[Visualization of right atrial flow patterns and quantification of pulmonary to systemic flow ratio in patients with...

To evaluate the ability of vector flow mapping (VFM) in visualizing right atrial flow and quantifying pulmonary to systemic flow ratio in patients with atrial septal defect (ASD).

VFM was performed on 30 patients with ASD and 50 healthy volunteers. The pulmonary to systemic flow ratio (Qp/Qs) was calculated using VFM and spectral doppler compared with that obtained through oximetric data derived from cardiac catheterization.

Blood streams from superior and inferior caval veins did not collide but turned forward, contributing to a forward clockwise vortex during systole on the subcostal bi-atrial plane in the healthy volunteers. The vortex was disrupted continuously by a left to right shunt in the patients with ASD during the hole cardiac cycle. The Qp/Qs measured by VFM was less angle-dependent in all the cases than the other methods. The mean value of Qp/Qs of the healthy volunteers calculated by apical three-chamber view and apical five-chamber view ranged from 0.84:1 to 1.15:1, which is consistent with the theoretical value 1 of no left to right shunts. The values of Qp/Qs of patients with ASD measured by VFM and spectral doppler showed no significant differences with those obtained through oximetric data [(2.18 +/- 0.48) vs. (2.29 +/- 0.76), P = 0.29; (2.30 +/- 0.91) vs. (2.29 +/- 0.76), P = 0.86]. However, the Qp/Qs value measured by VFM had a better correlation with the oximetric data than that measured by spectral doppler (r = 0.71, P < 0.001 vs. r = 0.38, P < 0.05). The inter-observer and intraobserver variability of Qp/Qs measured by VFM was 9.84% and 9.86% respectively.

VFM can visualize right atrial flow field in patients with ASD and quantify Qp/Qs in a more accurate way than spectral dopler.