Spatio-Temporal Image Correlation; the Key to fetal EchocaRdiography
Part III signs of decompensation in growth-restricted fetuses

IUGR is a common diagnosis and carries an increased risk of perinatal mortality
and morbidity. The prevalence is about 8% in the general population.
Identification of IUGR is crucial because proper evaluation and management can
result in a favourable perinatal outcome. This makes IUGR an important clinical
problem.

The pathogenesis of IUGR is multifactorial. The most common cause is
uteroplacental insufficiency. A deteriorating fetal condition might be detected
by specific characteristics at fetal cardiotocography (CTG) and
ultrasound/Doppler measurements. Possibly, decompensatio cordis plays an
important role in fetal demise. The fetal cardiac function can be determined by
fetal echocardiography.

Conventional ultrasound techniques together with techniques such as M-mode and
pulsed doppler have been used to estimate fetal cardiac function.
Two-dimensional and M-mode ultrasound- based studies have established a range
of cardiac dimensions in the normal and abnormal heart. For cardiac volume
calculations both 2D and M-mode ultrasound, however, have their limitations. A
more accurate and reproducible method to investigate cardiac function in this
subgroup could be very valuable to the obstetrician who has to make decisions
about a fetus with IUGR.

Spatio-Temporal image correlation (STIC) is the latest ultrasonographic
approach to clinical assessment of the fetal heart. STIC is an automated volume
acquisition, recording one single three-dimensional volume dataset. The cardiac
volumes are then displayed as one real-time cardiac cycle, played in a
cine-loop. This loop can be played in slow motion or stopped at any time for
analysis and because there is a volume dataset, each of the scan planes can be
moved and rotated while maintaining the synchronized cardiac loop.

Because STIC technology gives the investigator the opportunity to freeze the
three-dimensional cardiac loop in end-diastolic and end-systolic phase, more
accurate volume measurements can be used to calculate fetal heart stroke
volume, cardiac output and ejection fraction based on 3D volume measurements.

To study the role of decompensatio cordis in IUGR, this research will be
focused on two levels:

- ventricular function, measured bij STIC, in relation to conventional Doppler
ultrasonography in the peripheral vasculature
- visualisation and Doppler measurements of the coronary arteries

Hereby we hope to get more insight in the pathofysiology in fetuses with IUGR,
and to improve management and perinatal outcome.

The focus of this study is to get more insight in the pathophysiology of IUGR.
The main goal is to investigate the applicability of STIC in determining fetal
cardiac function in IUGR.

In this prospective longitudinal study we will look for signs of decompensation
in extremely growth-restricted fetuses by using STIC technology. The standard
treatment in patients with IUGR is follow-up by advanced ultrasonography every
two weeks for fetal biometry and twice a week for measurements of the amount of
amniotic fluid and Doppler recordings of the umbilical artery, the ductus
venosus and the middle cerebral artery. Besides these standard measurements,
we aim at performing the following additional parameters:

- STIC volume recordings, combined with color-STIC, for the offline analysis of
fetal cardiac function
- intracardiac and extracardiac Doppler measurements (umbilical vein,
atrioventricular valves)
- visualisation and Doppler recordings of the Coronary blood flow

Heart performance indices will be measured by STIC and compared with
conventional Doppler recordings. Longitudinal changes of these measurements in
fetuses with IUGR will be bescribed. By visualisation and/or making Doppler
measurements of the CBF, the relationship between IUGR and CBF will be examined
as well. After delivery, perinatal outcome (Apgar scores, cord arterial blood
gases and perinatal morbidity and mortality) are correlated to the prenatal
measurements.

Spatio-Temporal Image Correlation (STIC)

Ultrasound has been used since the 1970's. there are no proven adverse effects
of ukltrasound investigantions on foetus or mother.