Discussion
In our center; almost all pregnant women undergo a minimum of one
anomaly scan that includes fetal heart scanning based on the four
chamber and outflow views to screen for CHD. A detailed FE scanning by
an expert pediatric cardiologist is indicated when findings in these
views do not fulfill the normal criteria [18] or any other risk
factors associated with pregnancy that might cause CHD in fetus.
Deviation from normality in anomaly scan as per cardiac point of view
includes ICEF, abnormal cardiac position or axis, chamber dilatation and
or asymmetry, cardiomegaly, outflow tract abnormalities and fetal
arrhythmia [19]. Obtaining only a normal four chamber view and
outflow view are still not sufficient to exclude underlying cardiac
anomalies [20], hence; the anomaly scan may not be the ideal tool to
screen for fetal cardiac abnormalities [21]. FE is more sensitive
and more specific in the prenatal detection of CHD when compared to the
routine obstetric scanning or anomaly scan that can miss a large number
of cases [22]. In a study done by Archiron et al. [23], the rate
of detection of CHD was raised from 48%; when relying on the four
chamber view alone; to 78% when other views were incorporated.
Similarly, Carvalho et al. [24] reported a detection rate of 75%
with extended screening. In this series, discrepancies between the
anomaly scan and the FE were encountered in 35 hemodynamically
significant cases (small VSDs are not included). In all 35 cases showed
positive findings by FE though their anomaly scan was marked as
”Normal”. This highlights the need to raise the awareness of the
obstetricians and the obstetric ultra- sonographers that limited
screening of the fetal heart by the 4 chamber (sometimes with outflow
view) view may not be sufficient to totally exclude an underlying fetal
cardiac abnormality.
In this series, maximum cases (35.2%) were referred for ICEF on routine
obstetric ultrasound, only 6% of cases are referred for suspicion of
CHD by sonologist on the basis of abnormal 4 chamber view or outflow
tract view in anomaly scan and 0.6% cases were referred for abnormal
cardiac rhythm. In a study done by Meyer-Wittkopf et al. [18], cases
referred on basis of suspicious cardiac configuration and abnormal fetal
rhythm were (26%) and (5.7%) of
their studied population respectively and the percentage of FE scans
confirmed positive for CHD was 78%. Also in a study done by Chitra and
Vijayalakshmi [25], abnormal obstetric scan was the indication of
referral in 26.8% of their studied population. This highlights the role
of obstetric US scanning as an important screening tool for fetal
structural and rhythm abnormalities, though; unfortunately, we were not
able to compare between the accuracy of the obstetric and the FE
scanning as most of the referral letters included ICEF or “abnormal
cardiac views” without mentioning a definitive provisional diagnosis.
Currently, FE is reserved for high risk pregnancies where higher
incidence of CHD is traditionally expected [22], our study also
reflects that a large number of pregnant women referred for FE for their
bad obstetric history (11.5%), history of maternal illness (4.2%), and
history of CHD in mother (1%) or sibling (3.7%) or in family (0.5%).
Although; previous studies reported that most of the cases of CHDs occur
in low risk population with no identifiable prenatal risk factors [7,
16, 26].
The ideal timing for prenatal echocardiography is 18–22 weeks’
gestation [17]. In this series, the mean value of gestational age on
first FE scanning was 23 weeks. This compares favorably with previous
studies [25, 27, 28].
In this study fetal cardiac abnormalities were detected in 175 fetuses
(4%). CHDs in 149 (3.4%), fetal arrhythmia in 17 (0.4%)cardiomyopathy
in 3 (0.07%) fetuses and cardiac mass (Rhabdomyoma) in 6 fetuses
(0.14%). Of the structural CHDs, maximum number of cases were large
VSD, found in 24 (13.7%) cases, small VSD in 17 (9.7%) cases, TOF in
14(8%)cases, whereas VSD and pulmonary atresia in 4 (2.2%) cases, TOF
variant like TOF with APVS in 3(1.7%) cases. Complete AVSD and partial
AVSD were found in 13(7.4%) and 2 (1%) cases respectively. Quite a
large number,11 (6.3%) of cases of HLHS were found. Large ASD and CoA
were found in 8 (4.6%) cases in each. We found 6 (3.4%) cases each in
TGA with intact IVS, PA IVS and cardiac mass. Tricuspid atresia, mitral
atresia was found in 7 (2.2%) and 2 (1%) cases respectively. DORV with
VSD, DORV with VSD and PS, DORV with VSD and PA were found in 3
(1.7%).4(2.2%) and 1(0.5%) cases respectively. DCM were found in 3
(1.7%) cases. All other cases like Ebstain anomaly,
endocardial-fibro-elastosis, CCTGA were found in less than 1% cases
each.In their study, Chitra and Vijayalakshmi [25] detected CHD in
18.2%, fetal arrhythmias in 3.6% and rhabdomyomas in 0.6% of their
studied population. Among their CHD group, complex lesions were detected
in 70% of cases. Also, Meyer–Wittkopf et al. [18] detected CHD in
24.5%. The differences in the detection rate between different studies
can be attributed to the significant variations in the incidence of CHD
that do exist between different populations belonging to different
ethnicities [29].
