(1220) Novel approach to a computational evaluation of the waveform of umbilical artery Dopplers

Objective:
To develop a novel, quantitative method of evaluating waveform shapes of umbilical artery Dopplers (UAD) in fetuses with early diagnosis of fetal growth restriction (FGR). Our goal was to use shape analysis of waveforms to better predict which fetuses will ultimately develop Doppler abnormalities.

Study Design:
This was a test of concept study, evaluating the UAD waveforms in 10 patients diagnosed with early onset FGR, 5 of which were diagnosed with absent end diastolic flow during pregnancy, 5 of which never developed Doppler abnormalities. The image recorded of the UAD wave from at the time of diagnosis of FGR was analyzed in two ways: the slope ratio and the descending curve index (DCI). The curves generated during ultrasound exam were digitized using WebPlotDigitizer 5.2 (Automeris LLC, California, USA). Three wave forms within each image were averaged to account for variability. The slope ratio is the ratio of the descending slope to the ascending slope. The DCI is the ratio of the area under the descending curve to the area if the velocity decreased at a constant rate (Figure 1). Calculations and statistical analysis were performed in R 4.4.2.

Results:
On average, the 5 patients who developed absent end diastolic flow during the pregnancy, had a lower slope ratio and DCI. Analysis of variance of the 3 readings per subject, showed that the between-subject variance represented 53% and 17% of total variance for slope ratio and DCI, respectively.

Conclusion:
UAD are widely used as a component of fetal surveillance in pregnancies complicated by FGR. Current methods of analysis only include systolic and diastolic velocities, and the shape of the Doppler wave form remains unanalyzed. There may be significant information in further evaluation of the shape of the curve between systolic and diastolic velocities. We hypothesize that detailed quantitative waveform analysis at the time of diagnosis of FGR may improve prediction of those fetuses who will develop Doppler abnormalities. Additional studies on determining predictive accuracy and improved measurement repeatability are planned.