Sled John G, Stortz Greg, Cahill Lindsay S, Milligan Natasha, Ayyathurai Viji, Serghides Lena, Morgen Eric, Seravalli Viola, Delp Cassandra, McShane Cyrethia, Baschat Ahmet, Kingdom John, Macgowan Christopher K
Hospital for Sick Children , Toronto, Ontario , Canada.
Department of Medical Biophysics, University of Toronto , Toronto, Ontario , Canada.
Am J Physiol Heart Circ Physiol. 2019 May 1;316(5):H1105-H1112. doi: 10.1152/ajpheart.00704.2018. Epub 2019 Feb 22.
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. 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.
众所周知，通过多普勒超声测量的脐动脉内血液流动的搏动模式包含有用的诊断信息，并广泛用于监测有胎儿生长受限或死产风险的妊娠。动物研究已确定与血流方向相反传播的反射压力波是这些波形形状的一个重要因素。在本研究中，我们建立了一种测量人脐动脉反射波的方法，并评估它们对血流速度搏动的影响。从一家普通产科诊所招募了95名妊娠26至37周的孕妇，并通过多普勒超声进行检查。在脐带的三个位置记录每条脐动脉的血流速度波形。使用计算程序，识别出一对正向和反向传播的波，以解释沿脐带观察到的多普勒超声波形的变化。在符合数据质量要求的数据集中，130条动脉中的93条动脉的波形与波反射模型的吻合度在1.5%以内，反射幅度为正向波幅度的3%至52%。强烈的反射与脐带胎儿端和胎盘端搏动性的巨大差异有关。由于反射是由血管生物力学特性的转变引起的，这些观察结果为异常波形与具有临床意义的胎盘病理之间的联系提供了一个合理的机制，并可能导致更精确的筛查方法来检测并发胎盘疾病的妊娠。通过多普勒超声测量的脐动脉内血液流动的搏动模式包含有用的诊断信息，并广泛用于监测有胎儿生长受限风险的妊娠。基于对95名孕妇的研究，我们证明这些脐动脉波形的形状是由与血流方向相反传播的反射压力波的存在所解释的。
