiques de l'écoulement en aval de la valve. Tous les développements ont été effectués dans le solveur YALES2BIO (http://www.math.univ-montp2.fr/~yales2bio/) développé à l'IMAG, qui est donc disponible pour toutes autres améliorations, validations et études applicativesThis thesis deals with several scientific aspects inherent to the numerical simulation of fluid-structure interaction problems involving thin deformable membranes. Two specific cases relevant to cardiovascular biomechanics are considered: the interaction of the blood flow with the aortic valve (which occurs at the macroscopic scale), and the interaction of the red blood cells membrane with its inner and outer fluids (which occurs at the microscopic scale). In both cases, the fluid-structure interaction coupling is handled using an immersed boundary formalism, representing the membrane by a Lagrangian mesh moving through an Eulerian fluid mesh.When dealing with red blood cells dynamics, the membrane is considered to be an infinitely thin and massless structure. The first question which is addressed in the present thesis work is how to model the complex microstructure of the red blood cells membrane. A possible way to characterize a suitable membrane model is to simulate the optical tweezers experiment, which is a well-controlled experimental configuration enabling to study the individual mechanics of an isolated red blood cell in a large range of deformation. Some relevant membrane models are identified, but the deformation characteristics measured during the optical tweezers experiment reveal to be not selective enough to be used in a validation context. Additional deformation measurements are proposed, which could allow a better characterization of the red blood cell membrane mechanics.Regarding the macroscopic configurations, an innovative numerical method is proposed to handle numerical simulations of 3D continuum membranes, still within the immersed boundary formalism. In this method, called immersed thick boundary method, the membrane has a finite thickness. The accuracy and robustness of the method are demonstrated through a variety of well-chosen test cases. Then, the proposed method is applied to a realistic fluid-structure interaction problem, namely the interaction of a pulsatile (blood) flow with a biomimetic aortic valve. A combined experimental and numerical study is led, showing that the method is able to capture the global dynamics of the valve, as well as the main features of the flow downstream of the valve.All the developments were performed within the YALES2BIO solver (http://www.math.univ-montp2.fr/~yales2bio/) developed at IMAG, which is thus available for further improvements, validations and applicative studies
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Nozari, Ala. "Experimental cardiopulmonary cerebral resuscitation : A study of cerebral perfusion with special reference to the postresuscitation disturbances". Doctoral thesis, Uppsala University, Department of Surgical Sciences, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-459.
Testo completoAbstract (sommario):
Ischemic neuronal injury continues to be a major delimiting factor in achieving successful clinical outcomesafter resuscitation from cardiac arrest. In this thesis, a pig model of cardiopulmonary resuscitation (CPR) wasused to address the effects of different interventions on cerebral blood flow and oxygenation during CPR and theinitial postresuscitation period. A novel technique is presented to quantify the reperfusion oxidative injury.
Maximization of cerebral blood flow during CPR by open-chest cardiac compression, continuous aortic balloon occlusion, and intra-aortic administration of hypertonic saline-dextran (HSD) did not ameliorate thepostresuscitation hypoperfusion or improve the cerebral oxygen extraction ratio or tissue pH. These findings disaffirm earlier studies suggesting that conserving brain viability after global ischemia is mostly a question ofmaintaining high perfusion pressure.
Despite an increased cerebral perfusion pressure during CPR, intra-aortic administered epinephrineabove the aortic balloon occlusion did not further improve cerebral blood flow and oxygenation. This findingmay indicate adverse effects of epinephrine on cerebral vascular beds, possibly induced by a relatively highconcentration of epinephrine when administered above the site for aortic balloon occlusion.
The IV administration of equipotent doses of epinephrine or vasopressin during CPR resulted incomparable hemodynamic changes. The peak increase in cerebral cortical blood flow, however, was reachedapproximately 30 sec later by vasopressin. Furthermore, the second bolus of vasopressin during CPR did notaugment cerebral perfusion, whereas epinephrine did. Consequently, reports suggesting that vasopressin issuperior to epinephrine with respect to its effects on central hemodynamics and vital organ blood flow may bebiased by the pharmacodynamic differences between the drugs, depending on the time point at which blood flowmeasurements are performed.
In comparison with IV vasopressin, vasopressin administered above the aortic balloon occlusion resulted in a significant increase in cerebral perfusion pressure during CPR, but not after restoration of spontaneous circulation (ROSC). Cerebral cortical blood flow was, however, not improved during CPR, whereas a significant increase was recorded after ROSC. Relatively higher concentrations of vasopressin above the sitefor intra-aortic balloon occlusion may, therefore, predominantly induce cerebral cortical vasoconstriction duringCPR but induce vasodilatation after ROSC.
Assessment of oxidative stress or inflammation have been extremely difficult to attain. In our pig model of resuscitation, an association wasobserved between the duration of cardiac arrest and jugular bulb levels of 8-iso-PGF2α, a major isoprostane and a novel index of oxidative injury. 8-iso-PGF2α, and the prostaglandin 15-K-DH-PGF2α, increased within 5 min after ROSC and remained so up to 2 h, indicating the interval of time during which cerebral reperfusion oxidative injury and inflammatory response may occur and are potentially preventable.
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Kumar, Vivek Ashok. "Design and evaluation of scaffolds for arterial grafts using extracellular matrix based materials". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45869.
Testo completoAbstract (sommario):
For small diameter (<6 mm) blood vessel replacements, lack of collaterals and vascular disease preclude homografts; while synthetic analogs, ePTFE, expanded polytetrafluoroethylene, and PET, polyethyleneterephathalate, are prone to acute thrombosis and restenosis. It is postulated that the hierarchical assembly of cell populated matrices fabricated from protein analogs provides a new design strategy for generating a structurally viable tissue engineered vascular graft. To this end, synthetic elastin and collagen fiber analogs offer a novel strategy for creating tissue engineered vascular grafts with mechanical and biological properties that match or exceed those of native vessels. This work details techniques developed for the fabrication of prosthetic vascular grafts from a series of extracellular matrix analogs composed of nanofibrous collagen matrices and elastin-mimetic proteins, with and without cells, and subsequent evaluation of their biocompatibility and mechanical properties. The work details the fabrication and mechanical analysis of vascular grafts made from aforementioned protein analogs. Subesequent studies detail seeding and proliferation of rodent mesenchymal stem cells on protein-based composites to recapitulate the media of native vasculature. Finally detailing in vivo biocompatibility and stability of tissue engineered vascular grafts.
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Castro, Roberto Chaves. ""Circulação periférica em pacientes com insuficiência aórtica crônica e indicação de troca valvar"". Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/5/5131/tde-05092005-115223/.
