[Comparison of Doppler echocardiographic methods of determining cardiac minute volume].

In 40 patients without valvular disease, cardiac output was determined by pulsed Doppler echocardiography and thermodilution simultaneously. The sample volume was located in the center of the mitral valve ring, at the tips of the mitral leaflets and in the left ventricular outflow tract, directly proximal to the aortic valve leaflets. Circular cross-sectional areas of the mitral valve ring, aortic ring and bulbus of the aorta were calculated from the M-mode and two dimensional echocardiographic diameters. The mitral orifice was assumed to be an ellipse with varying short axes, determined as the mean diastolic leaflet separation in the M-mode and a constant long axis, derived from the maximal mitral orifice area or mitral ring diameter. Cardiac output was calculated by multiplying time-velocity integrals with different areas and heart rate. Cardiac output, measured by the thermodilution technique, ranged from 4.0 l/min to 10.2 l/min. Cardiac output determined by the different Doppler methods correlated significantly with the thermodilution measurements. Cardiac output measurements in the left ventricular outflow tract provided the best correlation coefficient (0.93) and a standard error of the estimate of 0.589 l/min, when the circular flow area was derived from the M-mode echo of the aortic ring.(ABSTRACT TRUNCATED AT 250 WORDS)