In a study done by Zhang et al. [30], the sensitivity and
specificity of FE in detecting CHD was 68.5% and 99.8% respectively
whereas, Soongswang et al. [31] detected sensitivity, specificity,
positive predictive value, negative predictive value and accuracy of
96.9%, 90.6%, 84.2%, 98.3% and 92.8% respectively. In this series,
postnatal studies revealed that FE was able to diagnose correctly all
cases of CHD (conotrunchal anomalies, atrioventricular canal, and
complex heart lesions), cardiomyopathy, and cardiac mass after exclusion
of cases which lost follow up. We encountered eight false negative
diagnoses;
Four cases with tiny muscular ventricular septal defects and two cases
with coarctation of aorta, one case of TGA with intact IVS and one case
of large VSD were missed by FE and were diagnosed postnatal. Neither of
our false negative cases had experienced any deteriorating hemodynamic
consequences in the postnatal period and they had come only to medical
attention in the view of recruitment for neonatal echocardiography
confirmation. One case of DORV type of VSD with PS turned out to be DORV
type of VSD with PA postnatal, because of progressive nature of the
disease The types of cardiac lesions missed in our study match favorably
with the study done by Meyer-Wittkopf et al. [18] who detected a
sensitivity of 98% in the prenatal diagnosis of CHD by FE. The
difficulty in the prenatal diagnosis of aortic coarctaion is well-known
in literature [32] and had been reported in previous studies [33,
34]. This confirms the need for sequential follow up studies as some
cardiac lesions have an evolving nature [35].
Fetal arrhythmias account for nearly 10–20% of total referrals for FE
[12]. Most of which are in the form of frequent ectopic beats with
the atrial ectopics being much more common than those of ventricular
origin. Tachyarrythmias are diagnosed when fetal heart rate is above 180
beats per minute. They include sinus, atrial, supraventricular and
ventricular tachycardia [36]. Fetal bradyarrythmia are diagnosed
when fetal heart rate is persistently below 100 beats per minute which
can be due to blocked atrial bigemeny or atrio-ventricular block or
sinus bradycardia (rare) [12].
In this series, we detected arrhythmias in 9.6% of the cardiac
anomalies. Of the fetal arrythmias, 13 fetuses had premature atrial
contraction, and 4 fetuses had congenital heart Among the four cases of
complete heart block, one required PPI, two on oral medication and one
was lost in follow up after initial neonatal examination. None of the
PAC required any kind of treatment Successful treatment of fetal
arrhythmia in utero and spontaneous resolution of premature atrial
contractions had been also reported by Soongswang et al. [31]. Of
their 17 cases diagnosed with fetal arrhythmia, Chitra and Vijayalakshmi
[25] reported bradycardia in 10 cases, tachyarrythmias in 5 cases,
ectopics in two cases and complete heart block in one case with maternal
lupus. They also observed lower association between fetal arrhythmia and
underlying structural heart diseases.
Early prenatal diagnoses provide the neonate with a better care in-utero
and in the post-natal period. Moreover; it allows for early family
counseling which allows the parents to be psychologically and
financially prepared to accept such a child [37] as it offers them
time to be fully aware of the pathophysiology of the detected anomaly;
also the treating physician will have enough time to explain the
severity and discuss the prognosis with parents so they can be able to
take a decision regarding the course of pregnancy. Missing such cases on
routine obstetric scanning or discovering them at late pregnancy would
have rendered decision taking more difficult [22]. Management of a
neonate with an antenatal diagnosis of CHD necessitates coordinate
collaboration between obstetricians, neonatologists, pediatric
cardiologists, fetal echo cardiographers and cardio- thoracic surgeons
[38, 39].The management plan is tailored for each case putting into
consideration the anticipated risk of hemodynamic instability, the
available medical resources, presence of feto-maternal complications,
the availability and the transportation distance to a specialized
cardiac center [39]. Based on our FE findings; delivery in a
tertiary care center with availability of pediatric cardiologist for
early neonatal echocardiographic confirmation and subsequent management
was decided for all cases with hemodynamically significant cardiac
abnormalities. Arrangement for future pacemaker was done for congenital
heart block. Prevention of termination with strict follow up was the
decision taken for cases with expected spontaneous resolution such as
ectopic, cardiomyopathy, rhabdomyomas. Early neonatal interventions were
done in few cases which were planned and arrangements were made before
delivery Termination has been offered in some cases with very complex
heart diseases which are not compatible with life.
Some studies have shown that neonates with CHD diagnosed antenatal tend
to be born earlier than expected when compared to those diagnosed
postnatal [40]. Though, the decision for the delivery
timing of a neonate with a prenatal diagnosis of CHD is affected greatly
by the presence or absence of maternal or fetal complications, the
advantages of term delivery should be always kept in mind [39]. In
our study, most of our cases were term deliveries. This reflects the
high standard of obstetric care offered to our population.