Automatic Cardiac Output Measurement (ACOM): Clinical applications of a new noninvasive tool

Abstract

This study sought to validate a new noninvasive method to measure cardiac output, in the clinical setting, using color Doppler flow integration. This method, the automatic cardiac output measurement (ACOM), using color Doppler was recently developed and validated in vitro. ACOM was performed at the aortic valve and in the left ventricular outflow tract in 106 subjects (60 men, mean age 52 ± 18) and compared with the echocardiographic pulsed-wave Doppler and a 2-D volume method. In 14 patients the noninvasive methods were correlated with the thermodilution technique. ACOM was feasible in 101 subjects (95%). The correlation factor between the values obtained with ACOM in the apical 5-chamber view and apical long-axis view was 0.75 at the aortic valve and 0.74 in the left ventricular outflow tract. Interoperator variability for ACOM in the apical 5-chamber and apical long-axis views were 0.93 and 0.75, respectively. The best comparison of ACOM with the pulsed-wave echo-Doppler technique occurred in the apical long-axis view (n = 79, r = 0.62), whereas the correlation with the 2-D volume method was poor. The most favorable comparison of ACOM with the thermodilution technique (n = 14) was also obtained in the apical long-axis view (5.408 ± 1.72 vs. 3.356 ± l.281/min. [mean ± SD], r = 0.71). Assuming the thermodilution technique as ‘gold standard’, the pulsed-wave echo-Doppler technique showed a better correlation (5.408 ± 1.72 vs. 4.664 ± l.281/min., r = 0.84). ACOM is a useful, reproducible, noninvasive tool for rapid automated measurements of cardiac output. There is, however, an underestimation when compared with the pulsed-wave Doppler echocardiography and the thermodilution techniques. Good 2-D echocardiographic images, adequate color filling of the outflow tract and high frame rates are prerequisites for accurate values. Further refinements of this new technique are needed to enhance its clinical value in the future.