Download The 20 week scan: an opportunity to detect or miss cardiac

The 20 week scan: an opportunity to detect or miss
cardiac anomalies?
M. Tabibi, J. Bawazir, A. Arafa
Department of Obstetrics and Gynaecology, Epsom and St Helier Hospital NHS trust, Epsom General Hospital, KT18 7EG
Introduction
Ultrasound screening for foetal structural abnormalities is generally recommended at 1921 weeks of gestational age. The accuracy in detecting malformations by ultrasound,
however, shows great variability among centres and operators. Congenital malformations
occur in 2-4% of all births. Despite their relatively low prevalence, foetal malformations
are responsible for approximately 30% of perinatal deaths in addition to considerable
infant
morbidity
in
developed
countries.
We describe two complicated cases of cardiac anomalies where the diagnosis was missed
during the anomaly scan between 20-22 weeks. The first case was of a baby found to
have Situs inversus (SI) where the diagnosis was made only during the postnatal check
up. The second case was of a baby with transposition of the great vessels (TGA).
Unfortunately, this was not diagnosed during the 20 week scan and was diagnosed
postnatally.
TGA is one of the most common cyanotic congenital heart defect in neonates. The
hallmark feature is ventriculoarterial discordance whereby the aorta arises from the
morphological right ventricle and the Pulmonary artery arises from the morphological
left ventricle. The prevalence is 0.2/1000 live births and according to one 13 year study,
the detection rate was 6.9% which improved to 25% in the last four years of the study(1).
A neonate with TGA will usually present primarily with cyanosis within the first 24
hours of life.
SI alone does not have clinical features however there is an increased association with
Congenital Heart Defects (CHD). One study showed 23% of babies with SI when
investigating dextrocardia. Of the babies with SI, 63% had structural cardiac
malformations and 10% had extracardiac features(2). SI can be part of a triad with
primary ciliary dyskinesia (PCD) and abnormal frontal sinuses, this is known as
Kartagener’s syndrome. SI can be seen in 41% of people with PCD(3) therefore a patient
with SI may present with pulmonary features and be diagnosed incidentally for SI as was
the case for our first patient.
Case 1
The first patient with SI was born at term by
normal vaginal delivery and did not require
resuscitation at birth. He was persistently
tachypnoeic with perioral cyanosis and
irritability. He was then admitted to Special
Care Baby Unit (SCBU). His chest x-ray
showed signs of congenital pneumonia and
was treated with 10 days of intravenous
antibiotics. After having an x-ray, it was
found that he had dextrocardia and
subsequent abdominal ultrasound confirmed
SI. Due to the SI and pneumonia, there was a
strong suspicion that the patient had primary
ciliary dyskinesia as he struggled with
copious chest secretions which improved
with physiotherapy.
Discussion
Early detection for cardiac anomalies, such as TGA, allows for the medical team and
families to better anticipate the potential complications of TGA and it can also improve
neonatal morbidity and mortality. First year mortality has been proven to be significantly
lower in cases with a prenatal diagnosis of TGA compared to those without (0.0% vs
11.4%, respectively)(4). Morbidity is also significantly lower in cases with a prenatal
diagnosis, those without a prenatal diagnosis had higher rates of hypoxia and renal
dysfunction.
Early detection is essential in management
however technical difficulties may arise in
diagnosing cardiac anomalies at such an
early stage. The routine antenatal scan at 20
weeks provides a four chamber view of the
heart using 2-D sonography to assess
structural integrity however sensitivity for
detection of TGA may be lacking. The
presence of an ‘I’ shaped aorta in the upper
mediastinum during the scan could be a
novel potential marker for antenatal
diagnosis of TGA. In one retrospective
evaluation, the ‘I’ shaped sign (fig.1) as
observed in 96.8% of cases of TGA (5).
Sonographers could receive further training
in identifying such a marker to allow for a
prenatal diagnosis of TGA.
Frequency of
0.2/1000 live
births
Detection rate
6.9%,
improving to
25%
Situs inversus with truncus arteriosus (7)
41% of people
with PCD
63% with structural
cardiac
malformations
Case 2
The second patient with TGA was born at term by normal vaginal delivery and
was in a good condition at birth with no resuscitation needed. There was a
maternal history of hereditary angioedema and alpha thalassaemia carrier but the
father was of low risk. On the postnatal ward, the patient was noted to have an
apnoeic episode, followed by vomiting. During this episode she showed signs of
cyanosis which lasted 30 seconds. After recovering from this episode, the patient
was brought to SCBU and was found to have low pre and post-ductal saturations
(79% and 85% respectively). These did not improve with oxygen. An
echocardiogram was performed which showed TGA with an atrial
communication and a small ventricular septal defect. An umbilical vein catheter
(UVC) had been placed and Prostaglandin E had been administered, along with
prophylactic antibiotics for sepsis cover.
Figure 1 (5)
Due to the difficult nature of prenatally diagnosing these cardiac anomalies,
healthcare professionals could apply other methods to diagnose early in the neonatal
stage if they are unable to diagnose prenatally. Methods such as pulse oximetry could
be utilised to minimise the risk of discharging infants with CHDs such as TGA. One
retrospective cohort study demonstrated that hospitals using pulse oximetry screening
diagnosed all neonates before discharge(6).
TGA
SI
(5)
The early detection of SI carries significance due
to the fact that almost half of people with PCD
have SI (Kartagener’s syndrome) and although
complications may not arise directly from SI,
complications may be due to PCD. 70-80% of
neonates with PCD present with respiratory
distress and there is an increase risk of developing
pneumonia(8), as we saw with our first patient. This
creates a great emotional burden on the parents of
babies born with such complications thus early
anticipation of potential PCD, by detecting SI in
the antenatal setting, may ease the shock factor
parents experience upon seeing their new-born
with respiratory distress
Conclusion
Whilst acknowledging the difficulty in detecting such anomalies, we must strive to
improve imaging techniques in the primary setting to prepare for potential future
management, ease the strain on secondary and tertiary health centres and most
importantly to better prepare the families of these babies. Early detection of these
anomalies would also give a choice to mothers for continuing or terminating pregnancies
as some parents may not wish for their children to experience complications as a result
of these anomalies. Further techniques are required to improve sensitive in detecting
anomalies such as TGA and SI
References
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international journal of obstetrics and gynaecology, 2008, Vol. 115, pp. 1096-1100.
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3. Laterality defects other than situs inversus totalis in primary ciliary dyskinesia: insights into situs ambiguus and heterotaxy. Shapiro, AJ, et al. 5, s.l. : Chest,
2014, Vol. 146, pp. 1176-1186.
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Ultrasound in obstetrics & gynecology: the official journal of the International Society of Ultarsound in Obstetrics and Gynecology, 2013, Vol. 41, pp. 667-671.
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Lannering, K and Mellander, M. 6, s.l. : Acta Paediatrica, 2015, Vol. 104, pp. 557-565.
7. Image from http://radiopaedia.org/articles/situs-inversus
8. Clinical and Genetic Aspects of Primary Ciliary Dyskinesia / Kartagener Syndrome. Leigh, MW, et al. 7, s.l. : Genetic Medicine, 2009, Vol. 11, pp. 473-487.