Background: Cardiac surgical patients often require invasive pulmonary artery catheters (PAC) to determine left ventricular filling pressures (LVFP) in order to guide fluid management. Tissue Doppler imaging (TDI) as derived by transthoracic echocardiography (TTE), non-invasively assesses pulmonary capillary wedge pressure (PCWP), which is a surrogate for LVFP. With the use of TDI as derived by TTE, the ratio of transmitral inflow to mitral annular velocity during early diastole (E/E’) correlates with PCWP. However, little is known on the role of TDI using intra-operative transesophageal echocardiography (TEE) in the assessment of LVFP during cardiac surgery. Objective: To determine if TDI indices obtained by intra-operative TEE during cardiac surgery accurately estimates PCWP using PAC as the gold standard. Methods: Patients undergoing cardiac surgery were prospectively enrolled at a single tertiary care centre. Conventional and novel echocardiographic parameters were evaluated using intra-operative TEE with concurrent invasive PAC monitoring before and after cardiopulmonary bypass (CPB). Results: The study population included 34 patients (26 males, mean age 649 years). The correlation between E/E’ using TEE and PCWP was poor to modest at best. Pre-CPB, the correlation ratio between mean E/E’ and PCWP was r=0.23. Post-CPB, the correlation ratio between mean E/E’ and PCWP was r=0.42. Conclusion: Intra-operative TEE was unable to accurately assess LVFP in patients undergoing cardiac surgery. The PAC continues to be the gold standard in the assessment of LVFP for this patient population.