Dissertations / Theses: 'Stenosis'

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Johansson, Elias. "Carotid stenosis." Doctoral thesis, Umeå universitet, Institutionen för folkhälsa och klinisk medicin, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-46396.

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Carotid stenosis is one of several causes of ischemic stroke and entails a high risk of ischemic stroke recurrence. Removal of a carotid stenosis by carotid endarterectomy results in a risk reduction for ischemic stroke, but the magnitude of risk reduction depends on several factors. If the delay between the last symptom and carotid endarterectomy is less than 2 weeks, the absolute risk reduction is >10%, regardless of age, sex, or if the degree of carotid stenosis is 50–69% or 70–99%. Thus, speed is the key. However, if many patients suffers an ischemic stroke recurrence within the first 2 weeks of the presenting event, an additional benefit is likely be obtained if carotid endarterectomy is performed even earlier than within 2 week after the presenting event. Carotid endarterectomy for asymptomatic carotid stenoses carries a small risk reduction for stroke. Screening for asymptomatic carotid stenosis requires a prevalence of >5% in the examined population, i.e., higher than in the general population; however, directed screening in groups with a prevalence of >5% is beneficial. The aims of this thesis were to investigate the length of the delay to carotid endarterectomy, determine the risk of recurrent stroke before carotid endarterectomy, and determine if a calcification in the area of the carotid arteries seen on dental panoramic radiographs is a valid selection method for directed ultrasound screening to detect asymptomatic carotid stenosis. Consecutive patients with a symptomatic carotid stenosis who underwent a preoperative evaluation aimed at carotid endarterectomy at Umeå Stroke Centre between January 1, 2004–March 31, 2006 (n=275) were collected retrospectively and between August 1, 2007–December 31, 2009 (n=230) prospectively. In addition, 117 consecutive persons, all preliminarily eligible for asymptomatic carotid endarterectomy and with a calcification in the area of the carotid arteries seen on panoramic radiographs, were prospectively examined with carotid ultrasound. The median delay between the presenting event and carotid endarterectomy was 11.7 weeks in the first half year of 2004, dropped to 6.9 weeks in the first quarter year of 2006, and had dropped to 3.6 weeks in the second half year of 2009. The risk of ipsilateral ischemic stroke recurrence was 4.8% within 2 days, 7.9% within 1 week, and 11.2% within 2 weeks of the presenting event. For patients with a stroke or transient ischemic attack as the presenting event, this risk was 6.0% within 2 days, 9.7% within 1 week, and 14.3% within 2 weeks of the presenting event. For the 10 patients with a near-occlusion, the risk of ipsilateral ischemic stroke recurrence was 50% at 4 weeks after the presenting event. Among the 117 persons with a calcification in the area of the carotid arteries seen on panoramic radiographs, eight had a 50–99% carotid stenosis, equalling a prevalence of 6.8% (not statistically significantly over the pre-specified 5% threshold). Among men, the prevalence of 50–99% carotid stenosis was 12.5%, which was statistically significantly over the pre-specified 5% threshold. In conclusion: The delay to carotid endarterectomy was longer than 2 weeks. Additional benefit is likely to be gained by performing carotid endarterectomy within a few days of the presenting event instead of at 2 weeks because many patients suffer a stroke recurrence within a few days; speed is indeed the key. The finding that near-occlusion entails an early high risk of stroke recurrence stands in sharp contrast to previous studies; one possible explaination is that this was a high-risk period missed in previous studies. The incidental finding of a calcification in the area of the carotid arteries on a panoramic radiograph is a valid indication for carotid ultrasound screening in men who are otherwise eligible for asymptomatic carotid endarterectomy.

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Lee, Paul Man-Yiu. "Critical coronary stenosis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq23948.pdf.

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Eklöf, Hampus. "On Renal Artery Stenosis." Doctoral thesis, Uppsala University, Department of Oncology, Radiology and Clinical Immunology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5945.

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Renal artery stenosis (RAS) is a potentially curable cause of hypertension and azotemia. Besides intra-arterial renal angiography there are several non-invasive techniques utilized to diagnose patients with suspicion of renal artery stenosis. Removing the stenosis by revascularization to restore unobstructed blood flow to the kidney is known to improve and even cure hypertension/azotemia, but is associated with a significant complication rate.

To visualize renal arteries with x-ray techniques a contrast medium must be used. In a randomized, prospective study the complications of two types of contrast media (CO₂ and ioxaglate) were compared. CO₂ was not associated with acute nephropathy, but induced nausea and had lower attenuation differences compared to Ioxaglate. Acute nephropathy was related to the ioxaglate dose and the risk was evident even at very low doses if the patients were azotemic with creatinine clearance <40 ml/min.

Evaluating patients for clinically relevant renal artery stenosis can be done utilizing several non-invasive techniques. MRA was retrospectively evaluated and shown to be accurate in detecting hemodynamically significant RAS. In a prospective study of 58 patients, evaluated with four methods for renal artery stenosis, it was shown that MRA and CTA were significantly better than ultrasonography and captopril renography in detecting hemodynamically significant RAS. The standard of reference was trans-stenotic pressure gradient measurement, defining a stenosis as significant at a gradient of ≥15 mmHg. The discrepancies were mainly found in the presence of borderline stenosis.

The outcome of percutaneous revascularization procedures showed a technical success rate of 95%, clinical benefit in 63% of treated patients, 30-day mortality 1.5% and major complication rate of 13%. The major complication rate for patients with baseline serum creatinine >300µmol/l was 32%. Our results compare favorably with published studies and guidelines.

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Kragsterman, Björn. "Carotid Artery Stenosis : Surgical Aspects." Doctoral thesis, Uppsala University, Department of Surgical Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6834.

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Randomised controlled trials (RCT) have demonstrated a net benefit of carotid endarterectomy (CEA) in stroke prevention for patients with severe carotid artery stenosis as compared to best medical treatment. Results in routine clinical practice must not be inferior to those in the RCTs. The carotid arteries are clamped during CEA which may impair the cerebral perfusion.

The aim of this thesis was to assess population-based outcomes from CEA, investigate risk factors for perioperative complications/late mortality and to evaluate effects of carotid clamping during CEA. In the Swedish vascular registry 6182 CEAs were registered during 1994-2003. Data on all CEAs were retrieved, analysed and validated. In the validation process no death or disabling stroke was unreported. The perioperative stroke or death rate was 4.3% for those with symptomatic and 2.1% for asymptomatic stenosis (the latter decreasing over time). Risk factors for perioperative complications were age, indication, diabetes, cardiac disease and contralateral occlusion. Median survival time was 10.8 years for the symptomatic and 10.2 years for the asymptomatic group.

Tolerance to carotid clamping during CEA under general anaesthesia was evaluated in 62 patients measuring cerebral oximetry, transit time volume flowmetry and stump pressure. High internal carotid artery flow before clamping and low stump pressure was associated with decreased oxygenation after clamping suggesting shunt indication.

In 18 patients undergoing CEA, jugular bulb blood samples demonstrated significantly altered levels of marker for inflammatory activation (IL-6) and fibrinolytic activity (D-dimer and PAI-1) during carotid clamping as compared to radial artery levels. This indicates a cerebral ischaemia due to clamping although clinically well tolerated.

In conclusion, the perioperative outcome after CEA in Sweden compared well with the RCTs results. Tolerance to carotid clamping may be evaluated by combining stump pressure and volume flow measurements. Although clinically tolerated clamping may induce a cerebral ischaemic response.

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Kragsterman, Björn. "Carotid artery stenosis : surgical aspects /." Uppsala : Acta Universitatis Upsaliensis : Univ.bibl. [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6834.

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McCann, Gerald Patrick. "Exercise limitation in aortic stenosis." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395082.

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Pawade, Tania Ashwinikumar. "Imaging calcification in aortic stenosis." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/29589.

