Reflected hemodynamic waves influence the pattern of Doppler ultrasound waveforms along the umbilical arteries

Abstract

The pulsatile pattern of blood motion measured by Doppler ultrasound within the umbilical artery is known to contain useful diagnostic information and is widely used to monitor pregnancies at risk of fetal growth restriction or stillbirth. Animal studies have identified reflected pressure waves traveling counter to the direction of blood flow as an important factor in the shape of these waveforms. In the present study, we establish a method to measure reflected waves in the human umbilical artery and assess their influence on blood velocity pulsation. Ninety-five pregnant women were recruited from a general obstetrics clinic between 26 and 37 wk of gestation and examined by Doppler ultrasound. Blood velocity waveforms were recorded for each umbilical artery at three locations along the umbilical cord. With the use of a computational procedure, a pair of forward and reverse propagating waves was identified to explain the variation in observed Doppler ultrasound waveforms along the cord. Among the data sets that met data quality requirements, waveforms in 93 of the 130 arteries examined agreed with the wave reflection model to within 1.5% and showed reflections ranging in magnitude from 3 to 52% of the forward wave amplitude. Strong reflections were associated with large differences in pulsatility between the fetal and placental ends of the cord. As reflections arise from transitions in the biomechanical properties of blood vessels, these observations provide a plausible mechanism for the link between abnormal waveforms and clinically significant placental pathology and could lead to more precise screening methods for detecting pregnancies complicated by placental disease. NEW & NOTEWORTHY The pulsatile pattern of blood motion measured by Doppler ultrasound within the umbilical artery is known to contain useful diagnostic information and is widely used to monitor pregnancies at risk of fetal growth restriction. We demonstrate based on a study of 95 pregnant women that the shape of these umbilical artery waveforms is explained by the presence of a reflected pressure wave traveling counter to the direction of blood flow.

A coupled one dimension and transmission line model for arterial flow simulation

“…While the study of Raines et al seems to favor a low value ( κ ~0.19) for tibial vessels, Formaggia et al use much higher values for the anterior and posterior tibial arteries with κ ~0.716 to 0.724, respectively. In a recent study for umbilical arteries, κ at the placental end ranges from 0.03 to 0.52 . Therefore, the presented boundary condition of reflection coefficient still needs to be justified with some experimental data.…”

“…In a recent study for umbilical arteries, κ at the placental end ranges from 0.03 to 0.52. 17 Therefore, the presented boundary condition of reflection coefficient still needs to be justified with some experimental data. Towards that end, the frequency-dependent hemodynamic impedance may be determined invasively in animal models, for example, in the umbilical artery of fetal sheep.…”

“…Towards that end, the frequency‐dependent hemodynamic impedance may be determined invasively in animal models, for example, in the umbilical artery of fetal sheep . However, noninvasive methods, in particular Doppler sonography‐based methods, need to be developed . Research on this topic is exemplified by the work in Reference where the ultrasound velocity waveforms are analyzed from their different harmonics.…”

“…However, noninvasive methods, in particular Doppler sonography‐based methods, need to be developed . Research on this topic is exemplified by the work in Reference where the ultrasound velocity waveforms are analyzed from their different harmonics. Interestingly, the authors of Reference found that the reflection coefficient explained 79% of total pulsatility variations between the fetal and placental ends of an umbilical artery, after analyzing the leading five harmonics of the velocity waveforms.…”

Maternal Smoking Induced Cardiovascular Risks in Fetuses: How Can in silico Models Help?

“…To our knowledge, this method has not been applied to the fetal CVS yet, but a 3Dlumped parameter model coupled method has been used to simulate the blood flow in the ductus venosus (Leinan et al, 2013). To study pressure wave propagation along the elastic arterial wall, the flow equations are solved from the frequency domain, using methods such as the Transmission Line Theory (Muller et al, 2017), or Fourier series analysis for the velocity waveforms (Sled et al, 2019).…”