Assessment of right ventricular (RV) function is crucial since RV failure with a reduced cardiac output (CO) is associated with compromised outcome in cardiac surgery. Echocardiographic evaluation of RV function is commonly used, but a reduction in tricuspid annular plane systolic excursion (TAPSE) and tricuspid annulus tissue Doppler imaging (S') have been observed independently of clinical signs of RV failure. This has led to uncertainty of these variables' validity in cardiac surgery. To describe transesophageal echocardiographic (TEE) measures of RV function during coronary artery bypass graft surgery with detailed haemodynamic assessment using pulmonary artery catheter (PAC) measurements to describe "natural" changes in the absence of RV failure. We prospectively studied 30 patients with concomitant PAC and TEE measurements at four time-points, namely after: anaesthesia induction, sternotomy, cardiopulmonary bypass (CPB) and upon arrival in the intensive care unit. TAPSE and S' were significantly reduced by 43% (p < 0.0001) and 22% (p = 0.006), respectively after CPB without any change in stroke volume (SV). RV ejection fraction (RVEF), RV fractional area change (RVFAC) and global longitudinal strain (RV-GLS) remained unchanged. SV measured with 3D echocardiography correlated with PAC measured SV (r = 0.66[95% CI 0.50; 0.78], p < 0.0001), but 3D showed a minor, but statistically significant underestimation of SV (8.5 ml (95% CI 2.7 ml; 14 ml, p = 0.004). TAPSE and S' were both reduced after CPB despite maintained CO. RVFAC, RVEF and RV-GLS remained stable, however, these measures were unable to detect minor changes in SV. 3D-echocardiographyshowed a strong correlation with SV measured by thermodilution, but with a consistent underestimation of approximately 10%.