Fetal Ventricular Diastolic Filling Characteristics in a Primate Model: The Role of Fetal Heart Rate and Pulmonary Vascular Impedance

Objectives: We hypothesized that fetal ventricular diastolic filling characteristics are related to fetal heart rate (FHR) and pulmonary vascular impedance. Methods: Rhesus monkeys underwent Doppler ultrasonography at near-term gestation. Tricuspid (TV) and mitral valve (MV) blood velocity waveforms were used to calculate maximum velocity (V-max) and velocity time integral (VTI) E/A ratios (early filling/ventricular filling during atrial contraction) at baseline and during maternal hyperoxygenation. Right pulmonary artery (RPA) pulsatility indices (PIs) and FHR were measured. Results: Hyperoxgenation significantly decreased FHR and RPA PI. The TV V-max and the MV VTI E/A ratios increased significantly and correlated with a decrease in FHR but not with a decrease in RPA PI. The TV and MV A-wave V-max decreased during hyperoxygenation and their decrease correlated significantly with a drop in FHR. Conclusions: Fetal ventricular diastolic filling characteristics are related to FHR but not to pulmonary vascular impedance.