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Results 451 - 500 of 1847
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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 ...
Solis Jorge J Division of Cardiology, Massachusetts General Hospital, Boston, MA 02114, - - 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 G Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, CA, - - 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 EM Department of Bioengineering and the McGowan Institute, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15219, - - 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 ...
Momani Lina L Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool L69 3GJ, UK. - - 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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
Jiao Guang-Yu - - 2008
BACKGROUND: Ventilator exhalation-valve performance during the expiratory phase has been studied in depth. An active exhalation valve uses servo-control technology that allows gas to be released from the exhalation valve during the inspiratory phase if the patient makes an expiratory effort. We conducted a bench study of active exhalation valve ...
Civelek A - - 2008
BACKGROUND: Tricuspid valve replacement (TVR) is rarely performed and is associated with a high morbidity and mortality. We report our experience with TVR and related adverse events. METHODS: Between January 1996 and December 2007, 35 patients underwent TVR with mechanical (n = 33) or bioprosthetic (n = 2) valves. Twenty-nine ...
Yamada Ryotaro - - 2009
The degree of mitral valve (MV) coaptation should be an important parameter in the assessment of functional mitral regurgitation (MR). This study aimed to quantify the degree of MV coaptation in experimental models of functional MR caused by acute left ventricular (LV) pressure overload, using real-time three-dimensional (3D) echocardiography. Using ...
Zheng Yizhe - - 2009
This work describes a simple and inexpensive approach for controlling the pneumatic valves that were invented in Quake's group to miniaturize the whole system for portable and disposable microfluidic devices. The valves are assembled from two parts. One is the polydimethylsiloxane (PDMS) channels formed by multilayer soft lithography. The other ...
Kheradvar Arash - - 2009
In the field of cardiology, the current ability to accurately detect diastolic dysfunction is unsatisfactory due to the lack of an effective diagnostic index. Isolated indexes obtained from echocardiography are all restricted to a certain aspect of ventricular diastolic function only, and individually cannot be regarded as a global representative ...
Vandenberghe Stijn - - 2008
Recently developed technologies allow aortic valve implantation off-pump in a beating heart. In this procedure, the native, stenotic aortic valve is not removed, but simply crushed by a pressure balloon mounted on a percutaneous catheter. Removal of the native aortic cusps before valve replacement may reduce the incidence of annular ...
Seo Seong-Heon - - 2008
A piezoelectric valve, which has a flow rate of about 463 mbar l/s, has been installed to fuel the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. The valve flow rate is in situ calibrated by analyzing the pressure rise curve while fueling the vessel at a constant rate. The calibration ...
Sadeghpour Anita - - 2008
OBJECTIVE: Few reports have been published on the Doppler-derived echocardiographic data for pulmonary valve prostheses (PVPs). The aim of this study was to provide a comprehensive Doppler echocardiographic assessment of PVPs. METHODS: We studied 40 patients (mean age 24.2) with PVPs: 13 (32.5%) mechanical and 27 (67.5%) bioprosthetic valves. After ...
Takeda Atsuhito - - 2008
BACKGROUND: Little is known about the precise morphometric data of the aortic arch at which the transcatheter pressure gradient is relieved in patients with aortic coarctation (CoA). METHODS AND RESULTS: Twenty-nine morphometric data were obtained from patients with CoA including the body surface area (BSA) adjusted angiographic diameter of the ...
Masuyama Shinji - - 2008
OBJECTIVE: Treatment of ischemic mitral regurgitation accompanied by strong tethering remains a challenge. Undersized ring annuloplasty is frequently associated with residual/recurrent mitral regurgitation caused by mitral-leaflet tethering. Although chordal cutting is a simple procedure for repairing severe tethering of the anterior mitral leaflet, it often affects mitral valvular-ventricular continuity. In ...
