Monitoring and diagnosing fetal cardiac (ar)rhythmias per CTG-registration and fetal ECG by the Monica AN24tm.

Fetal arrhythmias occur in as many as 1 to 3% of all pregnancies. Fetal cardiac
arrhythmias are mostly benign, but they can result in fetal hydrops which can
lead to intra-uterine mortality and premature birth. At the gestational age of
16 weeks, it*s possible to judge fetal heart frequency. The fetal cardiac
conduction system is developed and there is a regular heart rhythm between 100
and 180 bpm.
Electrocardiogram (ECG) is the basis to diagnose cardiac arrhythmias. Today
fetal cardiac arrhythmias can be diagnosed just indirectly by measurements of
echocardiography and fetal monitoring is achieved by ultrasound
CTG-registrations at hospital. These tests are snapshots and specialistic
expertise is necessary. Information of cardiac electric conduction of the fetal
heart cannot be acquired. Monitoring of fetal cardiac arrhythmias is only
possible by regularly making CTG-registrations and echocardiography in which
heart rhythm, cardiac function and fetal condition are assessed. Fetal ECGs may
be an extra tool in diagnosis and detection of fetal cardiac arrhythmias.
Fetal electrocardiogram (fECG) is a technique, which isn*t clinically applied
yet, because of some technical problems as low voltage signal and many noise,
like maternal heart beating.
Recent research on fECG showed that non-invasive fECGs are possible and more
detailed information will be given about fetal heart activity and conduction
comparing with measurements by echocardiography. However difficulties in
detecting small fetal QRS-complexes are shown in this research.
An other study shows fECG through maternal abdomen, suppressing maternal ECG.
Other noise like electronic signals, intra-abdominal signals, myo-electric
signals of abdominal muscles and uterine activity (especially during labor) are
filtered by algorithms and match filtering by Independent Component Analysis
(ICA). Quality of fECGs may be dependent on presence of vernix caseosa (from
gestational age of 28 weeks) and quantity of amnion fluid, by influencing the
conduction of the electrical signals. Now, clinical fetal monitoring occurs by
echographic CTG-registration. Ultrasound waves are sent into the maternal
abdomen and the CTG device measures fetal heart frequencies by catching the
reflection. Fetal condition can be judged after 30 minutes registration based
on fetal heart rhythm (variability, accelerations and decelerations). This
technique has some disadvantages. The pregnant women are fixed at bed during
registration, ultrasound has to be sent to the abdomen continuously, quality of
prolonged CTG-derivations depends on fetal movements, electrodes has often to
be replaced by trained staff. Pregnant women with adipositas have an
additional disadvantage in quality of registration, because ultrasound waves
penetrate badly through fatty tissue. At this moment, prolonged CTG
registration is impractical and loaded for the pregnant women.
The Monica AN24* is a new CTG method. It passively registries electric signals
from the maternal abdomen by standard stick-electrodes measuring fetal heart
beats. It is now possible to derive a fetal ECG from the raw data of the
CTG-registrations by the Monica. This makes it possible to measure elements of
fetal heart conduction, like PR-interval, width of QRS-complexes and
QT-intervals. Also true variability of heart frequency could be pointed out,
the *real* R-R variability.
The Monica AN24* has a lot of benefits: it is a passive method, and electric
signals better penetrate fatty tissue compared with ultrasound, so adipositas
theoretically has little influence on the quality of the fECGs. It is a small,
bearable monitor; the women will be mobile during registration. So, prolonged
continuous registration for fetal monitoring in fetal cardiac arrhythmias will
be less loaded for the pregnant women.
The Monica AN24* isn*t dependent on fetal movements, because of the electric
activity registered by the electrodes and replacement of the electrodes isn*t
necessary. All data are saved at the little monitor, so registration at home
will be possible. Monica AN24* registrations are mentioned since a gestational
age of 20 weeks.
The section Obstetrics of the LUMC has a Monica AN24* available with the aim to
use the new equipment for fetal monitoring, by prolonged and (eventually home)
CTG-registrations by pregnant women with fetal cardiac arrhythmias. There are a
few studies which have examined that gestational age (vernix caseosa, amount of
amnion fluid) and effects of BMI could influence the quality of electrical
CTG-registrations. The possibility of constructing complete fECGs, with
identification of P-waves, QRS-complexes and T-waves isn*t sufficient examined
yet.

The main goal of this study is to examine the clinical applicability of the
Monica AN24*, for the use of this device in the LUMC for prolonged
CTG-registrations in high risk pregnancies and particularly in monitoring fetal
cardiac arrhythmias. The CTG registrations by the Monica AN24* will be
validated and the influence of gestational age and BMI on quality of the
registrations will be examined.
Also, the possibilities to derive fetal ECGs from CTG-registrations of the
Monica AN24* will be examined.

• Is the quality of the CTG registrations by Monica AN24* through maternal
abdomen comparable with conventional ultrasound CTG-registrations?
• Does gestational age and maternal BMI influence the CTG quality of the Monica
AN24*?
• Is the Monica AN24* able to produce reliable fetal ECG-registration derived
from the CTGs by the Monica AN24*?
• Is the Monica AN24* CTG-registration useful for registering at home?
• What could be the role of the Monica AN24* by the diagnosis and treatment of
fetal cardiac arrhythmias?

Observation study, patient series. First, the new technique will be valuated. A
database will be created including as many as possible pregnant women with a
singleton pregnancy. Participants will be approached as soon as possible, but
regardless before gestational age of 20 weeks. All subjects get a questionnaire
about gestational age, BMI, parity and (congenital) abnormalities by other
pregnancies. Subsequently the participants will be divided in categories based
on their BMI (BMI<19, BMI 19-24,9, BMI 25-29,9, BMI >= 30). Also gestational age
will be classified in time intervals. Per interval the participant gets at
minimum one CTG-registration. The test will be at the same day when the
participant has an appointment with gynecologist or obstetrician at the section
Obstetrics of the LUMC. Two times both a CTG-registration by the Monica AN24*
as a conventional CTG registration will be made. Both registrations will take
30 minutes, so together it will no longer take than one hour extra per
appointment.
By Participants a standard ultrasound (SEO) is made at gestational age of 20
weeks. Thickness of maternal abdomen, fetal heart function, heart rhythm and
conduction of fetal heart will be regarded extra by 2D, M-mode and Doppler
echocardiography. This will take about 10 minutes more time compared to the
standard ultrasound.
At the end of the study CTG-registrations will be judged by the principal
investigator. Percentages of registered time will be noted, there will be no
paper strip, but the registration will be saved anonymous and digital. These
measures are taken, because clinical relevance of CTG-registrations by an
uncomplicated pregnancy is unknown.

Time interval Different tests
in weeks of gestational age Monica AN24 CTG registration Current CTG
registration SEO with prenatal echocardiography

19-24 weeks
x
x
25-29 weeks
x x
30-34 weeks
x x

This study uses non-invasive techniques. CTG-registration by the Monica AN24*
is a safe method, without risks for mother and/or unborn child. Electronic
activity will be passively received by standard stick-electrodes on the
maternal abdomen. The study will take about three times one hour extra for the
participant. Appointments will be coupled to already existing appointments with
obstetrics or gynecologist; so there is no need for extra traveling. An
allergic reaction at brown tape is possible; we will attend the participants
before placing the electrodes.
It is non-invasive research, minimal loaded, without risks for mother or unborn
child.