Testo completoAbstract (sommario):
Introdução: O recente aperfeiçoamento da ultra-sonografia permitiu a análise estrutural e funcional do vaso. Casuística e Métodos: 36 pacientes com insuficiência aórtica e indicação de troca valvar, divididos em grupos com pressão arterial diastólica (PAD) superior e inferior a 50mmHg, avaliados antes e seis meses após a cirurgia. A função arterial compreendeu a complacência, distensibilidade e a função endotelial pela dilatação fluxo-mediada e nitrato-mediada. Conclusão: A complacência e a distensibilidade foram maiores no grupo com menor PAD e diminuíram após a cirurgia. A disfunção endotelial foi presente em insuficiência aórtica crônica independente do nível da pressão arterial diastólicaIntroduction: The recent improvement of ultrasonography made possible a functional and structural analysis of the vessel. Methods: 36 patients with aortic insufficiency and valve replacement need, divided in 2 groups with diastolic blood pressure (DBP) above and below 50mmHg. Checked twice: before and 6 months after surgery. The arterial function comprised compliance, distensibility and endothelial function through flow-mediated dilatation and nitrate-mediated dilatation. Conclusion: The compliance and distensibility were higher in the group with lower DBP and decreased after surgery. Endothelial dysfunction was present in chronic aortic insufficiency no matter the level of DBP
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Junior, Antonio Aurelio de Paiva Fagundes. "Estudo do fluxo sanguíneo regional e dos marcadores de perfusão tecidual em pacientes com insuficiência cardíaca em uso de balão intra-aórtico". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/5/5131/tde-10122013-102948/.
Testo completoAbstract (sommario):
INTRODUÇÃO: O balão intra-aórtico (BIA) representa o mecanismo de assistência ventricular mais frequentemente utilizado em pacientes com insuficiência cardíaca (IC), no Brasil. OBJETIVO: Neste trabalho, avaliamos a ação do BIA sobre o fluxo sanguíneo carotídeo e braquial, além do seu efeito sobre os marcadores de perfusão tecidual e sobre o peptídeo natriurético cerebral (BNP). MÉTODOS: Entre julho de 2006 e maio de 2009, 33 pacientes foram avaliados, sendo 10 excluídos. Os pacientes foram inicialmente mantidos com o BIA em modo 1:1, com insuflação máxima, para a fase inicial do estudo (condição 1). Realizou-se coleta de gasometria arterial, venosa central e BNP (condição EXA1). Foi realizada ultrassonografia vascular de alta definição, para captação de imagens das curvas de velocidade de fluxo sanguíneo, e medida dos diâmetros arteriais sistólico e diastólico (condição MD1). Em seguida, foi avaliada a resposta vascular frente à hiperemia reativa (condição HR1). Realizado o estudo na condição 1, o BIA foi modificado para 1:3 com insuflação mínima (condição 2) e todos os exames laboratoriais (condição EXA 2) e ultrassonográficos (condição MD2 e condição HR2) foram repetidos. Após a condição 2, passou-se à condição 3, na qual o BIA foi novamente modificado para a assistência 1:1, com insuflação máxima. Da mesma forma que nas condições anteriores, foram realizados exames laboratoriais (condição EXA 3) e a ultrassonografia (condição MD3 e HR3). A avaliação estatística foi realizada através da análise de variância para medidas repetidas e o uso do teste não paramétrico de Friedman. RESULTADOS: A idade média dos pacientes selecionados foi de 49,7 ± 13 anos, sendo 17 (74%) do sexo masculino e 6 (26%) do sexo feminimo. Quanto à etiologia, 9 (39%) pacientes eram portadores de miocardiopatia isquêmica, 8 (34%) miocardiopatia dilatada idiopática, 4 (17%) tinham etiologia chagásica e 2 (8%) por valvopatias. A fração de ejeção, estimada pelo ecocardiograma variou de 14 a 40%, com Resumo média de 22 +-8%. Nove pacientes (39%) encontravam-se em fila para transplante cardíaco, no momento da inclusão no protocolo, e a mortalidade durante a internação foi de 60,8%. Analisados os dados laboratoriais, não houve, entre as três medidas realizadas, diferença com significância estatística nos valores de bicarbonato arterial (BIC), assim como, nos valores de excesso de base (BE). Também não detectamos mudanças na saturação venosa central de oxigênio (SVcO2), no nível sérico de BNP e no gradiente venoarterial de CO2(DeltaPCO2). Os resultados das análises da velocidade de fluxo, índice de fluxo carotídeo e integral velocidade-tempo na condição MD1, MD2 e MD3 não revelaram diferenças estatisticamente significantes. Analisado o território braquial, considerando a velocidade de fluxo braquial não houve diferença entre a condição MD1 e a condição MD2 e entre a condição MD1 e a condição MD3. Entretanto, identificamos diferença entre as condições MD2 e MD3 (p=0,01). Não encontramos diferença com significância entre as três condições considerando o índice de fluxo e a integral velocidade-tempo. Na prova de hiperemia reativa não encontramos alteração entre as condições HR1, HR2 e HR3, quando avaliamos a velocidade de fluxo, o índice de fluxo e a integral velocidade-tempo. A dilatação fluxo mediada da artéria braquial (DILA) encontrava-se alterada desde o momento inicial, porém o protocolo não revelou alterações entre HR1, HR2 e HR3. CONCLUSÃO: Em pacientes com insuficiência cardíaca, a assistência com o BIA não modificou o fluxo sanguíneo regional em território cerebral e muscular esquelético avaliados pelo fluxo da carótida e artéria braquial, respectivamente. Da mesma forma, não houve alteração da perfusão tecidual e função cardíaca avaliados pelos marcadores do metabolismo oxidativo e sobrecarga hídrica utilizados. A função endotelial avaliada na condição de duplo pulso de fluxo da artéria braquial propiciada pela assistência circulatória do BIA evidenciou-se alterada com dimunuição da reatividade vascularBACKGROUND: The intra-aortic balloon (IAB) represents the mechanism of ventricular assist more often used in patients with heart failure (HF) in our midst. OBJECTIVE: In this study, we evaluated the action of the IAB on the carotid and brachial blood flow, in addition to its effect on markers of tissue perfusion and the brain natriuretic peptide (BNP). METHODS: Between July 2006 and May 2009, 33 patients were evaluated, 10 were excluded. Patients were initially maintained with the IAB in 1:1 mode with maximum insufflation, for the initial phase of the study (condition 1). Held collection of arterial and central venous blood gases, and BNP (condition EXA1). Vascular ultrasonography was performed in high definition, to capture images of the curves of blood flow velocity, and measurement of systolic and diastolic arterial diameters (condition MD1). Then we evaluated the vascular responses to reactive hyperemia (condition HR1). Conducted the study in condition 1, the IAB was changed to 1:3 with minimal insufflation (condition 2) and all laboratory tests (condition EXA 2) and ultrasound (condition MD2 and HR2) were repeated. After the second condition, the IAB was again modified to 1:1, with maximum insufflation (condition 3). Similarly to the previous conditions, laboratory tests (condition EXA 3) and ultrasound (condition MD3 and HR3) were performed. Statistical evaluation was performed by analysis of variance for repeated measures and the use of Friedman nonparametric test. RESULTS: The mean age of the selected patients was 49.7 +- 13 years, 17 (74%) males and 6 (26%) were females. Concerning etiology, 9 (39%) patients had ischemic cardiomyopathy, 8 (34%), idiopathic dilated cardiomyopathy, 4 (17%) had Chagas disease and 2 were (8%) related to valvulopathy. Ejection fraction estimated by echocardiography ranged from 14 to 40%, with a mean of 22 +- 8%. Nine patients (39%) were in line for a heart transplant at the time of inclusion in the protocol and mortality during hospitalization was 60.8%. Analyzed laboratory data, among the three measurements, there was not statistically significant difference in the values of arterial bicarbonate (BIC) and base excess (BE). We also did not detect changes in central venous oxygen saturation (SCVO2) or in serum BNP level and venoarterial carbon dioxide gradient (DeltaPCO2). The results of the analysis of carotid flow velocity, index of carotid flow and velocity time integral in condition MD1, MD2 and MD3 revealed no statistically significant difference. Examined the brachial territory, there was no difference between the condition MD1 and MD2 and between MD1 and MD3 considering the flow velocity. However, there was difference between conditions MD2 and MD3 (p = 0.01). We found no significant difference between the three conditions considering the brachial flow index and velocity time integral. The flow-mediated dilation of the brachial artery (FMD) found itself changed from the initial moment, but the protocol does not reveal changes between HR1, HR2 and HR3. CONCLUSION: In heart failure patients, assistance with the BIA did not alter regional blood flow in brain and skeletal muscle territory assessed by flow carotid and brachial artery, respectively. Likewise, there was no change in tissue perfusion and cardiac function assessed by markers of oxidative metabolism and fluid overload used. Endothelial function evaluated on condition of dual pulse brachial artery flow provided by BIA circulatory support showed up changed with decreased vascular reactivity
36
Heitkemper, Megan. "The Development of Computational Methods and Device Design Considerations Towards Improving Transcatheter Heart Valve Engineering". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595406932637358.
