To define the technique of estimating ductal diameter (DD) that best correlates with echocardiographic markers of transductal shunt volume in preterm infants >7 days old with persistent patent ductus arteriosus (PDA).

We conducted a retrospective study of 104 neonates born at <30 weeks gestation that had targeted neonatal echocardiography evaluation of PDA performed between 7 and 30 days. We used univariate analysis to determine the association of echocardiographic markers of shunt volume with ductal size definitions: DD, DD indexed to weight, and DD indexed to left pulmonary artery diameter.

Two hundred echocardiograms were reviewed from 104 patients with a median gestational age of 25.4 weeks (range, 25-26.3 weeks) and a median birth weight of 810 g (range, 740-920 g). We found a weak correlation of each method of PDA size definition with individual echocardiographic markers of transductal shunt volume, of which nonindexed DD demonstrated the best correlation. The best correlation was found with markers of systemic hypoperfusion, such as diastolic flow reversal in the descending aorta (R² = 0.24) and celiac artery (R² = 0.21). Markers of pulmonary overcirculation, such as left ventricular end-diastolic diameter (R² = 0.19) and left ventricular output (R² = 0.17), showed fair correlation with nonindexed DD.

In preterm infants >7 days old with PDA, nonindexed DD demonstrated weak correlations with individual echocardiographic markers of shunt volume. These data highlight the need for comprehensive echocardiographic evaluation in addition to diameter measurements to provide a better understanding of the hemodynamic consequences of PDA.