Search Results
Results 501 - 550 of 1837
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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 ...
Nagao Taisuke - - 2008
PURPOSE: We developed a noninvasive method using magnetic resonance (MR) imaging to measure differences in intravascular and intracardiac pressure, and we investigated the feasibility of the method's use in a pulsatile flow phantom and human studies. METHODS: We measured 3 velocity components using phase contrast MR imaging on a 1.5T ...
Bechtel J F Matthias - - 2008
BACKGROUND AND AIM OF THE STUDY: It has been reported previously that the use of a decellularized pulmonary allograft (SynerGraft; CryoLife Inc.) for right ventricular outflow tract reconstruction in adults is associated with reduced immunization. The implantation appeared to be safe, but was not associated with any detectable clinical or ...
Berger Rachel Levine - - 2008
This is an unusual case of diastolic mitral regurgitation (MR) with a high diastolic velocity jet and prolonged jet duration related to a combination of acute severe aortic insufficiency and high-degree atrioventricular block. This case illustrates an interesting hemodynamic phenomenon with multiple transient decreases in the pressure gradient between the ...
Mendoza Carlos I - - 2008
We consider a capillary consisting of two coaxial cylinders whose core is filled with a nematic liquid crystal (LC) subjected to the simultaneous action of both a pressure gradient applied parallel to the axis of the cylinders and a radial low frequency electric field. We find the configuration of the ...
Lee Hwansung - - 2008
The cavitation intensity of a mechanical heart valve (MHV) may differ according to the geometry of the blood pump and driving mechanism. Our group is currently developing a pneumatic ventricular assist device (VAD), and the effects of different operating conditions on MHV cavitation in our pneumatic VAD were investigated. Tests ...
Sakamoto Yoshimasa - - 2008
The main problem that arises from patient-prosthesis mismatch after aortic valve replacement is a residual high transvalvular pressure gradient, resulting in left ventricular overload. It was demonstrated by Pibarot and Dumesnil that the indexed effective orifice area should be larger than 0.85-0.90 cm2/m2 to prevent any significant transvalvular pressure gradient ...
Lee Hwansung - - 2008
To investigate the characteristics of cavitation intensity, we performed a synchronized analysis of the visual images of cavitation and the pressure signals using a pulsatile device. The pulsatile device employed was a pneumatic ventricular assist device (PVAD) that is currently being developed by our group. A 23-mm Medtronic Hall valve ...
Ozay Batuhan - - 2008
BACKGROUND: The aims of this study were to elucidate the incidence of mitral regurgitation during off-pump coronary artery bypass (OPCAB) surgery to evaluate the relationship of the changes with ventricular function and possible mitral valve regurgitation caused by positioning. METHODS: Included in the study were 60 consecutive patients who underwent ...
Johnson Brandon E - - 2008
Pressure-polishing is a method for shaping glass pipettes for patch-clamp recording. We first developed this method for fabricating pipettes suitable for recording from small (<3 m) neuronal cell bodies. The basic principal is similar to glass-blowing and combines air pressure and heat to modify the shape of patch pipettes prepared ...
Zervides Constantinos - - 2008
It is widely accepted that venous valves play an important role in reducing the pressure applied to the veins under dynamic load conditions, such as the act of standing up. This understanding is, however, qualitative and not quantitative. The purpose of this paper is to quantify the pressure shielding effect ...
Allin David M DM Shunt Evaluation Laboratory & Academic Neurosurgical Unit, Addenbrooke's Hospital, P,O, Box 167, Hills Road, Cambridge CB2 2QQ, UK. - - 2008
The Polaris valve is a newly released hydrocephalus shunt that is designed to drain cerebrospinal fluid (CSF) from the brain ventricles or lumbar CSF space. The aim of this study was to bench test the properties of the Polaris shunt, independently of the manufacturer. The Polaris Valve is a ball-on-spring ...
Garcia J J Laval Hospital Research Center, Laval University, Quebec, Canada. - - 2008
Valve hydrodynamic performance is usually assessed by effective orifice area, transvalvular resistance, regurgitation and blood damage effect. Some studies suggest effects in effective orifice area due to cardiovascular resistance, compliance and angle position of the valve. We suppose that silicone rubber valves under study have a good performance under different ...
