Transoesophageal echocardiography is unreliable for cardiac output assessment after cardiac surgery compared with thermodilution

This randomised, single-blind, double-control study compared and established prospectively the best transoesophageal echocardiography methods for determining cardiac output in patients after cardiac surgery. Thirty patients undergoing coronary artery bypass grafting were included. Measurements were taken postoperatively, after stabilisation in the intensive care unit. Cardiac output was determined by transoesophageal echocardiography in randomised order through the aortic, mitral, and pulmonary valves, right and left ventricular outflow tracts, transgastric surface areas of the left ventricle and left ventricle two-dimensional volumes (Simpson's rules). 'Eyeball guessing' was done off-line. The best results were transaortic measurements using the triangular shape assumption of valve opening, but some values deviated considerably, and none of these approaches reached the limit of agreement set at 30% when compared to thermodilution. Eyeball guessing was comparable to the best transoesophageal echocardiography measurements. We conclude that transoesophageal echocardiography is an unreliable tool for determination of cardiac output in intensive care after cardiac surgery.