A Comparison of Thrombus Susceptibility for Two Pulsatile 50 cc Left Ventricular Assist Devices
Open Access
- Author:
- Navitsky, Michael Anthony
- Graduate Program:
- Bioengineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- Keefe B Manning, Thesis Advisor/Co-Advisor
- Keywords:
- thrombosis
ventricular assist device
fluid mechanics
platelet adhesion - Abstract:
- Left ventricular assist devices (LVADs) have proven successful as a bridge to transplant and more recently as a viable destination therapy. Despite increasing survival rates, destination therapy for pulsatile devices remains limited by adverse events including thrombus formation within the device. Thrombosis is correlated to the fluid dynamics within the device and has been shown to be a result of sustained wall shear rates below 500 s-1 on polyurethane, a material similar to that used within the Penn State pulsatile LVAD. A rotating disk is used to assess platelet adhesion to the device specific polyurethane urea material used for the blood sac within the Penn State LVAD. The effects of altered shear exposure upon adhesion are quantified across a physiologically relevant shear range. Particle image velocimetry (PIV) is then used to compare flow within two 50 cc LVAD designs to measure flow patterns and quantify wall shear rates in regions known to be susceptible to thrombus formation, from previous in vivo studies, to determine which design limits platelet adhesion to the greatest extent. The two designs differ in their front face geometry while maintaining identical stroke volume and port orientations. The V1 model has an outward facing “dome” whereas the front face of the V2 model is flat. A thrombus susceptibility metric, adapted from a computational study of the Penn State LVAD, is applied to objectively compare pump designs over the entire cardiac cycle. For each design, there are regions where wall shear rates remained below 500 s-1 for the entire cardiac cycle resulting in high thrombus susceptibility potential. Results of this study indicate that V2 has an overall lower propensity for thrombus formation and is the better design. Results of the study are correlated to findings of platelet and fibrin deposition on an implanted blood sac from a V2 device and are also compared to computations.