Moss Edward B - - 2008
PURPOSE: To measure closing pressure in a series of new Model FP7 silicone Ahmed Glaucoma Valves (AGVs), using an in vitro gravity-driven system, in which closing pressure was measured directly from a dual manometer/pressure reservoir. METHOD: A straight length of tubing served as an open manometer, which connected via a ...
Tanné David - - 2008
Recent clinical studies reported that prosthesis-patient mismatch (PPM) becomes clinically relevant when the effective orifice area (EOA) indexed by the body surface area (iEOA) is <1.2-1.25 cm(2)/m(2). To examine the effect of PPM on transmitral pressure gradient and left atrial (LA) and pulmonary arterial (PA) pressures and to validate the ...
Schipke, Kimberly Jo
The differentiation of myosin into the respective heavy chain isoforms has shown a correlation with high mechanical stress. Aortic valve myosin expression has been reported; however, the characterization of the pressure response has yet to be fully developed. Thus, a cyclic pressure bioreactor was developed to elucidate the á/â-myosin heavy ...
McGuire Shawn - - 2008
A successful dispensing device has been built for use in biotechnology applications requiring nanoliter volume liquid transfer. Air pressure is used as the primary driving force and is controlled via a high speed miniature solenoid valve as opposed to many existing systems that use a valve in line with constantly ...
Freund M W - - 2008
We describe a successful cardiac intervention in an infant, born at 32 weeks of gestation, with a birth weight of 1040 g, who had a critical pulmonary valve stenosis with the right ventricular pressure twice the systemic pressure. Continuous prostaglandin E infusion kept the arterial duct open and at the ...
Krishnamurthy Gaurav - - 2008
We measured leaflet displacements and used inverse finite-element analysis to define, for the first time, the material properties of mitral valve (MV) leaflets in vivo. Sixteen miniature radiopaque markers were sewn to the MV annulus, 16 to the anterior MV leaflet, and 1 on each papillary muscle tip in 17 ...
Weinzierl Martin R - - 2008
OBJECT: Previous reports suggest that the use of adjustable differential-pressure valves may improve shunt performance. The absence of a flow- or siphon-controlled mechanism, however, is a concern. The goal of this prospective study was to assess the efficacy of valve adjustments in preventing slitlike ventricles in children < 6 months ...
Li Chi-Pei - - 2008
BACKGROUND AND AIM OF THE STUDY: Cavitation occurs during mechanical heart valve closure when the local pressure drops below vapor pressure. The formation of stable gas bubbles may result in gaseous emboli, and secondarily cause transient ischemic attacks or strokes. It is noted that instantaneous valve closure, occluder rebound and ...
Sharp M Keith - - 2008
For a mechanical heart valve, a strong spike in pressure during closing is associated with valve wear and erythrocyte damage; thus, for valid in vitro testing, the mock circulation system should replicate the conditions, including pressure spikes, expected in vivo. To address this issue, a study was performed to investigate ...
Lee Meng-Luen - - 2008
PURPOSE: We report herein major determinants and long-term outcomes of balloon dilatation (BD) for 27 pediatric patients with isolated native valvular pulmonary stenosis (VPS). MATERIALS AND METHODS: From May 1997 to May 2003, 27 pediatric patients with VPS (pressure gradients >or= 40 mmHg) were enrolled in this retrospective study. Single-balloon ...
Chen Hao H Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109-1120, - - 2008
Pressure-actuated poly(dimethylsiloxane) (PDMS) valves have been characterized with respect to their electromechanical properties. Measurements of the valve opening and closing times, threshold pressures, and impedance spectra for closed valves can be used to assess the quality of the devices in general, determine their suitability for specialized applications, such as providing ...
He Zhaoming - - 2008
Mitral valve (MV) annulus mechanics and its effect on annulus dilatation are not well understood. The objective of the current study was to understand annulus tension (AT) during valve closure. A porcine MV rested on top of annulus rings with papillary muscles (PMs) held at slack, normal and taut conditions. ...
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