AUTOMATED CARDIAC-OUTPUT MEASUREMENT BY SPATIOTEMPORAL INTEGRATION OFCOLOR DOPPLER DATA - IN-VITRO AND CLINICAL VALIDATION

Background A new Doppler echocardiographic technique has been develope d for automated cardiac output measurement (ACOM) that assumes neither a flat how profile nor collinearity with the scan Line, but clinical validation of this method is lacking. Methods and Results In 165 subje cts (50 intensive care patients, 10 dobutamine echocardiography patien ts, and 105 normal volunteers; age, 49.4+/-19.3 years; 92 men), ACOM w as performed in the left ventricular outflow tract (LVOT), with the co lor baseline shifted to avoid aliasing. ACOM was also tested in a puls atile in vitro model. Stroke volume was calculated by double integrati on of Doppler signals in space (across the LVOT) and in time (through the systolic period), assuming hemiaxial symmetry: integral integral p i r v(r,t) dr dt, where v(r,t) is the velocity at a distance r from th e center of the LVOT at time t during systole. Stroke volume from ACOM was compared with thermodilution (TD), aortic valve pulsed-wave Doppl er (PWAO), and left ventricular echocardiographic (two-dimensional [2D ]) methods. There was good correlation between ACOM and PWAO (r=.93), TD (r=.86), and 2D (r=.74), with close agreement seen. ACOM had higher correlation and agreement with TD than did either PWAO (P<.02) or 2D (P<.01). ACOM was also able to track accurately the changes in cardiac output with dobutamine infusion in comparison with PWAO (r=.94). In v itro assessment demonstrated excellent correlation (r=.98, y=1.0x+1.94 ) with little impact of pulse repetition frequency or misalignment up to 30 degrees. Gain dependency was noted but could be optimized by vis ual inspection of the color image. Conclusions Automatic integration o f numerical data within color Doppler Bow fields is a feasible new met hod for quantifying flow. It is simpler and faster, requires fewer ass umptions, and uses only one apical view. ACOM is a promising new appro ach to echocardiographic quantification that deserves further study an d refinement.