Pulsed Ultrasonic Doppler Velocity Measurements Inside a Left Ventricular Assist Device

1986 ◽  
Vol 108 (3) ◽  
pp. 232-238 ◽  
Author(s):  
J. M. Tarbell ◽  
J. P. Gunshinan ◽  
D. B. Geselowitz ◽  
G. Rosenberg ◽  
K. K. Shung ◽  
...  
Keyword(s):  
Ventricular Assist Device ◽  
Single Channel ◽  
Left Ventricular ◽  
Doppler Velocity ◽  
Shear Stresses ◽  
Reynolds Stresses ◽  
Assist Device ◽  
Data Set ◽  
Ventricular Assist ◽  
Pulsed Ultrasonic

In this study we have employed a single channel, pulsed ultrasonic Doppler velocimeter to measure instantaneous velocity distributions within the pumping chamber of a ventricular assist device. Instantaneous velocities have been decomposed into periodic mean and turbulent fluctuating components from which estimates of Reynolds stresses within the chamber and mean shear stresses along the wall of the chamber have been obtained. A review of the complete data set indicates a maximum value of the mean wall shear stress of 25 dynes/cm2 and a maximum Reynolds stress of 212 dynes/cm2. These values are lower than those measured distal to aortic valve prostheses in vitro and are well below levels known to damage blood components. Core flow patterns, wall washing patterns and flow stagnation points are also revealed.

Numerical Study of Blood Flow at the End-to-Side Anastomosis of a Left Ventricular Assist Device for Adult Patients

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
Ning Yang ◽  
Steven Deutsch ◽  
Eric G. Paterson ◽  
Keefe B. Manning
Keyword(s):  
Left Ventricular Assist Device ◽  
Ventricular Assist Device ◽  
Numerical Study ◽  
Left Ventricular ◽  
Reynolds Stresses ◽  
Assist Device ◽  
Ventricular Assist ◽  
Left Ventricular Assist ◽  
Flow Splitting ◽  
Lvad Support

We use an implicit large eddy simulation (ILES) method based on a finite volume approach to capture the turbulence in the anastomoses of a left ventricular assist device (LVAD) to the aorta. The order-of-accuracy of the numerical schemes is computed using a two-dimensional decaying Taylor–Green vortex. The ILES method is carefully validated by comparing to documented results for a fully developed turbulent channel flow at Reτ=395. Two different anastomotic flows (proximal and distal) are simulated for 50% and 100% LVAD supports and the results are compared with a healthy aortic flow. All the analyses are based on a planar aortic model under steady inflow conditions for simplification. Our results reveal that the outflow cannulae induce high exit jet flows in the aorta, resulting in turbulent flow. The distal configuration causes more turbulence in the aorta than the proximal configuration. The turbulence, however, may not cause any hemolysis due to low Reynolds stresses and relatively large Kolmogorov length scales compared with red blood cells. The LVAD support causes an acute increase in flow splitting in the major branch vessels for both anastomotic configurations, although its long-term effect on the flow splitting remains unknown. A large increase in wall shear stress is found near the cannulation sites during the LVAD support. This work builds a foundation for more physiologically realistic simulations under pulsatile flow conditions.

scholarly journals Computational fluid dynamics simulation of hemolysis at different levels of circulatory support in the left ventricular assist device Sputnik

2021 ◽  
Vol 2091 (1) ◽  
pp. 012021
Author(s):  
A Romanova ◽  
D Telyshev
Keyword(s):  
Left Ventricular Assist Device ◽  
Ventricular Assist Device ◽  
Left Ventricular ◽  
Dynamics Simulation ◽  
Circulatory Support ◽  
Shear Stresses ◽  
Assist Device ◽  
Ventricular Assist ◽  
Left Ventricular Assist ◽  
Different Levels

Abstract Designing a ventricular assist device is a complex technological process, and testing a finished product requires a significant investment of money and time. Simulation allows research to conduct research early in the development of a device, thereby reducing time and material costs. In this work, the calculation of hemolysis in the left ventricular assist device Sputnik (Sputnik LVAD) is carried out. Three different levels of circulatory support were chosen. For the first level, the following parameters were selected: blood flow rate of 2 L/min. at a rotor speed of 8000 rpm; for the second - 4 L/min, 8500 rpm; for the third - 6 L/min, 9000 rpm. The distribution of scalar shear stresses and the index of hemolysis were obtained from the pathlines of the particles. When comparing three operating points of LVAD Sputnik, hemolysis indices were obtained using the Lagrangian model. The mean hemolysis indeces were 0.0284%, 0.0210%, 0.0155% for LVAD Sputnik operating at a fixed rate of 2, 4, 6 L/min at a pressure of 100 mm Hg, respectively. The calculation results show that the capacity of 6 L/min is better than 2 and 4 L/min.

Ultrastructural observations of the aorta of calves implanted with a mechanical left ventricular assist device

1990 ◽  
Vol 48 (3) ◽  
pp. 834-835
Author(s):  
J P Cassella ◽  
V Salih ◽  
T R Graham
Keyword(s):  
Left Ventricular Assist Device ◽  
Ventricular Assist Device ◽  
Left Ventricular ◽  
Aortic Tissue ◽  
Assist Device ◽  
Ventricular Assist ◽  
Transmission Electron ◽  
Left Ventricular Assist ◽  
Preliminary Study

Left ventricular assist systems are being developed for eventual long term or permanent implantation as an alternative to heart transplantation in patients unsuitable for or denied the transplant option. Evaluation of the effects of these devices upon normal physiology is required. A preliminary study was conducted to evaluate the morphology of aortic tissue from calves implanted with a pneumatic Left Ventricular Assist device-LVAD. Two 3 month old heifer calves (calf 1 and calf 2) were electively explanted after 128 days and 47 days respectively. Descending thoracic aortic tissue from both animals was removed immediately post mortem and placed into karnovsky’s fixative. The tissue was subsequently processed for transmission electron microscopy (TEM). Some aortic tissue was fixed in neutral buffered formalin and processed for routine light microscopy.

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