To study the role of blood flow in normal and abnormal heart development, an embryonic chicken model was developed. The effect of altered venous inflow on normal intracardiac blood flow patterns was studied by visualization of blood flow with India ink. At stage 17, India ink was injected into a ...

The feasibility of determining the time interval from left atrial appendage (LAA) flow was examined using transesophageal Doppler echocardiography. Time intervals were compared between LAA flow and mitral flow patterns during late diastole in 8 patients with mitral stenosis and in 12 controls. The start of ejection flow from the ...

BACKGROUND: Although Doppler color flow mapping is widely used to assess the severity of mitral regurgitation (MR), a simple, accurate, and quantitative marker of MR by color flow mapping remains elusive. We hypothesized that vena contracta width by color flow mapping would accurately predict the severity of MR. METHODS AND ...

The flow (Q) through regurgitant valves may be quantified by multiplying the area of an isovelocity contour (isovel) by its velocity. This was tested computationally and experimentally (using MRI). Q = 14 to 141 ml/s, using flat and conical orifice plates. Plotting Q versus isovelocity radius, a plateau was found ...

Analysis of jet momentum and proximal isovelocity surface area (PISA) have been shown to be accurate in quantitating regurgitant flow for axisymmetric free jets. However, eccentric jets directed against chamber walls are often encountered in clinical practice and could confound the assessment of regurgitant flow. Thus, we used direct digital ...

The examination conditions necessary for accurate measurement of regurgitant volume by the proximal flow convergence method applying a simple hemispheric equation remain uncertain. This study investigated the requirement for measuring regurgitant stroke volume from the combined continuous-wave and color Doppler proximal flow convergence approach. Twenty-five pulsatile flow rates were produced ...

An accurate and reliable method of regurgitant flow calculation is currently unavailable. The goal of this study was to define a new general method of flow calculation for orifices of different aspect ratios. The success of the method relies on matching the imaged flow field distribution obtained by color flow ...

Velocity profiles and Reynolds stresses downstream of heart valve prostheses are vital parameters in the study of hemolysis and thrombus formation associated with these valves. These parameters have previously been evaluated using single-point measurement techniques such as laser Doppler anemometry (LDA). The purpose of this study is to map the ...

Persistent atrial standstill, characterized by absence of atrial activity on surface and intracavitary electrograms, absence of atrial mechanical activity, and inability to stimulate the atria electrically, is a rare disorder. Left atrial appendage blood flow has been reported to be related to P wave during sinus rhythm or local atrial ...

BACKGROUND AND AIMS OF THE STUDY: During recent clinical trials the Medtronic Parallel bileaflet mechanical heart valve was found to have an unacceptable number of valves with thrombus formation when implanted in the mitral position. Thrombi were observed in the hinge region and also in the upstream portion of the ...

BACKGROUND AND AIMS OF THE STUDY: During recent clinical trials, the Medtronic Parallel bileaflet heart valve was found to have an unacceptable thrombosis complication rate. As patient- and material-related factors proved negative causes for this outcome, it was hypothesized that the flow fields within the valve's hinge pocket contributed to ...

Aortic helical flow may play an important role in plaque deposition, dissection formation, and organ perfusion. The authors have previously demonstrated, using in vitro flow models and transesophageal echocardiography, that helical flow begins in the mammalian aortic arch and continues into the descending thoracic aorta. The purpose of this study ...

OBJECTIVES: This study sought to compare the mitral valve areas of patients with rheumatic mitral valve stenoses as determined by means of four echocardiographic and Doppler methods with those obtained by direct anatomic measurements. BACKGROUND: There has been no systemic comparison between Doppler-determined valve areas and the true anatomic orifice ...

The behaviour of the blood flow passing through artificial heart values in aortic position is numerically simulated by discretizing the Navier-Stokes equations for viscous incompressible flow through the finite element method. Three different artificial valves, Starr-Edwards, St Jude and disc valves, are modelled by using the finite element method as ...

BACKGROUND AND AIM OF THE STUDY: Fluid stresses occurring in retrograde flow fields during valve closure may play a significant role in thrombogenesis. The squeeze flow and regurgitant jets can cause damage to formed blood elements due to high levels of turbulent shear stress. The aim of this study was ...

OBJECTIVES: This study sought to assess the diagnostic implications of the flow dependence of Doppler echocardiographic indexes of aortic valve stenosis. BACKGROUND: Although valve area has been shown to change with alterations in flow rate, the diagnostic consequences of this phenomenon remain unknown. Valve resistance has been suggested as a ...

OBJECTIVE: The objective of this study was to measure blood flow velocity changes through the tricuspid valve in intrauterine growth-restricted twins. STUDY DESIGN: Discordant twins were evaluated by measurement of tricuspid valve flow velocities. Twin pairs with one intrauterine growth-restricted fetus caused by uteroplacental insufficiency and one appropriately grown fetus ...

