Echocardiographic Z-Score to Predict Pulmonary-Systemic Flow Ratio in Children With Atrial Septal Defect.

Background: The correlation between pulmonary-to-systemic flow ratio (Qp/Qs) and right heart enlargement in children with atrial septal defect (ASD) remains unclear. This study aimed to (1) assess echocardiographic Z-scores of the right heart, and (2) determine whether they predict Qp/Qs. Methods and Results: This retrospective study included 175 children (median age 6.8 years; 68 males) with isolated ASD who underwent cardiac catheterization between 2013 and 2020 at 2 centers in Japan. Patients with genetic anomalies or other conditions affecting right heart size were excluded. Echocardiographic parameters were measured, converted to a Z-score, and compared with the catheterization data. In all patients, the Qp/Qs on cardiac catheterization (cQp/Qs) significantly correlated with the Z-scores of the right ventricular end-diastolic diameter of the basal (RVB), mid-cavity (RVM), and longitudinal length (RVL; r=0.54, 0.57, and 0.52, respectively). The average of these 3 parameters (ARV) showed the strongest correlation (r=0.63). Z-scores of the right atrium, tricuspid valve, and pulmonary artery showed weaker correlations. An ARV cut-off of +2.0 best predicted cQp/Qs ≥1.5 (area under the curve 0.85; 95% confidence interval 0.79-0.92; sensitivity 76.8%; specificity 82.4%). Regression-predicted cQp/Qs also significantly correlated with measured cQp/Qs (r=0.63). Conclusions: ARV may be a useful, non-invasive marker for assessing cQp/Qs and determining the indication for closure in children with ASD.