Search Results
Results 451 - 500 of 1823
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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 ...
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 ...
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 ...
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 ...
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 ...
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. ...
Cioffi Giovanni - - 2008
BACKGROUND: Left atrial systolic force (LASF) is a measure of atrial systolic function applied both in patients with systemic arterial hypertension and aortic valve disease. DESIGN AND METHODS: The method used for assessing LASF was described by Manning in 1993. It assumes a constant circular area for estimating the mitral ...
Acott Christopher John - - 2008
Basic life support (BLS) in a diving bell (DB) or deck decompression chamber (DDC) is difficult due to the confined space and limited equipment. Retrieval of the unconscious diver into the DB requires the use of a pulley system. Once inside the bell, space limitations dictate that any resuscitative efforts ...
Oyama Mark A - - 2008
Doppler echocardiography is useful in assessing the severity of obstructive cardiac lesions, such as mitral valve stenosis. The Doppler study can be used to calculate pressure half-time (PHT), which is defined as the time required for the pressure gradient across an obstruction to decrease to half of its maximal value. ...
Hussain Sayed T - - 2008
One of the commonly used parameters for evaluating aortic regurgitation is the rate of pressure decay data obtained from echocardiographic evaluation or cardiac catheterization. The measurement of the rate of equalization of pressure between the aorta and the left ventricle and its utility in the setting of aortic insufficiency has ...
Chen Guofang G Department of Pharmacology and MUSC Proteomics Center, Medical University of South Carolina, Charleston, SC 29425, USA. - - 2008
A simple light-actuated microvalve using a quartz halogen illuminator with tungsten filament was introduced to manipulate flow path effectively in micro-total analysis systems, which reduces system complexity and the need for on-chip integration. The microvalve device in cyclic olefin copolymer (COC) microchip functions very well based on the thermo-responsive polymer, ...
Mascherbauer Julia - - 2008
AIMS: Hypertension is a frequent finding in patients with aortic stenosis (AS). However, controversial data about the influence of systemic blood pressure on the quantification of AS have been published. METHODS AND RESULTS: Various models of AS (plates and biological valves) were studied in an in vitro circuit. Valve areas ...
Chew Gerard T - - 2008
OBJECTIVE: To investigate the effects of fenofibrate and coenzyme Q(10) (CoQ) on diastolic function, ambulatory blood pressure (ABP), and heart rate (HR) in type 2 diabetic subjects with left ventricular diastolic dysfunction (LVDD). RESEARCH DESIGN AND METHODS: We randomized, double-blind, 74 subjects to fenofibrate 160 mg daily, CoQ 200 mg ...
Guenzinger Ralf - - 2008
OBJECTIVE: The aim of this prospective randomized trial was to evaluate the impact of complete supraannular positioning of mechanical aortic bileaflet valves. METHODS: Between April of 2004 and November of 2006, 80 patients underwent aortic valve replacement with the complete supraannular Medtronic Advantage Supra (n = 40) (Medtronic Inc, Minneapolis, ...
Giardini Alessandro - - 2008
AIMS: This investigation sought to discern the relative accuracy of Doppler predictions of pressure drops in regurgitant jets across a broad spectrum of conditions, using an in vitro pulsatile flow model. METHODS AND RESULTS: We studied the accuracy of Doppler pressure gradients derived from regurgitant jet peak velocities using the ...
Dzemali Omer - - 2008
BACKGROUND AND AIM OF THE STUDY: Heart failure is common following aortic valve replacement, and optimal prosthesis function is crucial in this critical clinical setting. The study aim was to investigate the hemodynamic performance and leaflet kinematics of fresh and calcified biological aortic valves in a simulated low stroke volume ...
Cavendish Jeffrey J - - 2008
The use of the pressure sensor coronary guidewire is expanding into the peripheral circulation as well as into the realm of valvular heart disease. Small mechanistic studies and case reports have described the use of pressure wire technology in the renal and femoral arteries as well as in mechanical aortic ...
Gustafsson Ulf - - 2009
Aim To elucidate the complexity of left ventricular motion throughout the cardiac cycle, we studied regional rotation in detail. Regional rotation in six subdivisions of the circumference at three levels was studied by using speckle-tracking echocardiography in 40 healthy subjects. At the basal level the inferoseptal segments rotated significantly more ...
