Preexisting mitral regurgitation improves signifi cantly in the majority of patients after implantation of LVAD. The mechanism of MR in most of these patients is functional. Optimal LVAD settings result in reduction in LV dimension, mitral valve annulus diameter, tenting area and regurgitant volume. Organic or mixed organic and functional etiology of MR before surgery may result in persistence of MR after LVAD therapy resulting in nonoptimal hemodynamic and clinical results. Organic MR should therefore be identified before LVAD implantation. © 2011, Wiley Periodicals, Inc.