Novacor left ventricular assist filling and ejection in the presence of device complications. In order to better understand the relationship among certain device related complications and Novacor left ventricular assist system (LVAS) pumping parameters, a Mock Circulatory Loop was utilized to simulate the following clinically realistic conditions: 1) inflow valve regurgitation, 2) inflow cannula obstruction, 3) outflow valve regurgitation, and 4) outflow cannula obstruction. Various pumping parameters (e.g., pump rate, stroke volume, pump output) were recorded at baseline (control) and during each simulation. Additionally, pump volumes were continuously recorded and differentiated for calculation of rates of pump filling (FR) and ejection (ER). The results indicate that perfusion pressures and rates of filling and ejection change significantly in the presence of device complications. The implications of these findings, as relates to assessment of pump operation in LVAS patients, are discussed. 