The rapid assessment of the response of right ventricular (RV) performance to decreasing levels of mechanical assistance may be an important adjunct in determining if a patient can tolerate the removal of such a device. This report describes the use of on-line pressure area relationships to assess RV function in a patient supported with an RV assist device (RVAD). Mid RV short axis cross-sectional area was measured on-line by transesophageal echocardiography with an automated endocardial border detection feature. RV pressure was measured with a high fidelity catheter. Pressure and area were plotted simultaneously on a computer workstation interfaced with the pressure and echo systems to yield on-line pressure area loops. The following indices of RV performance were calculated while RVAD flow was decreased in 1 L/min increments: stroke work' (SW' = ∫PdA)[mmHg*cm2], stroke area (SA = Maximum Area-Minimum Area)[cm2], and fractional area change (FAC = SA/Maximum Area*100)[%]. SW', SA, and FAC significantly increased with decreasing RVAD flow: SW'(from 32 to 61 mmHg*cm2), SA (from 2.58 to 4.37 cm2), and FAC (from 20 to 32%). In conclusion, the increase in these parameters of RV performance with decreasing mechanical assistance suggested that this patient would tolerate removal of the RVAD, which was subsequently successful. This method of on-line pressure area relationships may be useful to predict the need for further mechanical assistance.