This study was performed to develop and validate Doppler color flow methods for quantifying forward transmitral flow rates and volumes with isovelocity aliasing contours. We undertook computer modeling of flows and studied an animal model with strictly controlled mitral flows. Finite element analysis was first used to establish the isovelocity ...

BACKGROUND AND AIMS OF THE STUDY: Normal prosthetic valves have regurgitation that varies according to valve type and design. The Björk-Shiley prosthetic mitral valve is a tilting disc valve that has undergone design changes since its introduction. From 1969 to 1981, Delrin, was used to make the disc occluder. After ...

In 84 patients mitral regurgitation was quantified by angiography. The mechanism of regurgitation was determined by echocardiography (organic, n = 54, functional, n = 30). The radii of the proximal isovelocity surface areas in the flow convergence region for 28 and 41 cm.s-1 blood flow velocity and the area and ...

The Dacron sewing ring material of the St. Jude Medical mechanical heart valve (St. Jude Medical, Inc., St. Paul, Minn.) was passively impregnated with rifampicin (60 mg/ml) both in its unsealed state and after sealing by the methods of preclotting in blood, autoclaving in blood, and autoclaving in 20% albumin. ...

The proximal acceleration technique is a promising technique for quantification of regurgitant valve flow. Although the shape of the regurgitant proximal isovelocity field has been shown to vary with orifice size, geometry, and driving pressure, normally the centerline velocity alone is used for estimation of flow. In this model study ...

A method for quantifying mitral and tricuspid regurgitant volume that utilizes a measure of jet orifice velocity U(0) - m/sec), a distal centerline velocity (U(m) - m/sec), and the intervening distance (X - cm) was recently developed; where jet flow rate (Q(cal) - L/min) is calculated as Q(cal) = (U(m)X)(2)/(26.46U(o)). ...

A method for quantifying peak mitral and tricuspid regurgitant jet flow rate that utilizes a measure of jet orifice velocity (Uo, m s-1), a distal centerline velocity (Um, m s-1), and the intervening distance (X, cm) was recently developed. This method, however, modeled the regurgitant jet as a free jet, ...

Flow injection devices for atomic absorption spectrometry usually are equipped with a sixport-valve consisting of two PTFE-cylinders. This kind of valve can be substituted by an arrangement of tubing clamp valves. The advantages and limits of this new injection technique for flow injection atomic absorption spectrometry are discussed.

It has been argued that the aortic valve area (AVA) in patients with aortic stenosis increases with flow. Others, however, have attributed the apparent increase to flow dependence of the empiric constant in the Gorlin formula. We examined the changes in AVA during changes in transvalvular flow induced by dipyridamole ...

The flow through a bileaflet mechanical heart valve during the first half of systole was predicted using computational fluid dynamics (CFD). A three-dimensional model of the geometry of the ventricle, valve, sinus and aorta was developed. Flow through the valve was assumed to be Newtonian and laminar. The peak systolic ...

OBJECTIVES: This study sought to investigate the applicability of a current implementation of a three-dimensional echocardiographic reconstruction method for color Doppler flow convergence and regurgitant jet imaging. BACKGROUND: Evaluation of regurgitant flow events, such as flow convergences or regurgitant jets, using two-dimensional imaging ultrasound color flow Doppler systems may not ...

Flow visualization and pressure measurements were carried out in a singel valve saphenous vein casting which was made from a saphenous vein segment obtained from a bypass patient at Cedars Sinai Medical Center. Dye was injected to understand the flow around the valve. The dye showed very complex flow patterns ...

OBJECTIVE: To study peristalsis and drainage of the stented ureter under normal physiological conditions. PATIENTS AND METHODS: Fifteen non-obstructed patients with ureteric stents and 15 control subjects (i.e. 45 unstented ureters and 15 stented ureters) had ureteric jets and flow analysed using colour Doppler ultrasound (CDU). Cross-sectional and longitudinal studies ...

OBJECTIVE: This study was undertaken to investigate the feasibility and accuracy of determination of stroke volume and cardiac output by calculating transmitral flow volume using the flow convergence region method in patients with mitral stenosis. PATIENTS AND INTERVENTIONS: Fifty-six patients with rheumatic mitral stenosis were studied using imaging and Doppler ...

Recent studies have shown good agreement between proximal regurgitant jet size obtained with transthoracic color flow mapping and regurgitant fraction in patients with mitral regurgitation. To evaluate this in patients with tricuspid regurgitation, we analyzed 40 patients in sinus rhythm, 16 with free jets and 24 with impinging jets, comparing ...

OBJECTIVES: This study sought to elevate the effect of proximal flow constraint induced by the left ventricular wall on the accuracy of calculated flow rates and to assess a possible correction factor to adjust the proximal convergence angle. We further defined under which hydrodynamic and geometric conditions it is necessary ...

For evaluation of pulmonary venous flow (PVF) in mitral stenosis, transthoracic and transesophageal echocardiography were performed in 33 patients with mitral stenosis and 20 normal controls. The peak systolic flow velocity of the PVF was significantly lower in patients with mitral stenosis and atrial fibrillation. The peak diastolic flow velocity ...

