Fluid Dynamic Investigation of the ATS 3F Enable Sutureless Heart Valve

2011 ◽  
Vol 6 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Sebastian Stühle ◽  
Daniel Wendt ◽  
Guojun Hou ◽  
Hermann Wendt ◽  
Matthias Thielmann ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Strain Rate ◽  
Heart Valves ◽  
Aortic Wall ◽  
Peak Flow ◽  
Fluid Dynamic ◽  
Maximum Velocity ◽  
Jet Flow ◽  
Clinical Results

Objective Currently, sutureless heart valves (SHV) reveal good clinical results during aortic valve replacement. The aim of this study was to evaluate the fluid dynamics of the ATS 3F Enable SHV in the ascending aorta and their influence on the aortic wall in an in vitro setup. Methods A two-dimensional particle image velocimetry study with an image rate of 15 Hz was conducted to evaluate the fluid dynamics of the SHV in the aortic flow field. The prosthesis (diameter, 23 mm) was placed inside a silicone mock aorta under pulsatile flow conditions. Velocities, vorticity, and strain rate were obtained and calculated with a fixed frequency (70 Hz) at constant stroke volume (70 mL). Results 3F Enable showed a jet flow type profile with a maximum velocity of 1.01 ± 0.13 m/s during peak flow phase (PFP). The jet flow was surrounded by ambilateral vortices with a slightly higher percentage of clockwise than counterclockwise vorticity (377 ± 57/s vs 389 ± 76/s), strain rate (370 ± 79/s for elongation vs — 370 ± 102/s for contraction) was nearly similar. The point-of-interest analysis revealed a higher velocity for bottom compared with upper aortic wall (0.28 ± 0.07 m/s vs 0.31 ± 0.06 m/s, P = 0.024). All values were lower during acceleration and deceleration phase compared with PFP. Conclusions The peak flow of the 3F Enable SHV seems to be little higher compared with native aortic valves, thus simulating nearly physiologic conditions. Vorticity and strain rate are high during PFP and low during other phases and might have an influence on the aortic wall as well.

A Numerical Investigation of the Fluid Flow in a Chandler Loop for Thrombus Studies

2013 ◽  
Author(s):  
Hisham Touma ◽  
Iskender Sahin ◽  
Tidimogo Gaamangwe ◽  
Maud B. Gorbet ◽  
Sean D. Peterson
Keyword(s):  
Laminar Flow ◽  
Stress Field ◽  
Strain Rate ◽  
Rotation Rate ◽  
Fluid Dynamic ◽  
Working Fluid ◽  
Straight Tube ◽  
Dean Number ◽  
Chandler Loop

The Chandler loop is an artificial circulatory platform for in vitro hemodynamic experiments. In most experiments, the working fluid is subjected to a stress field via rotation of the Chandler loop, which, in turn, induces biochemical responses of the suspended cells. For very low rotation rates, the stress field can be approximated using laminar flow in a straight tube as a model. However, as the rotation rate increases, while still maintaining laminar flow, the effect of the tube curvature causes the stress field to deviate considerably from the straight tube approximation. In this manuscript, we investigate the flow and associated strain rate field of an incompressible Newtonian fluid in a Chandler loop as a function of the governing non-dimensional fluid dynamic parameters. We find that the Dean number, which is proportional to the rotation rate, is the dominant parameter in determining the fluid strain rate. We propose an empirical formula for predicting the average fluid strain rate magnitude in the working fluid that is valid over a wide parameter space to be used in lieu of the common, yet restrictive, straight tube-based prediction.

scholarly journals Fluid–Structure Interaction and In Vitro Analysis of a Real Bileaflet Mitral Prosthetic Valve to Gain Insight Into Doppler-Silent Thrombosis

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Annalisa Dimasi ◽  
Daniela Piloni ◽  
Laura Spreafico ◽  
Emiliano Votta ◽  
Riccardo Vismara ◽  
...  
Keyword(s):  
Prosthetic Valve ◽  
Heart Valves ◽  
Fluid Dynamic ◽  
Fluid Structure Interaction ◽  
Prosthetic Heart Valves ◽  
False Negatives ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Vitro Analysis

