ultrasound diagnosis of fatal anomalies

5 The Heart
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General Considerations
Congenital heart disease is relatively frequent,
with an incidence of eight per 1000 live births
(0.8%, or one affected child in 125 births). Half of
these cases constitute severe cardiac anomalies,
which require surgical intervention after birth.
Not all malformations are detected prenatally, as
some are due to the presence of the physiological
fetal circulation between the heart and the
great vessels (a normal state before birth)persisting
even after birth; the malformations are
therefore only detected after birth (e.g., open
ductus arteriosus/Botallo duct). The rate of detection
of cardiac anomalies during prenatal
screening is extremely variable; according to the
literature, it ranges from 5% to 85%, so that at
best 17 of 20 cardiac anomalies may be detected
prenatally, or at worst only one in 20. There are
three reasons for this wide variation.
1 Time of Screening
On the one hand, the frequency of cardiac malformations
depends on the age of the pregnancy
(cardiac anomalies which lead to spontaneous
demise in early pregnancy are rarely detected at
a later gestational stage). On the other hand, the
sensitivity of the method of examination depends
on the gestational age—i.e., the percentage
in which the anomaly is detected. In our experience,
the best time for cardiac screening is
around 21 weeks. In obese patients, a control
screening examination may further be necessary
at 23 to 24 weeks. The present trend is to detect
cardiac anomalies as early as possible; in individual
cases, this can mean as early as
12 weeks.
2 Personal Competence
“You can only detect what you know.” An experienced
examiner who has seen a large number
of cardiac malformations in pregnancy and
who only carries out ultrasound examinations
obviously has more certainty in his or her diagnosis
and thus has a better chance of detecting
an anomaly than an examiner who provides basic
care and only carries out ultrasound examinations
in pregnancy occasionally.
3 Quality of the Equipment
The quality of ultrasound equipment varies considerably,
with new equipment costing anything
between $20 000 and $200 000. In addition to B-
mode sonography, color flow imaging Doppler
sonography is a must for detecting fetal cardiac
anomalies, as it establishes the direction of
blood flow and determines flow velocities in
such a way that detailed hemodynamic evaluation
is possible.
If cardiac anomaly is suspected after prenatal
screening, then the following measures are
taken:
1. In case of cardiac or any other anomalies, it
is important to obtain a second opinion from
another specialist in ultrasound screening to
confirm the initially suspected diagnosis.
2. If the diagnosis of cardiac malformation is
confirmed, then a detailed examination of the
structures involved must be carried out. This is
easier said than done, as it may take up to
2 hours in a physician’s practice to confirm the
diagnosis with certainty and to decide what sort
of consequences the anomaly may have. It is useful
to involve a pediatric cardiologist at this stage
who can interpret this and who can also counsel
the patient.
3. Cardiac anomalies may be an isolated finding,
may appear in association with other malformations,
or may constitute part of a syndrome.
Thus, it is absolutely necessary to do a
complete and detailed fetal screening for other
malformations to confirm either an isolated
finding or a complex syndrome with an accompanying
cardiac anomaly.
4. Cardiac malformation may indicate a chromosomal
anomaly—for example, an AV septal
defect is associated with trisomy 21 in about 50%
of cases. After an anomaly of this type has been
diagnosed, the parents should be informed
about further tests that are available for detecting
genetic abnormalities (amniocentesis and
the prenatal Quick test, especially the fluorescent
in-situ hybridization (FISH)test, placental
biopsy, or fetal blood sampling).
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