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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Transmission Probability of Embolic Debris Through the Aortic Arch and Daughter Vessels During a Transcatheter Aortic Valve Replacement Procedure

Wirth, Jessica Lena 01 June 2019 (has links) (PDF)
Cerebral ischemia leading to an ischemic stroke is a possible complication of a transcatheter aortic valve replacement (TAVR) procedure. This is because embolic debris can become dislodged and travel through the aortic arch, where they either continue to the descending aorta and join the systemic circulation or travel into the cerebral vasculature through the three daughter vessels that branch off the top of the aortic arch. These three vessels are the brachiocephalic artery, the left subclavian artery, and the left common carotid artery. These three vessels lead either directly or indirectly to the cerebral vasculature, where the diameter of vessels become very small. If a large enough embolus travels into the cerebral vasculature, it can become stuck in the small cerebral vessels, blocking blood flow and cutting off the supply of oxygen to brain cells. The purpose of this study is to expand upon previous work in order to 1) create a more accurate physics simulation of blood and debris flow through the aortic arch 2) report on embolic debris distribution through the aortic arch and 3) analysis on which physical parameters affect embolic debris distribution. The physical parameters analyzed were particle diameter and particle density. This study was performed by creating a finite element model in COMSOL Multiphysics™ using a SolidWorks model of an aortic arch, with dimensions taken from a patient’s CT scan. Computational fluid dynamics was performed using a pulsatile pressure waveform throughout the aortic arch with a non-constant viscosity model. Once the velocity profile through the aortic arch matched with value ranges from literature, the particle tracing study was implemented. Both a pulsatile pressure waveform and a constant pressure model were analyzed, as well as a constant viscosity model and a non-constant viscosity model. The pulsatile pressure waveform influenced particle distribution and is recommended for future studies since this model leads to pulsatile flow, which is representative of flow through the aorta. It was seen that the non-constant viscosity model did not have a large effect on the velocity profile, but more than doubled the surface average value of viscosity. It also had an effect on the particle distribution through the aortic arch. Small diameter emboli were more likely to flow into the descending aorta, the brachiocephalic artery, and the left subclavian artery; larger emboli were more likely to flow into the left common carotid. Lower density emboli were more likely to flow into the descending aorta and the brachiocephalic artery. Averaging all densities and sizes, it was determined 44.8% of emboli flow into the three daughter vessels, but ultimately only 30.61% of emboli flow into the cerebral vasculature and have the potential to cause an ischemic stroke.
72

Patienters erfarenheter av att ha genomgått en kranskärlsoperation

Isaksson, Jenny, Fransson, Elsa January 2016 (has links)
Bakgrund: En kranskärlsoperation är ett behandlingsalternativ till dem som har en kranskärlssjukdom. Den utförs främst vid komplicerade fall och innebär att med nya kärl skapa en förbindelse förbi det förkalkade kranskärlet runt hjärtat. Operationen är stor och påfrestande, och innebär flera förändringar i livet.   Syfte: Syftet med denna litteraturstudie är att belysa patienters erfarenheter av att ha genomgått en kranskärlsoperation.   Metod: En litteraturstudie utfördes genom att granska 10 vetenskapliga kvalitativa studier som stödjer författarnas syfte. Studierna analyserades och sammanställdes till ett resultat.   Resultat: Operationen påverkade deltagarna och deras återhämtning på olika sätt. Besvärliga kroppsliga symtom kunde visa sig under återhämtningen. Många tankar och funderingar väcktes som skapade oro och rädsla. Stöd och information hade en betydande roll och operationen krävde livsstilsförändringar som kunde vara svåra att anpassa sig till.   Konklusion: Brist på information och avsaknad av länk till sjukhuset efter utskrivning, ledde till rädsla och oro vilket skapade en otrygghet. Ytterligare forskning om stöd och information behövs för att kunna hjälpa och tillfredsställa patienters behov.
73

