Objective: Continuous flow ventricular assist devices, cfVADs have been steadily gaining acceptance as a long-term treatment for end-stage heart failure. Although they have contributed to improved survival, serious complications, such as bleeding and stroke, jeopardizes the quality of life of patients, and may require pump exchange or result in death due to pump thrombosis. Although this is a multi-factorial problem, an important factor is the micro-fluid-dynamics within the blood flow path. We previously demonstrated that the stability and coherence of the flow in an axial-flow blood pump Heartmate II (HM2, Thoratec, Pleasanton, CA) could be classified in three zones of operation in steady flow conditions. The purpose of this study is to examine the flow field under clinically relevant pulsatile conditions, using high-speed videography.