Testo completo
37
Goudot, Guillaume. "Applications innovantes des ultrasons en pathologie vasculaire : utilisation de l'imagerie ultrarapide dans l'analyse de la rigidité artérielle et des ultrasons pulsés en thérapie Arterial stiffening assessed by ultrafast ultrasound imaging gives new insight into arterial phenotype of vascular Ehlers–Danlos mouse models Aortic wall elastic properties in case of bicuspid aortic valve Segmental aortic stiffness in bicuspid aortic valve patients compared to first-degree relatives Wall shear stress measurement by ultrafast vector flow imaging for atherosclerotic carotid stenosis Pulsed cavitational therapy using high-frequency ultrasound for the treatment of deep vein thrombosis in an in vitro model of human blood clot". Thesis, Sorbonne Paris Cité, 2018. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=2215&f=13951.
Testo completo
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Hernández, Enríquez Marco. "Transcatheter Aortic Valve Implantation: Moving Forward to Minimize Vascular and Bleeding Complications = Implante Transcatéter de Válvula Aórtica: Avanzando hacia la Reducción de Complicaciones Vasculares y Hemorrágicas". Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/669896.
Testo completoAbstract (sommario):
INTRODUCTION:
TAVI has settled as the standard of care of AS for inoperable, high-risk, and selected intermediate-risk patients undergoing aortic valve replacement. Vascular and bleeding complications are related to worst outcomes.
HYPOTHESES:
a. The reduction and early recognition of vascular and bleeding complications might improve clinical outcomes in patients treated with TAVI.
b. A full percutaneous transfemoral approach for TAVI is related to a lower rate of major bleedings in comparison to the surgical cut-down approach.
c. The development of post-TAVI thrombocytopenia has a prognosis value in short-term clinical outcomes.
d. The kinetics of drop platelet count (DPC) after TAVI are different according to the type of valve implanted.
MATERIALS AND METHODS:
Sub-project 1: “Comparison of complications between percutaneous puncture or surgical cut-down for transfemoral access in TAVI”
Data from the Spanish TAVI Registry were analyzed. Patients undergoing transfemoral TAVI in 41 Spanish centers from January 2010 to July 2015 were included. Subjects were divided into percutaneous puncture (PG) and cut-down group (CG). A propensity-matched comparison was performed to avoid selection bias. Vascular and bleeding complications were evaluated at 30-days and mid-term follow-up.
Sub-project 2: “Study of Thrombocytopenia after TAVI”
a. Patients from 2 Spanish centers between 2012 to 2016 were included. Subjects with severe baseline thrombocytopenia (<100x109/L) and peri-procedural death were excluded. Laboratory analyses were performed. Two groups were created according the DPC: ≤30% or >30%. Clinical, procedural characteristics and outcomes were collected retrospectively.
b. Patients treated with transfemoral TAVI in a French high-volume center from 2008 to 2016 were included. Exclusion criteria were non-transfemoral approach, severe baseline thrombocytopenia and peri-procedural death. The study protocol was like the previous study.
RESULTS:
Sub-project 1
A total of 2,465 transfemoral TAVI patients were included. The PG had 1,833 patients (74,3%) and the CG had 632 patients (25,6%). Propensity matching score resulted in 615 pairs.
Vascular complications at 30-days were significantly higher in the PG (RR 2,66; IC95% [1,85-3,64], p = <0,001) mainly driven to minor vascular complications. In contrast, the bleeding complications were higher in the CG (RR 0,45; IC95% [0,26-0,78], p = 0,003).
At a mean follow-up of 323 days, the rates remained similar. Higher rates of vascular complications in the PG: 15% vs. 5,1% (HR 2,23; IC95% [1,6-3,11]; p = <0,001) and higher rates of major bleedings in the CG: 3,4% vs. 1,6% (HR 0,57; IC95% [0,35-0,95], p = 0,03).
Sub-project 2
a) The analyzed population included 195 patients: 100 (52,2%) treated with self-expanding valves (SEV) and 95 (48,8%) with balloon-expandable valves (BEV). The mean percentage of DPC was 31,9±15,3%. The DPC was significantly higher in the BEV population in comparison to SEV (36,3±15,1% vs 27,7±14,4, p<0,001). After multivariate analysis, the use of BEV was independently associated to a DPC>30% (67,4% vs. 36,0%; OR 3,4; 95% CI, 1,42-8,16). AT 30-days, the DPC>30% was associated to a higher rate of major and life-threatening bleedings, vascular complications, sepsis, and death. At 1-year there were no differences in mortality. (6,35% vs. 10,0%; HR 1,54; 95% CI, 0,56-4,25).
b) A total of 609 were included. The mean DPC was 32,5±13,9%. The DPC was higher in the BEV group (33.9±14.2 vs 30.7±13.4%, p=0.006), and the nadir was reached significantly later in comparison with the SEV group. (3,0±1,3 vs 2,5±1,1 days, p<0,001). After the multivariate analysis, the factors related to a DPC>30% were the use of BEV, known coronary disease and preserved left ventricle ejection fraction. At 30-days the DPC>30% was associated to a higher rate of major and life-threatening bleedings (6,8 vs 2,1%, p=0.009) and death (3,5 vs 0,8%, p=0.036). At 1-year there were no differences in mortality
CONCLUSIONS:
1. The reduction and early recognition of vascular and bleeding complications is associated to an improvement in clinical outcomes in patients treated with TAVI.
2. The completely percutaneous approach of transfemoral TAVI yielded lower rate of major bleedings and higher rate of minor vascular complications in comparison to the surgical cut-down and closure.
