Noninvasive assessment of Doppler-derived estimated fetal interatrial pressure-gradient indices using ductus venosus and pulmonary vein velocities in late-onset fetal growth restriction: a prospective case-control study.

BACKGROUND: Fetal growth restriction (FGR) is associated with progressive hemodynamic deterioration and subclinical cardiac dysfunction. The modified Bernoulli equation applied to ductus venosus and pulmonary vein Doppler velocities allows noninvasive estimation of fetal interatrial pressure gradients; however, the utility of this approach in FGR has not been empirically evaluated.

METHODS: This prospective case-control study, conducted at a single tertiary referral center, enrolled 40 late-onset FGR fetuses meeting Delphi consensus criteria and 40 gestational age-matched controls. Doppler-derived estimated interatrial pressure-gradient indices were calculated noninvasively by applying the modified Bernoulli equation to ductus venosus and pulmonary vein Doppler peak velocities obtained sequentially during the same examination session. In addition, standard arterial and venous fetal Doppler indices were recorded. Group comparisons were performed using the Mann-Whitney U test, with effect sizes quantified by Cliff's delta.

RESULTS: No significant difference was observed in any of the three estimated interatrial pressure gradient indices between FGR and control fetuses (p = 0.447, p = 0.665, and p = 0.729, respectively). Pulmonary vein D-wave velocity was significantly reduced in FGR fetuses (18.20 [IQR 13.43-22.40] vs. 20.90 [IQR 15.97-25.60] cm/s; p = 0.021), whereas ductus venosus velocity parameters did not differ between groups. In a subgroup analysis of eight FGR fetuses with umbilical artery pulsatility index at or above the 95th centile, all three gradient indices were significantly lower than in controls (p ≤ 0.010), with large effect sizes (Cliff's δ 0.581 to 0.762).

CONCLUSIONS: Doppler-derived estimated interatrial pressure-gradient indices do not differ significantly between FGR and control fetuses in the absence of ductus venosus a-wave abnormalities. In an exploratory subgroup analysis, significantly lower gradient indices were observed in fetuses with UA PI at or above the 95th centile; this finding should be considered hypothesis-generating. Furthermore, pulmonary vein D-wave velocity was significantly reduced in FGR fetuses, a finding that may reflect altered left ventricular diastolic filling dynamics; however, definitive conclusions regarding diastolic dysfunction require dedicated cardiac function assessment. Collectively, these findings provide the first characterization of Doppler-derived estimated interatrial pressure-gradient indices in late-onset FGR and suggest that interatrial hemodynamic alterations emerge only at more advanced stages of fetoplacental compromise.