Lee Hwansung - - 2008
In previous studies, we investigated the mechanism of mechanical heart valve (MHV) cavitation and cavitation intensity with a nonsynchronized experiment system. Our group is currently developing a pneumatic ventricular assist device (PVAD), and in this study we investigated MHV cavitation intensity in the PVAD using a synchronized analysis of the ...
Fukuda Shota - - 2008
BACKGROUND: Earlier studies demonstrated the ability of real-time 3-dimensional (3D) echocardiography (3DE) to measure left ventricular outflow tract (LVOT) area (A(LVOT)) in patients with hypertrophic cardiomyopathy (HCM). However, its clinical value is unknown. OBJECTIVE: We sought to investigate the feasibility and accuracy of real-time 3DE-derived A(LVOT) to diagnose significant LVOT ...
Lo Chi-Wen - - 2008
Accelerated testing provides a substantial amount of data on mechanical heart valve durability in a short period of time, but such conditions may not accurately reflect in vivo performance. Cavitation, which occurs during mechanical heart valve closure when local flow field pressure decreases below vapor pressure, is thought to play ...
Kuo Alexander S - - 2008
Pulmonic valve incompetence has been observed during implantation of total artificial lungs (TAL) and may contribute to right ventricular dysfunction in certain attachment modes. The roles of pulmonary system resistance and inertia on valve function were examined retrospectively using data from attachments of a prototype TAL in six pigs. The ...
Bottio Tomaso - - 2008
BACKGROUND AND AIM OF THE STUDY: In-vivo echocardiographic studies are limited by several confounding factors and technical pitfalls, and consequently the hypothetical differential hydraulic behavior between different prosthetic heart valves has not been identified. However, for surgeons it is essential to know the functional and geometric characteristics of the prostheses ...
Arteaga Roque B - - 2008
BACKGROUND: Several modalities to diagnose diastolic dysfunction by transthoracic echocardiography (TTE) exist. We compared the ratio of early mitral filling velocity (E) to early diastolic velocity by tissue Doppler imaging at the medial (E/E'm) and the lateral (E/E'l) mitral annulus and developed a model to diagnose elevated left ventricular end-diastolic ...
Hartley Craig J CJ Department of Medicine, Section of Cardiovascular Sciences, Baylor College of Medicine and The Methodist Hospital, Houston, TX 77030, USA. - - 2008
Aortic banding produces pressure overload cardiac hypertrophy in mice, leading to decompensated heart failure in four to eight weeks, but the effects on coronary blood flow velocity and reserve are unknown. To determine whether coronary flow reserve (CFR) was reduced, we used noninvasive 20-MHz Doppler ultrasound to measure left main ...
Hoffman Matthew R MR Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, - - 2009
Measuring subglottal pressure (P(s)) with complete interruption can be problematic due to unsteady plateaus in supraglottal pressure data traces during balloon valve interruption. Subjectively determining when the graph plateaus neglect the effects of laryngeal, auditory, and other physical reflexes may alter patient effort and glottal configuration. If the P(s) estimation ...
Debl Kurt - - 2008
In Doppler echocardiography, a triphasic mitral inflow filling pattern with a mid-diastolic flow velocity (L) is usually related to elevated filling pressures and delayed myocardial relaxation. Furthermore, additional triphasic mitral annulus velocity with a mid-diastolic component (L') at tissue Doppler imaging (TDI) demonstrates an even more advanced diastolic dysfunction. In ...
Daimon Masao - - 2008
OBJECTIVE: Most studies of the pathogenesis of functional mitral regurgitation (MR) have focused on alterations in ventricular function and geometry. We used a novel 3D echocardiographic method to assess abnormalities in mitral annular (MA) geometry and motion in patients with ischemic MR (IMR) and compared these data to those obtained ...
Turkmen Funda - - 2008
BACKGROUND: Cardiac valve calcification is a frequent finding in chronic haemodialysis patients. Left ventricular hypertrophy (LVH) is a significant predictor of cardiovascular mortality in patients with end-stage renal disease. We evaluated the influence of aortic valve sclerosis (AVS) on the development of LVH in chronic haemodialysis patients. METHODS: A total ...
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