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BACKGROUND Aortic stenosis is a common and potentially fatal condition in which fibro-calcific changes within the valve leaflets lead to the obstruction of blood flow. Severe symptomatic stenosis is an indication for aortic valve replacement and timely referral is essential to prevent adverse clinical events. Calcification is believed to represent the central process driving disease progression. 18F-Fluoride positron emission tomography computed tomography (PET-CT) and CT aortic valve calcium scoring (CT-AVC) quantify calcification activity and burden respectively. The overarching aim of this thesis was to evaluate the applications of these techniques to the study and management of aortic stenosis. METHODS AND RESULTS REPRODUCIBILITY The scan-rescan reproducibility of 18F-fluoride PET-CT and CT-AVC were investigated in 15 patients with mild, moderate and severe aortic stenosis who underwent repeated 18F-fluoride PET-CT scans 3.9±3.3 weeks apart. Modified techniques enhanced image quality and facilitated clear localization of calcification activity. Percentage error was reduced from ±63% to ±10% (tissue-to-background ratio most-diseased segment (MDS) mean of 1.55, bias -0.05, limits of agreement - 0·20 to +0·11). Excellent scan-rescan reproducibility was also observed for CT-AVC scoring (mean of differences 2% [limits of agreement, 16 to -12%]). AORTIC VALVE CALCIUM SCORE: SINGLE CENTRE STUDY Sex-specific CT-AVC thresholds (2065 in men and 1271 in women) have been proposed as a flow-independent technique for diagnosing severe aortic stenosis. In a prospective cohort study, the impact of CT-AVC scores upon echocardiographic measures of severity, disease progression and aortic valve replacement (AVR)/death were examined. Volunteers (20 controls, 20 with aortic sclerosis, 25 with mild, 33 with moderate and 23 with severe aortic stenosis) underwent CT-AVC and echocardiography at baseline and again at either 1 or 2-year time-points. Women required less calcification than men for the same degree of stenosis (p < 0.001). Baseline CT-AVC measurements appeared to provide the best prediction of subsequent disease progression. After adjustment for age, sex, peak aortic jet velocity (Vmax) ≥ 4m/s and aortic valve area (AVA) < 1 cm2, the published CT-AVC thresholds were the only independent predictor of AVR/death (hazard ratio = 6.39, 95% confidence intervals, 2.90-14.05, p < 0.001). AORTIC VALVE CALCIUM SCORE: MULTICENTRE STUDY CT-AVC thresholds were next examined in an international multicenter registry incorporating a wide range of patient populations, scanner vendors and analysis platforms. Eight centres contributed data from 918 patients (age 77±10, 60% male, Vmax 3.88±0.90 m/s) who had undergone ECG-gated CT within 3 months of echocardiography. Of these 708 (77%) had concordant echocardiographic assessments, in whom our own optimum sex-specific CT-AVC thresholds (women 1377, men 2062 AU) were nearly identical to those previously published. These thresholds provided excellent discrimination for severe stenosis (c-statistic: women 0.92, men 0.88) and independently predicted AVR and death after adjustment for age, sex, Vmax ≥4 m/s and AVA < 1 cm2 (hazards ratio, 3.02 [95% confidence intervals, 1.83-4.99], p < 0.001). In patients with discordant echocardiographic assessments (n=210), CT-AVC thresholds predicted an adverse prognosis. BICUSPID AORTIC VALVES Within the multicentre study, higher continuity-derived estimates of aortic valve area were observed in patients with bicuspid valves (n=68, 1.07±0.35 cm) compared to those with tri-leaflet valves (0.89±0.36 cm p < 0.001,). This was despite no differences in measurements of Vmax (p=0.152), or CT-AVC scores (p=0.313). The accuracy of AVA measurments in bicuspid valves was therefore tested against alternative markers of disease severity. AVA measurements in bicuspid valves demonstrated extremely weak associations with CT-AVC scores (r2=0.08, p=0.02) and failed to correlate with downstream markers of disease severity in the valve and myocardium and against clinical outcomes. AVA measurements in bicuspid patients also failed to independently predict AVR/death after adjustment for Vmax ≥4 m/s, age and gender. In this population CT-AVC thresholds (women 1377, men 2062 AU) again provided excellent discrimination for severe stenosis. CONCLUSIONS Optimised 18F-fluoride PET-CT scans quantify and localise calcification activity, consolidating its potential as a biomarker or end-point in clinical trials of novel therapies. CT calcium scoring of aortic valves is a reproducible technique, which provides diagnostic clarity in addition to powerful prediction of disease progression and adverse clinical events.

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Boyd, C. S. "Radiological evaluation of renal artery stenosis." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426973.

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Kattach, Hassan. "Blood pressure control in aortic stenosis." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526473.

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Försth, Peter. "On Surgery for Lumbar Spinal Stenosis." Doctoral thesis, Uppsala universitet, Institutionen för kirurgiska vetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-262525.

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The incidence of lumbar spinal stenosis (LSS) is steadily rising, mostly because of a noticeably older age structure. In Sweden, LSS surgery has increased continuously over the years and is presently the most common argument to undergo spine surgery. The purpose of the surgery is to decompress the neural elements in the stenotic spinal canal. To avoid instability, there has been a tradition to do the decompression with a complementary fusion, especially if degenerative spondylolisthesis is present preoperatively. The overall aims of this thesis were to evaluate which method of surgery that generally can be considered to give sufficiently good clinical results with least cost to society and risk of complications and to determine whether there is a difference in outcome between smokers and non-smokers. The Swespine Register was used to collect data on clinical outcome after LSS surgery. In two of the studies, large cohorts were observed prospectively with follow-up after 2 years. Data were analysed in a multivariate model and logistic regression. In a randomised controlled trial (RCT, the Swedish Spinal Stenosis Study), 233 patients were randomised to either decompression with fusion or decompression alone and then followed for 2 years. The consequence of preoperative degenerative spondylolisthesis on the results was analysed and a health economic evaluation performed. The three-dimensional CT technique was used in a radiologic biomechanical pilot study to evaluate the stabilising role of the segmental midline structures in LSS with preoperative degenerative spondylolisthesis by comparing laminectomy with bilateral laminotomies. Smokers, in comparison with non-smokers, showed less improvement after surgery for LSS. Decompression with fusion did not lead to better results compared with decompression alone, no matter if degenerative spondylolisthesis was present preoperatively or not; nor was decompression with fusion found to be more cost-effective than decomression alone. The instability caused by a decompression proved to be minimal and removal of the midline structures by laminectomy did not result in increased instability compared with the preservation of these structures by bilateral laminotomies. In LSS surgery, decompression without fusion should generally be the treatment of choice, regardless of whether preoperative degenerative spondylolisthesis is present or not. Special efforts should be targeted towards smoking cessation prior to surgery.

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Sandhu, G. S. "Management of adult benign laryngotracheal stenosis." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1324556/.

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Upper airway stenosis has a significant impact on the quality of life and sometimes on life itself. The incidence of this condition is likely to be increasing as survival rates following periods of ventilation on Intensive Care Units (ICUs) improve (1, 2). Paediatric laryngotracheal stenosis is a well researched discipline and treatment includes airway augmentation with rib grafts and tracheal or cricotracheal resection with end-to-end anastomosis. At the start of my research, in 2005, adult laryngotracheal stenosis was poorly researched and the treatment options were tracheostomy, tracheal resection or cricotracheal resection, each with associated morbidity and mortality. This thesis investigates the aetiology, incidence, screening and alternative treatment options, which include endoscopic techniques, for the management of acquired adult benign laryngotracheal stenosis. The commonest causes for this condition are ventilation on intensive care units and inflammatory disorders such as Wegener's granulomatosis, idiopathic subglottic stenosis and sarcoidosis. In January 2004 a prospective database was set up in the busiest airway reconstruction unit in the United Kingdom. Data was collected on all new adult patients with upper airways stenosis. At the completion of this research in January 2010, 400 patients had been entered on this database. Due to the rarity of this condition, it was not possible to design randomised trials to compare different treatment options. This thesis is an integrated series of prospective cohort studies, with the aim of developing a greater understanding of adult airway stenosis, with a particular emphasis on minimally invasive endoscopic techniques. This research has shown that 72% of patients with post-intubation airway stenosis can be treated with these minimally invasive endoscopic techniques. Effective new treatments have been devised for the management of inflammatory stenoses when the results of previous treatments had not been effective. New tools for assessing the airway and outcome measures have also been proposed.

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Shalhoub, Joseph. "Risk stratification in atherosclerotic cartoid stenosis." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9063.