3. A post-procedural DPC>30% is related with worse clinical outcomes at 30-days after TAVI.
4. The use of balloon-expandable valves seems to be associated with a higher risk of drop on platelet counts after TAVI.El Implante Transcatéter de Válvula Aórtica (TAVI) se ha consolidado como el tratamiento de elección en pacientes inoperables, de alto y seleccionados con intermedio riesgo quirúrgico. Las complicaciones vasculares y hemorrágicas están asociadas a peores resultados clínicos y a mayor estancia intrahospitalaria. Subproyecto 1: “Comparación entre las complicaciones de la punción percutánea y disección quirúrgica en el Implante Transfemoral de Válvula Aórtica” Análisis retrospectivo del Registro Nacional TAVI. Se incluyeron pacientes tratados con TAVI transfemoral en 41 centros españoles desde enero 2010 hasta julio 2015. Se evaluaron la complicaciones vasculares y hemorrágicas a los 30 días y a medio término. Asimismo, se evaluó la frecuencia de ictus, daño renal agudo, infarto del miocardio y muerte. Para reducir el sesgo de selección se realizó un “score de propensión”. Subproyecto 2: “Estudio de la Trombocitopenia después del Implante Transcatéter de Válvula Aórtica” a) Se incluyeron pacientes tratados con TAVI en 2 centros españoles entre enero 2012 y diciembre 2016. Se excluyeron pacientes con plaquetopenia severa basal (<100x109/L) y con muerte peri-procedimiento. Se realizaron analíticas seriadas durante el ingreso. El seguimiento clínico se realizó a los 30 días, 3 meses y 1 año posterior al procedimiento. Se recogieron las características basales, del procedimiento y los eventos clínicos en una base de datos. Se crearon 2 grupos de acuerdo con el porcentaje de caída de plaquetas: ≤30% y >30%. b) Se incluyeron pacientes tratados con TAVI transfemoral en un centro francés de alto volumen de TAVI, entre enero 2008 y diciembre 2016. Se excluyeron los pacientes con acceso no transfemoral, con plaquetopenia severa pre-procedimiento y con muerte peri-procedimiento. El protocolo del estudio fue similar al del estudio previo. La disminución y el reconocimiento temprano de complicaciones vasculares y hemorrágicas permite mejores resultados clínicos en pacientes tratados con TAVI. El abordaje completamente percutáneo de la TAVI se asoció a una tasa menor de sangrados mayores y a una mayor tasa de complicaciones vasculares menores en comparación con el abordaje quirúrgico. La caída en el porcentaje de plaquetas >30% se relaciona con peores resultados clínicos a los 30 días post-TAVI. El uso de las prótesis balón-expandibles parece asociarse a un mayor riesgo de disminución de plaquetas.
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Menut, Marine. "Chirurgie endovasculaire virtuelle pour patient-spécifique : Application au traitement de l'anévrisme de l'aorte thoracique". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI047/document.
Testo completoAbstract (sommario):
Les maladies cardiovasculaires sont la première cause de mortalité dans le monde chez les personnes âgées de plus de 65 ans. Parmi les maladies artérielles, l'anévrisme, maladie asymptomatique, est une dilatation localisée et permanente de la paroi d'une artère aboutissant à la formation d'une poche de taille variable. Soumis aux impulsions sanguines, l'anévrisme augmente progressivement et lorsqu'il se rompt, provoque une hémorragie interne pouvant entraîner la mort. Ce projet de recherche concerne le traitement endovasculaire des Anévrismes de l'Aorte Thoracique dont le traitement consiste à déployer une endoprothèse par voie fémorale. Actuellement, les chirurgiens planifient leurs interventions uniquement à partir d'informations issues de l'imagerie médicale. Cette procédure n'est pas totalement fiable et des limites liées à des configurations anatomiques complexes et à la difficulté du geste minimalement invasif persistent. Dans ce contexte, l'objectif est de développer un outil numérique réalisant des simulations virtuelles de ce traitement endovasculaire. Afin d'appréhender le comportement mécanique complexe du tissu artériel, des expérimentations avec une technique de corrélation d'images ont été réalisées sur des prélèvements humains d'aortes thoraciques. Des simulations d'écoulement sanguin dans l'aorte thoracique ont ensuite été réalisées chez un patient sain avec le logiciel OpenFOAM dans lequel un modèle rhéologique prenant en compte les effets viscoélastique et rhéofluidifiant du sang a été développé. En parallèle et en prévision de la modélisation complète de l'acte chirurgical, des calculs numériques sur la montée des outils chirurgicaux dans l'aorte thoracique ont été réalisés en se basant sur des travaux précédents au laboratoire sur la montée des outils dans l'aorte abdominale. L'approche envisagée s'inscrit ainsi dans le cadre des gestes médicaux et chirurgicaux assistés par ordinateur afin de proposer une solution personnalisée opérationnelle pour le choix d'un système de largage et d'une endoprothèse adaptésCardiovascular diseases are the leading cause of death worldwide. Their analysis leads to multidisciplinary problems that require diversity, transversal and complementary approaches. This contribution is part of a research project in Computer Aided Surgery and intends to contribute to the improvement of TEVAR procedures in terms of accuracy and optimization of the operating strategy. In this study, stereocorrelation technique is used to measure the strain field under a human aortic arch in order to identify its mechanical behaviour. Blood flow simulations in the thoracic aorta were then carried out for a healthy patient using the open source OpenFOAM software. A rheological model derived from polymer rheology, considers viscous, shear thinning and other stress overshoot behaviours. In parallel and in anticipation of the complete modeling of the surgical procedure, numerical calculations ofthe rise of the surgical tools in the thoracic aorta were carried out based on previous work in the laboratory regarding the abdominal aorta. This study aims to virtually simulate the whole endovascular stent graft procedure for an aortic aneurysm. This procedure has a high rate of short-term success and its indication compared to open surgery is increasing. Despite many benefits such as reduced blood loss and reduced recovery time, the hindsight is insufficient and there are limitations related to complex anatomical configurations. This procedure therefore needs to be more reliable and secure. In this context, it is important to identify the mechanical behavior of the aorta for further numerical simulations
40
Freercks, Robert Jeremy. "The impact of vascular calcification on ambulatory and central aortic blood pressure in a South African dwelling dialysis population : a clinical, radiological and pathophysiological study of vascular health in a young prevalent dialysis population in a developing country". Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11995.
Testo completoAbstract (sommario):
Includes abstract.Includes bibliographical references.
In Sub-Saharan Africa, the prevalence of vascular calcification (VC) in CKD-5D is unknown. We undertook to determine the effect of ethnicity on VC, the risk factors for VC, the utility of abdominal X-ray (AXR) in predicting coronary calcium score (CCS) and the effect of VC on central aortic systolic pressure (CASP) and left ventricular mass index (LVMI) in South African dialysis patients. ... Black race significantly protects from VC in South African CKD-5D patients and warrants further study. The AXR is a useful screening tool for CCS in our population. VC does not appear to influence CASP in our population.
41
Orra, Hussein Amin. ""Estudo experimental da transmissão da pulsatilidade da endoprótese à parede do aneurisma da aorta após correção endoluminal"". Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/5/5132/tde-21122005-140229/.
