Search Results
Results 401 - 450 of 1818
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Schleicher Martina - - 2010
Long-term function of biological heart valve prostheses (BHV) is limited by structural deterioration leading to failure with associated arterial hypertension. The objective of this work was development of an easy to handle real-time pulse reactor for evaluation of biological and tissue engineered heart valves under different pressures and long-term conditions. ...
Dall'osto David R - - 2010
Pressure signals measured by two four-element vertical line arrays, centered at depths 25 and 50 m, during an experiment off the New Jersey coast in Summer 2006 (SW06, depth 80 m) are combined to determine the pressure gradient of the received signal. The pressure gradient is converted to an estimate ...
Marston Timothy M - - 2010
Grazing illumination of a target close to a flat interface as well as evanescent wave illumination of a buried target can produce significant vertical acoustic pressure gradients at a target. A prior experiment [Espana et al., J. Acoust. Soc. Am. 126, 2187 (2009)] demonstrated the selective coupling to a mode ...
Dénes Mónika M Gottsegen György Hungarian Institute of Cardiology, H-1096 Budapest, Hungary. - - 2010
Both systolic and diastolic tissue Doppler (TD) velocities have an important diagnostic and prognostic role in cardiology. We aimed to compare TD velocities between two different echocardiography systems. Thirty-one consecutive patients (mean age: 65.2 +/- 17.5 years; 12 males) were enrolled. Systolic (Sa), early (Ea), and late (Aa) diastolic velocities ...
Ishikawa Takamichi - - 2010
This report presents the case of an 8-year-old male with biventricular hypertrophic obstructive cardiomyopathy who achieved a successful reduction of the pressure gradients by treatment with cibenzoline. Ultrasound echocardiography showed marked intraventricular septal hypertrophy and left midventricular and right ventricular outflow obstructions. A cardiac catheterization revealed left midventricular and right ...
Aihara Yasuo - - 2010
OBJECTIVE: Programmable shunt valve systems have improved the management of patients with hydrocephalus. However, associated problems such as over-drainage and slit-like ventricles, even in patients with anti-siphon devices installed, still remain unresolved. METHODS: We conceived a novel tandem shunt valve system to overcome the problems with existing shunt valve systems. ...
Verdonck Pascal - - 2010
A fluid is a medium which deforms, or undergoes motion, continuously under the action of a shearing stress and includes liquids and gases. Applying biofluid mechanics to the cardiovascular system requires knowledge of anatomy and geometry, pressure data and blood flow, volume and velocity measurements. A good example is the ...
Kreutzer Guillermo O - - 2010
The first atriopulmonary anastomosis (APA) with neither a valve in the inferior vena cava (IVC) nor an Glenn shunt was performed in 1971. A fenestration was intentionally left in the atrial septum. In a second patient, the APA incorporated the patient's own pulmonary valve, which had been removed from the ...
Khodarahmi Iman - - 2010
Pressure gradient across a Gaussian-shaped 87% area stenosis phantom was estimated by solving the pressure Poisson equation (PPE) for a steady flow mimicking the blood flow through the human iliac artery. The velocity field needed to solve the pressure equation was obtained using particle image velocimetry (PIV). A steady flow ...
Hjerrild Britta E - - 2010
BACKGROUND: To investigate aortic dimensions in women with Turner syndrome (TS) in relation to aortic valve morphology, blood pressure, karyotype, and clinical characteristics. METHODS AND RESULTS: A cross sectional study of 102 women with TS (mean age 37.7; 18-62 years) examined by cardiovascular magnetic resonance (CMR- successful in 95), echocardiography, ...
SzymaƄski Piotr P Department of Adult Congenital Heart Diseases, Institute of Cardiology, Warszawa, Poland. - - 2010
The development of significant tricuspid regurgitation (TR) is associated with an unfavorable clinical outcome in patients with systemic right ventricles. Increased knowledge about the factors contributing to its presence would help prevent its progression. This was a retrospective analysis of the factors predictive of significant TR in 60 patients with ...
Yong Gerald - - 2009
BACKGROUND: During hemodynamic assessment prior to antegrade balloon aortic valvuloplasty (BAV), unanticipated transmitral valve pressure gradients (MVG) were noted frequently. AIM: To determine the prevalence and significance of a significant MVG in patients with aortic stenosis and no previously diagnosed mitral valve stenosis. METHOD: Retrospective chart review of patients with ...