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Introduction: Key trials and a Cochrane systematic review in asymptomatic carotid stenosis have highlighted the need to identify a high-risk subgroup of patients with carotid stenosis who may benefit from intervention. Traditionally, this risk stratification has considered structural imaging and clinical factors. However, using only these approaches, still a significant number of patients are missed. Biological attributes are acknowledged as key determinants of thrombo-embolic events. Functional and hybrid structural-functional imaging, and circulating biomarkers allow exploration of plaque biology non-invasively, in vivo. The importance of innate immunity in atherosclerosis is now established, with a recent interest in macrophage phenotypic polarisation in atherosclerosis supported by in vitro and experimental data, with the hypothesis of an M1 macrophage predominance associated with unstable plaques. The emergence of systems biology has been seen to facilitate understanding of biological pathways and generate hypotheses, although the utility of this approach for the examination of human atherosclerosis tissue has not been fully explored. Aims: (i) To employ functional imaging to probe carotid atherosclerosis in vivo; (ii) to assess the plaque microenvironment in determination of the balance of macrophage populations in unstable compared with stable atherosclerosis; (iii) to investigate whether late phase (LP-) contrast enhanced ultrasound (CEUS) reflects plaque biological features; (iv) to examine the utility of systems biology techniques in distinguishing symptomatic from asymptomatic carotid atherosclerosis tissue, and in hypothesis generation; and (v) to evaluate a putative biomarker for carotid atherosclerosis and plaque vulnerability. Methods: Patients with carotid stenosis, both symptomatic and asymptomatic, have undergone systematic collection of data, fresh carotid endarterectomy (CEA) specimens, and plasma. Thirty-two patients with 36 carotid stenoses underwent 11C-PK11195 PET/CT. Thirty-seven patients had dynamic (D-) and LP-CEUS carotid imaging. CEA specimens were assessed by immunohistochemical techniques, as well as atheroma cell culture with supernatant multi-analyte profiling (MAP). MAP data was subject to Ingenuity Pathway Analysis. CEA specimens were further examined using systems biology methodologies: transcriptomics with Affymetrix Human Exon 1.0 ST arrays; proteomics and lipidomics by liquid chromatography (LC) coupled to tandem triple quadrupole mass spectrometry (MS); and metabolite profiling by nuclear magnetic resonance and LC-MS. Furthermore, venous and arterial plasma was quantified for the lysozyme, a putative biomarker in carotid atherosclerosis. Results: 11C-PK11195 PET allowed the non-invasive quantification of intraplaque inflammation in patients with carotid stenoses and, when combined with CTA, provided an integrated assessment of plaque structure, composition and biological activity. 11C-PK11195 PET/CT distinguished between recently symptomatic vulnerable plaques and asymptomatic plaques with a high positive predictive value. D-CEUS and LP-CEUS (at a cut-off of zero) was able to distinguish symptomatic and asymptomatic plaques. Atheroma cell culture and supernatant MAP revealed that symptomatic human atherosclerotic carotid disease is associated with a cytokine and chemokine pattern consistent with the predominance of pro-inflammatory M1-type macrophage polarisation. Furthermore, IFNγ signatures are observed, including the novel finding of CCL20 with its significant elevation in symptomatic atherosclerosis. MAP of supernatants from patients who had undergone ipsilateral carotid LP-CEUS revealed significantly higher levels of IL6, MMP1 and MMP3, as well as greater CD68 and CD31 immunopositivity, in those with high (≥0) compared with low (<0) LP-CEUS signal. This suggests that LP-CEUS was able to reflect plaque biology. Transcriptomic analysis was able to clearly separate stenosing plaque and intimal thickening, as well as unstable and stable atherosclerosis, finding differential expression and alternative splicing of interferon regulatory factor 5 between stenosing plaque and intimal thickening. Proteomic analysis of the salt extract fraction from carotid atherosclerotic plaques identified 2,470 proteins implicated in 33 bio-molecular functions and having their origins previously described in 14 different cellular compartments. There were 159 proteins which, based upon the number of assigned spectra, were significantly different between symptomatic and asymptomatic atherosclerosis. Through lipidomic analysis, 150 lipid species from 9 different classes were identified, of which 24 were exclusive to atherosclerotic plaques. A comparison of 28 carotid endarterectomy specimens revealed differential lipid signatures of symptomatic compared with asymptomatic lesions, as well as stable and unstable plaque areas. Similarly, LC-MS metabolite profiling of organic plaque extract was able to separate symptomatic from asymptomatic atherosclerosis. Arterial and venous plasma lysozyme levels were seen to distinguish individuals with carotid atherosclerosis from matched control subjects. Furthermore, arterial plasma lysozyme levels were significantly higher in patients with symptomatic than asymptomatic carotid stenosis. Conclusions: These findings support the use of hybrid structural-functional imaging, and the utility and use of a systems biology approach in identifying significantly different and biologically relevant variations in atherosclerosis tissue, and in hypothesis generation for further study. The data presented concurs with recent reports in the literature linking the lipidic/organic component of atherosclerosis with the generation of a pro-inflammatory plaque microenvironment prone to lesion development, instability and the complications thereof. The importance of innate immunity has been highlighted with the demonstration of a predominance of M1 macrophage polarisation and evidence of Th17/IL17 signalling in unstable atherosclerosis. It is hoped that this work will contribute to the ongoing refinement of multi-factorial risk stratification in carotid atherosclerosis.

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Ihlberg, Leo. "Surveillance for infrainguinal vein graft stenosis." Helsinki : University of Helsinki, 2001. http://ethesis.helsinki.fi/julkaisut/laa/kliin/vk/ihlberg/.

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Anderson, David Barrett. "Optimising Management of Lumbar Spinal Stenosis." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25075.

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Low back pain is the leading cause of disease burden globally, impacting over half a billion people. Low back pain is a broad classification of a condition which includes multiple clinical presentations, such as spondylosis, discogenic pain, muscle and ligament injuries, and lumbar spinal stenosis (LSS). This thesis has focused on LSS, which itself is a leading cause of pain, disability, and reduced quality of life among older adults. Eight chapters are included in this thesis that aims to improve the management of LSS. Chapter One was an introduction to LSS, its diagnosis, prevalence, and current management. Chapter Two outlined the largest known cohort study of emergency department attendance and hospital admission for low back pain conditions (e.g., LSS, disc protrusion) in New South Wales, Australia, between 2005 and 2014. This cohort study found that attendance to emergency departments and hospital admissions increased over the 10-years of the study, possibly due to the ageing Australian population, given an increase in the mean age of the people who presented over the study period. The study also found that people who were from lower socioeconomic backgrounds or who were managed under a worker’s compensation scheme had lower odds of being admitted to hospital following their presentation to the emergency department with a low back pain condition. Having demonstrated that both the attendance rates to hospital emergency departments and the mean age of the population presenting for low back pain had increased in recent years, more information on currently endorsed treatments for LSS, the most common lumbar pain presentation among older people, was sought. Chapter Three was a systematic review of international LSS clinical practice guidelines that examined the quality of the guidelines themselves, and the evidence supporting their treatment recommendations. Chapter Three found that around three-quarters of the recommendations presented in international practice guidelines for LSS were based on poor-quality evidence. There were no recommendations in the guidelines based on high-quality evidence. This study also identified that overall, guidelines made more recommendations in favour of surgery and injections than for medications and other non-surgical treatments, despite the evidence for both interventions being comparable. The absence of good evidence to support treatments for LSS highlighted the need for more high-quality studies to be conducted on LSS. To assist with increasing the number of high-quality studies conducted on LSS, a series of studies were planned to help inform the design of future studies. Initially, two systematic reviews were planned on key aspects of study design. The first review in Chapter Four was on the measurement properties of outcome measures and the second, presented in Chapter Five, on placebo-controlled trials of surgery for musculoskeletal conditions, including spinal conditions. Although the choice of appropriate outcome measures should be at the centre of trial design, their measurement properties are often overlooked. The review on outcome measures outlined in Chapter Four aimed to identify the walking test(s) with the best measurement properties in people with LSS. Walking tests were selected as the outcome of priority, as people living with LSS often nominate walking ability as the most important part of their condition that they want improved. A systematic review and meta-analysis were therefore conducted on the measurement properties used to assess LSS. This study found that there was a limited number of studies assessing the key measurement properties of validity, reliability, and responsiveness. Of the data that were available, the self-paced walking test and walking item of the Oswestry Disability Index were recommended to be used together before and after any intervention for LSS. Next, the review on placebo-controlled trials of surgery for musculoskeletal conditions was completed as presented in Chapter Five. The rationale for this review was based upon the findings of Chapter Three confirming the lack of studies utilising high-quality methods including randomisation, placebo-controls, and adequate blinding. It is well known that randomised, placebo-controlled trials are the gold standard for determining the efficacy of interventions, because of their ability to account for placebo and other non-specific effects. A systematic review was conducted in Chapter Five to investigate the number and quality of existing randomised placebo-controlled trials of surgical management of musculoskeletal conditions. Whilst the study found that no randomised placebo-controlled trials had been completed on LSS, 18 trials had been completed on other musculoskeletal conditions (e.g., vertebroplasty for vertebral compression fractures). Chapter Five found a rapid increase in the number of placebo-controlled trials of musculoskeletal conditions, from 2 trials before the year 2000 to 20 trials between 2001 and 2020. The study also found that the majority of trials (59%) used a high-fidelity placebo control, which was the degree in which the placebo procedure mimicked all but the ‘active’ component of the surgical procedure being assessed. Minimal fidelity placebo controls were those that had only minimal resemblance to the surgical procedure, such as using a skin incision only, when assessing meniscal repair. The vast use of high-fidelity placebo surgery suggests an increased focus on accounting for non-specific effects and maximising blinding of patients in placebo trials of musculoskeletal surgery. Considering the level of fidelity and other methodological aspects of placebo-controlled trials of surgery can help to improve their feasibility and impact on policy and practice. Following decisions on level of treatment fidelity, another important aspect to trial design in placebo-trials included engaging key stakeholders in the design process, as discussed by Beard et al (2020) in their Lancet paper on consideration and methods of placebo studies. In Chapter Six, LSS patients considered eligible for spine surgery were surveyed to determine their opinions, including barriers to participation in a placebo-controlled surgical trial. The study suggested that a placebo-controlled trial was feasible, with just under 1 in 5 eligible patients with LSS stating that they would consider participation in a placebo-surgical trial of LSS. Following the engagement of LSS patients, spinal surgeons were then consulted in Chapter Seven, to better understand how they viewed the current evidence supporting LSS. Surgeons were also asked what change they expected following spine surgery, including on neurogenic claudication following lumbar decompression. The key findings in Chapter Seven were that spine surgeons expected a mean improvement in neurogenic claudication by 3 months post-surgery of 86% (median: 87%, interquartile range (IQR): 80%, 91%), using a +/- 100% change scale. The majority of surgeons also rated the quality of evidence for lumbar decompression procedures, including decompression alone, decompression with fusion, and interspinous spacer, as low to moderate, supporting the need for future studies. The combined results of Chapter Six and Seven then helped inform the first randomised placebo-controlled trial of decompression for LSS, which has its protocol outlined in Appendix One.

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Cowell, Sarah Joanna. "Lipid-lowering therapy in calcific aortic stenosis." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/29075.

