Search Results
Results 251 - 300 of 876
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Laffon Eric - - 2004
The purpose of the present study was to non-invasively compare ascending aortic blood flow and cross-sectional area (CSA) variations vs time in Mustard or Senning repaired (MSR) patients against those of healthy volunteers at rest. Velocity-encoded MR imaging was performed in 10 male patients (age range 18-24 years, median age ...
Lurie Fedor - - 2003
The purpose of this study was to investigate the blood flow changes and venous wall movements that occur in the perivalvular area during venous flow, to learn how these physiologic events influence the movements of the valve cusps, and to learn how the movements of the valve cusps influence the ...
Muzzi Ruthnéa Al - - 2003
This study was performed to test the hypothesis that measurements of jet area by Doppler color flow imaging will correlate with the severity of mitral regurgitation. Although Doppler color flow imaging is widely used to assess the severity of mitral regurgitation (MR), an accurate and quantitative marker of MR by ...
Ge Liang - - 2003
A numerical method is developed for simulating unsteady, 3-D, laminar flow through a bileaflet mechanical heart valve with the leaflets fixed. The method employs a dual-time-stepping artificial-compressibility approach together with overset (Chimera) grids and is second-order accurate in space and time. Calculations are carried out for the full 3-D valve ...
Manning Keefe B - - 2003
The regurgitant flow fields of clinically used mechanical heart valves have been traditionally studied in vitro using flow visualization, ultrasound techniques, and laser Doppler velocimetry under steady and pulsatile flow. Detailed investigation of the forward and regurgitant flow fields of these valves can elucidate a valve's propensity for blood element ...
Lim W L - - 2003
In this study, the closing dynamics of two impinging rods were experimentally analyzed to simulate the cavitation phenomena associated with mechanical heart valve closure. The purpose of this study was to investigate the cavitation phenomena with respect to squeeze flow between two impinging surfaces and the parameter that influences cavitation ...
Roberts Brad J - - 2003
Qualitative grading of mitral regurgitation severity has significant pitfalls secondary to hemodynamic variables, sonographic technique, blood pool entrainment, and the Coanda effect. Volumetric and proximal isovelocity surface area methods can be used to quantitate regurgitant orifice area, regurgitant volume, and regurgitant fraction, but have several limitations and can pose technical ...
Laffon Eric - - 2003
The respective roles of the windkessel effect, which is related to the vessel compliance, and of the returning pressure wave, which is reflected off peripheral resistances, in generating the total diastolic blood flow in the ascending aorta (VT: coronary + flow through the upper part of the ascending aorta) were ...
Schlitt Axel - - 2003
The aim of the present study was to investigate the efficacy of three different parenterally administered anticoagulants for the prevention of thrombus formation on artificial heart valves in an experimental rabbit model. Unfractionated heparin was administered intravenously in group I (n = 10), Enoxaparin subcutaneously in group II (n = ...
Ito Hiroyuki - - 2003
Two kinds of flow patterns consisting of random dots were presented simultaneously to subjects to investigate whether or not two kinds of vection occur simultaneously. One pattern induces vertical linear self-translation, whereas the other induces self-rotation around a vertical axis (when either pattern is presented alone). Three sets of conditions ...
Nakamura M - - 2003
A computational fluid dynamics study of intraventricular flow during early diastole was carried out using a 3D model of the human left ventricle (LV). It was found that a vortical flow formed under the aortic orifice and then grew in size and extended laterally along the ventricular wall towards the ...
Saxena Rahul - - 2003
OBJECTIVE: The aim of this study was to evaluate the hinge flow field characteristics of the Medtronic Advantage bileaflet valve and compare them with the flow fields of the St Jude Medical standard valve. The present study provides laser Doppler velocimetry results for the Advantage and St Jude Medical valves ...
Shu Mark C S - - 2003
BACKGROUND AND AIM OF THE STUDY: An integrated macro/micro approach was used to evaluate flow within the pivots of the Medtronic ADVANTAGE bileaflet heart valve. Results were compared with those obtained with the St. Jude Medical bileaflet heart valve. METHODS: The integrated macro/micro approach consists of both a macroscopic hydrodynamic ...
