[Calculation of intracardiac shunt using Doppler echocardiography]

The purpose of this study was to assess the accuracy of a quantitative two-dimensional Doppler echocardiographic method for estimation of intracardiac shunts. The ratio of pulmonary to systemic flow (Qp/Qs) was evaluated by duplex Doppler echocardiography in 20 patients with various intracardiac shunts. Right and left ventricular stroke volumes (RSV, LSV) were determined from the recordings of ejection blood flow velocity and diameter at the level of the pulmonary and aortic orifices in each ventricular outflow tract. The ratio RSV/LSV, determined by duplex Doppler echocardiography, was compared with Qp/Qs by oxymetry. The Doppler echocardiograms were of sufficient quality for shunt calculation in 15/20 patients (75%). The RSV/LSV for ten normal subjects was 0.99 +/- 0.05 (mean +/- SD), whereas the RSV/LSV for 15 patients with intracardiac shunts, 2.6 +/- 0.5, was significantly higher than that for normal subjects (p less than 0.01). In 12/15 patients, the Doppler study estimated the severity of intracardiac shunting correctly. The presence of complex anatomic situations, a wide pulmonary artery or significant semilunar regurgitation seem to have a negative impact on the Doppler echocardiographic shunt calculation. Our findings indicate that, with a few limitations, the Doppler index RSV/LSV is clinically useful in the estimation of the magnitude of the shunt flow in patients with intracardiac shunts.