Yap Choon Hwai - - 2010
Calcific aortic valve (AV) disease has a high prevalence in the United States, and hypertension is correlated to early onset of the disease. The cause of the disease is poorly understood, although biological and remodeling responses to mechanical forces, such as membrane tension, have been hypothesized to play a role. ...
Sekar Priya - - 2009
Aortic arch recoarctation is responsible for significant morbidity and mortality after the Norwood Stage I procedure. Cuff blood pressure (BP) gradients and echocardiographic Doppler gradients are routinely used as noninvasive screening tests for early detection, but accuracy has not been systematically tested. We sought to evaluate the ability of cuff ...
Attaran R R - - 2009
BACKGROUND: Pulmonary arterial pressure measurement is an integral part of the pre-heart transplant evaluation. In the clinical arena, the correlation and agreement between pulmonary artery systolic pressure (PASP) measured by Doppler echocardiography versus catheterization in pre-heart transplant patients has not been studied. METHODS: Data on all patients evaluated for heart ...
Anavekar Nandan S - - 2009
The 2D echocardiographic examination of the heart provides insight into structure and function, providing a precise anatomical display of the cardiovascular anatomy with high temporal resolution. Prior to advances in 2D imaging, Doppler echocardiography had been the mainstay of cardiovascular noninvasive assessment. Doppler echocardiography, remains an integral part of the ...
Kim Jitae - - 2009
An automated, pre-programmed, multiplexed hydraulic valve actuator is described. The valve is membrane-based and normally open. In contrast to the membrane-based pneumatic valve, the hydraulic valve uses hydraulic liquid to exert the control pressure. The line pressure is controlled with a roller moving over a prefabricated topology. Multiple rollers, each ...
Chen Chien-Fu - - 2009
A facile method enabling the integration of elastomeric valves into rigid thermoplastic microfluidic chips is described. The valves employ discrete plugs of elastomeric polydimethylsiloxane (PDMS) integrated into the thermoplastic substrate and actuated using a threaded stainless steel needle. The fabrication process takes advantage of poly(ethylene glycol) (PEG) as a sacrificial ...
Jaschke Paul R - - 2009
A procedure for modification of the valve stem of a 40 K French pressure cell is described. The modification should be done by a machinist and requires a metalworking lathe. After modification of the valve stem, a torlon 4203 plastic ball is used between the valve stem and valve seat ...
Lin Tsung-Hsien - - 2009
OBJECTIVES: We previously found the association between mitral chordae tendinae ruptures (MCTR) and hypertension. Tissue inhibitor of metalloproteinase-2 (TIMP2), which expresses differently under pressure loads, could trigger a signal cascade instigating cardiac fibrosis, possibly predisposing to MCTR. We aimed to elucidate the relationship between the TIMP2 and hypertension and the ...
Hamlington Peter E - - 2009
A new fundamentally based formulation of nonlocal effects in the rapid pressure-strain correlation in turbulent flows has been obtained. The resulting explicit form for the rapid pressure-strain correlation accounts for nonlocal effects produced by spatial variations in the mean-flow velocity gradients and is derived through Taylor expansion of the mean ...
Parameswaran Anoop C - - 2009
Studies have shown very good correlation between Doppler-derived gradients and gradients obtained by cardiac catheterization (cath) in aortic stenosis (AS). However, the phenomenon of pressure recovery may lead to significant overestimation of aortic valve (AV) gradients by Doppler echocardiography (echo). We hypothesized that echo-derived gradients will be higher in mild-moderate ...
Kim Kyoung-Hun - - 2009
There is no definite adjustment protocol for patients shunted with programmable valves. Therefore, we attempted to find an appropriate method to adjust the valve, initial valve-opening pressure, adjustment scale, adjustment time interval, and final valve-opening pressure of a programmable valve. Seventy patients with hydrocephalus of various etiologies were shunted with ...
Solis Jorge - - 2009
Cardiac resynchronization therapy (CRT) has been shown to reduce functional mitral regurgitation (MR). It has been proposed that the mechanism of MR reduction relates to geometric change or, alternatively, changes in left ventricular (LV) contractile function. Normal mitral valve (MV) function relies on a balance between tethering and closing forces ...
