Instantaneous Cross-sectional Flow Velocity Profiles: A Comparative Study of Two Ultrasound Doppler Methods Applied to an In Vitro Pulsatile Flow Model

1990 ◽  
Vol 3 (6) ◽  
pp. 451-464 ◽  
Author(s):  
Stein O. Samstad ◽  
Hans G. Torp ◽  
Knut Matre ◽  
Ole Rossvoll ◽  
Leidulf Segadal ◽  
...  
Keyword(s):  
Comparative Study ◽  
Flow Velocity ◽  
Pulsatile Flow ◽  
Flow Model ◽  
Velocity Profiles ◽  
Cross Sectional ◽  
Ultrasound Doppler

Left atrial cross-sectional area is a novel measure of atrial shape associated with cardioembolic strokes

Heart ◽  
2020 ◽  
Vol 106 (15) ◽  
pp. 1176-1182
Author(s):  
Timothy C Tan ◽  
Maria Carmo Pereira Nunes ◽  
Mark Handschumacher ◽  
Octavio Pontes-Neto ◽  
Yong-Hyun Park ◽  
...  
Keyword(s):  
Ischaemic Stroke ◽  
Flow Velocity ◽  
Left Atrial ◽  
Velocity Profiles ◽  
Left Ventricular ◽  
Cross Sectional Area ◽  
Left Ventricular Ejection ◽  
Sectional Area ◽  
Cross Sectional

ObjectiveCardioembolic (CE) stroke carries significant morbidity and mortality. Left atrial (LA) size has been associated with CE risk. We hypothesised that differential LA remodelling impacts on pathophysiological mechanism of major CE strokes.MethodsA cohort of consecutive patients hospitalised with ischaemic stroke, classified into CE versus non-CE strokes using the Causative Classification System for Ischaemic Stroke were enrolled. LA shape and remodelling was characterised by assessing differences in maximal LA cross-sectional area (LA-CSA) in a cohort of 40 prospectively recruited patients with ischaemic stroke using three-dimensional (3D) echocardiography. Flow velocity profiles were measured in spherical versus ellipsoidal in vitro models to determine if LA shape influences flow dynamics. Two-dimensional (2D) LA-CSA was subsequently derived from standard echocardiographic views and compared with 3D LA-CSA.ResultsA total of 1023 patients with ischaemic stroke were included, 230 (22.5%) of them were classified as major CE. The mean age was 68±16 years, and 464 (45%) were women. The 2D calculated LA-CSA correlated strongly with the LA-CSA measured by 3D in both end-systole and end-diastole. In vitro flow models showed shape-related differences in mid-level flow velocity profiles. Increased LA-CSA was associated with major CE stroke (adjusted relative risk 1.10, 95% CI 1.04 to 1.16; p<0.001), independent of age, gender, atrial fibrillation, left ventricular ejection fraction and CHA2DS2-VASc score. Specifically, the inclusion of LA-CSA in a model with traditional risk factors for CE stroke resulted in significant improvement in model performance with the net reclassification improvement of 0.346 (95% CI 0.189 to 0.501; p=0.00001) and the integrated discrimination improvement of 0.013 (95% CI 0.003 to 0.024; p=0.0119).ConclusionsLA-CSA is a marker of adverse LA shape associated with CE stroke, reflecting importance of differential LA remodelling, not simply LA size, in the mechanism of CE risk.

Effect of Tapering on Pulsatile Flow Through a U-Tube Model of the Human Aortic Arch

2010 ◽  
Author(s):  
Masaru Sumida
Keyword(s):  
Velocity Profile ◽  
Pulsatile Flow ◽  
Velocity Profiles ◽  
Cross Sectional Area ◽  
Flow Rate Ratio ◽  
Sectional Area ◽  
Cross Sectional ◽  
Turn Angle ◽  
Flow Through ◽  
The Cross

An experimental investigation of pulsatile flow through a tapered U-tube was performed to study the blood flow in the aorta. The experiments were carried out in a U-tube with a curvature radius ratio of 3.5 and a 50% reduction in the cross-sectional area from the entrance to the exit of the curved section. Velocity measurements were conducted by a laser Doppler velocimetry for a Womersley number of 10, a mean Dean number of 400 and a flow rate ratio of 1. The velocity profiles for pulsatile flow in the tapered U-tube were compared with the corresponding results in a U-tube having a uniform cross-sectional area. The striking effects of the tapering on the flow are exhibited in the axial velocity profiles in the section from the latter half of the bend to the downstream tangent immediately behind the bend exit. A depression in the velocity profile appears at a smaller turn angle Ω in the case of tapering, although the magnitude of the depression relative to the cross-sectional average velocity decreases. The value of β, which indicates the uniformity in the velocity profile over the cross section, decreases with increasing Ω, whereas it rapidly increases immediately behind the bend exit.

scholarly journals Cross-sectional early mitral flow-velocity profiles from color Doppler in patients with mitral valve disease.