Angiografi av arteria testicularis / Angiography of the testicular artery

Nordmark, Lars January 1979 (has links)
In addition all patients examined by means of using testicular angiography before the first of November 1978» have been included. 123 patients were intended for angiography, 13 of them bilaterally. The intention with the investigation was to determine whether selective angiography of the testicular artery might be a useful examination in cases of a non-palpable testis and in patients with different intrascrotal lesions. There is a description of a useful method of investigation. The normal angiographic anatomy of the testicular artery is also de­scribed, both retroperitoneally and in the scrotum. In cases with a non-palpable testis it is shown that it is easy to distinguish between agenesis and cryptorchism. The normal magnification angiography of the testis is shown and how various intrascrotal lesions alter the picture. Finally some cases with retroperitoneal lesions are presented in which the testicular artery is committed. / <p>Diss. Umeå : Umeå universitet, 1979, härtill 4 uppsatser</p> / digitalisering@umu
74

Antiarrhythmic effects of ischaemic preconditioning in anaesthetised rats : studies on the roles of bradykinin and nitric oxide

Sun, Wei January 1995 (has links)
No description available.
75

The regulation of apolipoprotein B expression in the human hepatocyte cell line, HepG2

Wang, Timothy Wai-Ming January 1996 (has links)
No description available.
76

Drug-induced vasodilation in human forearm resistance vasculature

Dawes, Matthew January 2001 (has links)
No description available.
77

Visualisation methods for the analysis of blood flow using magnetic resonance imaging and computational fluid dynamics

Gariba, Munir Antonio January 2000 (has links)
No description available.
78

The basis of smooth muscle proliferation in human saphenous vein in vitro

George, Sarah Jane January 1994 (has links)
No description available.
79

Insights into the relationship between coronary calcification and atherosclerosis risk factors

Nicoll, Rachel January 2016 (has links)
Introduction Coronary artery disease (CAD) is the most common cause of death in Europe and North America and early detection of atherosclerosis is a clinical priority. Diagnosis of CAD remains conventional angiography, although recent technology has introduced non-invasive imaging of coronary arteries using computed tomographic coronary angiography (CTCA), which enables the detection and quantification of coronary artery calcification (CAC). CAC forms within the arterial wall and is usually found in or adjacent to atherosclerotic plaques and is consequently known as sub-clinical atherosclerosis.  The conventional cardiovascular (CV) risk factors used to quantify the estimated 10-year coronary event risk comprise dyslipidaemia, hypertension, diabetes mellitus, obesity, smoking and family history of CAD. Nevertheless, their relationship with significant (&gt;50%) stenosis, their interaction with the CAC score and their predictive ability for CAC presence and extent has not been fully determined in symptomatic patients.   Methods   For Papers 1-4 we took patients from the Euro-CCAD cohort, an international study established in 2009 in Umeå, Sweden. The study data gave us the CAC score and the CV risk factor profile in 6309 patients, together with angiography results for a reduced cohort of 5515 patients. In Papers 1 and 2 we assessed the risk factors for significant stenosis, including CAC as a risk factor. Paper 2 carried out this analysis by geographical region: Europe vs USA and northern vs southern Europe. Paper 3 investigated the CV risk factors for CAC presence, stratified by age and gender, while Paper 4 assessed the CV risk factors for CAC extent, stratified by gender.  In paper 5 we carried out a systematic review and meta-analysis of all studies of the risk factor predictors of CAC presence, extent and progression in symptomatic patients. From a total of 884 studies, we identified 10 which fitted our inclusion criteria, providing us with a total of 15,769 symptomatic patients. All 10 were entered in the systematic review and 7 were also eligible for the meta-analysis.   Results Paper 1:           Among risk factors alone, the most powerful predictors of significant coronary stenosis were male gender followed by diabetes, smoking, hypercholesterolaemia, hypertension, family history of CAD and age; only obesity was not predictive. When including the log transformed CAC score as a risk factor, this proved the most powerful predictor of &gt;50% stenosis, but hypercholesterolaemia and hypertension lost their predictive ability. The conventional risk factors alone were 70% accurate in predicting significant stenosis, the log transformed CAC score alone was 82% accurate but the combination was 84% accurate and improved both sensitivity and specificity.  Paper 2:           Despite some striking differences in profiles between Europe and the USA, the most important risk factors for &gt;50% stenosis in both groups were male gender followed by diabetes. When the log CAC score was included as a risk factor, it became by far the most important predictor of &gt;50% stenosis in both continents, followed by male gender. In the northern vs southern Europe comparison the result was similar, with the log CAC score being the most important predictor of &gt;50% stenosis in both regions, followed by male gender.  Paper 3:           Independent predictors of CAC presence in males and females were age, dyslipidaemia, hypertension, diabetes and smoking, with the addition of family history of CAD in males; obesity was not predictive in either gender. The most important predictors of CAC presence in males were dyslipidaemia and diabetes, while among females the most important predictors of CAC presence were diabetes followed by smoking. When analysed by age groups, in both males and females aged &lt;70 years, diabetes, hypertension and dyslipidaemia were predictive, with diabetes being the strongest; in females aged &lt;70 years, smoking was also predictive. Among those aged ≥70 years, the results are completely different, with only dyslipidaemia being predictive in males but smoking and diabetes were predictive in females.  Paper 4:           In the total cohort, age, male gender, diabetes, obesity, family history of CAD and number of risk factors predicted an increasing CAC score, with the most important being male gender and diabetes. In males, hypertension and dyslipidaemia were also predictive, although diabetes was the most important predictor. Diabetes was similarly the most important risk factor in females, followed by age and number of risk factors. Among patients with CAC, hypertension, dyslipidaemia and diabetes predicted CAC extent in both males and females, with diabetes being the strongest predictor in males followed by dyslipidaemia, while diabetes was also the strongest predictor in females, followed by hypertension. Quantile regression confirmed the consistent predictive ability of diabetes.  Paper 5:           In the systematic review, age was strongly predictive of both CAC presence and extent but not of CAC progression. The results for CAC presence were overwhelmed by data from one study of almost 10,000 patients, which found that white ethnicity, diabetes, hypertension and obesity were predictive of CAC presence but not male gender, dyslipidaemia, family history or smoking. With respect to CAC extent, only male gender and hypertension were clearly predictive, while in the one study of CAC progression, only diabetes and hypertension were predictive. In the meta-analysis, hypertension followed by male gender, diabetes and age were predictive of CAC presence, while for CAC extent mild-moderate CAC was predicted by hypertension alone, whereas severe CAC was predicted by hypertension followed by diabetes.   Conclusion Our investigation of the Euro-CCAD cohort showed that the CAC score is far more predictive of significant stenosis than risk factors alone, followed by male gender and diabetes, and there was little benefit to risk factor assessment over and above the CAC score for &gt;50% stenosis prediction. Regional variations made little difference to this result. Independent predictors of CAC presence were dyslipidaemia and diabetes in males and diabetes followed by smoking in females. The risk factor predictors alter at age 70. The most important risk factor predictors of CAC extent were male gender and diabetes; when analysed by gender, diabetes was the most important in both males and females. Our studies have consistently shown the strong predictive ability of male gender in the total cohort and diabetes in males and females and this is reflected in the meta-analysis, which also found hypertension to be independently predictive. Interestingly, dyslipidaemia does not appear to be a strong risk factor.
80

