Intravascular ultrasound contrast agent: an aid in imaging intervillous blood flow?

The aim of this study was to evaluate the applicability of an intravascular ultrasound contrast agent in examination of the uteroplacental circulation. Uteroplacental circulation in 25 singleton third trimester pregnancies was examined by power Doppler, first without and then with contrast agent enhancement (Levovist, Schering AG, Germany). Eight subjects had fetal growth retardation and 17 had normal-sized fetuses. The effect of the contrast agent was evaluated using computerized power Doppler signal intensity measurements. The Doppler signal intensity in the uteroplacental vessels increased within 25 sec of brachial venous injection of the contrast agent, yielding an effect which was recognizable up to 5-8 min later. There was clear enhancement of uteroplacental flow imaging after addition of the contrast agent in all of the examined pregnancies. The mean percentual intensity changes after administration of the contrast agent were 33 per cent (P<0.001) in the sub-placental myometrial area and 8 per cent (P<0.001) in the intraplacental area. No association was found between fetal growth retardation and intensity changes or absolute intensity parameters. In conclusion, intravascular ultrasound contrast agent facilitates imaging of the uteroplacental circulation. It may have a valuable role in determination of intervillous blood flow and in imaging blood perfusion in different regions of the placenta.