Venous Flow Variation Predicts Preoperative Pulmonary Venous Obstruction in Children with Total Anomalous Pulmonary Venous Connection

Background: Identifying preoperative pulmonary venous obstruction in total anomalous pulmonary venous connection is important to guide treatment planning and risk prognostication. No standardized echocardiographic definition of obstruction exists in the literature. Definitions based on absolute velocities are affected by technical limitations and variations in pulmonary venous return. The authors developed a metric to quantify pulmonary venous blood flow variation: pulmonary venous variability index (PVVI). The aim of this study was to demonstrate its accuracy in defining obstruction. Methods: All patients with total anomalous pulmonary venous connection at a single institution were identified. Echocardiograms were reviewed, and maximum (V_max), mean (V_mean), and minimum (V_min) velocities along the pulmonary venous pathway were measured. PVVI was defined as (V_max − V_min)/V_mean. These metrics were compared with pressures measured on cardiac catheterization. Echocardiographic measures were then compared between patients with and without clinical preoperative obstruction (defined as a need for preoperative intubation, catheter-based intervention, or surgery within 1 day of diagnosis), as well as pulmonary edema by chest radiography and markers of lactic acidosis. One hundred thirty-seven patients were included, with 22 having catheterization pressure recordings. Results: V_max and V_mean were not different between patients with catheter gradients ≥ 4 and < 4 mm Hg, while PVVI was significantly lower and V_min higher in those with gradients ≥ 4 mm Hg. The composite outcome of preoperative obstruction occurred in 51 patients (37%). Absolute velocities were not different between patients with and without clinical obstruction, while PVVI was significantly lower in patients with obstruction. All metrics except V_max were associated with pulmonary edema; none were associated with blood gas metrics. Conclusions: The authors developed a novel quantitative metric of pulmonary venous flow, which was superior to traditional echocardiographic metrics. Decreased PVVI was highly associated with elevated gradients measured by catheterization and clinical preoperative obstruction. These results should aid risk assessment and diagnosis preoperatively in patients with total anomalous pulmonary venous connection.