Testo completoAbstract (sommario):
Objetivo: Medir a pulsatilidade da parede do aneurisma de aorta humano antes e depois de sua correção endoluminal. Método: Cinco aneurismas foram submetidos à perfusão pulsátil antes e depois do implante de uma endoprótese. Resultado: o nível da coluna de água oscilou durante a pulsação com variações de 17, 16, 13, 7 e 25 cm antes da colocação da endoprótese. Depois da prótese, a oscilação diminuiu em todos os casos para 13, 12, 9, 3,5 e 23 cm, respectivamente. Conclusão: A pulsação da endoprótese é transmitida à parede do aneurismaObjective: To measure the pulsatility of human aortic aneurysms before and after exclusion with endograft. Method: Five aneurysms were submitted to pulsatile perfusion before and after implantation of a bifurcated endograft. Result: The level of the water column oscillated during pulsation, in each case, with an amplitude of 17, 16, 13, 7 and 25 cm before the endograft insertion. After that, the amplitudes dropped to, respectively 13, 12, 9, 3.5 and 23 cm.Conclusion: Pulsation of an endograft is transmitted to the aneurysm wall even in the absence of endoleak
42
Moscarelli, Marco. "A multi-centre randomized controlled trial investigating the effect of remote ischaemic preconditioning (RIPC) on blood and myocardial biomarkers of stress and injury-related signalling in patients having isolated coronary artery bypass grafting (CABG) or aortic valve replacement (AVR) using cardiopulmonary bypass (CPB)". Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/61481.
Testo completoAbstract (sommario):
Objective: To compare markers of cardiac injury, inflammatory and oxidative responses, and myocardial cellular changes in the left and right ventricles of patients undergoing isolated coronary artery bypass grafting (CABG) or aortic valve replacement (AVR) using cardiopulmonary bypass (CPB) and cardioplegic arrest with or without remote ischaemic preconditioning (RIPC). Methods: Two conditions were studied for each surgical stratum (CABG or AVR): (a) no RIPC and (b) RIPC following anaesthesia and before sternotomy. The control group (no RIPC) represented standard clinical practice. Left and right ventricular biopsies were collected before CPB and at the end of ischaemic cardioplegic arrest. Blood samples were collected before, during, and after the operation. Results: Between March 2012 and April 2014, 124 patients agreed to participate in the study; 64 and 60 patients formed the CABG and AVR populations, respectively, and were randomised to receive RIPC or sham treatment. There were no differences in troponin release between groups (geometric mean ratio 0.92 (0.75,1.10), p=0.9; and 0.9 (0.35,1.44), p=0.65 CABG and AVR respectively). The postoperative course in each group was similar with no mortality. There were no significant differences in phosphorylation potential or energy charge in left and right ventricle biopsies or in circulating inflammatory markers between groups. No serious adverse events were reported. Conclusions: RIPC did not confer significant cardioprotection as measured by troponin I release. This result was possibly related to the inability of the study to stratify anaesthesia regimens. Both RIPC and Tru-Cut ventricle biopsy procedures were safe.
43
Simon, Helene Anne. "Numerical simulations of the micro flow field in the hinge region of bileaflet mechanical heart valves". Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/34861.
Testo completoAbstract (sommario):
Native heart valves with limited functionality are commonly replaced by a bileaflet mechanical heart valve (BMHV). However, despite their widespread use, BMHVs still cause major complications, including hemolysis, platelet activation, and thromboembolic events. These complications are believed to be due to the non-physiologic hemodynamic stresses imposed on blood elements by the hinge flows. Three-dimensional characterization of the hinge flows is therefore crucial to ultimately design BMHVs with lower complication rates. This study aims at simulating the pulsatile 3D hinge flows of various BMHVs placed and estimating the thromboembolic potential associated with each hinge.
The hinge and leaflet geometries of clinical BMHVs are reconstructed from micro-computed tomography scans. Simulations are conducted using a Cartesian sharp-interface immersed-boundary methodology combined with a second-order accurate fractional-step method. Physiologic flow boundary conditions and leaflet motion are extracted from the Fluid-Structure-Interaction simulations of the BMHV bulk flow. The accuracy of the solver is assessed by comparing the results with experimental data. The numerical results are analyzed using a particle tracking approach coupled with existing blood damage models to relate the flow structures to the risk for blood damage.
Calculations reveal complex, unsteady, and highly 3D flow fields. Zones of flow stagnation and recirculation, favorable to thrombosis and regions of elevated shear stresses, which may induce platelet activation, are identified throughout the hinge and cardiac cycle. The hinge gap width and, more importantly, the shape of the hinge recess and leaflet are found to impact the flow distribution. Avoiding sharp corners or sudden shape transitions appear as key geometrical design parameters to minimize flow disturbances and thromboembolic potential.
The computed flows underscore the need to perform full 3D pulsatile simulations throughout the cardiac cycle to fully capture the complexity and unsteadiness of the hinge flows. Though based only on three different designs, this study provides general guidelines to optimize the hinge design based on hemodynamic performance and thromboembolic potential. The developed framework enables rapid and cost-efficient pre-clinical evaluation of prototype BMHV designs prior to valve manufacturing. Application to a wide range of hinges with varying design parameters will eventually help in determining the optimal hinge design.
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Amaral, Nathalia Oda. "Envolvimento do núcleo pré-óptico mediano (MnPO) na recuperação cardiovascular induzida pela infusão de salina hipertônica em animais submetidos ao choque hemorrágico". Universidade Federal de Goiás, 2014. http://repositorio.bc.ufg.br/tede/handle/tede/4502.