Messika-Zeitoun David - - 2003
AIMS: In mitral stenosis (MS) transvalvular flow and velocity continually change throughout diastole but for mitral valve area (MVA), flow-dependent variations (valve reserve) are unknown. These physiologic changes can be studied by the proximal isovelocity surface area (PISA) method, using the high temporal resolution of colour M-mode, essential for simultaneous ...
Truesdell R A - - 2003
In many low-Reynolds number mixing applications, the absence of turbulence makes it difficult to achieve proper mixing of two fluids. In this paper, flow visualization is used to obtain quantitative measurements of mixing that occurs when combining two pulsatile fluid streams at a Y-connection. Mixing results from the interface distortion ...
Goubergrits L - - 2003
Clinical applications of ventricle assist devices continue to be problematic due to thromboembolic complications. The problem originates mainly at the valves, which are usually made of an antithrombogenic material, such as cross-linked bovine pericardium. However, wherever the blood flow is stagnant or forms a recirculation region, a thrombus is likely ...
Coisne Damien - - 2003
BACKGROUND: Color Doppler imaging of the convergent region is promising for quantifying valvular regurgitation. Nevertheless, proximal isovelocity surface area method has limitations. We sought to determine the optimal localization to measure the most precise flow rate using a new approach: the interaliasing distance. METHODS: A finite volume-based program was used ...
Mangano Santi - - 2003
In non-Asiatic population, apical hypertrophic cardiomyopathy represents 1% to 2% of hypertrophic cardiomyopathies. The presence of an apical ventricular aneurysm occurs in 1% of patients with the apical variant of hypertrophic cardiomyopathy. We present two patients with hypertrophic cardiomyopathy, both illustrating an early diastolic paradoxic jet flow between the apex ...
Michelsen Axel - - 2003
Progress in understanding dance communication in honeybees is reviewed. The behaviour of both dancers and follower bees contain flexible and stereotypic elements. The transfer of specific information about direction and distance probably involves more than one sensory modality. The follower bees need to stay behind the dancer (within the angle ...
Ootaki Yoshio - - 2003
BACKGROUND: Surgical closure of trabecular ventricular septal defects is difficult and often unsuccessful. OBJECTIVE: We performed closure of trabecular ventricular septal defects by sandwiching the septum between 2 polyester felt patches placed in the left ventricle and right ventricle without ventriculotomy. METHODS: Eleven patients (7 boys and 4 girls) underwent ...
Yotsumoto Goichi - - 2003
Erythropoietic protoporphyria (EPP) is a disorder of heme synthesis that causes excessive accumulation of protoporphyrin. The predominant clinical feature is photosensitivity triggered by light at wavelengths near 400 nm. We describe a 52-year-old man with EPP who underwent aortic valve replacement due to severe regurgitation. To prevent burn injuries, astral ...
Shi Yubing - - 2003
BACKGROUND AND AIM OF THE STUDY: Most previous computational fluid dynamics (CFD) studies of blood flow in mechanical heart valves (MHVs) have not efficiently addressed the important features of moving leaflet and blood-leaflet interaction. Herein, computationally efficient approaches were developed to study these features and to obtain better insight into ...
Brown J R - - 2003
A commercial inline constant flow valve for hand-compression hydraulic sprayers was tested to evaluate its capability to maintain constant pressure to the nozzle down to a preset cut-out pressure. The flow-control valve provided consistent flow rates when used with the H.D. Hudson X-Pert 9.5-liter hand-compression sprayers. This flow valve may ...
DeGroff Curt G - - 2003
BACKGROUND: In the echocardiographic evaluation of coarctation of the aorta, the degree of antegrade diastolic flow (diastolic runoff) noted on spectral Doppler tracings traditionally was thought to be solely dependent on lesion severity. However, recent in vitro experiments suggest the presence of this spectral Doppler pattern is as much related ...
Bennett James S - - 2003
A problem may arise in ventilation design when the contaminant source is located in the worker's wake, where turbulence and vortex formation can carry the contaminant into the breathing zone even though the source is downwind. It was found previously that forced directional variations in the flow can reduce or ...