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We hypothesised that (a) risk factors for atherosclerosis would predict, and (b) lipid lowering therapy would retard, disease progression and clinical outcome in patients with calcific aortic stenosis. Objectives: In patients with aortic stenosis, (i) to compare the magnitude and reproducibility of measures of valvular stenosis and calcification, (ii) to determine the effect of intensive lipid lowering therapy on disease progression and clinical outcome, and (iii) to describe predictors of disease progression and clinical outcome. Methods: In the Scottish Aortic stenosis and Lipid lowering Therapy, Impact on Regression (SALTIRE) trial, 155 patients aged 68±11 years (range 34-85) with aortic valve stenosis underwent helical computed tomography and Doppler echocardiography. In a double blind randomised controlled trial, 77 patients were assigned to atorvastatin 80 mg daily and 78 to matched placebo over a medium period of 25 months. Of the 155 patients, 102 had detectable coronary artery calcification on computed tomography with 48 of these patients being randomised to atorvastatin and 54 to placebo. Conclusions: Calcification of the aortic valve is closely associated with the severity of aortic stenosis with heavy calcification suggesting the presence of severe aortic stenosis that requires urgent cardiological assessment. In contrast to observational studies, intensive lipid-lowering therapy does not halt the progression or induce regression of aortic stenosis or coronary artery calcification. Long-term, large-scale, randomised, controlled trials are needed to establish the role of statin therapy in patients with calcific aortic stenosis. The major predictors of disease progression and clinical outcome remain baseline measures of disease severity; namely aortic-jet velocity, aortic valve calcification and serum BNP concentration. With the exception of hypertension the presence of atherosclerotic risk factors and vascular disease are not predictive. Our findings suggest that atherogenesis does not provide a major contribution to the progression of aortic stenosis.

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Simons, Dianne Margaret. "The hydrodynamics of idiopathic hypertrophic subaortic stenosis." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/10257.

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Das, Paul Kumar. "Prediction of symptom onset in aortic stenosis." Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414771.

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Cheshire, Nicholas John. "Risk factors in infra-inguinal graft stenosis." Thesis, University of Leicester, 1993. http://hdl.handle.net/2381/34301.

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Intimal hyperplasia appears to be the universal vessel response to injury and is important in atherogenesis. In animal and in-vitro models, the initiation and promotion of this process has been associated with a number of risk factors found in the circulation. In man, approximately 25% of infrainguinal bypass grafts develop stenosis due to smooth muscle cell proliferation but it is not known if circulating risk factors influence this process. In these studies, circulating risk factors have been correlated with the development of hyperplastic stenoses in infrainguinal bypass grafts. Non-hyperplastic causes of stenosis have been excluded by peri-operative graft assessment. Duplex scanning and angiography were used to detect new stenoses occuring in the first postoperative year. Logistic regression shows association between graft stenoses and; continued cigarette smoking and elevated circulating levels of fibrinogen, Lp(a) and 5-HT. These associations are independent of graft material or whether grafts were studied prospectively or retrospectively. There were some differences in stenosis associated risk factors between vein and PTFE graft groups on univariate analysis. These results suggest that circulating risk factors do play a role in intimal hyperplasia and stenosis of human infrainguinal bypass grafts and support other work demonstrating a reduction in graft patency in association with similar abnormalities.

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Izeki, Masanori. "Reduction of Atlantoaxial Subluxation Causes Airway Stenosis." Kyoto University, 2014. http://hdl.handle.net/2433/185188.

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Bull, Sacha Colette. "Aortic stenosis : pathophysiological effects on the myocardium and predictors of clinical events : physiology of the myocardium in aortic stenosis." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:a05f5eea-ae68-43a5-84b3-d9a0a1ee40ce.

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The management of the asymptomatic patients with severe aortic stenosis (AS) is challenging; clinicians have to balance the risks of early surgery against the risk that irreversible myocardial damage may occur with a conservative management strategy. It has become increasingly apparent that prognosis in asymptomatic AS depends not only on the degree of valvular stenosis, but also on the myocardial response to pressure overload and understanding the mechanisms of myocardial decompensation may help to guide management in the future. The degree of myocardial fibrosis, microvascular dysfunction, hypertrophy and left ventricular (LV) geometry may all play important roles. However, current guidelines for management of asymptomatic AS limit assessment of the myocardium to the measurement of ejection fraction with echocardiography. More advanced techniques may provide greater information that could be clinically useful. This thesis seeks to further our understanding of the mechanisms of the myocardial response to AS, using Cardiac Magnetic Resonance (CMR) in patients with moderate and severe AS. Myocardial perfusion in AS is examined in chapter 3. The results show that CMR first pass perfusion can be carried out safely and is well tolerated by AS patients. Microvascular dysfunction in these patients was associated with age, exercise time and markers of diastolic dysfunction. Myocardial strain is examined in chapter 4, utilizing a new software tool to look at strain throughout the left ventricle, and also to explore the relationship between strain and myocardial fibrosis. The results show that there are significant variations in circumferential strain measurements, depending on slice position in the LV, and also that there was no relationship found between strain and the degree of LV fibrosis. In chapter 5, the potential of CMR T1 mapping to identify fibrosis is examined using a new shortened non-contrast sequence (ShMOLLI - Shortened Modified Look-Locker Inversion) developed in our unit. CMR T1 values were validated against histological quantification of myocardial fibrosis in a large group of moderate and asymptomatic AS. A good correlation was found between ShMOLLI derived T1 values, with T1 values increasing with the severity of AS. The clinical value of measuring myocardial perfusion and LV global strain is examined in chapter 6 by linking these to prognosis. Measurement of circumferential strain could predict prognosis in asymptomatic AS, but myocardial perfusion showed poor ability to predict events. In conclusion, this thesis offers further insights into the changes that occur in the myocardium of patients with asymptomatic moderate and severe AS, using established and new CMR techniques. The clinical value of measuring these CMR parameters to aid risk stratification is shown, and the future potential for monitoring new therapies in these patients is discussed in the final chapter.

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21

Jönsson, Anders. "Surgical treatment of left main coronary artery stenosis /." Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-736-7/.

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22

Jansson, Karl-Åke. "On lumbar spinal stenosis and disc herniation surgery /." Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-257-8/.

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23

Bouma, Berto Jorrit. "Clinical decision making in elderly with aortic stenosis." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2005. http://dare.uva.nl/document/78202.

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24

Shrum, Jeff. "Platelet adhesion in an asymmetric stenosis flow model." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100235.

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Platelets have been shown to be a main contributor to thrombus formation in stenotic arteries leading to acute coronary syndromes. It is thought that increased activation and adhesion of platelets under variable shear and complex flow conditions contribute to thrombosis. The objective of this work was to evaluate the relationship between asymmetric stenosis hemodynamics and platelet adhesion using in-vitro models developed to properly simulate physiological conditions. In this study, platelet rich plasma was circulated through stenotic and straight coronary artery models. Adhesion results were obtained by post-perfusion fluorescent labelling and imaging of adhered platelets. Analysis of platelet area coverage has shown maximum adhesion occurs in the distal region of the stenosis. Most likely this is due to increased exposure time of platelets to the wall of the recirculation zone following the stenosis and that exposure being directly after a period of high shear stress. This result gives us a better understanding of the importance of both shear and flow conditions in coronary artery thrombosis.

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25

Barkhordarian, Reza. "Subaortic stenosis in hearts with intact ventricular septum." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511290.

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26

Chen, Lijia. "Rapid angiographic stenosis progression : systematic and local factors." Thesis, St George's, University of London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299283.

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27

Georgoula, C. "Molecular genetic analysis of infantile hypertrohpic pyloric stenosis." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/16124/.

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The aim of this study was to identify susceptibility genes for the common disease Infantile Hypertrophic Pyloric Stenosis (IHPS) using a whole genome screening approach. IHPS is a form of gastrointestinal obstruction with an incidence between 1 and 5 per 1000 live births. It is characterized by hypertrophy of the pyloric smooth muscle, which develops after birth in response to enteral feeds and leads to gastric outlet obstruction with projectile vomiting. IHPS is commonly inherited as a multifactorial trait with a marked male preponderance but monogenic and syndromic forms are also described. Molecular genetic studies have previously identified two IHPS predisposing regions (IHPS1 [MIM #179010] and IHPS2 [MIM #610260]), which seem to account for a small subset of IHPS cases. DNA samples from over 500 IHPS families were collected in total. This work included the molecular analysis of a proportion of those families. A pedigree with 8 affected individuals was analysed using a SNP-based genome-wide linkage scan and a locus for monogenic IHPS on chromosome 16q24 was identified (LOD score 3.7). Analysis of candidate gene SLC7A5 did not reveal any mutations and analysis of 14 further multiplex pedigrees for evidence of linkage to 16q24 did not result in significant LOD scores supporting locus heterogeneity. Additionally, a SNP-based genome-wide linkage analysis of 81 pedigrees identified 2 more IHPS predisposing loci on chromosomes 11q14-q22 (Z_max= 3.9, p<0.0001; HLOD_max = 3.4, alpha = 0.34) and Xq23 (Z_max = 4.3, p<0.00001; HLOD_max = 4.8, alpha = 0.56), and a region of potential interest on chromosome 3, (Z_max = 2.70, p<0.003; HLOD_max = 1.78, alpha=0.52). These three regions each harbor candidate genes that are members of the canonical transient receptor potential (TRPC) family of ion channels raising the hypothesis that IHPS may be a channelopathy.

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28

Porter, R. W. "Spinal stenosis and disorders of the lumbar spine." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/22563.