Circulation ◽  
1992 ◽  
Vol 86 (3) ◽  
pp. 748-755 ◽  
Author(s):  
S O Samstad ◽  
O Rossvoll ◽  
H G Torp ◽  
T Skjaerpe ◽  
L Hatle
Keyword(s):  
Mitral Valve ◽  
Flow Velocity ◽  
Mitral Valve Disease ◽  
Color Doppler ◽  
Velocity Profiles ◽  
Valve Disease ◽  
Cross Sectional ◽  
Mitral Flow

scholarly journals Cross sectional early mitral flow velocity profiles from colour Doppler.

Heart ◽  
1989 ◽  
Vol 62 (3) ◽  
pp. 177-184 ◽  
Author(s):  
S O Samstad ◽  
H G Torp ◽  
D T Linker ◽  
O Rossvoll ◽  
T Skjaerpe ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Velocity Profiles ◽  
Colour Doppler ◽  
Cross Sectional ◽  
Mitral Flow

A Finite-Element Simulation of Pulsatile Flow in Flexible Obstructed Tubes

1982 ◽  
Vol 104 (2) ◽  
pp. 119-124 ◽  
Author(s):  
E. Rooz ◽  
D. F. Young ◽  
T. R. Rogge
Keyword(s):  
Finite Element ◽  
Pulsatile Flow ◽  
Continuity Equation ◽  
Element Model ◽  
Momentum Equation ◽  
Cross Sectional ◽  
One Dimensional ◽  
Element Simulation ◽  
The One

A finite-element model for pulsatile flow in a straight flexible partially obstructed tube is developed. In the unobstructed sections of the tube the model considers the continuity equation, the one-dimensional momentum equation, and an equation of state relating tube cross-sectional area to pressure. For the obstructed region, a nonlinear relationship between the flow and the pressure drop across the stenosis is considered. The applicability of a model is checked by comparing predicted flow and pressure waveforms with corresponding in-vitro experimental measurements obtained on a mechanical system. These comparisons indicate that the model satisfactorily predicts pressures and flows under variety of frequencies of oscillation and stenosis severities.

An In Vitro Comparative Study of St. Jude Medical and Edwards-Duromedics Bileaflet Valves Using Laser Anemometry

1989 ◽  
Vol 111 (4) ◽  
pp. 298-302 ◽  
Author(s):  
R. Fatemi ◽  
K. B. Chandran
Keyword(s):  
Comparative Study ◽  
Laser Doppler Anemometry ◽  
Fluid Dynamic ◽  
Velocity Profiles ◽  
Flow Conditions ◽  
Tilt Axis ◽  
Jude Medical ◽  
Laser Anemometry ◽  
Bileaflet Valves

An in vitro comparative study of St. Jude (SJ) and Edwards-Duromedics (DM) Bileaflet valves was performed under steady and physiological pulsatile flow conditions in an axisymmetric chamber using Laser Doppler Anemometry (LDA). LDA measurements were conducted in two different orientations; in the first orientation, the LDA traverse was perpendicular and, in the second orientation, parallel to the tilt axis of the leaflets. The axial velocities were measured in both orientations at two different locations distal to the valves. The velocity profiles at peak systole show the presence of stronger vortex in the sinus region for flow past SJ valve in the first orientation compared to the DM valve. Velocity profile distal to the SJ valve in second orientation was relatively flat where as for the DM valve, a jet-like flow was present. The differences found in the velocity profiles between the two valves can be attributed to the differences in geometry with thicker leaflets, smaller angle of leaflets opening and the presence of the leaflet curvature for the DM valve. The results obtained in this study do not show any fluid dynamic advantages due to the curved leaflet geometry of the DM valve.

scholarly journals A pulsatile flow model for in vitro quantitative evaluation of prosthetic valve regurgitation

2000 ◽  
Vol 33 (3) ◽  
pp. 341-346
Author(s):  
S. Giuliatti ◽  
L. Gallo Jr. ◽  
O.C. Almeida-Filho ◽  
A. Schmidt ◽  
J.A. Marin-Neto ◽  
...  
Keyword(s):  
Quantitative Evaluation ◽  
Pulsatile Flow ◽  
Prosthetic Valve ◽  
Flow Model ◽  
Valve Regurgitation
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