The aim of this study was to determine the effects of the HeartWare left ventricular assist device (HVAD) (HeartWare International, Inc, Framingham, MA) on hemodynamics, ventricular function, and exercise capacity. Between July 2009 and March 2011, 46 patients with advanced heart failure had implantation of the HVAD. Of these patients, 30 had subsequent assessments for transplantation and these patients formed the study cohort. Thirty patients had assessments at a mean of 201±86 days and 13 went on to have a second assessment at 351±86 days. There were marked improvements in hemodynamics and exercise capacity at both assessments, with significant decreases in right and left heart filling pressures; increases in cardiac index, New York Heart Association class, and peak exercise oxygen consumption; and reduction in pulmonary vascular resistance (all P<.05). Left ventricular end-diastolic and end-systolic dimensions were unchanged at the first assessment, although there was a significant reduction in end-diastolic diameter at the second assessment (P<.01). There were no significant changes in a visual grade of right ventricular function. After up to 1 year of support, the HVAD system results in significant benefits in overall heart failure status, with improved hemodynamics and exercise capacity. This occurs in the absence of marked changes in left ventricular size or right ventricular function.