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This is a submission of 57 publications on the subject of "Spinal stenosis and disorders of the lumbar spine". It describes work personally carried out or personally supervised, between 1978 and 1997. 30 publications describe studies of spinal stenosis. The development of the vertebral canal is investigated from archaeological material, foetal collections and by the studies of volunteers. Intrauterine factors are identified which influence the canal's size and shape. Epidemiological studies are presented which have measured the canal in large numbers of volunteer adults and children, and patients with low back pain. The clinical significance of the vertebral canal size in various back pain syndromes is identified and described. The patho-physiological mechanism of neurogenic claudication is investigated, demonstrating by a series of clinical and laboratory studies, that multiple level stenosis in a developmentally small canal, causes venous congestion of the cauda equina. Laser Doppler studies show that as a result of this venous congestion, there is probably a failure of arterial vasodilatation in response to exercise, responsible for leg symptoms when walking. Papers describe the natural history of stenosis syndromes, and how calcitonin was introduced and investigated as a method of conservative management of neurogenic claudication. 27 parallel publications describe investigations of other lumbar spine disorders. Biomechanical and ergonomic studies show that hard work can be good for the spine. In prolapse of the lumbar intervertebral disc, laboratory studies demonstrate the importance of pre-existing degeneration and the formation of a free fragment. The mechanism of the clinical signs of disc protrusion, their repeatability and new signs are described. Spondylolisthesis is investigated. Studies examine back pain epidemiology, the differential diagnosis and classification of back pain, and spinal surgery and failed surgery. There is an appendix by title only, which records many of these studies in 7 text books and 19 contributory chapters.

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29

Sen, Sayan. "Assessment of intra-coronary pressure and flow velocity relations distal to coronary stenoses to derive a novel index of stenosis severity." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/25062.

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The optimal treatment for patients with stable angina remains controversial. Coronary angioplasty is increasingly performed in stable patients to reduce symptoms. Over the last 20 years there has been an accumulation of data demonstrating that an objective physiological approach to revasularisation is superior to the tradional angiographic approach. Several intra-coronary indices of stenosis severity have been proposed using pressure alone, flow velocity alone or a combination of both pressure and flow velocity. The most clinically used index, Fractional Flow Reserve (FFR) uses pressure alone to estimate the effect of a stenosis on blood flow within the coronary artery. Potent vasodilators are administered during its measurement to ensure the intra-coronary conditions are suitable for pressure to be used as a surrogate for flow. Despite the wealth of evidence supporting its use to guide coronary resvascularisation its adoption is poor. One reason is the need for the potent vasodilators that add time and cost to the procedure, cannot be given to every patient, are associated with side effects and in some regions of the world are simply unavailable. In this series of studies I will use combined pressure and flow velocity measurements to analyse the phasic relations of pressure and flow velocity distal to coronary stenoses. I aim to identify a period in the cardiac cycle that naturally provides the requisite intra-coronary condition for a pressure only index of stenosis severity - stable intra-coronary microvascular resistance. I will then compare the index derived over this period to existing pressure only and flow based indices of stenosis severity. Finally I will perform a detailed analysis of diastole to detemonstrate why this period is suitable by relating wave-mechanics to traditional pressure and flow mechanics.

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30

Peltonen, T. (Tuomas). "Endothelial factors in the pathogenesis of aortic valve stenosis." Doctoral thesis, University of Oulu, 2008. http://urn.fi/urn:isbn:9789514289880.

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Abstract Calcified aortic valve disease represents a spectrum of disease spanning from mild aortic valve sclerosis to severe aortic valve stenosis (AS), being an actively regulated disease process and showing some hallmarks of atherosclerosis. The calcified aortic valve lesion develops endothelial injury and is characterized by inflammation, lipid accumulation, renin-angiotensin system activation and fibrosis. There is no approved pharmacological treatment available in AS. This study was aimed to characterize gene expression of endothelial factors in aortic valves in patients representing different stages of calcified aortic valve disease to reveal new targets for pharmacological interventions in AS. Aortic valves obtained from 75 patients undergoing valve replacement surgery were studied. Expression of natriuretic peptides (ANP, BNP and CNP), their processing enzymes (corin and furin), natriuretic receptors (NPR-A, NPR-B and NPR-C), endothelin-1 (ET-1), endothelin converting enzyme-1 (ECE-1), endothelin receptors A and B (ETA and ETB), and apelin pathway (apelin and its receptor APJ) was characterized by reverse-transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. AS was characterized by distinct downregulation of gene expression of CNP, its processing enzyme furin and the target receptor NPR-B. Furthermore, increased amount of ET-1 and its target receptor ETA as well as imbalance between ETA and ETB receptors and downregulated endothelial nitric oxide synthase (eNOS) gene expression were observed. Finally, gene expression of apelin and APJ receptor were significantly upregulated in stenotic valves when compared to controls in combination with disequilibrium between expression of angiotensin II receptors AT1 and AT2. The study provides a better understanding of molecular mechanisms associated with calcific aortic valve disease and suggest potential targets for novel therapeutic interventions.

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31

Crawley, F. A. M. "Carotid artery stenosis : the role of angioplasty and surgery." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598140.

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32

Dionisio, Kathie L. (Kathie Lynn). "Ex-vivo 3D assessment of carotid stenosis with ultrasound." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32364.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (p. 71-74).
Atherosclerosis causes heterogeneous remodeling of arterial structure and composition in the carotid vessel wall. It has been shown that the progression of the disease can be monitored by tracking changes in the carotid intima-media thickness (IMT). Non-invasive peripheral vascular ultrasound (U/S) of the carotid artery is a non-invasive, cost effective, accepted means of measuring IMT. Traditionally, evaluation of IMT in the carotid has been limited to 2D U/S scans. This method is disadvantageous as 2D scans are scan plane dependent, limiting the area over which one can evaluate the extent of the disease. Reproducing the identical scan plane on subsequent scans is also difficult. Evaluation of the carotid vessel wall in 3D will allow for a more complete and reproducible assessment of disease through IMT measurements. We have constructed a fully 3D image processing scheme for analyzing carotid U/S volumes to extract the inner and outer vessel wall boundaries. Sequences of 2D B-mode U/S cross sections of ex-vivo carotid specimens are collected and voxelized to create 3D U/S volumes. By applying a 3D directionally sensitive, edge preserving filter to the U/S volumes, we obtain 3D edge fields that are more distinct than traditional gradient edge fields. Initial point selection of the boundaries, together with these enhanced 3D edge fields, are used with a deformable surface to extract the final inner and outer vessel boundaries. Through intra- and inter-observer tests on IMT differences, we show that the 3D boundaries extracted using our automatic technique are more reproducible than boundaries extracted from manual point selection.
by Kathie L. Dionisio.
S.M.

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33

Rask, Peter. "Aortic stenosis : diagnostic use and hemodynamic effects of dipyridamole." Doctoral thesis, Umeå universitet, Klinisk fysiologi, 1995. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-118692.

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34

Roberts, Elved Bryn. "Assessment of coronary artery stenosis using myocardial contrast echocardiography." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1445931/.

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The theoretical advantage of perfusion data over wall motion data for diagnosing coronary artery stenosis relates to the temporal sequence of these phenomena in the ischaemic cascade. Myocardial perfusion evaluation could thus provide earlier information than wall motion assessment, with important clinical consequences. This thesis examines myocardial perfusion assessment using ultrasound and micro-bubble contrast in stable coronary artery stenosis. The first set of experiments were undertaken to establish both a means of infusing Optison (GE Healthcare, UK), and of displaying static frame contrast signal using Power Contrast Imaging (Acuson Sequoia, Siemens Medical Solutions, Mountain View, CA, USA.). Three Optison concentrations, five infusion rates, and five trigger intervals were evaluated. This revealed an appropriate concentration and infusion rate for Optison and identified an ideal trigger interval of one in four cardiac cycles. The second part of this study evaluated Power Contrast Imaging with Optison infusion in stable single or double vessel coronary artery stenosis. Perfusion assessment during Adenosine vasodilator stress was compared with standard wall motion assessment during Dobutamine stress, coronary angiography being the diagnostic standard. Among twenty-eight subjects and eighty-four coronary territories, Power Contrast Imaging had low sensitivity but equivalent specificity compared to wall motion assessment. The third component of this research evaluated micro-bubble preserving real time Coherent Contrast Imaging (Acuson Sequoia , Siemens Medical Solutions) alongside Optison infusion in stable single or double vessel coronary stenosis. Thirty-eight subjects and one hundred and fourteen coronary arteries were evaluated. Each subject underwent Dobutamine stress, during which standard wall motion, contrast wall motion, and contrast perfusion imaging were all assessed, the diagnostic standard being coronary angiography. This demonstrated that contrast wall motion evaluation is accurate and that combined contrast wall motion and perfusion imaging is at least equivalent to standard wall motion imaging alone for detecting underlying coronary stenosis.

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35

Broyd, Christopher. "Coronary haemodynamics and wave intensity analysis in aortic stenosis." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/23961.

