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Current left ventricular assist devices are designed to provide full hemodynamic support for patients with end-stage failing hearts, but their use has been limited by operative risks, low reliability, and device-related morbidity. Such concerns have resulted in minimum use of left ventricular assist devices for destination therapy. We hypothesize that partial circulatory support, which could be achieved with small pumps implanted with less-invasive procedures, might expand the role of circulatory support devices for treatment of heart failure.We examine the hemodynamic effects of partial left ventricular support using a previously described computational model of the cardiovascular system. Results from simulations were validated by comparison with an in vivo hemodynamic study.Simulations demonstrated that partial support (2–3 L/min) increased total cardiac output (left ventricular assist device output plus native heart output) by more than 1 L/min and decreased left ventricular end-diastolic pressure by 7 to 10 mm Hg with moderate-to-severe heart failure. Analyses showed that the hemodynamic benefits of increased cardiac output and decreased left ventricular end-diastolic pressure are greater in less-dilated and less-dysfunctional hearts. Both the relationships between ventricular assist device flow and cardiac output and ventricular assist device flow and left atrial pressure predicted by the model closely approximated the same relationships obtained during hemodynamic study in a bovine heart failure model.Results suggest that a pump with a flow rate of 2 to 3 L/min could meaningfully affect cardiac output and blood pressure in patients with advanced compensated heart failure. The development of small devices capable of high reliability and minimal complications that can be implanted with less-invasive techniques is supported by these findings.