Testo completoAbstract (sommario):
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In recent decades, several studies have demonstrated that hyperosmolarity induced by hypertonic saline infusion (HS) it’s a benefit for hypovolemic hemorrhage treatment. The median preoptic nucleus (MnPO) is known to receive information from central osmoreceptors and peripheral afferents about plasma osmolarity changes, reflexively modulating autonomic and neuroendocrine adjustments, primarily through its projections to the paraventricular nucleus (PVN). The present study aim to determine MnPO involvement in cardiovascular recovery induced by HSI in rats subjected to hemorrhagic shock (HC). Wistar rats (250 - 300 g) were prepared to record mean arterial pressure (MAP), heart rate (HR), renal blood flow (RBF) and aortic (ABF). The renal vascular conductance (RVC) and aortic (AVC) were calculated through the ratio between RBF and ABF with MAP, respectively. Hemorrhagic shock was induced by blood withdrawal over 10 min until the MAP reached approximate values of 60 mmHg. The sodium overload by infusion HS (3 M NaCl, 1.8 ml ∙ kg-1 body mass index) was made 2 min after the nanoinjection (100 nL) of GABA agonist muscimol (4 mM experimental group 1 - EXP 1 ), α-adrenergic antagonist phentolamine (13 mM ; experimental group 2 - EXP 2) or isotonic saline (NaCl, 0.15 M, control group - CON) in MnPO. This resulted in HC CON (n=6) MAP reduction (98.4 ± 5.3 to 62.2 ± 1.1 mmHg after 20 min HC, p<0.05), a decrease in RVC (- 59.4 ± 9.2%, 20 min after HC, p<0.05) and did not alter the AVC (-11.5 ± 10.5%, 20 min after HC) and HR (387.2 ± 12 to 351.7 ± 13 bpm after 20 min HC). HC promoted in EXP 1 (n=6) MAP reduction (98 ± 5.4 to 61 ± 0.7 mmHg after 20 min HC, p<0.05), a decrease in RVC (-64.8 ± 10.9%, 20 min after CH, p<0.05) and CVA (-32.3 ± 4.4%, 20 min after HC, p<0.05) and did not alter HR (389 ± 23.9 ± 17.1 to 360 bpm after 20 min HC). In EXP 2 (n=6) HC resulted in a MAP reduction (102.0 ± 4.2 to 62.0 ± 1.1 mmHg, 20 min after HC, p<0.05), a decrease in CVR (-27.6 ± 5.8% after 20 min HC, p <0.05), CVA (-4.5 ± 4.1% after 20 min HC, p<0.05) and HR (387 ± 14 to 347 ± 7.4 bpm after 20 min HC). HS infusion enabled MAP restoration (105.2 ± 3 mmHg, 60 min after infusion of HS, p<0.05), did not alter HR (400 ± 18.4 bpm, 60 min after infusion of HS) raised the RVC to baseline xi levels (-14.6 ± 14.2%, 60 min after infusion of HS, p<0.05) and reduced AVC (- 27.4 ± 4.3%, 60 min after infusion HS, p<0.05) in CON. HS infusion in EXP 1 was not able to restore MAP (54 ± 3.8 mmHg, 60 min after infusion of HS, p<0.05) and RVC (- 48.1 ± 9.7%, 60 min after infusion of HS, p<0.05), did not alter HR (361 ± 15.3 bpm, 60 min after infusion of HS) and was able to promote an increase in AVC similar to baseline (-23.2 ± 10.6%, 60 min after infusion HS, p<0.05) levels. In EXP 2, HS infusion enabled MAP restoration (89 ± 3.3 mmHg, 60 min after infusion of HS, p<0.05) but this return to baseline was delayed and occurred only 50 min after HS infusion (88 ± 3.3 mmHg), HR return (379 ± 6.5 bpm, 60 min after infusion of HS) and RVC to basal levels (-16.1 ± 8.9%, 60 min after infusion HS, p<0.05) and an increase in AVC 10 min after HS infusion (20.3 ± 6.4%, p<0.05), which was restored to levels similar to baseline at registration end (-15.7 ± 6.2%, 60 min after infusion of HS, p<0.05). Together, the results obtained in this study showed that MnPO plays an important role in cardiovascular recovery induced by HS infusion in HC cases. Furthermore, the cardiovascular adjustments involved in this resuscitation seem to depend partly on adrenergic neurotransmission in this nucleus.
Nas últimas décadas, estudos demonstram que a hiperosmolaridade induzida pela infusão de salina hipertônica (SH) traz grandes benefícios para o tratamento da hemorragia hipotensiva. O núcleo pré-óptico mediano (MnPO) é conhecido por receber informações de osmoreceptores centrais e de aferentes periféricos acerca das mudanças na osmolaridade plasmática, modulando os ajustes autonômicos e neuroendócrinos, principalmente através de suas projeções para o núcleo paraventricular do hipotálamo (PVN). O presente estudo buscou determinar o envolvimento do MnPO na recuperação cardiovascular induzida pela infusão intravenosa de solução SH em ratos submetidos ao choque hemorrágico (CH). Ratos Wistar (250 – 300 g) foram anestesiados e instrumentados para registros de pressão arterial média (PAM), frequência cardíaca (FC), fluxo sanguíneo renal (FSR) e aórtico (FSA). Os valores de condutância vascular renal (CVR) e aórtica (CVA) foram calculados a partir da razão entre o FSR ou o FSA e a PAM, respectivamente. O choque hemorrágico foi induzido através da retirada de sangue ao longo de 10 min até que a PAM atingisse valores aproximados de 60 mmHg. A sobrecarga de sódio, pela infusão de SH (NaCl 3 M; 1,8 ml ∙ kg-1 de massa corpórea), foi realizada 2 min após a nanoinjeção (100 nL) do agonista gabaérgico muscimol (4 mM; grupo experimental 1 – EXP 1); do antagonista α-adrenérgico fentolamina (13 mM; grupo experimental 2 – EXP 2) ou de salina isotônica (NaCl; 0,15 M; grupo controle - CON) no MnPO. O CH provocou no CON (n=6) uma redução da PAM (98,4 ± 5,3 para 62,2 ± 1,1 mmHg, 20 min após CH; p<0,05), uma queda na CVR (-59,4 ± 9,2%, 20 min após CH; p<0,05) e não alterou a CVA (-11,5 ± 10,5%, 20 min após CH) e a FC (387,2 ± 12 para 351,7 ± 13 bpm, 20 min após CH). O CH promoveu no EXP 1 (n=6) uma redução da PAM (98 ± 5,4 para 61 ± 0,7 mmHg, 20 min após CH; p<0,05), uma queda na CVR (-64,8 ± 10,9%, 20 min após CH; p<0,05) e na CVA (-32,3 ± 4,4%, 20 min após CH; p<0,05) e não alterou a FC (389 ± 23,9 para 360 ± 17,1 bpm, 20 min após CH). No EXP 2 (n=6) o CH resultou em uma redução da PAM (102,0 ± 4,2 para 62,0 ± 1,1 mmHg, 20 min após CH; p<0,05), uma queda na CVR (- 27,6 ± 5,8%, 20 min após CH; p<0,05) e na FC (387 ± 14 para 347 ± 7,4 bpm, ix 20 min após CH) não alterando a CVA (-4,5 ± 4,1%, 20 min após CH; p<0,05) A infusão de SH possibilitou a restauração da PAM (105,2 ± 3 mmHg, 60 min após infusão de SH; p<0,05), não alterou a FC (400 ± 18,4 bpm, 60 min após infusão de SH), elevou a CVR a níveis basais (-14,6 ± 14,2%, 60 min após infusão de SH; p<0,05) e reduziu a CVA (-27,4 ± 4,3%, 60 min após infusão de SH; p<0,05) no CON a infusão de SH no EXP 1 não foi capaz de restaurar da PAM (54 ± 3,8 mmHg, 60 min após infusão de SH; p<0,05) e a CVR (-48,1 ± 9,7%, 60 min após infusão de SH; p<0,05), não alterou a FC (361 ± 15,3 bpm, 60 min após infusão de SH) e foi capaz de promover uma elevação da CVA a níveis semelhantes aos basais (-23,2 ± 10,6%, 60 min após infusão de SH; p<0,05). No EXP 2, a infusão de SH possibilitou a restauração da PAM (89 ± 3,3 mmHg, 60 min após infusão de SH; p<0,05) porém esse retorno aos valores basais foi tardio e só ocorreu a partir de 50 min da infusão de SH (88 ± 3,3 mmHg), um retorno da FC (379 ± 6,5 bpm, 60 min após infusão de SH) e da CVR a níveis basais (-16,1 ± 8,9%, 60 min após infusão de SH; p<0,05) e uma elevação da CVA 10 min após a infusão de SH (20,3 ± 6,4%, p<0,05) que se restabeleceu a níveis semelhantes aos basais ao final do registro (-15,7 ± 6,2%, 60 min após infusão de SH; p<0,05). Em conjunto, os resultados obtidos no presente trabalho demostraram que o MnPO exerce um importante papel na recuperação cardiovascular induzida pela infusão de SH em quadros de CH. Ademais, os ajustes cardiovasculares envolvidos nessa ressuscitação parecem depender parcialmente da neurotransmissão adrenérgica neste núcleo.
