PDF(Pubmed)
Abstract：
Introduction: In the fetus, a large proportion of the superior vena cava blood flow (QSVC) comes from the brain. To provide the possibility of using this blood flow as a representation of fetal brain circulation, we aimed to determine the fetal QSVC and its fraction of cardiac output during the second half of physiological pregnancies. Materials and Methods: This was a prospective longitudinal study specifically designed for studying fetal hemodynamic development. Healthy women with singleton low-risk pregnancies were included. Ultrasonography was performed at 4-weekly intervals from 20+0 gestational weeks to term. Doppler velocity recordings of the superior vena cava (SVC) and cardiac ventricular outflow tracts were used to obtain the time-averaged maximum velocities (TAMxV). Vessel diameters were measured to calculate their cross-sectional areas (CSA): π(diameter/2)2. Blood flow (Q) was computed as: h *TAMxV*CSA, h being the spatial blood velocity profile, to obtain QSVC and cardiac outputs. The sum of left and right ventricular cardiac outputs constituted the combined cardiac output (CCO). Ultrasound biometry based estimated fetal weight and brain weight were used to normalize the flow. QSVC was also expressed as the fraction (%) of CCO. Gestational age specific percentiles were established for each blood flow parameter using multilevel modeling. Results: Totally, 134 of the 142 included women were eligible for the study with 575 sets of observations. The SVC mean diameter (19-52 mm), mean TAMxV (8.83-16.14 cm/s), and QSVC (15.4-192.0 ml/min) increased significantly during the second half of pregnancy (p < 0.001) while the mean QSVC normalized by estimated fetal weight (49 ml/min/kg) and by estimated brain weight (50 ml/min/100 g) were relatively stable. Similarly, the mean CCO increased (156-1,776 ml/min; p < 0.001) while the normalized CCO (509 ± 13 ml/min/kg) and QSVC as a fraction of CCO (10 ± 0.92%) did not change significantly with gestational age. Conclusion: We provide reference values for fetal QSVC which increases significantly with gestation, and constitutes roughly 10% of the fetal CCO at any time during the second half of pregnancy.
摘要：
简介：在胎儿中，上腔静脉血流（QSVC）很大一部分来自大脑。为了提供使用这种血流作为胎儿脑循环代表的可能性，我们旨在确定生理性妊娠后半期胎儿QSVC及其心输出量分数.材料和方法：这是一项专门为研究胎儿血流动力学发育而设计的前瞻性纵向研究。包括单胎低风险妊娠的健康妇女。超声检查从20+0孕周到足月间隔4周进行。上腔静脉（SVC）和心室流出道的多普勒速度记录用于获得时间平均最大速度（TAMxV）。测量容器直径以计算它们的横截面积(CSA):π(直径/2)2。血流量（Q）计算为：h*TAMxV*CSA，h是空间血流速度曲线，获取QSVC和心输出量。左心室和右心室心输出量的总和构成组合心输出量(CCO)。使用基于估计的胎儿体重和脑体重的超声生物统计学来使流量归一化。QSVC也表示为CCO的分数(%)。使用多水平建模为每个血流参数建立妊娠年龄特异性百分位数。结果：完全，142名女性中有134名符合575组观察结果的研究条件。SVC平均直径（19-52mm），平均TAMxV（8.83-16.14cm/s），在妊娠后半期，QSVC（15.4-192.0ml/min）显着增加（p<0.001），而平均QSVC通过估计的胎儿体重（49ml/min/kg）和估计的脑体重（50ml/min/100g）相对稳定。同样，平均CCO增加(156-1,776ml/min;p<0.001),而标准化CCO(509±13ml/min/kg)和作为CCO分数的QSVC(10±0.92%)没有随着胎龄显著变化.结论：我们为胎儿QSVC提供了参考值，该参考值随妊娠而显着增加。在怀孕后半期的任何时候，大约占胎儿CCO的10%。