Perry Tjörvi E - - 2003
Although atherosclerosis and valvular heart disease are among the leading causes of morbidity and mortality in developed nations, the substitute blood vessels and heart valves currently available all have significant limitations. During the past 10 years, a new field called tissue engineering has emerged, and several research groups are focusing ...
Fogel Mark A - - 2003
BACKGROUND: The right aortic arch is not uncommon in pediatrics. Flow dynamics in this type of aortic arch, which is important for cardiac energetics, organ perfusion, and Doppler flow calculations, have not been defined. Although there are complex secondary flow patterns, bulk axial flow makes up most of the energy ...
Mohan Jagdish C - - 2002
OBJECTIVES: The purpose of this study was to compare the effect of changes in flow rate on the mitral valve area (MVA) derived from two-dimensional echocardiographic planimetry and Doppler pressure half-time (PHT) methods in patients with mitral stenosis (MS). BACKGROUND: Dobutamine stress echocardiography has been proposed as a means of ...
Brown Donald J - - 2002
Clinical evaluation of patients with aortic stenosis entails hemodynamic determinations and interpretations that depend on complex blood flow patterns. Although pressure gradient and Doppler velocity are intrinsically adjusted for a wide range of species and body size, they are highly flow-dependent indices that can vary among patients with physically identical ...
Nauen Jennifer C - - 2002
Although considerable progress has been made within the last decade in experimental hydrodynamic analyses of aquatic locomotion using two-dimensional digital particle image velocimetry (two-dimensional DPIV), data have been limited to simultaneous calculation of two out of the three flow velocity variables: downstream (U), vertical (V) and lateral (W). Here, we ...
Amberger C N - - 2002
A four-year-old German shepherd mixed-breed dog was presented with an asymptomatic heart murmur. An atrial septal defect associated with tricuspid and mitral dysplasia (atrioventricular canal defect) was diagnosed. The pulmonary to systemic blood flow ratio was in the range of 2.5:1 (Qp:Qs ratio). Echocardiography and flow pattern across the valves ...
Zhang Zhaoyan - - 2002
Voice production involves sound generation by a confined jet flow through an orifice (the glottis) with a time-varying area. Predictive models of speech production are usually based on the so-called quasi-steady approximation. The flow rate through the time-varying orifice is assumed to be the same as a sequence of steady ...
Leo Hwa-Liang - - 2002
OBJECTIVE: The design of bileaflet mechanical heart valves includes some degree of leakage flow on valve closure for the reverse flow to wash the hinge and pivot region of the valve. It is believed that this reverse flow helps to prevent areas of stasis and inhibit microthrombus formation. However, the ...
Belforte Guido - - 2002
A tracheo-oesophageal valve is used for the rehabilitation of patients who have lost vocal function due to a total laryngectomy. The valve is positioned in a surgically created fistula between the airway and the upper oesophagus at the level of the post-laryngectomy stoma. It permits passage of air from the ...
Pipitone Salvatore - - 2002
Apical ventricular septal defects (VSD) may spontaneously become restricted or may even close following tissue outgrowth within the right ventricle in the region of the apical muscle bundles. We report a case of spontaneous restriction of an apical VSD localized within the right ventricle in the region of prominent apical ...
Schlitt A - - 2002
BACKGROUND: The aim of our study was to investigate the efficacy of the combination of clopidogrel and aspirin in the prevention of thrombus formation on artificial heart valves in an experimental rabbit model as compared to anticoagulation with warfarin. METHODS: Studies were performed after oral administration of clopidogrel and aspirin ...
Ohte Nobuyuki - - 2002
The mechanism of emergence and the clinical significance of apically directed intraventricular flow during isovolumic relaxation were investigated. The relation between the spatial distribution of the flow and left ventricular (LV) apical wall motion abnormality, as well as LV performance, was studied in 97 patients who underwent cardiac catheterization for ...