Saraiva Roberto M - - 2009
BACKGROUND: Left atrial (LA) volume is a prognostic index in chronic mitral regurgitation (MR). However, little is known about LA function in this setting. We hypothesized that LA dysfunction is related to pulmonary hypertension in chronic MR. METHODS: Seventy-one patients with organic chronic MR who underwent real-time 3-dimensional transthoracic echocardiography ...
Fritz Brad G - - 2010
Vertical hydraulic gradient is commonly measured in rivers, lakes, and streams for studies of groundwater-surface water interaction. While a number of methods with subtle differences have been applied, these methods can generally be separated into two categories; measuring surface water elevation and pressure in the subsurface separately or making direct ...
Ben-Dor Itsik - - 2009
The aim of this study was to assess the change in coronary flow in patients who underwent percutaneous aortic valve replacement (PAVR) for severe aortic stenosis. The left main coronary artery was visualized using transesophageal echocardiography in 17 patients who underwent PAVR. The peak systolic and diastolic velocities of coronary ...
Kim H J - - 2009
Aortic flow and pressure result from the interactions between the heart and arterial system. In this work, we considered these interactions by utilizing a lumped parameter heart model as an inflow boundary condition for three-dimensional finite element simulations of aortic blood flow and vessel wall dynamics. The ventricular pressure-volume behavior ...
Lee Hwansung - - 2009
Our group is currently developing a pneumatic ventricular assist device (PVAD), and in previous studies, we reported the mechanical heart valve (MHV) cavitation intensity at the inlet valve in the PVAD only. In this study, we investigated the effect of the running conditions on the cavitation intensity both for the ...
Seker Erkin - - 2009
An analytical solution is presented for the nonlinear pressure-flow relationship of deformable passive valves, which are formed by bonding a deformable film over etched channels separated by a weir. A fluidic pathway connecting the channels is opened when the upstream pressure creates a tunnel along a predefined narrow strip where ...
Krishnamurthy Gaurav - - 2009
Excised anterior mitral leaflets exhibit anisotropic, non-linear material behavior with pre-transitional stiffness ranging from 0.06 to 0.09 N/mm(2) and post-transitional stiffness from 2 to 9 N/mm(2). We used inverse finite element (FE) analysis to test, for the first time, whether the anterior mitral leaflet (AML), in vivo, exhibits similar non-linear ...
Ishikawa T - - 2009
BACKGROUND: Mitral valve regurgitation (MR) causes increased left atrial pressure (LAP) and is associated with occurrence of clinical signs. It will be useful to understand diurnal variations of LAP for the management of MR. HYPOTHESIS: Circulatory parameters and diurnal rhythm are linked to clinical signs in cardiac diseases. LAP also ...
Chiavegato David - - 2009
Pulmonary hypertension has been associated with mitral insufficiency caused by chronic degenerative valve disease in dogs. Our aim was to search for associations between left atrial to aortic root ratio, end-systolic and end-diastolic volume indices, and changes in the right ventricular to right atrial pressure gradient as estimated by the ...
Lo Ronalee - - 2009
An implantable manually-actuated drug delivery device, consisting of a refillable drug reservoir, flexible cannula, check valve, and suture tabs, was investigated as a new approach for delivering pharmaceuticals to treat chronic ocular diseases. Devices are fabricated by molding and bonding three structured layers of polydimethylsiloxane. A 30 gauge non-coring needle ...
Glover G W - - 2009
BACKGROUND: There are few data describing the performance of the Whisperflow continuous positive airway pressure (CPAP) generator. METHODS: (i) (a) A static test of 11 Whisperflow devices examining maximum flow generation with no load and with 2.5, 5, 7.5, 10, 15, and 20 cm H2O valve loading, at varying Fi(O2). ...
Joyce Erinn M - - 2009
Defects in the pulmonary valve (PV) occur in a variety of forms of congenital heart diseases. Quantitative information on PV collagen fiber architecture, and particularly its response to diastolic forces, is necessary for the design and functional assessment of approaches for PV repair and replacement. This necessity is especially the ...
Lee Dong Woo - - 2009
We propose high-radix microfluidic multiplexers that effectively address a large number of flow channels with a few control lines having pressure valves of different thresholds. Previous binary multiplexers address only two flow channels by controlling identical threshold pressure valves in two control lines; that is, they address 2(n/2) flow channels ...
