Determination of cardiac output by single gated pulsed Doppler echocardiography

The aim of the study was to evaluate the use of single gated pulsed Doppler cross-sectional echocardiography for measurement of the cardiac output. Pulsed Doppler echocardiography was used to assess both area and blood velocity at the aortic orifice. Stroke volume estimates were determined by multiplying area by systolic time velocity integral as measured from the parasternal and apical approach, respectively. We investigated a group of 17 healthy individuals and a group of 20 patients with coronary artery disease. In the first group no change was found in aortic area during systole (P less than 0.01). During a follow-up of two weeks no change in aortic area was observed either (P less than 0.01). Intraobserver, interobserver and day-to-day variability of the aortic area, expressed as the coefficient of variation was 3.6 +- 5.2%, 4.6 +- 5.7% and 7.8 +- 3.8% (mean +- 1 SD), respectively. The interobserver variability of the time velocity integrals was 6.0 +- 6.2%. In the second group the cardiac output as measured with the thermodilution method ranged from 3.8 to 8.0 l/min. Comparison of the Doppler and thermodilution technique for measurement of cardiac output showed a correlation coefficient of r = 0.76 (P less than 0.001) and the following regression equation: CO (Doppler) = 1.0 x CO (thermodilution)-700 ml. The Doppler method underestimated cardiac output relative to the thermodilution method.