Diastolic forward flow in the fetal main pulmonary artery and its implication for fetal cardiac cycle evaluation

Objectives: To examine if the fetal main pulmonary artery diastolic forward flows (MPADFs) are detected consistently, if the waves from fetal MPADFs coincide with those from atrial contractions, and the reproducibility of the cardiac cycle measurements using this technique. Methods: Two examiners performed a fetal pulsed Doppler echocardiography of the four chamber (4CV), ductal arch (DA) and short axis (SA) views on 44 women with singleton pregnancies. Time intervals between atrial contraction peaks and those between MPADF peaks were compared. Atrioventricular (AV) and ventriculoatrial (VA) intervals were measured from MPADF waves in DA and SA views and compared between observers. Intraclass correlation coefficients (ICCs) were calculated as a measure of inter-observer reproducibility. Results: In all observations, MPADFs were demonstrated. The mean time intervals between atrial contraction peaks from 4CV and those between MPADF peaks from DA and SA views were not significantly different. The mean AV and VA intervals were not significantly different between observers. Comparison of measurements of two observers had substantial agreements. Conclusions: Our data show that MPADFs can be found consistently and coincide with atrial contractions. As cardiac cycle measurements can be done with considerable reproducibility, this technique may be useful in assessing fetal cardiac cycle.