Experimental Investigation of VSS in Virtual Red Blood Cells and Platelets in the Flow of a PVAD Using Pseudo-Tracking Analysis

Abstract

Ventricular assist devices (VAD) improve patient’s survival rates at the heart transplant waiting list. Notwithstanding, VADs are not perfect replacements for a failing heart having their design and operational issues resulting in hemolysis and thrombogenesis. Both blood degradation processes are associated with viscous shear stress (VSS). Therefore, one way to experimental evaluate VSS values along residence time that red blood cells and platelets are subject to is pseudo-tracking. In pseudo-tracking method a postprocessing is done in particle image velocimetry (PIV) data, so particles can be generated inside the velocity field and their pathlines will provide VSS values. For better accuracy in this Lagrangian approach, temporal resolution is a must. Therefore, time-resolved PIV (TRPIV) technique for the VAD is a solution. In this work, the pneumatic pediatric assist device (PVAD) developed by Instituto do Coração (InCor) was measured using a TR-PIV at 70 beats per minute (bpm), and a pseudo-tracking analysis developed at MATLAB was done with two reconstructed particles. The first reconstructed particle was created near the inlet valve and the second near the outlet valve. Both reconstructed particles were generated at the beginning of PVAD’s diastole and their instantaneous and integrated VSS with resident time values were compared to literature thresholds for erythrocytes and thrombocytes.