Prsa Milan, Sun Liqun, van Amerom Joshua, Yoo Shi-Joon, Grosse-Wortmann Lars, Jaeggi Edgar, Macgowan Christopher, Seed Mike
From the Division of Pediatric Cardiology, Department of Pediatrics (M.P., L.S., L.G.-W., E.J., M.S.), Department of Diagnostic Imaging (J.v.A., S.-J.Y., M.S.), and Department of Physiology and Experimental Medicine (C.M.), University of Toronto and Hospital for Sick Children, Toronto, Canada.
Circ Cardiovasc Imaging. 2014 Jul;7(4):663-70. doi: 10.1161/CIRCIMAGING.113.001859. Epub 2014 May 29.
Phase-contrast MRI with metric-optimized gating is a promising new technique for studying the distribution of the fetal circulation. However, mean and reference ranges for blood flow measurements made in the major fetal vessels using this technique are yet to be established.
We measured flow in the major vessels of the fetal circulation in 40 late-gestation normal human fetuses using phase-contrast MRI (mean gestational age, 37 [SD=1.1] weeks). Flows were indexed to the fetal weight, which was estimated from the fetal volume calculated by MRI segmentation. The following mean flows (in mL/min per kilogram; ±2SD) were obtained: combined ventricular output, 465 (351, 579); main pulmonary artery, 261 (169, 353); ascending aorta, 191 (121, 261); superior vena cava, 137 (77, 197); ductus arteriosus, 187 (109, 265); descending aorta, 252 (160, 344); pulmonary blood flow, 77 (0, 160); umbilical vein, 134 (62, 206); and foramen ovale, 135 (37, 233). Expressed as percentages of the combined ventricular output, the mean flows±2 SD were as follows: main pulmonary artery, 56 (44, 68); ascending aorta, 41 (29, 53); superior vena cava, 29 (15, 43); ductus arteriosus, 41 (25, 57); descending aorta, 55 (35, 75); pulmonary blood flow, 16 (0, 34); umbilical vein, 29 (11, 47); and foramen ovale, 29 (7, 51). A strong inverse relationship between foramen ovale shunt and pulmonary blood flow was noted (r=-0.64; P<0.0001).
Although too small a sample size to provide normal ranges, these results are in keeping with those predicted in humans based on measurements made in fetal lambs using radioactive microspheres and provide preliminary reference ranges for the late-gestation human fetuses. The wide range we found in foramen ovale shunting suggests a degree of variability in the way blood is streamed through the fetal circulation.
采用优化指标门控的相位对比磁共振成像（MRI）是一种研究胎儿循环分布的很有前景的新技术。然而，使用该技术测量胎儿主要血管血流的均值及参考范围尚未确定。
我们使用相位对比MRI测量了40例孕晚期正常人类胎儿的胎儿循环主要血管中的血流（平均孕周为37[标准差=1.1]周）。血流以胎儿体重进行校正，胎儿体重通过MRI分割计算出的胎儿体积来估算。获得了以下平均血流值（以每千克体重毫升/分钟计；±2标准差）：联合心室输出量，465（351，579）；主肺动脉，261（169，353）；升主动脉，191（121，261）；上腔静脉，137（77，197）；动脉导管，187（109，265）；降主动脉，252（160，344）；肺血流量，77（0，160）；脐静脉，134（62，206）；卵圆孔，135（37，233）。以联合心室输出量的百分比表示，平均血流±2标准差如下：主肺动脉，56（44，68）；升主动脉，41（29，53）；上腔静脉，29（15，43）；动脉导管，41（25，57）；降主动脉，55（35，75）；肺血流量，16（0，34）；脐静脉，29（11，47）；卵圆孔，29（7，51）。观察到卵圆孔分流与肺血流量之间存在强烈的负相关关系（r=-0.64；P<0.0001）。
尽管样本量太小无法提供正常范围，但这些结果与基于对胎羊使用放射性微球测量所得结果预测的人类情况相符，并为孕晚期人类胎儿提供了初步参考范围。我们发现的卵圆孔分流的广泛范围表明血液在胎儿循环中流动的方式存在一定程度的变异性。