Kelly Stuart G D - - 2002
Computational fluid dynamics (CFD) analysis can provide detailed, three-dimensional predictions of blood flow through mechanical heart valves, which can help to optimize valve hemodynamics and reduce the potential for blood clotting. A number of CFD studies, considering both forward and retrograde flow through valves, have been published. In this paper, ...
Fogel Mark A - - 2002
PURPOSE: To determine regional flow dynamics in the normal aorta (Ao) in children. Understanding flow dynamics in children is important in cardiovascular energetics, in designing improved aortic reconstructions by crafting the surgery to mimic normal aortic flow, and in Doppler flow calculations. The objective of this study was to determine ...
Nauen Jennifer C - - 2002
As members of the derived teleost fish clade Scombridae, mackerel exhibit high-performance aquatic locomotion via oscillation of the homocercal forked caudal fin. We present the first quantitative flow visualization of the wake of a scombrid fish, chub mackerel Scomber japonicus (20-26 cm fork length, FL), swimming steadily in a recirculating ...
Mori Daisuke - - 2002
An idealized CFD model and a realistic one were used to investigate the effect of the 3-D distortion of the aortic arch on the blood flow and its pathophysiological significance with respect to the pathogenesis of the aortic aneurysm. From the results of the flow simulations, the distortion of the ...
Kerner Boris S - - 2002
Results of an empirical study of congested patterns measured during 1995-2001 at German highways are presented. Based on this study, various types of congested patterns at on and off ramps have been identified, their macroscopic spatial-temporal features have been derived, and an evolution of those patterns and transformations between different ...
Lurie Fedor - - 2002
The purpose of this investigation was to study the mechanism of venous valve closure in physiologic conditions in situ, particularly the clarification of the role of reversed flow through the valve in the closure of the valve cusps. A second purpose was the study of temporal relations between movements of ...
Lurie Keith G - - 2002
Despite aggressive measures for the treatment of cardiovascular collapse and cardiac arrest, the hypotension associated with these malignant processes usually leads to profound vital-organ ischemia and death. A fundamental therapeutic challenge of such life-threatening processes is the restoration of adequate blood flow to the heart and the brain. However, to ...
Liu Pinming - - 2002
OBJECTIVE: Transesophageal echocardiography was performed during closed-chest cardiopulmonary resuscitation (CPR) in in-hospital cardiac arrest to further explore the hemodynamic mechanism of CPR. METHODS: CPR attempts were performed according to advanced cardiovascular life support guidelines in 6 cases of in-hospital cardiac arrest. Multi-plane transesophageal echocardiography was carried out within 15 min ...
Kaiser Andreas M - - 2002
PURPOSE: After proctocolectomy for ulcerative colitis or familial adenomatous polyposis, creation of a continent ileostomy is one of the surgical options. Although most patients will be offered a pull-through procedure, the continent ileostomy is a valuable alternative in patients who are either not candidates for or have failed an ileal ...
Coisne Damien - - 2002
BACKGROUND: This study was designed to develop and test a total digital 3-dimensional (3D) color flow map reconstruction for proximal isovelocity surface area (PISA) measurement in the convergent region. METHODS: Asymmetric flow convergent velocity field was created in an in vitro pulsatile model of mitral regurgitation. Image files stored in ...
Langhelle Audun - - 2002
The use of an inspiratory impedance threshold valve (ITV) during cardiopulmonary resuscitation (CPR) should reduce intrathoracic pressure during natural chest recoil or active chest decompression. This might in turn improve venous return and thereby organ blood flow. The haemodynamic effects during both standard CPR and active compression-decompression (ACD)-CPR with and ...
Kilner Philip J - - 2002
Through cardiac looping during embryonic development, human and other vertebrate hearts adopt sinuous curvatures with marked changes in direction of flow at atrial, ventricular and arterial levels. We used magnetic resonance phase velocity mapping to study flow through the hearts of resting volunteers, and Doppler ultrasound to record changes with ...
Rusk Rosemary A - - 2002
Accurately quantifying transmitral flow volume is clinically important not only as a measure of cardiac output, but also as a value from which to subtract aortic flow, for determining the severity of mitral regurgitation. However, controversy exists over the accuracy of pulsed Doppler for mitral flow quantification because of the ...
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