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Introduction: Coronary Wave Intensity Analysis (WIA) provides an invasive measure of energy transfer within the coronary circulation. I set out to derive a non-invasive measure of the backward expansion wave (BEW) responsible for coronary flow and assess it during exercise and in aortic stenosis (AS). Methods: 17 patients (mean age 60, 11 male) with normal cardiac function underwent invasive LAD WIA calculation using a pressure- and flow-tipped wire. Non-invasive WIA was calculated immediately after angiography from simultaneous PW Doppler of the LAD and a suprasystolic-cuff derived measure of central pressure. Non-invasive WIA was then assessed in 9 healthy volunteers whilst exercising on an exercise bike, 25 patients with varying degrees of AS (AVmax range: 2.41-5.43m/s) and 29 patients before, after and at 6 and 12 months following aortic valve intervention for severe AS. Results: Mean peak BEW was -14.7 ± 8.7x104 Wm-2s-2 invasively and -14.4 ± 8.2 Wm-2s-2 non-invasively and increased with exercise (at peak: -20.5±6.8Wm-2s-2, p=0.02) along with a rise in coronary flow (28.8cm/s to 42.1cm/s, p 0.06). A significant correlation was noted with the BEW and AS severity, strongest when valvulo-arterial impedence was assessed (r=-0.66, p<0.001). In severe AS, a reduction in coronary flow (0.41 to 0.33m/s, p<0.01) and the BEW (-22.1 vs 10.9x104Wm-2s-2, p<0.01) was seen after intervention. With LVH regression BEW increased (-21.6±12.6x104 Wm-2s-2 at 6 months) without a significant change in coronary flow. Conclusion: It is possible to construct a non-invasive measure of coronary WIA thus markedly increasing its applicability. Using this technique, the BEW is seen to increase during progressive levels of exercise accounting for the increase in coronary flow. The BEW progressively climbs with increasing AS, falls to sub-normal levels after aortic valve intervention but then increases to normal levels with LVH regression.

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36

Akherat, S. M. Javid Mahmoudzadeh. "Development of a predictne framework to forecast venous stenosis." Thesis, Illinois Institute of Technology, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10243926.

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The end stage renal disease (ESRD) patient population is growing at a troubling rate, calling for a focused attention to investigate the chronic kidney diseases, their characteristics and our lines of defense against them. One major medical treatment for ESRD patients is hemodialysis which is facilitated through vascular access (VA). The vascular access of particular interest in this investigation as well as the med- ical community is the brachiocephalic fistula (BCF), which is a form of arteriovenous fistula (AVF), created surgically by connecting the brachial artery and the cephalic vein. It is commonly used for elderly patients and for those with poor circulation systems, e.g. diabetics. The extreme hemodynamic environment that BCF creates triggers the onset of neointimal hyperplasia (NH) in most of these patients which leads to access failure and a high morbidity and mortality rate. This process happens in a matter of months, providing an excellent translational medicine experimental stage to observe as the vessel walls react and adapt to the new hemodynamically violent conditions. Through extensive analysis of the venous deformation and subsequent hemodynamics of a patient cohort of 160, a prognosticative framework to predict the vein deformation in these patients prior to the occurrence of the failure has been developed. The obtained results are the consequence of the integration of clinical practice and computational science. The proposed method was first based on our hypothesis which roots the NH in non-physiological wall shear stresses (WSS), and was then improved and modified using rigorous optimization and numerical approaches. This finding is essential to the modification of the current VA techniques to increase the patency of the AVFs, to prevent the diminishing functionality of the access, and to increase the life expectancy of ESRD patients. Moreover, this finding will further assist us in comprehension of the human vasculature growth and remodeling (G&R;) through bypassing the analysis of unknown biological phenomena, as it is achieved purely by juxtaposing well-defined mathematical, physical, and medical concepts.

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37

Korpela, Antti. "Healing of airway anastomoses and stenting of airway stenosis." Helsinki : University of Helsinki, 2000. http://ethesis.helsinki.fi/julkaisut/laa/kliin/vk/korpela/.

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38

MOSCHETTA, DONATO. "UNRAVELLING SEX-DEPENDENT MECHANISMS IN CALCIFIC AORTIC VALVE STENOSIS." Doctoral thesis, Università degli Studi di Milano, 2022. https://hdl.handle.net/2434/947275.

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Calcific aortic valve stenosis (CAVS) is the most common form of heart valve disease and affects about 3% of the population. Its prevalence increases with age, without a causal relation between ageing and CAVS development. To date, CAVS is a slow, progressive, multifactorial disorder considered to be actively driven by several cellular and molecular processes. Its natural history consists of a long clinically silent phase of non-uniform leaflet thickening with or without minimal calcification, known as aortic valve sclerosis (AVSc), without significant obstruction of blood flow, followed by the symptomatic stage, the aortic valve stenosis (AS). Currently, there is no pharmacological therapy preventing CAVS progression nor treating patients with AS. As a result, surgical or percutaneous aortic valve replacement remain the only treatments for severe AS, leaving the pathological molecular and cellular mechanisms unsolved. One of the first trigger of the pathology due to the oxidative stress is the endothelial dysfunction, followed by local inflammation and interstitial cells (VIC) differentiation into myofibroblasts and osteoblasts. Activated valve endothelial cells, undergoing endothelial to mesenchymal transition (EndMT), begin to express mesenchymal adhesion molecules and facilitate monocytes infiltration and local inflammation. These environmental changes induce VIC trans-differentiation into myofibroblast- and osteoblast-like cells. Activated VICs carry out a progressive extracellular matrix (ECM) pathological rearrangement characterized by the activation of fibrosis and calcification processes, which ultimately drive to fibro-calcific deposit formation. In the last years different studies reported sex-related difference in molecular mechanisms in the context of CAVS. In particular, it was shown that men with AS show a higher aortic valve calcium (AVC) load than women. Recently, it has been described that woman aortic valve leaflets were more fibrotic than man ones. Hence, it has been hypothesized that the mechanisms underlying CAVS progression could be different between the two sexes. We confirmed the evidence on sex-related calcium load in a meta-analysis performed on almost three thousand AS patients. Based on our results, AVC load, evaluated by computed tomography, is higher in man AS patients than in woman ones, even normalizing the data for the state of the pathology and for the aortic 9 annulus area. By the CT scan images analysis, we confirmed also the higher prevalence of fibrotic tissue in woman AS patients, than in men. In silico analysis of whole tissue RNA microarray revealed that the cellular composition of the aortic valve was different between men and women with CAVS. In particular, women showed a prevalence of mesenchymal cells, while in men there was a prevalence of inflammatory cells. This finding was in line with the analysis of circulating cytokines: pro inflammatory cytochines such as IL1β, TNFα, INFβ, and INFγ were upregulated in men CAVS patients. Based on these premises, we isolated and characterized VICs from AS patients and performed RNA sequencing to evaluate the differentially expressed molecular mechanisms. Among pathways overactivated in men there was the mitochondrial gene expression and this finding was confirmed by the higher mitochondrial damage in AS VICs from men respect to the one from women. We hypothesized that the mitochondrial damage caused a lower ATP production, therefore we evaluated the effects of a synthetic ATP equivalent, the 2ThioUTP, on the extracellular calcification of VICs from CAVS men. The in vitro 2ThioUTP administration showed indeed lower extracellular calcification of CAVS VICs both in normal and pro-calcifying conditions. All these data, taken together with robust literature evidences, shed light on the influence of sex in the development and progression of CAVS disease. Further studies are needed to better define the sexual dimorphism of this detrimental pathology. The recognition of sex-specific molecular mechanisms, linked to AS onset, may help in the identification of a gender-specific targeted therapy. In this direction, novel pharmacological therapies intended to reduce or even halt CAVS progression could be discovered, providing the basis for a personalized medicine approach in the context of CAVS.

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39

Seale, Anna Nancy. "Pulmonary vein stenosis : a population-based study of total anomalous pulmonary venous connection and the impact of pulmonary vein stenosis and a study of congenital pulmonary vein stenosis : the United Kingdom, Ireland and Sweden collaborative study." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607643.

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40

Zhao, Ying. "Effect of valve replacement for aortic stenosis on ventricular function." Doctoral thesis, Umeå universitet, Institutionen för folkhälsa och klinisk medicin, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-46809.

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Background：Aortic stenosis (AS) is the commonest valve disease in the West. Aortic valve replacement (AVR) remains the only available management for AS and results in improved symptoms and recovery of ventricular functions. In addition, it is well known that AVR results in disruption of LV function mainly in the form of reversal of septal motion as well as depression of right ventricular (RV) systolic function. The aim of this thesis was to study, in detail, the early and mid-term response of ventricular function to AVR procedures (surgical and TAVI) as well as post operative patients’ exercise capacity. Methods：We studied LV and RV function by Doppler echocardiography and speckle tracking echocardiography (STE) in the following 4 groups; (1) 30 severe AS patients (age 62±11 years, 19 male) with normal LV ejection fraction (EF) who underwent AVR, (2) 20 severe AS patients (age 79±6 years, 14 male) who underwent TAVI, (3) 30 healthy controls (age 63±11 years, 16 male), (4) 21 healthy controls (age 57±9 years, 14 male) who underwent exercise echocardiography. Results: After one week of TAVI, the septal radial motion and RV tricuspid annulus peak systolic excursion (TAPSE) were not different from before, while surgical AVR had significantly reversed septal radial motion and TAPSE dropped by 70% compared to before. The extent of the reversed septal motion correlated with that of TAPSE (r=0.78, p<0.001) in the patients as a whole after AVR and TAVI (Study I). Compared with controls, the LV twist function was increased in AS patients before and normalized after 6 months of surgical AVR. In controls, the LV twist correlated with LV fractional shortening (r=0.81, p<0.001), a relationship which became weak in patients before (r=0.52, p<0.01) and after AVR (r=0.34, p=ns) (Study II). After 6 months of surgical AVR, the reversed septal radial motion was still significantly lower than before. The septal peak displacement also decreased and its time became prolonged. In contrast, the LV lateral wall peak displacement increased and the time to peak displacement was early. The accentuated lateral wall peak displacement correlated with the septal peak displacement time delay (r=0.60, p<0.001) and septal-lateral time delay (r=0.64, p<0.001) (Study III). In 21 surgical AVR patients who performed exercise echocardiography, the LV function was normal at rest but different from controls with exercise. At peak exercise, oxygen consumption (pVO2) was lower in patients than controls. Although patients could achieve cardiac output (CO) and heart rate (HR) similar to controls at peak exercise, the LV systolic and early diastolic myocardial velocities and strain rate as well as their delta changes were significantly lower than controls. pVO2 correlated with peak exercise LV myocardial function in the patients group only, and the systolic global longitudinal strain rate (GLSRs) at peak exercise was the only independent predictor of pVO2 in multivariate regression analysis (p=0.03) (Study IV). Conclusion: Surgical AVR is an effective treatment for AS patients, but results in reversed septal radial motion and reduced TAPSE. The newly developed TAVI procedure maintains RV function which results in preservation of septal radial motion. In AS, the LV twist function is exaggerated, normalizes after AVR but loses its relationship with basal LV function. While the reversed septal motion results in decreased and delayed septal longitudinal displacement which is compensated for by the accentuated lateral wall displacement and the time early. These patients remain suffering from limited exercise capacity years after AVR.