Prince Martin R - - 2007
Characterization of vascular lesions on the basis of visual estimation of percentage stenosis is a valuable but limited procedure. In this issue, Lum et al (1) describe a fast, noninvasive four-dimensional MR method for accurate determination of pressure gradient maps, which correlate with direct pressure gradient measurements across vascular lesions ...
Abe Yukio - - 2008
Mitral regurgitation, when it arises from functional restriction of mitral leaflet closure, can be relieved by surgical cutting of the mitral tendineae chordae. We hypothesized that high intensity focused ultrasound (HIFU) might be useful as a noninvasive extracorporeal technique for cutting mitral chordae. As a pilot study to test this ...
Cui Wei - - 2007
BACKGROUND: Mean mitral valve pressure gradient (MVPG) is one of the key measures of the severity of mitral stenosis. The method for calculating MVPG, however, is complex and time consuming. The purpose of this study is to establish a new simple method for calculating MVPG. METHODS: Hemodynamic data were analyzed ...
Gur M - - 2008
We aimed to investigate the association between aortic distensibility (AD) and left ventricle myocardial performance index (MPI) in patients with newly diagnosed hypertension (HT). We studied 49 patients with HT and 24 healthy control subjects. AD was calculated from the echocardiographically derived ascending aorta diameters. The MPI was calculated from ...
Domec Jean-Christophe - - 2007
Our goals were to quantify how non-embolism-inducing pressure gradients influence trunk sapwood specific conductivity (k(s)) and to compare the impacts of constant and varying pressure gradients on k(s) with KCl and H2O as the perfusion solutions. We studied six woody species (three conifers and three angiosperms) which varied in pit ...
Kheradvar Arash - - 2007
Several studies have suggested that the mitral annulus displacement and velocity in early diastole can be used as indicators of diastolic performance. The peak velocity of the mitral annulus away from the LV apex during early diastole, which indicates the rate of longitudinal expansion of the LV, is reduced in ...
Timek Tomasz A - - 2007
BACKGROUND: Our prior studies suggest that mitral annular septal-lateral (SL) diameter is the chief determinant of "Alfieri stitch" tension, but hemodynamic parameters may also play a role. We approximated the central edge of the mitral leaflets with a miniature force transducer to measure tension (T) at the leaflet approximation point ...
Seddon P - - 2007
Interrupter resistance (R(int)) is a widely used measure of airway caliber, but concerns remain about repeatability and sensitivity. Some R(int) variability may derive from the linear back-extrapolation algorithm (LBE 30/70) usually used to estimate driving pressure. To investigate whether other methods of estimating driving pressure could improve repeatability and sensitivity, ...
Rhodes Katherine D - - 2007
BACKGROUND AND AIM OF THE STUDY: Pressure recovery is a source of discrepancy between Doppler-derived and catheter aortic valve pressure drops. Pressure recovery occurs where the stenotic jet reattaches to the aortic wall. An equation to predict the jet reattachment location has been developed based on the density and viscosity ...
Jouan Jerome - - 2007
BACKGROUND AND AIM OF THE STUDY: In a previous sono-metric study, changes were described that occurred in the normal tricuspid valve during the cardiac cycle. However, the wealth of data available suggested the need for reporting further findings that should contribute to a better understanding of the dynamics of the ...
Arai Shiori - - 2007
CASE DESCRIPTION: A 5-year-old male German Shepherd Dog was evaluated because of a 5-month history of progressive lethargy, weight loss, and heart failure. CLINICAL FINDINGS: On physical examination, bounding femoral pulses and systolic and diastolic murmurs were detected. Echocardiography revealed severe aortic valve insufficiency (AVI) and a large vegetative lesion ...
Uzun Mehmet - - 2007
INTRODUCTION: Although its accuracy has been documented in many studies, the proximal isovelocity surface area (PISA) method is not used widely for mitral valve area (MVA) measurement. In this study, we prepared a new nomogram and tested its use in MVA assessment. MATERIAL AND METHODS: The study included 23 patients ...
