There are many conditions and diseases that affect voice production. One of these, subglottic stenosis (SGS), is characterized by a narrowing of the trachea near the cricotracheal junction. SGS causes dyspnea (labored breathing) and frequently surgery is necessary to eliminate the airway obstruction. SGS is also believed to adversely affect voice quality. While significant research has been conducted to study the effect of SGS on breathing, relatively few studies concerning its effect on voice production have been performed. The purpose of this research was to provide quantitative results concerning the predicted effects of SGS on vocal fold (VF) vibration and resulting sound production, and to provide tools for more extensive research involving synthetic VF models in the future. This was achieved through an experimental procedure in which a device simulating SGS was coupled with synthetic VF models and acoustic, aerodynamic, and vibratory measurements were acquired. Additionally, a device was developed and tested to study the effects of VF posturing using synthetic VF models. The design of the device is anticipated to serve as a useful tool in future experiments.The device simulating SGS was capable of creating an artificial stenosis of adjustable severity. The device was designed so that synthetic VF models inserted into rigid plates could be placed on top of the device, downstream of the stenosis. An experiment was conducted with the SGS device in conjunction with synthetic four-layer VF models in which flow and pressure were measured, radiated sound data were recorded, and visual data from a high-speed camera were captured as the percent obstruction was changed. The effects of subglottic stenosis were quantified using metrics such as onset pressure, glottal area, smoothed cepstral peak prominence (CPPS), harmonic-to-noise ratio (HNR), acoustic spectra, air flow, and pressure below and above the stenosis. The results show that the glottal area was not noticeably affected by the stenosis until 80% or 90% obstruction, and flow resistance through the stenosis was not significantly affected until 85% obstruction. However, changes in acoustics occurred as low as 65% or 70% obstruction.An MRI-compatible posturing device was developed which was capable of causing abduction/adduction and elongation in synthetic VF models. The device was used to adduct synthetic VF models from an abducted position into a pre-determined final phonatory posture as high-speed video and pressure data were collected. The device adducted to final phonatory posture in 500 ms, and phonation was initiated 680 ms later. In addition, the elongation of the synthetic models was varied as high-speed data were collected. The frequency of vibration of the four-layer models was found to not vary significantly when the models were elongated.

Heart disease remains the most important non-obstetric cause of maternal mortality and morbidity during pregnancy, despite its low incidence of less than 1%. This is due to the decline in the number of deaths from haemorrhage, infection and toxemia. In addition, a striking change in the pattern of proportional distribution of organic heart disease in pregnant women is being noted, with a decrease in chronic rheumatic lesions and an increase in congenital cardiac disease. In the Third World rheumatic mitral valve disease remains a most important condition during pregnancy. It is currently rarely seen in Europe and the United States. Mitral stenosis is the most commonly encountered rheumatic heart lesion that complicates pregnancy. The normal circulatory changes during pregnancy aggravate this lesion as the reduced, fixed valve area obstructs blood flow from the left atrium to the left ventricle, causing pulmonary congestion and oedema. Careful and regular follow up of these patients is essential, and surgery is indicated if optimal medical management fails. Cardiac surgery duting pregnancy represents a risk to both the foetus and the mother. For most procedures extracorporeal circulation and heparinization are necessary and adds to the · adverse effects of the operation. Closed mitral valvotomy, however, is an excellent low risk operative procedure in patients with tight mitral stenosis without causing undue harm to the foetus. Cuttler described the first attempted surgery of the mitral valve in 1923 and since then the procedure has been improved to benefit many patients with tight mitral stenosis. The first reports of closed mitral valvotomy during pregnancy were in 1952. Al though a more precise valvotomy can be obtained with an open procedure, the closed operation avoids the risks of extracorporeal circulation, particularly detrimental to the foetus. This report is a review of the Groote Schuur Hospital experience of patients with mitral stenosis requiring closed mitral valvotomy during pregnancy since 1965. The aims of the study are to analyse the outcome of the pregnancy, the effects of valvotomy during pregnancy on both the mother and the foetus, and the outcome regarding restenosis of the mitral valve.

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UA Open Access Publishing Fund / Background: The use of intra-aortic balloon pump (IABP) via the trans-femoral approach has been established for hemodynamic support in patients undergoing high-risk percutaneous coronary intervention (PCI). However, there are various challenges associated with its use, especially in patients with aortoiliac occlusive arterial disease. Case presentation: We describe a case of high-risk PCI with IABP support complicated by intra-procedural detection of severe abdominal aortic stenosis that was successfully overcome with angioplasty of the stenotic lesion. Conclusions: Our report highlights distal abdominal aortic stenosis as a potential barrier to successful PCI with IABP support, and angioplasty as an effective means to overcome it.

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.

