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Reference values of fetal aortic flow velocity waveforms and associated intra‐observer reliability in normal pregnancies
Author(s) -
Bahlmann F.,
Wellek S.,
Reinhardt I.,
Krummenauer F.,
Merz E.,
Welter C.
Publication year - 2001
Publication title -
ultrasound in obstetrics and gynecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.202
H-Index - 141
eISSN - 1469-0705
pISSN - 0960-7692
DOI - 10.1046/j.1469-0705.2001.00306.x
Subject(s) - medicine , blood flow , vascular resistance , doppler effect , cardiology , aorta , aortic arch , pulsatility index , gestation , fetus , hemodynamics , pregnancy , physics , biology , astronomy , genetics
Objectives It was the aim of the present study to calculate new Doppler reference ranges for blood flow velocities ( V max , V mean , V min ) and resistance indices (PI, RI) for the fetal descending aorta by automatic waveform analysis. Design Cross‐sectional prospective study. Subjects Nine hundred and twenty‐six low‐risk pregnancies at 18–41 weeks' gestation. Methods Aortic blood flow velocities were derived with pulsed‐wave color Doppler. Measurements were carried out at the level of the diaphragm. Reference ranges for the individual measuring parameters were constructed based on a growth function from a four‐parameter class of monotonic continuous functions according to the smallest square principle. Further investigated were intra‐observer reliability and the influence exerted by different measuring sites (aortic arch, diaphragm, below the renal vessels) on the aortic Doppler flow spectrum. Results Although a significant increase in aortic blood flow velocity was observed at 18–41 weeks' gestation ( V max = 48.2 cm/s to 110.3 cm/s ( P < 0.001), V mean = 20 cm/s to 47.5 cm/s ( P < 0.001) and V min = 7.6 cm/s to 18.6 cm/s ( P < 0.001)), there were no significant changes in the pulsatility or resistance indices. The resistance indices PI and RI as well as absolute blood flow velocities ( V max, V min) were significantly lower with increasing distance from the heart. Initial decreases were measured between the aortic arch and the diaphragm: PI, 2.34 to 1.87 ( P < 0.0001); RI, 0.87 to 0.79 ( P < 0.0001); V min : 8.5 cm/s to 15.0 cm/s ( P < 0.0001). Furthermore, systolic blood flow velocities ( V max ) were decreased below the renal vessels from 97 cm/s to 64 cm/s ( P < 0.0007). No significant changes were recorded in intensity‐weighted mean flow velocities ( V mean ). The intra‐observer reliability was low, but of no clinical relevance. Conclusions At constant measuring conditions, the reference ranges for blood flow velocities and resistance indices in the fetal aorta calculated by the authors serve as the basis for Doppler ultrasound antenatal examinations in a normal patient population and enable the early diagnosis of fetal risk. Copyright © 2001 International Society of Ultrasound in Obstetrics and Gynecology