Richards Andrew L AL Department of Biomedical Engineering, North Carolina State University, Raleigh, NC 27695, - - 2009
The development of a novel surgical tool or technique for mitral valve repair can be hampered by cost, complexity, and time associated with performing animal trials. A dynamically pressurized model was developed to control pressure and flowrate profiles in intact porcine hearts in order to quantify mitral regurgitation and evaluate ...
Noor Ahmad A Department of Cardiology, National Institute of Cardiovascular Diseases, Karachi. - - 2009
To identify the determinants of decrease in pulmonary hypertension after percutaneous balloon mitral commissurotomy. Quasi experimental study. National Institute of Cardiovascular Diseases, Karachi, from March to October 2007. Adult patients with severe mitral stenosis and pliable valve having no significant mitral regurgitation, aortic valve disease, or left atrial thrombus were ...
Haaf P - - 2009
BACKGROUND: The hemodynamic characteristics of different heart valve prostheses have been investigated in vitro with a novel pulse duplicator. A novel valved stent for transapical or percutaneous valve implantation has been compared with a native heart valve and mechanical heart valves. METHODS: All experiments were designed to imitate both physiologic ...
Ruel Jean - - 2009
This paper reports the design, manufacturing, and characterization of a new bioreactor dedicated to the development of tissue-engineered heart valve substitutes. First, a comprehensive review of the state of the art in bioreactors is presented and a rigorous classification is put forward. The existing bioreactors found in literature are organized ...
He Zhaoming - - 2009
Proper leaflet coaptation of the mitral valve is vital for a healthy functioning heart. Chordal tension directly affects leaflet coaptation. The C-shaped transducer used previously to measure chordal tension was too big for tension measurement of multiple chordae and their branches. A new method is needed to measure chordal tension ...
Sezai Akira - - 2009
PURPOSE: The effectiveness of the ATS valves includes their durability and the quietness of the valve sound. However, a cine-fluoroscopic study revealed an incomplete opening of the valve leaflet. An overall evaluation of the ATS valve was conducted by transesophageal echocardiography. METHODS: The patients were divided into two groups based ...
Song Ze-Zhou - - 2009
A 83-year-old woman presented with a 25-year history of hypertension which was long-standing, uncontrolled, severe hypertension because of irregular oral administration of antihypertensive drug underwent an echocardiographic examination as part of an evaluation of hypertension. She described chest distress associated with activity, syncope for three times in the past one ...
Schievano Silvia - - 2009
BACKGROUND AND AIM OF THE STUDY: Percutaneous mitral valve (MV) dilatation is routinely performed for mitral stenosis using either a single balloon (SB) or double balloon (DB) technique. The study aim was to compare the two techniques using the finite element (FE) method. METHODS: An established FE model of the ...
Momani Lina - - 2009
Hydrocephalus is caused by blockage or reabsorption difficulty that upsets the natural balance of production and absorption of cerebrospinal fluid in the brain, resulting in a build-up of the fluid in the ventricles of the brain. One of the recent advances in the treatment of hydrocephalus is the invention of ...
Lee Hwansung - - 2009
The aim of this study was to observe mechanical heart valve (MHV) cavitation pits resulting from in vivo testing of an electrohydraulic total artificial heart (EHTAH). During in vivo testing with three sets of valves (one set used in two animals), the slope of the driving pressure (left and right ...
Tian Bian - - 2009
In this paper we describe the design and testing of a micro piezoresistive pressure sensor for a Tire Pressure Measurement System (TPMS) which has the advantages of a minimized structure, high sensitivity, linearity and accuracy. Through analysis of the stress distribution of the diaphragm using the ANSYS software, a model ...
Mullens Wilfried - - 2009
The ratio of early transmitral velocity to tissue Doppler mitral annular early diastolic velocity (E/Ea) has been correlated with pulmonary capillary wedge pressure (PCWP) in a wide variety of cardiac conditions. The objective of this study was to determine the reliability of mitral E/Ea for predicting PCWP in patients admitted ...
Dzemali O - - 2008
AIM: Despite continuous development of anticalcification treatment for bioprosthetic valves, calcification remains one major cause of structural failure. The aim of this study is to investigate changes in hemodynamic performance and leaflet kinematics in progressively calcified pericardial and porcine aortic valve prostheses. METHODS: Five pericardial (Edwards Perimount Magna) and 5 ...
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