A study of the wall shear rates created by hematocrit on an elevated beat rate in the 12 cc Penn State pediatric ventricular assist device
- Restrictions on Access:
- Open Access.
- Ventricular assist devices (VADs) support patients with a weakened or failing heart. VADs are implanted as a bridge-to-transplant, bridge to recovery, or destination therapy. Development of similar devices for pediatric patients has been pursued due to its clinical need. However, previous studies have demonstrated that in order to reduce risk of thrombosis in pulsatile pediatric ventricular assist devices (PVADs), shear rates above 500 s-1 were needed. The average heart rate of pediatric patients is expected to be between 100 and 160 beats per minute (bpm). The hematocrit percent on pediatric patients ranges between 20 to 60%. There was a need to evaluate the fluid dynamics and shear rates at elevated beat rates and throughout the range of hematocrit. This study aimed to quantify the shear rates within the 12cc Penn State PVAD at an elevated beat rate and varying hematocrit using PIV and in-house algorithms. Fluids simulating 20%, 40%, and 60% hematocrit were examined under 75 bpm and 120 bpm heart rates to account for elevated beat rates. In-house algorithms were used to calculate shear rates along the PVAD from images of three planes within the device captured with particle image velocimetry. Shear rates were calculated along seven surfaces within the PVAD defined by their curvature. All conditions demonstrated key flow patterns that created shear rates above the threshold throughout most of the PVAD. Strong inflow jets created high shear rates across most of the surfaces close to the inlet and transformed into rotational flow by mid diastole. Rotational flow dissipated early in systole as a strong outflow jet was formed. The outflow jet created high shear rates across most surfaces near the outlet. Regions near the outlet, surfaces 4 and 5, exhibited low shear rates throughout systole at lower hematocrit conditions, which presented a risk of thrombosis. Half of surface 7 exhibited low shear rates throughout the cycle due to its location relative to the inflow jets at lower hematocrit conditions, which present a risk of thrombosis. Three-dimensional flow also reduced shear rates on surface 2 in some conditions, which may have produced risk of thrombosis later in systole. Higher, more uniform shear rates were observed on all fluids at the elevated beat rate. Therefore, higher beat rates help improve wall washing and lower risks of thrombosis on patients with lower hematocrit.
- Dissertation Note:
- B.S. Pennsylvania State University 2020.
- Technical Details:
- The full text of the dissertation is available as an Adobe Acrobat .pdf file ; Adobe Acrobat Reader required to view the file.
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