The possibility that the discharge coefficient (Cd) for a mechanical heart valve (MHV) is affected by valvular stenosis is addressed. A 29 mm bileaflet (Si. Jude Medical) mitral valve is tested on a cardiovascular duplicator (CVD) in its normal state and under two degrees of simulated stenosis. Stenoticity is simulated ...

BACKGROUND AND AIM OF THE STUDY: The importance of chordal preservation techniques in maintaining improved left ventricular function after mitral valve replacement has been well documented clinically. Currently, the choice of prosthetic valve used in chordal preservation is dependent upon the surgeon's preference. However, the transvalvular flow characteristics of common, ...

Spatial appreciation of flow velocities using Doppler color flow mapping has led to quantitative evaluation of the zone of flow convergence proximal to a regurgitant orifice. Based on the theory of conservation of mass, geometric analysis, assuming a series of hemispheric shells of increasing velocity as flow converges on the ...

OBJECTIVES: The aims of this study were to define the hydrodynamic mechanisms involved in the occurrence of hemolysis in prosthetic mitral valve regurgitation and to reproduce them in a numeric simulation model in order to estimate peak shear stress. BACKGROUND: Although in vitro studies have demonstrated that shear stresses > ...

BACKGROUND: The aim of the present study was to evaluate dynamic changes in aortic regurgitant (AR) orifice area with the use of calibrated electromagnetic (EM) flowmeters and to validate a color Doppler flow convergence (FC) method for evaluating effective AR orifice area and regurgitant volume. METHODS AND RESULTS: In 6 ...

OBJECTIVES: The purpose of this study was to develop a rational and objective method for selecting a region in the proximal flow field where the hemispheric formula for calculating regurgitant flow rates by the flow convergence technique is most accurate. BACKGROUND: A major obstacle to clinical implementation of the proximal ...

The most descriptive measure of valvular insufficiency is the regurgitant volume. Current techniques for measuring it, however, are invasive and semi-quantitative at best. Cape and colleagues have recently developed a non-invasive technique for the quantitation of regurgitant flows corresponding to free jets cases. This technique is, unfortunately, not applicable to ...

OBJECTIVES: The aim of the present study was to validate a digital color Doppler-based centerline velocity/distance acceleration profile method for evaluating the severity of aortic regurgitation. BACKGROUND: Clinical and in vivo experimental applications of the flow convergence axial centerline velocity/distance profile method have recently been used to estimate regurgitant flow ...

BACKGROUND AND AIM OF THE STUDY: The non-invasive, in-vivo assessment of prosthetic valve function is compromised by the lack of accurate measurements of the transvalvular flow fields or hemodynamics by current techniques. Short echo time magnetic resonance imaging (MRI) may provide a method for the non-invasive, in vivo assessment of ...

The in vitro testing of artificial heart valves is often performed with simple fluids like glycerol solutions. Blood, however, is a non-Newtonian fluid with a complex viscoelastic behavior, and different flow fields in comparable geometries may result. Therefore, we used different polymer solutions (Polyacrylamid, Xanthan gum) with blood-like rheological properties ...

In vitro velocity data were obtained downstream of two versions of the Leeds polyurethane trileaflet heart valve in a simulated pulsatile flow regime using laser Doppler velocimetry. The main difference between the two valves studied was the manufacturing method used to create the valves. The film-fabricated valve was constructed from ...

Although velocity profiles downstream of mechanical valves have been measured in-vitro using Laser Doppler Anemometry (LDA), these studies have not measured velocities in the immediate proximity of the leaflets since the LDA technique prevents velocities from being measured in the immediate vicinity of any structure. Laser based Digital Particle Image ...

BACKGROUND AND AIM OF THE STUDY: The squeeze-flow that develops during valve closure is believed to cause cavitation in mitral mechanical heart valves (MHVs). METHODS: Squeeze-flow was studied in tilting disc MHVs using two different numerical approaches. In the first decoupled analysis, experimental measurements of valve closing velocities were input ...

The effect of aortic outflow on the quantification of mitral regurgitation by the flow convergence method was investigated by both in vitro experiments and computational simulations. Digital analysis of the color Doppler M-mode images was compared with results obtained with laser Doppler anemometry, an engineering gold standard, and three-dimensional computational ...

This paper comprises a study of the secondary flow patterns that can develop in the human aortic arch. Clinical evidence of these secondary flows has been obtained by Kilner et al. using magnetic resonance velocity mapping techniques. Some of their results are presented for comparison in this paper. Four difference ...

OBJECTIVES: The aim of the present study was two-fold: first, to quantify characteristic parameters of the pulmonary venous flow pattern in patients with mitral regurgitation by using magnetic resonance phase velocity mapping; second, to determine whether this pattern is dependent on the vein being investigated and the direction of the ...