Non-invasive automated assessment of the ratio of pulmonary to systemic flow in patients with atrial septal defects by the colour Doppler velocity profile integration method.

BACKGROUND The recent introduction of the automated cardiac flow measurement (ACM) method, using spatiotemporal integration of the Doppler velocity profile, provides a quick and accurate automated calculation of cardiac output. OBJECTIVE To evaluate the ACM method against oximetry during cardiac catheterisation for estimating the Qp/Qs (pulmonary to systemic flow) ratio in patients with an atrial septal defect. METHODS Left and right ventricular stroke volume (LVSV, RVSV) were calculated by ACM in 22 patients with an atrial septal defect who underwent cardiac catheterisation and in 11 patients without heart disease (control group). With ACM, the Qp/Qs ratio was estimated from RVSV divided by LVSV. In the patients with an atrial septal defect, the Qp/Qs ratio was assessed by oximetry at the time of cardiac catheterisation. RESULTS There was a good correlation between LVSV and RVSV obtained by ACM in the control group (r = 0.98, y = 0.97x + 0.25, SEE = 2.9 ml). The mean difference between LVSV and RVSV by ACM was -1.25 (2.76) ml. The Qp/Qs ratio obtained by ACM in the control group was 0.98 (0.06). The Qp/Qs ratio in patients with an atrial septal defect was significantly higher than in the control group (3.11 (1.20), p < 0.001). ACM determination of the Qp/Qs ratio correlated well with oximetry determination (r = 0.86, y = 0.75x + 0.55, SEE = 0.64). The mean difference between ACM and oximetry for the measurement of the Qp/Qs ratio was -0.28 (0.69). CONCLUSIONS The newly developed ACM method is clinically useful for non-invasive automated estimations of the Qp/Qs ratio in patients with an atrial septal defect.