[Increased signal intensity of velocity measurements in duplex sonography by using the contrast agent levovist: a prospective, randomized study in a fetal sheep model].

PURPOSE

To evaluate the potential diagnostic advantages of the contrast agent Levovist for signal enhancement of small adjoining fetal vessels and to study the effect of Levovist before and during acute fetal hypoxia on the fetal circulation and the fetal blood flow velocities.

MATERIALS AND METHODS

A prospective, randomized study was performed in 12 fetal sheep before and during acute fetal hypoxia produced by complete occlusion of the maternal common iliac artery. Two groups of animals were studied, comprising animals with (study group, n = 6) and without (control group, n = 6) Levovist. In the study group, Levovist was administered intravenously by a pump (modified IVAC P 4000, Schering, Berlin). Duration and intensity of signal enhancement were measured in the fetal aorta, the common carotid artery and the ophthalmic artery of both groups before and during hypoxia. Concurrently, fetal heart rates as well as systolic and diastolic blood flow velocities in all three vessels were recorded in both groups.

RESULTS

The increased signal intensity of up to 15 dB in the study group resulted in improved differentiation and imaging quality of adjoining small fetal vessels when compared with the control group. Neither before nor during acute hypoxia, significant differences of the fetal heart rate and the systolic and diastolic blood flow velocities were observed between the two groups (p > 0.05). In the study group, no emboli were caused by Levovist in any fetal tissue or in the placenta.

CONCLUSION

The contrast agent Levovist improves the detection and accuracy of monitoring flow velocities in small fetal vessels by increasing the intensity of the Doppler signal without affecting fetal heart rate or fetal blood flow velocities.