Pulsed Doppler transesophageal echocardiographic determination of cardiac output in human beings: comparison with thermodilution technique.

Measurement of cardiac output is a clinically valuable and widely used index of cardiac function. Although transesophageal echocardiography has been used to assess left ventricular function, little data exist on the accuracy of this technique in the measurement of cardiac output. Therefore cardiac output derived by pulsed Doppler transesophageal echocardiography and thermodilution methods were compared in adult patients being mechanically ventilated. The left ventricular outflow tract diameter was determined from a transgastric long-axis view of the left ventricle by using the transverse plane and longitudinal plane of the transesophageal scope. The cross-sectional area of the left ventricular outflow tract was calculated from the diameter assuming a circular shape. Pulsed Doppler recordings were obtained at the left ventricular outflow tract. Doppler time-velocity integrals were measured from the leading edge of the velocity curve. Cardiac output derived by transesophageal echocardiography was calculated as time-velocity integral multiplied by left ventricular outflow tract area and heart rate. Cardiac output derived by transesophageal echocardiography from the transverse plane (n = 26) and longitudinal plane (n = 22) were correlated with simultaneous thermodilution measurements. Thermodilution-derived cardiac output demonstrated excellent correlation with cardiac output measured by using transesophageal echocardiography from the transverse plane (r = 0.97, SEE = 0.84 L/min; p < 0.0001) and longitudinal plane (r = 0.95, SEE = 0.97 L/min; p < 0.0001). Transesophageal echocardiography is a promising technique in the measurement of cardiac output and expands the clinical use of this modality in the assessment of cardiac function.