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Guimond, Stephen. "Computational fluid dynamics investigation of the orientation of a pediatric left ventricle assist device cannula to reduce stroke events". Honors in the Major Thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/561.
Testo completoAbstract (sommario):
Ventricle Assist Devices (VADs), which are typically either axial or centrifugal flow pumps implanted on the aortic arch, have been used to support patients who are awaiting cardiac transplantation. Success of the apparatus in the short term has led to long term use. Despite anticoagulation measures, blood clots (thrombi) have been known to form in the device itself or inside of the heart. The Ventricle Assist Devices supply blood flow via a conduit (cannula) implanted on the ascending aorta. Currently, the implantation angle of the VAD cannula is not taken into consideration. Since the VADs supply a significant amount of blood flow to the aorta, the implantation angle can greatly affect the trajectory of the formed thrombi as well as the cardiac flow field inside of the aortic arch. This study aims to vary the implantation angle of a pediatric Left Ventricle Assist Device (LVAD) through a series of computational fluid dynamics (CFD) software simulations focusing on the aortic arch and its branching arteries of a 20 kg pediatric patient in order to reduce the occurrence of stroke.B.S.M.E.
Bachelors
Engineering and Computer Science
Mechanical Engineering
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Ribeiro, Juliana Caldas. "Avaliação da hemodinâmica encefálica em pacientes de alto risco submetidos a cirurgia cardíaca: papel do balão de contrapulsação intra-aórtico". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/5/5131/tde-06042017-085222/.
Testo completoAbstract (sommario):
Introdução: A cirurgia cardíaca resulta em taxa considerável de complicações neurológicas, incluindo delirium, disfunção cognitiva e acidente vascular cerebral isquêmico. Supõe que a fisiopatologia envolva embolia, aterotrombose, hipofluxo, redução do débito cardíaco e alterações da autorregulação cerebral. O balão de contrapulsação intra-aórtico (BIA) é um dispositivo de assistência circulatória comumente utilizado no perioperatório de pacientes de alto risco com o objetivo de otimização do débito cardíaco e da perfusão coronária. Apesar do benefício hemodinâmico do BIA, não é conhecido seu efeito na hemodinâmica encefálica. Objetivo: Avaliar os efeitos do BIA na hemodinâmica encefálica em pacientes de alto risco submetido a cirurgia cardíaca com circulação extracorpórea (CEC). Métodos: Trata-se de um subestudo do estudo clínico prospectivo e randomizado \"Balão de contra-pulsação intra-aórtico eletivo em pacientes de alto risco submetidos a cirurgia cardíaca\", realizado no Instituto do coração do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo entre 2014 e 2016. Dos 181 pacientes incluídos no estudo randomizado, 67 pacientes foram incluídos no subestudo. Os pacientes eram adultos, submetidos a cirurgia cardíaca de revascularização miocárdica (RM) com fração de ejeção menor ou igual a 40% e/ou EuroScore maior ou igual a 6. Os mesmos foram randomizados para uso do BIA logo após a indução anestésica ou para grupo controle. A velocidade de fluxo sanguíneo cerebral (VFSC) pelo ultrassom Doppler transcraniano e a pressão arterial (PA) pelo Finometer foram continuamente gravados por 5 minutos antes da cirurgia (T1), 24h após (T2) e 7 dias após (T3). O índice de autorregulação (ARI) foi estimado através da resposta ao degrau da VFSC a mudanças na PA, derivados da análise da função de transferência. As seguintes complicações clínicas neurológicas foram avaliadas: delirium, disfunção cognitiva e acidente vascular cerebral isquêmico. Resultados: Dos pacientes incluídos no estudo, 34 foram alocados para a estratégia de uso profilático do balão intra-aórtico e 33 para a estratégia controle. Não houve diferenças significativas entre os grupos BIA e controle respectivamente, nos três tempos de avaliação, em relação ao ARI (T1 - 5,5 ± 1,9 vs 5,7 ± 1,7; T2 - 4,0 ± 1,9 vs 4,1 ± 1,6; T3 - 5,7 ± 2,0 vs 5,7 ± 1,6, P= 0,978) e em relação à VFSC (T1 - 57,3 ± 19,4 vs 59,3 ± 11,8; T2 - 74,0 ± 21,6 vs 74,7 ± 17,5; T3 - 71,1 ± 21,3 vs 68,1 ± 15,1; P=0,952). O grupo BIA e o grupo controle apresentaram incidência semelhante de complicações neurológicas (delirium na unidade de terapia intensiva - 26,5% vs 24,2%, P=0,834, acidente vascular cerebral isquêmico - 3,0% vs 2,9%, P=1,00, e declínio cognitivo pós-operatório através das escalas Mini Mental State Examination MMSE - 16,7% vs 40,7%; P= 0,073 e Avaliação Cognitiva Montreal MoCA - 79,16% vs 81,5%; P= 1,000). Conclusões: O uso profilático do BIA em pacientes de alto risco submetidos à cirurgia de revascularização do miocárdio não altera a hemodinâmica encefálica e não está associado ao aumento de complicações neurológicas como delirium, declínio cognitivo e acidente vascular cerebral isquêmicoIntroduction: Cardiac surgery is associated with a high incidence of neurologic complications, such as delirium, cognitive decline and stroke. The pathophysiology probably involves embolism, thrombosis, decreased cardiac output and abnormalities in cerebral autoregulation. The intraaortic balloon pump (IABP) is an assist device commonly in high-risk patients undergoing cardiac surgery aiming to increase the cardiac output and to improve the coronary perfusion. However, the effect of the IABP on the cerebral hemodynamic is unknown. Objectives: To assess the effect of IABP on cerebral hemodynamics in high-risk patients undergoing cardiac surgery with cardio-pulmonary bypass (CPB). Methods: This is a substudy of the randomized controlled trial \"Intraaortic Balloon Counterpulsation in Patients Undergoing Cardiac Surgery (IABCS trial)\", performed at the Heart Institute/University of Sao Paulo, from 2014 to 2016. Of the 181 patients included in the IABCS, 67 were included if they were submitted to cardiac surgery and if they had one of these two criteria: left ventricular ejection fraction equal or lower than 40% and/or EuroSCORE equal or higher than 6. Patients were allocated to the strategy of prohylatic IABP after anesthesia induction or to control. Cerebral blood flow velocity (CBFV) through transcranial Doppler and blood pressure (BP) through Finometer or intra-arterial line were continuously recorded over 5 minutes preoperatively (T1), after 24h (T2) and 7 days after surgery (T3). Autoregulation index (ARI) was estimated from the CBFV response to a step change in BP derived by transfer function analysis. The following complications neurologic were evaluated: delirium, cognitive decline and stroke. Results: Of the included patients, 34 were allocated to the IABP group and 33 to control group. There were no significant differences between the IABP and the control respectively in the following parameters: ARI (T1 - 5.5 ± 1.9 vs 5.7 ± 1.7; T2 - 4.0 ± 1.9 vs 4.1 ± 1.6; T3 - 5.7 ± 2.0 vs 5.7 ± 1.6, P= 0.978), CBFV (T1 - 57.3 ± 19.4 vs 59.3 ± 11.8; T2 - 74.0 ± 21.6 vs 74.7 ± 17.5; T3 - 71.1 ± 21.3 vs 68.1 ± 15.1; P=0.952). Both groups (IABP and control) had similar incidence of neurological complications (delirium - 26.5% vs 24.2%, P=0.834, stroke - 3.0% vs 2.9%, P=1.00, and cognitive decline through the scales Mini Mental State Examination MMSE - 16,7% vs 40,7%; P= 0.073 and Montreal Cognitive Assessment MoCA - 79.16% vs 81.5%; P= 1.000). Conclusions: The prophylactic use of IABP in high-risk patients undergoing cardiac surgery does not change the cerebral hemodynamic and is not associated with higher incidence of neurologic complications such as delirium, cognitive decline and stroke
47
Eazzetta, Benedict A. "Flow visualization of the human abdominal aorta". Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/17800.
