Advanced heart failure patients may receive a Left Ventricular Assist Device (LVAD) to improve blood flow. An LVAD is a surgically implanted mechanical pump. After an LVAD is implanted, the heart often undergoes volume reduction and exhibits signs of restoration of normal cardiac geometry and function. Clinical studies show a reduction in left ventricle (LV) vortex circulation and kinetic energy (KE) after LVAD implantation, which we hypothesize is due to LV volume (LVV) reduction. The goal of this study is to measure the LV flow and vortex dynamics in LV models representing the volume reduction in the LVAD-assisted heart using Particle Image Velocimetry (PIV). Three silicone LV models were created with volume variation, and studied separately in the SDSU cardiac simulator to see the effects of ejection fraction (EF), LVV, and LVAD support on LV flow. Thoratec Heartmate II LVAD was used and the 2D velocity field in the LV mid-plane was measured for a full cardiac cycle. This field was further analyzed using MATLAB to calculate the pulsatility index along with the vortex circulation and KE of the large clockwise (CW) and smaller counter-clockwise (CCW) vortices that form in the LV. The effect of EF on LV flow without LVAD support was studied in the 100 and 150 ml LV models and produces a clear increase in vortex circulation, KE, and pulsatility with higher EF. The effect of LVV in the absence of LVAD support was compared for matched EF. The vortex circulation and KE of the CW vortex showed a decrease with decreased LVV. Addition of the LVAD to the LV resulted in an increase in flow as well as an increase in vortex circulation and KE. The pulsatility decreases with LVV reduction. The studies demonstrate that vortex circulation and KE are decreased with LVV and EF, and increased with the addition of an LVAD. Because LVAD patients are often experiencing all of these simultaneously, the net effect on the EF flow in not always clearly predictable. The results help to explain our previous study of an LVAD patient in which LVV decreased dramatically following LVAD implantation.