Numerical analysis of different cardiac functions and support modes on blood damage potential in an axial pump

Abstract

Background:

Cardiac functions and support modes of left ventricular assist device (LVAD) will influence the pump inner flow field and blood damage potential.

Methods:

Computational fluid dynamics (CFD) method and lumped-parameter-model (LPM) were applied to investigate the impacts of cardiac functions under full (9000 rpm) and partial (8000 rpm) support modes in an axial pump.

Results:

The constitution of hemolysis index ( $HI$ ) in different components of the pump was investigated. $HI$ was found to be more sensitive to positive incidence angles ( $i$ ) compared with negative incidence angles in rotors. Negative incidence angles had little impact on $HI$ both in rotors and the outlet guide vanes. The improved cardiac function made only a minor difference in $H{I}_{ave}$ (estimated average $HI$ in one cardiac cycle) by 9.88%, as the flow rate expanded mainly to higher flow range. Switching to partial support mode, however, would induce a periodic experience of severe flow separation and recirculation at low flow range. This irregular flow field increased $H{I}_{ave}$ by 47.97%, remarkably increasing the blood damage potential.

Conclusion:

This study revealed the relationship between the blade incidence angle $i$ and $HI$ , and recommended negative-incidence-angle blade designs as it yielded lower $HI$ . Moreover, to avoid flow range below 50% of the design point, careful evaluations should be made before switching support modes as weaning procedures in clinical applications.