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41

Refson, Jonathan Simon. "Vein graft stenosis and the human vascular smooth muscle cell." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/7763.

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42

Nouraei, Seyed Ahmad Reza. "An investigation of the surgical physiology of adult laryngotracheal stenosis." Thesis, University of Bath, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616576.

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Abnormal narrowing of the larynx, trachea, or bronchi, -Laryngotracheal Stenosis- increases airflow resistance and manifests as exertional dyspnoea, stridor, and effort intolerance. This clinical presentation is very similar to those of lower airway diseases. It is common therefore for this rare condition to be misdiagnosed and incorrectly managed. I addressed this potentially fatal diagnostic shortcoming by developing a simple physiological index, derived from routine spirometry data of approximately 10,000 patients, that can reliably diagnosis laryngotracheal stenosis. Undertaking shared-airway anaesthesia presents unique challenges since many standard anaesthetic techniques cannot be used and the reduced safety margin in a critically-narrowed airway makes anaesthesia hazardous. I studied the physiology of intravenous anaesthesia induction with positive-pressure ventilation, and showed underlying physiological differences between spontaneous and positive-pressure ventilation in airway stenosis which favours intravenous induction and positive-pressure ventilation, and which contrasts with traditional anaesthesia teaching in this area.

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43

Teien, Dag. "Assessment of aortic stenosis with special reference to Doppler ultrasound." Doctoral thesis, Umeå universitet, Klinisk fysiologi, 1986. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-103813.

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44

Knutsson, Björn. "Lumbar spinal stenosis : Body mass index and the patient's perspective." Doctoral thesis, Uppsala universitet, Ortopedi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-264589.

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During recent decades, lumbar spinal stenosis (LSS) has become the most common indication for spine surgery, a change that coincides with a higher worldwide prevalence of overweight and obesity. Thus, surgical treatment of LSS in the overweight and obese population is common and increasing in scope. The overall aim of this thesis was to investigate whether body mass index (BMI) is related to the development of LSS, and whether BMI is linked to outcome after surgery for LSS. We further evaluated whether there are specific experiences of LSS from a patient perspective. Data were obtained for all patients registered in the Swedish Spine Register who had undergone surgery for LSS between January 1, 2006 and June 30, 2008. After adjusting for differences in baseline characteristics, patients with obesity showed both poorer results after surgery and a higher rate of dissatisfaction than patients with normal weight (odds ratio 1.73; 95% confidence interval, CI, 1.36-2.19). Furthermore, patients with obesity in the cohort reported modest weight loss at follow-up (2.0 kg; 95% CI, 1.5-2.4), and only 8% reported a clinical important weight loss 2 years after surgery. Our analysis of 389,132 construction workers, showed that overweight (incidence rate ratio, IRR 1.68; 95% CI, 1.54-1.83) and obesity (IRR 2.18; 95% CI, 1.87-2.53) were associated with an increased future risk in developing LSS when compared with patients with normal weight. To gain insight into the patients' perspective of LSS, we performed interviews with 18 patients who were on a waiting list for LSS surgery. The transcripts, analyzed with content analysis, revealed that living with LSS is a physical, mental and social challenge in which resources to cope with the condition are of major importance. In summary, obesity is associated with poorer results after surgery, and patients with obesity report modest weight loss during follow-up. In addition, obesity is associated with an increased risk to develop LSS. Our findings revealed that being a patient with LSS, naturally involves considerable suffering and pain, but it also implies being a person with his or her own resources who is able to cope with these adverse conditions.

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45

Garoff, Maria. "Carotid calcifications in panoramic radiographs in relation to carotid stenosis." Doctoral thesis, Umeå universitet, Institutionen för odontologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-119794.

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Calcifications in carotid atheromas can be detected in a panoramic radiograph (PR) of the jaws. A carotid artery calcification (CAC) can indicate presence of significant (≥ 50%) carotid stenosis (SCS). The aim of this thesis was to (1) determine the prevalence of SCS and burden of atherosclerotic disease among patients revealing CACs in PRs, (2) determine the prevalence of CACs in PRs among patients with SCS, (3) analyze whether the amount of calcium and/or (4) the radiographic appearance of the CACs, can improve the positive predictive value (PPV) for SCS detection among patients with CACs in PRs. The thesis is based on four cross-sectional studies. Two patient groups were prospectively and consecutively studied. Group A represented a general adult patient population in dentistry examined with PR presenting incidental findings of CACs. These patients were examined with carotid ultrasound for presence or absence of SCS and their medical background regarding atherosclerotic related diseases and risk factors was reviewed. An age and gender matched reference group was included for comparisons. Group B comprised patients with ultrasound verified SCS, examined with PR prior to carotid endarterectomy. The PRs were analysed regarding presence of CACs. The extirpated plaques were collected and examined with cone-beam computed tomography (CBCT) to determine the amount of calcium. The radiographic appearance of CACs in PRs from Group A and B were evaluated for possible association with presence of SCS. In Group A, 8/117 (7%) of patients with CAC in PRs revealed SCS in the ultrasound examination, all were found in men (8/64 (12%)). Patients with CACs in PRs revealed a higher burden of atherosclerotic disease compared to participants in the reference group (p <0.001). In Group B, where all patients had SCS, 84% revealed CACs in PRs and 99% of the extirpated plaques revealed calcification. CACs with volumes varying between 1 and 509 mm3 were detected in the PRs. The variation in volume did not correlate to degree of carotid stenosis. The radiographic appearance that was most frequently seen in neck sides with SCS (65%) was also frequently found in neck sides without SCS (47%) and therefore the PPV did not improve compared to the PPV solely based on presence of CACs. CACs in PRs are more associated with SCS in men than in a general population and patients with CACs in PRs have a higher burden of atherosclerotic disease. The majority of patients with SCS show CACs in PRs and the majority of extirpated carotid plaques reveal calcification. The volume of CAC and specified radiographic appearance does not increase the PPV for SCS in patients with CACs in PRs. In conclusion patients with CACs in PRs, and without previous record of cardiovascular disease, should be advised to seek medical attention for screening of cardiovascular risk factors.
Bakgrund Inom ramen för specialist- och allmäntandvård utförs panoramaröntgen-undersökningar dagligen på såväl barn som vuxna. En panoramaröntgenbild (PB) är en översiktsbild som är specifikt anpassad till att återge området för tänder och käkar. Utöver det, avbildas även delar av halsen och som bifynd ibland förkalkningar belägna i området för halspulsådern (karotiskärlet). Dessa förkalkningar kallas för karotisförkalkningar och är ett tecken på åderförkalkning. Åderförkalkning består i huvudsak av en fettrik plackansamling i kärlväggen. Placket kan med tiden förkalkas till varierande grad. Det är dessa förkalkningar vi kan se i PB. När en åderförkalkning ökar i volym kan den utgöra en förträngning i kärlet. Då förträngningen av kärldiametern är ≥ 50% benämns åderförkalkningar belägna i karotiskärlet för ”signifikanta karotisstenoser” (SKS). Graden av förträngning bedöms som regel med ultraljudsundersökning av halskärlen. Bitar av SKS kan lossna varvid det bildas små blodproppar. Eftersom halspulsådern försörjer främre hjärnhalvan med blod så kan dessa bitar täppa till ett av hjärnans blodförsörjande kärl och leda till stroke (slaganfall). För att minska risken att drabbas av stroke kan man ibland operera bort SKS (karotisplacket). Syfte Syftet med denna avhandling var att ta reda på (1) hur många av de patienter som blir undersökta med PB inom tandvården som uppvisar karotisförkalkningar, hur stor andel som har SKS samt utreda om patienter med förkalkningar i PB i större utsträckning är drabbade av hjärtkärlsjukdomar/risk faktorer, (2) hur ofta utopererade karotisplack innehåller kalk och hur ofta patienter med känd SKS uppvisar karotisförkalkningar i PB, (3) huruvida förkalkningsmängden i utopererade karotisplack är korrelerad till förträngningsgrad, och (4) huruvida det finns något specifikt radiografiskt utseende på karotisförkalkningar i PB som kan användas för att identifiera en större andel patienter med SKS bland patienter som uppvisar karotisförkalkningar i PB, det vill säga minska risken för att skicka patienter utan SKS på ultraljudsundersökning. Material och metoder Materialet bestod av två huvudgrupper av patienter. Grupp A bestod av patienter undersökta inom tandvården med PB som uppvisat karotisförkalkningar. Alla dessa patienter undersöktes med ultraljud för att bedöma förekomst av SKS. Den medicinska journalen granskades avseende tidigare förekomst av åderförkalkningsrelaterade sjukdomar och risk faktorer. En köns- och åldersmatchad kontrollgrupp utan karotisförkalkningar i PB analyserades på motsvarande sätt för jämförelse. Grupp B bestod av patienter med känd SKS som före operativt avlägsnande av karotisplack undersöktes med PB. PB granskades avseende förekomst av karotisförkalkning och utopererade karotisplack avseende kalkinnehåll. Förkalkningsmängden i de utopererade karotisplacken korrelerades dels till möjlighet att identifiera karotisförkalkning i PB samt till förträngningsgraden i kärlen. Karotisförkalkningarnas utseende delades in i grupper för att utvärdera om vissa utseenden i större utsträckning kunde associeras till förekomst av SKS. Resultat I Grupp A uppvisade 8/117 (7%) patienter SKS, alla var män, 8/64 (12%). Patienter med karotisförkalkningar i PB hade oftare åderförkalkningsrelaterade sjukdomar och risk faktorer (p < 0,001). I Grupp B hade 84% av patienterna med SKS karotisförkalkning i PB. Bland de utopererade karotisplacken innehöll 99% förkalkningar och förkalkningsvolymen varierade från 1-509 mm3. Möjligheten att upptäcka karotisförkalkning i PB var oberoende av om förkalkningsvolymen var stor eller liten. Förkalkningsvolymen var heller inte korrelerad till hur stor förträngning av kärlet en SKS (≥ 50%) orsakat. Ett radiografiskt utseende på karotisförkalkningar i PB noterades i 65% av de halssidor som hade en SKS. Detta specifika radiografiska utseende återfanns dock även i 47% av halssidor utan SKS. Andelen falskt positiva patienter var således fortsatt hög. Slutsats Vi fann att 12% män med karotisförkalkningar i PB, undersökta i en generell population inom tandvården, uppvisar SKS. Patienter med karotisförkalkningar i PB uppvisar fler riskfaktorer och är oftare drabbade av hjärt-kärlsjukdomar än patienter utan karotisförkalkningar i PB. Majoriteten av patienter med SKS uppvisar karotisförkalkningar i PB och nära 100% av utopererade karotisplack innehåller kalk. Förkalkningsmängden påverkar inte möjligheten att upptäcka karotisförkalkning i PB. Förkalkningsmängd och specificerade radiografiska utseenden hos karotisförkalkningar i PB förutsäger inte SKS bättre än definitionen ”förkalkning ja eller nej”. Dessa parametrar kan således inte användas till att förfina urvalet bland patienter som uppvisar karotisförkalkning i PB mot högre andel patienter med SKS. Individer med karotisförkalkningar i PB bör uppmanas konsultera vården för undersökning av eventuella risk faktorer för hjärt-kärlsjukdom.

