Talbert D G
Institute of Obstetrics and Gynaecology, Royal Postgraduate Medical School, Queen Charlotte's and Chelsea Hospital, London, UK.
Ultrasound Obstet Gynecol. 1995 Oct;6(4):261-71. doi: 10.1046/j.1469-0705.1995.06040261.x.
High pulsatility indices (PIs) and/or notches on the Doppler flow velocity waveforms of the uterine artery have been interpreted as indications of high placental flow impedance, and are known to be associated with poor fetal outcome. A software model of the uteroplacental blood path and its use to investigate possible interactions within the uteroplacental unit in more detail are described. Increasing transcotyledonary resistance to represent intervillous obstruction raised the cotyledonary core pressure and spiral artery PI. Increased spiral artery flow resistance, representing failed spiral artery invasion, reduced the cotyledonary core pressure and reduced the spiral artery PI. In vivo, such changes in cotyledonary core pressure would modify the transplacental water balance, promoting oligohydramnios for spiral artery invasion failure and polyhydramnios for villous obstruction. Both mechanisms increased the uterine and arcuate PI, but failed to produce a notch. It was found that notch formation depended on terms representing increased compliance (distensibility) of the uterine and/or arcuate artery walls, which have no direct effect on uteroplacental mean flow. The same mechanism steepened and increased uterine artery peak systolic flow, contributing to increased PI. The notch phenomenon seems to be an indicator of abnormal maternal artery wall status, independent of placental obstructive mechanisms, which can mask obstructive PI changes. Computer analysis of the frequency index profile should allow separation.
子宫动脉多普勒血流速度波形上的高搏动指数（PIs）和/或切迹被解释为胎盘血流阻抗高的迹象，并且已知与不良胎儿结局相关。本文描述了子宫胎盘血路的软件模型及其用于更详细研究子宫胎盘单元内可能相互作用的用途。增加跨绒毛膜阻力以表示绒毛间隙阻塞会升高绒毛叶核心压力和螺旋动脉搏动指数。增加螺旋动脉血流阻力，代表螺旋动脉侵入失败，会降低绒毛叶核心压力并降低螺旋动脉搏动指数。在体内，绒毛叶核心压力的这种变化会改变经胎盘水平衡，导致螺旋动脉侵入失败时羊水过少，绒毛间隙阻塞时羊水过多。这两种机制都会增加子宫和弓形动脉搏动指数，但不会产生切迹。研究发现，切迹的形成取决于代表子宫和/或弓形动脉壁顺应性（扩张性）增加的因素，这些因素对子宫胎盘平均血流没有直接影响。相同的机制会使子宫动脉收缩期峰值血流变陡并增加，导致搏动指数增加。切迹现象似乎是母体动脉壁异常状态的指标，与胎盘阻塞机制无关，后者可能掩盖阻塞性搏动指数变化。对频率指数曲线的计算机分析应能实现区分。