Testo completo
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La, Civita Giorgio. "Studio numerico di flussi non Newtoniani in un arco aortico". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Cerca il testo completoAbstract (sommario):
Si è studiata una procedura completamente open source per lo studio CFD del flusso sanguigno a partire da dati TAC, considerando il comportamento non newtoniano del sangue.
La prima parte del progetto si è incentrata sulla validazione del codice implementato in Open-FOAM per la modellazione della reologia non Newtoniana secondo la legge di Casson, modello scelto per le proprietà del sangue. Si è riusciti con successo a validare il codice per diversi regimi di moto che vanno dal laminare al turbolento (col modello k-omega SST), ottenendo un buon accordo con le misurazioni sperimentali utilizzate per il confronto. La seconda parte invece prevedeva lo studio di un arco aortico reale, condotto con la collaborazione del Prof. Dott. Davide Pacini e del Dott. Lucio Careddu del Policlinico Sant’Orsola-Malpighi di Bologna, che hanno fornito le immagini TAC del caso studiato. La modellazione delle immagini TAC mediante ITK-SNAP e Meshlab ha permesso di produrre una superficie con una qualità sufficiente per poter essere utilizzata nel processo di generazione della griglia di calcolo mediante cfMesh. Ottenuta la mesh, si è passati a simularne il comportamento mediante Open-FOAM. Lo studio è stato impostato utilizzando curve reali di pressione e flusso volumetrico. Sono stati condotti due studi con due set di condizioni al contorno (Casi) diversi, per studiare la stabilità del codice e la sua capacità di sopperire alla mancanza di dati. Ogni Caso è stato poi analizzato con tre modelli fluidodinamici: modello laminare, modello k-kl-omega e modello k-omega SSTLM. Per tutti gli studi è stato condotto uno studio stazionario, considerando le pareti come perfettamente rigide (complianza trascurabile). I risultati ottenuti mostrano per ogni caso un ottimo accordo tra i vari modelli, confermando la validità delle ipotesi fatte. Inoltre i valori di flusso volumetrico calcolati sono in accordo con i dati sperimentali utilizzati, suggerendo la corretta conduzione delle analisi fatte.
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Sénejoux, François. "Etudes phytochimique et pharmacologique de Ziziphora clinopodioides (Lamiaceae), Nitraria sibirica (Nitrariaceae) et Echinops integrifolius (Asteraceae), plantes anti-hypertensives de la Pharmacopée ouïghoure". Thesis, Besançon, 2011. http://www.theses.fr/2011BESA3009/document.
Testo completoAbstract (sommario):
Affectant près d'un milliard de personnes dans le monde, l'hypertension artérielle représente un facteur de risque majeur de pathologies cardiovasculaires et d'insuffisance rénale et constitue l'une des principales causes de mortalité. L'identification de traitements anti-hypertenseurs efficaces et tenant compte des particularités des différentes populations du globe présente ainsi un intérêt capital en termes de santé publique. Notre travail a été consacré à l'étude de plantes anti-hypertensives de la Pharmacopée ouïghoure, principale ethnie de la Région autonome du Xinjiang, vaste territoire montagneux et désertique situé au Nord-Ouest de la Chine. L'objectif de la thèse a été d'apporter des arguments scientifiques, phytochimiques et pharmacologiques, permettant de valider et valoriser l'utilisation traditionnelle de ces plantes. La première partie du travail a démontré sur le modèle d'aortes isolées de rat l'effet vasodilatateur de Ziziphora clinopodioides Lam. (Lamiaceae). L'étude des mécanismes impliqués a permis d'identifier une action indépendante de l'endothélium vasculaire et secondaire à une modification des conductances calciques et potassiques. La réalisation d'un fractionnement bioguidé a permis l'identification de 7 métabolites vasoactifs d'origine phénolique. Dans une deuxième partie, les propriétés vasodilatatrices et hypotensives des fruits Nitraria sibirica Pall. (Nitrariaceae) ont été démontrées. L'endothélium vasculaire et la voie du monoxyde d'azote ont été identifiés comme les éléments fondamentaux de cette action vasodilatatrice. Dans une troisième partie, nos travaux ont étudié pour la première fois les effets vasorelaxants et la composition chimique d'Echinops integrifolius Kar. & Kir. (Asteraceae) et ont permis de caractériser 11 métabolites incluant des triterpènes, des flavonoïdes ainsi qu'une coumarine. En conclusion, notre travail de thèse a permis d'apporter, pour la première fois, des arguments expérimentaux soutenant l'usage anti-hypertensif des espèces Ziziphora clinopodioides et Nitraria sibirica. L'étude phytochimique d'Echinops integrifo/ius a également offert des informations chimiotaxonomiques utiles concernant cette espèce et le genre EchinopsAffecting nearly one billion people worldwide, hypertension is the most important risk factor for cardiovascular disease and kidney failure and it is also one of the leading causes of death. The identification of efficient antihypertensive treatments taking into account the specificities of different populations of the world is an important public-health challenge. Our work has been dedicated to the study of anti-hypertensive plants from the Uighur Pharmacopoeia, one of the major ethnie groups in the Xinjiang Autonomous Region, a large desert and mountainous area from the northwestern China. The aim of this work was to provide phytochemical and pharmacological evidences to validate and to enhance the traditional use of these plants. First, the vasodilating properties of Ziziphora clinopodioides Lam. (Lamiaceae) have been shown by using the in vitro model of isolated rat aortic rings. Our data reported an endothelium-independent effect related to changes in calcium and potassium conductances. ln addition, a bioguided fractionation has been carried out and led to the identification of seven vasorelaxant phenolic compounds. Second, the vasodilating and the hypotensive effects of the fruits of Nitraria sibirica Pail. (Nitrariaceae) have been demonstrated and the contribution of vascular endothelium and nitric oxide pathway has been pointed out. Finally, the vasorelaxant properties and the chemical composition of Echinops integrifolius Kar. & Kir. have been investigated for the first time. Eleven secondary metabolites have been isolated including triterpenes, flavonoids and coumarins. ln conclusion, our results provide scientific evidences supporting the traditional use of Ziziphora clinopodioides and Nitraria sibirica as antihypertensive therapy. Additionaly, the phytochemical study of Echinops integrifolius gives chemotaxonomical data about that species and Echinops genus
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Moore, James E. Jr. "Steady and pulsatile flow visualization in the human abdominal aorta". Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/16351.
Testo completo