Echocardiographic automated cardiac output measurement of pulmonary output and quantification of intracardiac shunt

Background The quantification of intracardiac shunt (ICS) with echocardiographic pulsed-wave Doppler (PWD) method using pulmonary-to-systemic flow ratio (QP/QS ratio) remains difficult and may induce false quantification of pulmonary output. We sought to validate the recent echocardiographic automated cardiac output measurement (ACM) for the calculation of pulmonary output and the quantification of ICS in adults. Methods One hundred and twenty consecutive patients were divided in 1) 40 patients who underwent echocardiographic and invasive explorations (group I) with groups IA (quantification of ICS using ACM, PWD and invasive oximetric methods in 20 patients) and IB (calculation of pulmonary output with ACM, PWD and thermodilution methods in 20 patients); 2) 80 patients underwent calculation of aortic and pulmonary outputs using echocardiographic ACM and PWD methods (group II). Results The feasibility of ACM and conventional PWD methods for the calculation of pulmonary output was respectively 93.3% and 90%. Correlations between ACM and invasive pulmonary output were strong (r2=0.92 vs. r2=0.80 for PWD). The best correlation and agreement between invasive and echocardiographic QP/QS ratio were observed with ACM (r=0.96 vs. r=0.82 for PWD). Intracardiac shunts were best-classified with ACM, as compared to PWD (respectively 94% and 72%); sensitivities and specificities for evaluation of significant ICS were 92.3% and 100% with ACM (85% and 40% with PWD). Conclusions This study shows that ACM is a reliable and accurate echocardiographic method for calculating pulmonary output and quantifying ICS in adults and may be routinely performed in clinical practice.