Alterations in gait parameters with peripheral artery disease: The importance of pre-frailty as a confounding variable

Toosizadeh, Nima, Stocker, Hannah, Thiede, Rebecca, Mohler, Jane, Mills, Joseph L, Najafi, Bijan 12 1900 (has links)
Although poor walking is the most common symptom of peripheral artery disease (PAD), reported results are inconsistent when comparing gait parameters between PAD patients and healthy controls. This inconsistency may be due to frailty, which is highly prevalent among PAD patients. To address this hypothesis, 41 participants, 17 PAD (74 +/- 8 years) and 24 aged-matched controls (76 +/- 7 years), were recruited. Gait was objectively assessed using validated wearable sensors. Analysis of covariate (ANCOVA) tests were used to compare gait parameters between PAD and non-PAD groups, considering age, gender, and body mass index as covariates, while stratified based on frailty status. According to the Fried frailty index, 47% of PAD and 50% of control participants were non-frail and the rest were classified as pre-frail. Within non-frail participants, gait speed, body sway during walking, stride length, gait cycle time, double-support, knee range of motion, speed variability, mid-swing speed, and gait initiation were significantly different between PAD and control groups (effect size d = 0.75 +/- 0.43). In the pre-frail group, however, most of the gait differences were diminished except for gait initiation and gait variability. Results suggest that gait initiation is the most sensitive parameter for detecting gait impairment in PAD participants when compared to controls, regardless of frailty status (d = 1.30-1.41; p<0.050). The observed interaction effect between frailty and PAD on gait parameters confirms the importance of assessing functionality in addition to age to provide more consistency in detecting motor performance impairments due to PAD.

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