The use of a left ventricular assist device (LVAD) as a bridge to transplant is associated with a 52% incidence of RV failure requiring additional inotropic or mechanical support (RVAD). This study evaluated the differential performance of the RV free wall and septum to identify the need for additional RV support. Cross-sectional views of the RV were obtained immediately before, and 1 hr after, Novacor LVAS implantation in 12 consecutive patients using transesophageal echocardiography. Each image was divided into a free wall portion (FW) and a septal portion (SP) by grids drawn from the center of gravity of the end-diastolic endocardial outline to the junction between the FW and the SP. Percentage change between preimplant and postimplant for RV ejection fraction (RVEF), fractional area change for the FW (FAC-FW) and the SP (FAC-SP), and fractional shortening of the FW to SP distance (F-S) is reported for patients based upon the need for RV support: minimal (Group 1), maximal (Group 2). After LVAS implantation, patients showed a reduction in SP fractional area change. However, this reduction was most pronounced in Group 2. The degree of SP impairment may explain the mechanism of RV failure in patients on an LVAD.