Aortic Isthmus Doppler Velocimetry in Fetuses with Intrauterine Growth Restriction: A Literature Review

Abstract Intrauterine growth restriction (IUGR) is associated with poor perinatal prognosis and a higher risk of stillbirth, neonatal death, and cerebral palsy. Its detection and the evaluation of its severity by new Doppler velocimetric parameters, such as aortic isthmus (AoI), are of great relevance for obstetrical practice. The AoI is a vascular segment that represents a point of communication between the right and left fetal circulations. It is considered to be a functional arterial shunt that reflects the relationship between the systemic and cerebral impedances, and has recently been proposed as a tool to detect the status of hemodynamic balance and prognosis of IUGR in fetuses. In the present review, we noticed that in healthy fetuses, the AoI net flow is always antegrade, but in fetuses with IUGR the deterioration of placental function leads to progressive reduction in its flow until it becomes mostly retrograde; this point is associated with a drastic reduction in oxygen delivery to the brain. The more impaired the AoI flow is, the greater is the risk of impairment in the Doppler velocimetry of other vessels; and the alterations of the AoI Doppler seem to precede other indicators of severe hypoxemia. Although there seems to be an association between the presence of retrograde flow in the AoI and the risk of long-term neurologic disability, its role in the prediction of perinatal morbi-mortality remains unclear. The AoI Doppler seems to be a promising tool in the management of fetuses with IUGR, but more studies are needed to investigate its employment in clinical practice.摘要 宫内生长受限（Intrauterine growth restriction, IUGR）与不良围产期预后、死胎、新生儿死亡及脑瘫的更高风险密切相关。采用主动脉峡部（aortic isthmus, AoI）等新型多普勒流速参数对其进行检测并评估严重程度，对产科临床实践具有重要意义。AoI是连接胎儿左右循环的血管节段，被认为是反映体循环与脑循环阻抗关系的功能性动脉分流，近期被提议作为检测胎儿宫内生长受限血流动力学平衡状态与预后的工具。在本综述中，我们观察到：健康胎儿的AoI净流量始终为正向，但宫内生长受限胎儿的胎盘功能恶化会导致其流量进行性降低，最终转为以逆向为主；该特征与脑氧输送的大幅减少相关。AoI血流受损程度越严重，其他血管多普勒流速检测异常的风险就越高；且AoI多普勒异常似乎先于重度低氧血症的其他预警指标出现。尽管AoI逆向血流的存在与远期神经功能残疾风险似乎存在关联，但其在预测围产期病亡率中的作用仍不明确。AoI多普勒检测有望成为宫内生长受限胎儿管理的有效工具，但仍需更多研究探索其在临床实践中的应用价值。