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46

Dweck, Marc Richard Leslie. "Assessment of aortic stenosis using modern non-invasive imaging techniques." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/8136.

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Introduction. Aortic stenosis is characterised both by progressive narrowing of the valve and the hypertrophic response of the left ventricle. The purpose of this thesis was to study the contribution of inflammation and calcification to valve narrowing using Positron Emission and Computed Tomography (PET/CT) and to investigate the hypertrophic response using cardiovascular magnetic resonance (CMR). Methods. PET/CT studies. Patients with aortic sclerosis and mild, moderate and severe stenosis were prospectively compared to matched control subjects. Aortic valve severity was determined by echocardiography. Calcification and inflammation in the aortic valve and coronary arteries were assessed by sodium 18-‐fluoride (18F-‐NaF) and 18-‐fluorodeoxyglucose (18F-‐FDG) uptake using PET. CMR studies. Consecutive patients with moderate or severe aortic stenosis undergoing CMR were enrolled into a registry. Patients who received gadolinium contrast were categorised into absent, mid-‐ wall or infarct patterns of late gadolinium enhancement (LGE) by blinded independent observers. Patients follow-‐up was completed using patient questionnaires, source record data and the National Strategic Tracing Scheme. After excluding those patients with concomitant triggers to LV remodeling, the extent and patterns of hypertrophy were investigated based upon measurements of indexed LV mass, indexed LV volume and the relative wall mass. Results. PET/CT studies. 121 subjects (20 controls; 20 aortic sclerosis; 25 mild, 33 moderate and 23 severe aortic stenosis) were studied. Quantification of tracer uptake within the valve demonstrated excellent inter-‐observer reproducibility with no biases and limits of agreement of ±0.21 (18F-‐NaF) and ±0.13 (18F-‐FDG) for maximum tissue-‐to-‐background ratios (TBR). Activity of both tracers was higher in patients with aortic stenosis than control subjects (18F-‐NaF: 2.87±0.82 vs 1.55±0.17; 18F-‐ FDG: 1.58±0.21 vs 1.30±0.13; both P<0.001). 18F-‐NaF uptake displayed a progressive rise with valve severity (r2=0.540, P<0.001) with a more modest increase observed for 18F-‐FDG (r2=0.218; P<0.001). Amongst patients with aortic stenosis, 91% had increased 18F-‐NaF (>1.97) and 35% increased 18F-‐ FDG (>1.63) uptake. Increased 18F-‐NaF uptake was also observed in the coronary arteries in a subset of patients with atherosclerosis. These patients (n=40) had higher rates of prior cardiovascular events (p=0.016) and angina (p=0.023), and higher Framingham risk scores (p=0.011). CMR studies. 143 patients (aged 68±14 years; 97 male) were followed up for 2.0±1.4 years and 27 died. Compared to those with no LGE (n=49), univariate analysis revealed that patients with mid-‐wall fibrosis (n=54) had an eight-‐fold increase in all-‐cause mortality despite similar aortic stenosis severity and coronary artery disease burden. Patients with an infarct pattern (n=40) had a six-‐fold increase. Mid-‐wall fibrosis (HR 5.35 [95% CI 1.16-‐24.56]; P=0.03) emerged as an independent predictor of all cause mortality by multivariate analysis. The pattern of LV remodelling was studied in 91 patients (61±21 years; 57 male) and displayed wide variation comprising normal ventricular geometry (n=11), concentric remodelling (n=11), asymmetric remodelling (n=11), concentric hypertrophy (n=34), asymmetric hypertrophy (n=14) and LV decompensation (n=10). The magnitude of the hypertrophic response was unrelated to the severity of aortic valve narrowing. Conclusions. Modern imaging techniques have provided important insights in to the pathology underlying aortic stenosis and suggest that valvular calcification and myocardial fibrosis have a key role. Both represent important potential targets for future therapeutic interventions.

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47

Konala, Bhaskar Chandra. "Effect of Arterial Wall-Stenosis Compliance on Coronary Diagnostic Parameters." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1291146768.

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48

Clark, Elizabeth. "Models and Mechanisms to Evaluate Tissue Engineered Vascular Graft Stenosis." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492735573118956.

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49

Anderson, Kailyn M. "Noonan Syndrome Spectrum Disorders in Patients with Valvar Pulmonary Stenosis." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1495807026761869.

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50

Treibel, Thomas Alexander. "Aortic stenosis : a myocardial disease : insights from myocardial tissue characterisation." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1574742/.

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Aortic stenosis (AS) is a disease of not just the valve, but also of the myocardium. Patient symptoms and outcome are determined by the myocardial response; a crucial but poorly understood process. Diffuse and focal myocardial fibrosis play a key role. Until recently, both could only be assessed using invasive histology, but now cardiovascular magnetic resonance (CMR) offers late gadolinium enhancement (LGE) and extracellular volume fraction (ECV) techniques. In this thesis, I developed new methods to quantify ECV by synthetic ECV and cardiac CT. I then explored myocardial remodelling and fibrosis in patients with severe AS undergoing aortic valve replacement (AVR) using myocardial biopsy, CMR, biomarkers and a wide range of clinical parameters. Prior to AVR, CMR in patients with severe AS revealed important differences in myocardial remodelling between sexes, otherwise missed on echocardiography alone. Given apparently equal valve severity, the myocardial response to AS appeared unexpectedly maladaptive in men compared to women. Intra-operative myocardial biopsy revealed three pattern of fibrosis: endocardial fibrosis, microscars (mainly in the subendomyocardium), and diffuse interstitial fibrosis. Biopsy best captured the transmural gradient of fibrosis and microscars, while on CMR, LGE captured mainly microscars and ECV captured mid-myocardial related functional changes beyond LGE. Combining LGE and ECV allowed better stratification of AS patients. Incidentally, I found that 6% of AS patients older then 65 years had wild-type transthyretin amyloid deposits on cardiac biopsy, which was associated with poor outcome. This is now the basis of a BHF research fellowship. Following AVR, I demonstrated for the first time non-invasively that diffuse fibrosis regresses (focal fibrosis did not), which is accompanied by structural and functional improvements suggesting that human diffuse fibrosis is plastic, measurable by CMR and a potential therapeutic target.

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Dissertations / Theses on the topic 'Stenosis'

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