Transcatheter aortic valve implantation (TAVI) is an effective alternative treatment option for patients with severe aortic stenosis, who are at a high risk for conventional surgical aortic valve replacement or considered inoperable. Despite the short- and mid-term survival benefits of TAVI, adverse clinical events, such as paravalvular leak, aortic rupture, and coronary occlusion, have been reported extensively. Many of these adverse events can be explained from the biomechanics perspective. Therefore, an in-depth understanding of biomechanical interaction between the device and native tissue is critical to the success of TAVI. The objective of this thesis was to investigate the biomechanics involved in the TAVI procedure using patient-specific finite element (FE) simulations. Patient-specific FE models of the aortic roots were reconstructed using pre-procedural multi-slice computed tomography images. The models incorporated aged human aortic material properties with material failure criteria obtained from mechanical tests, and realistic stent expansion methods. TAV deployment and tissue-device interaction were simulated; and the simulation results were compared to the clinical observations. Additionally, parametric studies were conducted to examine the influence of the model input on TAVI simulation results and subsequently the potential clinical complications such as paravalvular leak, annular rupture, and coronary artery occlusion. The methodology presented in this thesis could be potentially utilized to develop valuable pre-procedural planning tools to evaluate device performance for TAVI and eventually improve clinical outcomes.

Compliant (flexible) structures play an important role in several biofluid problems including flow in the lungs, heart and arteries. Atherosclerosis is a vascular disease which causes a remodelling of the arterial wall causing a restriction (stenosis) by thickening the intima and the formation of vascular plaque by the deposit of fatty materials. This remodelling alters the compliance of the artery stiffening the arterial wall locally. A common location for this to occur is in the carotid artery which supplies blood to both the brain and the face. It can lead to complete occlusion of the artery in the extreme case and is a major cause of stroke and ischemic infarction. Stroke is the third largest cause of death in the U.S.A., but even if not fatal it can cause coma, paralysis, speech problems and dementia. Atherosclerosis causes a change in the local hemodynamics. It can produce areas of flow separation and low wall shear stress, which can lead to endothelial dysfunction and to promotion of plaque growth. In-vitro modelling with artificial flow phantoms allows the fluid mechanics of the circulatory system to be studied without the ethical and safety issues associated with animal and human experiments. Extensive work has been performed using both experimental and computational techniques to study rigid models representing the arterial system. Computational methods, in which the equations governing the flow and the elastic walls are coupled, are maturing. There is a lack of experimental data in compliant arterial systems to validate the numerical predictions. This thesis sets out to address the problems associated with the in vitro experimental analysis of compliant structures representing the human vasculature. A novel construction technique that produced idealised compliant geometries representing both a healthy and stenosed carotid artery from transparent silicone material was developed. A complete analysis was performed of the circumferential and longitudinal response of the geometry, which allowed for dynamic similarity between in vitro and in vivo conditions to be achieved. Inherent difficulties associated with thin walled phantom construction were overcome, which included the design of a novel endplate that allowed for a smooth transition from the flow system to the flow phantom and a bottom up silicone injection system that ensured the phantom was free of bubbles. The final phantom evolution had a wall thickness that could be produced to within a tolerance of 5%. The constructed flow phantom was ported to a flow system producing a physiological inlet flow waveform scaled to in vitro conditions via Reynolds and Womersley number matching. Experimental analysis was performed using a laser based optical technique, particle image velocimetry (PIV). A novel Light Emitting Diode (LED) illumination system was also implemented to obtain to obtain high speed planar PIV measurements. The combined set up of the LED light source, driver unit components and fibre optics for high speed imaging costs in the region of $US 650 which provides a far cheaper option in comparison to the pulse laser system (In the region of $US 50,000). Results obtained in the healthy geometry were compared to a rigid geometry with the same dimensions. It was found that compliance reduced the peak velocity experienced. It also caused a reduction in wall shear stress (WSS) observed and acted to ameliorate the magnitude of the WSS. This is physiologically significant as high WSS can promote atherosclerosis. The introduction of a stenosis caused an increase in the peak velocity observed over the cardiac cycle. A large increase in WSS can be seen to occur in the stenosis throat in both a symmetric and asymmetric stenosed geometry. It is also evident that stenosis eccentricity is important, with asymmetry (where the centre of the stenosis does not coincide with the centre of the artery) producing a major change in WSS and flow field. The study of the flow field downstream of a symmetric stenosis exit showed a Kelvin-Helmholtz vortex ring system to occur between the jet exiting the stenosis throat and the low velocity reverse flow region that surrounded it. The strength of these vortices varied between the acceleration and deceleration phase, demonstrating the failings of a quasi-steady assumption. It was shown that varying the external pressure applied to the flow phantom, along with stenosis eccentricity, affected the inlet flow and pressure waveform and the failings of the common assumption to idealise the physiological flow wave with a sinusoidal input was presented.

Lam Wai-man Wynnie. / "April 2002." / Thesis (M.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 109-134). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.

This diploma work is focused on using economic analysis methods to compare cost-effectivness of an innovative technology for treating aortic stenosis that is transcatheter implantation of an artificial valve CoreValve by Medtronic with traditional treatments. During the analyses we utilized only publicly available data which are often too general while more specific data might not be available because they do not exist or are not publicly available. This work sets up a theoretical foundation for the analyses, performs the analyse sof the product, PEST analyses and cost analyses. Since pacient's willigness to pay index (WTP) in the Czech republic has not yet been measured for this treatment, it is not posible to confirm the cost-effectivness of CoreValve, even though it has been confirmed in several countries based on the literature search related to this topic.

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