Two-dimensional echocardiographic determination of ventricular volumes in the fetal heart: Validation studies in fetal lambs

The determination of ventricular volumes in the fetal heart from two-dimensional echocardiography (2DE) may give a better estimate of fetal ventricular size than simple diameter measurements, but the accuracy of this method has not been established. In fetal lambs, we tested whether ventricular volume calculations from 2DE using a biplane Simpson's rule algorithm are accurate. Calculations of left and right ventricular end-diastolic volumes from 2DE were compared with cast volumes of these ventricles. Also, at different levels of left atrial pressure, left ventricular stroke volumes calculated from 2DE were compared with stroke volumes measured simultaneously by an electromagnetic flowmeter. There was a good correlation between volumes determined from 2DE (γ axis) and from casts (x axis) for both the left (r=0.92; y=0.2+1.1x; SEE=0.19 ml) and right ventricle (r=0.90; y=0.7+0.9x; SEE=0.21 ml). Left ventricular stroke volumes calculated from 2DE correlated well with those measured by the electromagnetic flowmeter (r=0.87; y=0.2+0.9x; SEE=0.27 ml). Thus, calculation of fetal ventricular volumes from 2DE images using a biplane Simpson's rule method is feasible and accurate.