The authors previously published data that describe acute alterations in ventricular dimensions and in the severity of mitral and tricuspid regurgitation (MR/TR) after initiation of left ventricular assist device (LVAD) pumping. In the current study, measurements of ventricular size and regurgitant jet area acquired after LVAD implantation are presented. Eight patients had LVAD implanted pending cardiac transplantation (duration of assist 70-279 days; mean, 162 ± 29 days). Echocardiograms were obtained at the time of LVAD implant and later during LVAD support (mean time for late echo, 95 ± 32 days post-implant). Comparisons of pre-implant with late post- implant data showed: increased TR jet area (4.8 ± 1.0 cm2 vs. 8.0 ± 1.7 cm2 P < 0.05); increased right ventricular (RV) end-systolic dimension (31 ± 4 vs 40 ± 5 mm, P < 0.05); and increased RV end-diastolic dimension (35 ± 4 vs. 45 ± 5 mm, P < 0.065). Decreased MR jet area and decreased LV dimensions (P < 0.05) also were noted on comparison of pre-implant and late post-implant data. There were no significant differences between any immediate post-implant and late post-implant echocardiographic measurements. No patient had clinical evidence of RV failure. LV mechanical assist causes an acute increase in TR, presumably by volume loading the RV. TR and RV enlargement persisted but did not discernibly worsen on subsequent post- implant echocardiograms. LV dimensions and MR remained less than the pre- implant values on later post-implant determinations.