Prosthetic valve thrombosis (PVT) is a serious complication affecting prosthetic heart valves. The transvalvular mean pressure gradient (MPG) derived by Doppler echocardiography is a crucial index to diagnose PVT but may result in false negatives mainly in case of bileaflet mechanical valves (BMVs) in mitral position. This may happen because MPG estimation relies on simplifying assumptions on the transvalvular fluid dynamics or because Doppler examination is manual and operator dependent. A deeper understanding of these issues may allow for improving PVT diagnosis and management. To this aim, we used in vitro and fluid–structure interaction (FSI) modeling to simulate the function of a real mitral BMV in different configurations: normally functioning and stenotic with symmetric and completely asymmetric leaflet opening, respectively. In each condition, the MPG was measured in vitro, computed directly from FSI simulations and derived from the corresponding velocity field through a Doppler-like postprocessing approach. Following verification versus in vitro data, MPG computational data were analyzed to test their dependency on the severity of fluid-dynamic derangements and on the measurement site. Computed MPG clearly discriminated between normally functioning and stenotic configurations. They did not depend markedly on the site of measurement, yet differences below 3 mmHg were found between MPG values at the central and lateral orifices of the BMV. This evidence suggests a mild uncertainty of the Doppler-based evaluation of the MPG due to probe positioning, which yet may lead to false negatives when analyzing subjects with almost normal MPG.

scholarly journals An In Vitro Fluid Dynamic Study of Pediatric Cannulae: The Value of Animal Studies to Predict Human Flow

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Tobias C. Long ◽  
Joseph J. Pearson ◽  
Andrew C. Hankinson ◽  
Steven Deutsch ◽  
Keefe B. Manning
Keyword(s):  
Fluid Dynamics ◽  
Heart Rate ◽  
Animal Studies ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Ventricular Assist Devices ◽  
Animal Testing ◽  
Pressure Drops ◽  
Aortic Cannula

A challenge to the development of pediatric ventricular assist devices (PVADs) is the use of the aortic cannulae attached to the devices. Cannulae used for pediatric application have small diameters and large pressure drops. Furthermore, during the development of the 12cc Penn State pediatric PVAD, particle image velocimetry (PIV) illustrated that hematocrit levels, through changes in blood viscoelasticity, affected the fluid dynamics. The objective of this study is to compare the fluid dynamics of a pediatric viscoelastic blood analog and a goat viscoelastic blood analog within the PVAD aortic cannula. Two acrylic models were manufactured to model the aortic cannula (6 mm and 8 mm diameters). PIV data was collected to examine the flow at the outlet of the VAD and in the aortic cannula at heart rates of 50 and 75 beats per minute (bpm). Three planes of data were taken, one at the centerline and two 1.5 mm above and below the centerline. Three more planes of data were taken orthogonal to the original planes. While a 75 bpm heart rate was used to represent normal operating conditions, a 50 bpm heart rate represented use of the PVAD during weaning. At 75 bpm, differences were evident between the two different fluids and the two models. Separation zones developed in the plane below the centerline for the higher hematocrit pediatric blood analog. This study raises question to the usefulness of animal testing results in regard to how well they predict the outcome of pediatric patients.

Velocity and Shear Stress Distribution Downstream of Mechanical Heart Valves in Pulsatile Flow

1989 ◽  
Vol 12 (4) ◽  
pp. 261-269 ◽  
Author(s):  
M. Giersiepen ◽  
U. Krause ◽  
E. Knott ◽  
H. Reul ◽  
G. Rau
Keyword(s):  
Shear Stress ◽  
Heart Valves ◽  
Laser Doppler Anemometry ◽  
Fluid Dynamic ◽  
In Vitro Study ◽  
Turbulent Shear ◽  
Momentum Exchange ◽  
Jude Medical ◽  
Turbulent Shear Stress

