Comparison of Cardiac Output of Both 2 and 3 Dimensional Transoesophageal Echocardiography With Transpulmonary Thermodilution During Cardiac Surgery

Abstract

Purpose: Transpulmonary thermodilution (TD) is the gold standard for cardiac output (CO) monitoring during cardiac surgery but is feasible with TOE, but 2D TOE underestimates CO due to assumption of a circular LVOT, when 3D TOE demonstrates it is ovoid. The aim of this study is to determine if 3D TOE correlates better with TD than 2-D TOE. Methodology: After ethics approval, 50 adult patients without more than mild valvular regurgitation or A who were scheduled for bypass cardiac surgery were recruited prospectively at two institutions. CO was measured simultaneously by TD and TOE (2D/3D) before and after CPB. CO was calculated using the continuity method (product of VTI, area and heart rate) using the modal and outer-edge trace of the LVOT VTI. The aortic valve area was estimated with planimetry by both 2D and 3D TOE. Agreement analysis was performed using the Deming model II regression analysis and Bland-Altman technique (TD as the reference method). Results: Proportional but not fixed bias was present for the VTI modal method but not for any other method. Correlation for LVOT modal was poor (0.40) and CO was underestimated (mean bias = -1.59 L.min-1), but the limits of agreement were similar to other methods. Tracing the edge of the LVOT VTI rather than the modal line reduced the bias (-0.59 L.min-1), and improved correlation (0.92). 3D planimetry of the AV and continuous wave Doppler had the best agreement with TD. The mean bias approached zero for the 3D methods but with similar limits of agreement. Conclusion: For 2D measurements, tracing around the LVOT VTI rather than through the modal line improved precision. The other 2D and 3D measurements of CO showed absence of bias, and reasonable agreement with TD.