272: Fetal right ventricular filling characteristics: Role of fetal heart rate and afterload


      We hypothesized that heart rate and afterload significantly affect the fetal tricuspid valve (TV) blood velocity waveform pattern at term gestation.

      Study Design

      18 rhesus macaque monkeys underwent Doppler ultrasonography at 150-157 gestational days (term 165 days). Tricuspid valve (TV), right pulmonary artery (RPA) and ductus arteriosus (DA) blood velocity waveforms were obtained at baseline and during maternal hyperoxygenation (100% oxygen). Using the TV blood velocity waveform, peak velocities during early ventricular filling (E) and filling during atrial contraction (A) were measured and their ratio (E/A) was calculated. Pulsatility index (PI) values were obtained from RPA and DA blood velocity waveforms. Fetal heart rate (FHR) was measured from TV blood velocity waveforms. Paired t-test comparisons were used in statistical analysis.


      Hyperoxgenation resulted in a significant increase in the TV E/A ratio and DA PI, while it was also associated with a significant decrease in RPA PI and FHR. The change in TV E/A ratio was negatively correlated with the change in FHR (r = −0.687, p = 0.003). No significant correlation (r = 0.262, p = 0.328) was found in the change between TV E/A ratio and RPA PI.


      During maternal hyperoxygenation, the fetal TV E/A ratio increased and FHR and RPA PI decreased. A decrease in RPA PI reflects diminished pulmonary vascular impedance and right ventricular afterload. While fetal heart rate can modify right ventricular filling characteristics, a drop in right ventricular afterload is not related to changes in TV blood velocity waveform patterns.
      Tabled 1Cardiac Indices by Oxygenation - mean (SD)
      Base0.57 (0.42)176 (24.35)29.44 (19.62)2.44 (0.27)
      Oxygen0.90 (0.30)152 (14.74)6.13 (3.90)2.89 (0.71)