Although left ventricular assist devices (LVADs) have had success in supporting severe heart failure patients, thrombus formation within these devices still limits their long term use. Research has shown that thrombosis in the Penn State pulsatile LVAD, on a polyurethane blood sac, is largely a function of the underlying fluid mechanics and may be correlated to wall shear rates below 500 s−1. Given the large range of heart rate and systolic durations employed, in vivo it is useful to study the fluid mechanics of pulsatile LVADs under these conditions. Particle image velocimetry (PIV) was used to capture planar flow in the pump body of a Penn State 50 cubic centimeters (cc) LVAD for heart rates of 75–150 bpm and respective systolic durations of 38–50%. Shear rates were calculated along the lower device wall with attention given to the uncertainty of the shear rate measurement as a function of pixel magnification. Spatial and temporal shear rate changes associated with data collection frequency were also investigated. The accuracy of the shear rate calculation improved by approximately 40% as the resolution increased from 35 to 12 μm/pixel. In addition, data collection in 10 ms, rather than 50 ms, intervals was found to be preferable. Increasing heart rate and systolic duration showed little change in wall shear rate patterns, with wall shear rate magnitude scaling by approximately the kinematic viscosity divided by the square of the average inlet velocity, which is essentially half the friction coefficient. Changes in in vivo operating conditions strongly influence wall shear rates within our device, and likely play a significant role in thrombus deposition. Refinement of PIV techniques at higher magnifications can be useful in moving towards better prediction of thrombosis in LVADs.
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October 2011
Research Papers
A Fluid Dynamics Study in a 50 cc Pulsatile Ventricular Assist Device: Influence of Heart Rate Variability
Jason C. Nanna,
Jason C. Nanna
Department of Bioengineering,
The Pennsylvania State University
, 205 Hallowell Building, University Park, PA 16802 e-mail:
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Michael A. Navitsky,
Michael A. Navitsky
Department of Bioengineering,
The Pennsylvania State University
, 205 Hallowell Building, University Park, PA 16802 e-mail:
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Stephen R. Topper,
Stephen R. Topper
Department of Bioengineering,
The Pennsylvania State University
, 205 Hallowell Building, University Park, PA 16802 e-mail:
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Steven Deutsch,
Steven Deutsch
Department of Bioengineering,
The Pennsylvania State University
, 205 Hallowell Building, University Park, PA 16802 e-mail:
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Keefe B. Manning
Keefe B. Manning
Department of Bioengineering,
The Pennsylvania State University
, 205 Hallowell Building, University Park, PA 16802 e-mail:
Search for other works by this author on:
Jason C. Nanna
Department of Bioengineering,
The Pennsylvania State University
, 205 Hallowell Building, University Park, PA 16802 e-mail:
Michael A. Navitsky
Department of Bioengineering,
The Pennsylvania State University
, 205 Hallowell Building, University Park, PA 16802 e-mail:
Stephen R. Topper
Department of Bioengineering,
The Pennsylvania State University
, 205 Hallowell Building, University Park, PA 16802 e-mail:
Steven Deutsch
Department of Bioengineering,
The Pennsylvania State University
, 205 Hallowell Building, University Park, PA 16802 e-mail:
Keefe B. Manning
Department of Bioengineering,
The Pennsylvania State University
, 205 Hallowell Building, University Park, PA 16802 e-mail: J Biomech Eng. Oct 2011, 133(10): 101002 (10 pages)
Published Online: October 31, 2011
Article history
Received:
June 15, 2011
Revised:
August 29, 2011
Online:
October 31, 2011
Published:
October 31, 2011
Citation
Nanna, J. C., Navitsky, M. A., Topper, S. R., Deutsch, S., and Manning, K. B. (October 31, 2011). "A Fluid Dynamics Study in a 50 cc Pulsatile Ventricular Assist Device: Influence of Heart Rate Variability." ASME. J Biomech Eng. October 2011; 133(10): 101002. https://doi.org/10.1115/1.4005001
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