Ten mechanical valves (TAD 27 mm): Starr-Edwards Silastic Ball, Björk-Shiley Standard, Björk-Shiley Concave-Convex, Björk-Shiley Monostrut, Hall-Kaster (Medtronic-Hall), OmniCarbon, Bicer Val, Sorin, Saint-Jude Medical and Hemex (Duromedics) are investigated in a comparative in vitro study. The velocity and turbulent shear stress profiles of the valves were determined by Laser Doppler anemometry in two different downstream axes within a model aortic root. Depending on the individual valve design, velocity peaks up to 1.5 m/s and turbulent shear stress peaks up to 150 N/m2 were measured during the systolic phase. These shear stress peaks mainly occurred in areas of flow separation and intense momentum exchange. Directly downstream of the valves (measuring axis 0.55.dAorta) turbulent shear stress peaks occurred at peak systole and during the deceleration phase, while in the second measuring axis (1.5.dAorta) turbulence levels were lower. Shear stress levels were high at the borders of the fluid jets. The results are discussed from a fluid-dynamic point of view.

The Effect of Dipyridamole and RA 233 on Human Platelet Function in Vitro

1973 ◽  
Vol 29 (03) ◽  
pp. 694-700 ◽  
Author(s):  
Paul L. Rifkin ◽  
Marjorie B. Zucker
Keyword(s):  
Mechanism Of Action ◽  
Human Blood ◽  
Glass Bead ◽  
Heart Valves ◽  
Human Platelet ◽  
Drug Effects ◽  
Simple Relation ◽  
Prosthetic Heart Valves ◽  
Induced Aggregation

SummaryDipyridamole (Persantin) is reported to prolong platelet survival and inhibit embolism in patients with prosthetic heart valves, but its mechanism of action is unknown. Fifty jxM dipyridamole failed to reduce the high percentage of platelets retained when heparinized human blood was passed through a glass bead column, but prolonged the inhibition of retention caused by disturbing blood in vitro. Possibly the prostheses act like disturbance. Although RA 233 was as effective as dipyridamole in inhibiting the return of retention, it was less effective in preventing the uptake of adenosine into erythrocytes, and more active in inhibiting ADP-induced aggregation and release. Thus there is no simple relation between these drug effects.

Haemodynamic in vitro characteristics of heart valves for percutaneous applications

2007 ◽  
Vol 55 (S 1) ◽  
Author(s):  
UA Stock ◽  
T Attmann ◽  
M Hartrumpf ◽  
RU Kuehnel ◽  
M Wendt ◽  
...  
Keyword(s):  
Heart Valves

Cell-free human pulmonary heart valves for rvot reconstruction in pediatric patients: first clinical results

2008 ◽  
Vol 56 (S 1) ◽  
Author(s):  
S Cebotari ◽  
I Tudorache ◽  
A Lichtenberg ◽  
E Cheptanaru ◽  
S Barnaciuc ◽  
...  
Keyword(s):  
Heart Valves ◽  
Pediatric Patients ◽  
Clinical Results

IN VITRO UPTAKE OF RADIOACTIVE 131I LABELLED L-TRIIODOTHYRONINE BY HUMAN ERYTHROCYTES AS AN INDEX OF THYROID FUNCTION

1960 ◽  
Vol XXXIV (II) ◽  
pp. 305-311 ◽  
Author(s):  
M. G. Woldring ◽  
A. Bakker ◽  
H. Doorenbos
Keyword(s):  
Thyroid Function ◽  
Incubation Time ◽  
Clinical Results ◽  
Human Erythrocytes ◽  
Red Cell ◽  
Clinical Value ◽  
Blood Samples ◽  
In Vitro Uptake

ABSTRACT The red cell triiodothyronine uptake technique as used in our hospital is described. Incubation time is of almost no importance. The temperature during incubation should be 37° C. Further improvement of the technique is obtained when all blood samples are brought up to 40 % haematocrit prior to incubation. Clinical results are discussed. It is yet too early to give a definite assessment of its clinical value, but it is definitely superior to the measurement of the BMR.

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