Antonini-Canterin F - - 2008
OBJECTIVE: Left atrial (LA) size is an important predictor of outcome after mitral valve replacement in patients with symptomatic chronic mitral regurgitation (MR). Data on LA remodelling after mitral valve repair (MVr) for chronic non-ischaemic MR are scarce. The aim of this study was to assess changes in LA size ...
Schwarzwald Colin C - - 2007
OBJECTIVE: To assess the feasibility, describe the techniques, and determine the reliability of transthoracic echocardiography for characterization of left atrial (LA) size and LA mechanical function in horses. ANIMALS: 6 healthy adult horses. PROCEDURES: Repeated echocardiographic examinations were performed independently by 2 observers in standing, unsedated horses by use of ...
Nakahara Kuniaki - - 2007
Codman-Hakim programmable valves allow neurosurgeons to adjust the opening pressure to the patient's particular clinical needs. However, the pressure control cam is extremely small, so identification of the pressure indicator and its operation is somewhat difficult when initially setting the opening pressure before implantation. We employed a commercial loupe on ...
Votta Emiliano - - 2007
BACKGROUND: Functional mitral regurgitation (FMR) is the inability of mitral leaflets to coapt due to a combination of functional and geometrical factors. Valve competence is commonly restored by undersized annuloplasty, reducing the native annulus anteroposterior dimension. In case of severe FMR, this solution may be inadequate. The use of rings ...
Bergström Maria - - 2007
BACKGROUND: High intraabdominal pressures during laparoscopy (greater than 15 mm Hg) are dangerous. Pressures developed during translumenal endosurgery when using flexible endoscopes without feed-back regulation are unknown. OBJECTIVE: To measure and control intraabdominal pressures during transgastric endosurgery. DESIGN: In a blinded study, intraabdominal pressures during unregulated transgastric cholecystectomy and tubal ...
Zhang Pei - - 2007
BACKGROUND AND AIM OF THE STUDY: Mechanical heart valve (MHV) cavitation has been widely investigated by negative pressure transient (NPT) measurements. Whilst NPT is believed to be the cause of cavitation as the valve occluder approaches its fully closed position, some valves are also more prone to cavitation initiation. The ...
Shimura Kiyohito - - 2007
A miniature valve that operates between a chip port and a tube fitting was developed. The valve functions by means of a rotor, 3 mm in diameter and 1.5 mm in height, made of Teflon, with a 0.2-mm diameter hole at its center that is co-axial with the tube fitting. ...
Fricker Zachary P - - 2007
A unique, air-based system has been developed and implemented for rapid and accurate determination of pressure drop versus flow rate characteristics of generic catheter lumens; dimensionless scaling parameters can be effectively used to express these characteristics in units of blood flow used in the clinical setting. Theoretical models are compared ...
Blauwet Lori A - - 2007
Few reports have been published on the normal Doppler-derived echocardiographic data for CarboMedics (CarboMedics Inc., Austin, TX) prosthesis function in the mitral position. The purpose of this study was to provide a comprehensive Doppler echocardiographic assessment of normal CarboMedics mitral prosthesis function in a large number of patients. All of ...
Wainwright Peter C - - 2007
Successful prey capture by aquatic suction feeders depends on the ability of the predator to generate a flow of water external to the mouth that overcomes any movements and forces that the prey uses to resist the suction flow. Elucidating the nature and magnitude of these forces is a key ...
Lobo Luis - - 2008
Of 100 Estrela Mountain dogs, 74 were examined to obtain echocardiographic reference values for the breed. The influence of bodyweight, age and sex on different echocardiographic parameters was studied using either analysis of variance or regression analysis. Statistically significant differences were found between sex and heart rate as well as ...
Pan Tingrui - - 2007
In this paper, we present two remotely adjustable check-valves with an electrochemical release mechanism for implantable biomedical microsystems. These valves allow one to vary the opening pressure set-point and flow resistance over a period of time. The first design consists of a micromachined check-valve array using a SU-8 polymer structural ...
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