Keywords
neonatology - perinatology - pediatric cardiology - pulmonology
Case History
A 37 weeks' gestation male infant was born to a 31 years old gravida 2, para 1 mother
with a dichorionic diamniotic twin pregnancy. Parents were nonconsanguineous and family
history was noncontributory. She had a spontaneous healthy pregnancy with protective
antenatal serology. Her Group B streptococcus (GBS) status was unknown and gestational
diabetes screen was normal. First trimester screening for trisomy 18, 13, and 21 was
negative. At 20 weeks' gestation, ultrasound findings were suggestive of partial anomalous
pulmonary venous return (PAPVR) and suspected coarctation of aorta for twin A. There
was, however, no growth discordance between the twins.
A fetal echocardiogram at 26 weeks and 6 days' gestation age confirmed findings of
PAPVR with right inferior pulmonary vein draining into the right atrium, narrowing/hypoplasia
of the right branch of pulmonary artery, and a suspicion of coarctation of the aorta.
Subsequent ultrasounds confirmed cardiac findings in twin A with growth restriction
at 35 weeks' gestation. Both twins had ultrasounds findings of normal amniotic fluid
indices and biophysical profiles.
The twins were born at 37 weeks' gestation by cesarean section because of evolving
growth discordance. Twin B weighed 3.5 kg at birth with no respiratory distress and
preductal oxygen saturations of 90% in room air. Twin B remained well to discharge
home.
Twin A had a decreased breath sounds in the right hemithorax with an ejection systolic
murmur of grade 3/6 intensity heard in the pulmonary area. Heart rate was 160/min
and blood pressure in the right arm was 65/40 mm Hg. Lower limbs were cool to touch
with weak femoral and posterior tibial arterial pulsation. Preductal blood pressure
measured with right arm: 64/36, mean 48 mm Hg, while postductal blood pressure measured
with right leg: 54/28, mean 37 mm Hg.
Postnatal echocardiography confirmed coarctation of the isthmus of the aorta, following
which a prostaglandin infusion was started. He required a maximum of 1 L/min of nasal
cannula flow with 25% fraction of inspired oxygen (FiO2) to maintain preductal oxygen saturations greater than 90%. The first chest X-ray
([Fig. 1]) showed atelectasis of the right hemithorax with a mediastinal shift to the right
which raised concern of the diagnosis of scimitar syndrome. A chest computed tomography
(CT) angiogram performed on day 3 of life showed hypoplastic right lung ([Fig. 2]) with only two bronchi, a hypoplastic right pulmonary artery and PAPVR of the right
pulmonary vein to the inferior vena cava (IVC) essentially at the level of the atrial–caval
junction ([Figs. 3]
[4]
[5]). There were no identified systemic collaterals, or evidence of scimitar vein stenosis.
Imaging of the lung bases demonstrated no evidence of a sequestration, but definite
leftward herniation of the medial basal right lower lung parenchyma across the midline
was present in the central inferior chest anterior to the distal esophagus and descending
thoracic aorta, consistent with the presence of a pseudohorseshoe lung malformation
([Figs. 6] and [7]).
Fig. 1 Anteroposterior (AP) supine chest radiograph: There is abnormal added dense opacity
and volume loss in the right hemithorax. The left heart border and cardiac size are
normal. There is no focal abnormality of the left lung or bony thorax. Decreased right
thoracic loss of volume may suggest hypogenetic lung in a child with known partial
anomalous pulmonary venous return (PAPVR).
Fig. 2 Axial chest computed tomography (CT) angiogram (lung windows): The right lung is
small compared with the normal sized left lung and the mediastinal structures are
shifted rightwards due to volume loss in the right thorax. The right pulmonary artery
is small/hypoplastic (open arrow) compared with left pulmonary artery (black arrow).
Fig. 3 Axial image from contrast-enhanced computed tomography (CT) chest (lung windows)
showing small right lower lung and anomalous pulmonary venous drainage (scimitar vein)
draining into the posterior inferior vena cava (IVC) near the level of the junction
with the right atrium.
Fig. 4 Maximum intensity projection (MIP) sagittal reformatted contrast-enhanced computed
tomography (CT) image demonstrates abnormal obliquely and vertically oriented draining
vein from the right lower lobe entering the posterior aspect of inferior vena cava
(IVC) at its junction with the right atrium.
Fig. 5 Maximum intensity projection (MIP) coronal reformatted contrast-enhanced computed
tomography (CT) image demonstrates abnormal pulmonary venous drainage. The right inferior
pulmonary vein is joining the posterolateral aspect of the right atrium/superior vena
cava (RA/SVC) junction.
Fig. 6 Contrast-enhanced computed tomography (CT) chest maximum intensity projection (MIP)
sagittal reformatted image demonstrating coarctation of the distal transverse aorta
at the isthmus (black arrow).
Fig. 7 Axial image from contrast-enhanced computed tomography (CT) chest (lung windows)
showing bulging pulmonary parenchyma (isthmus) from the medial right lung base crossing
the midline with adjacent enveloping pleural reflection or pseudohorseshoe lung (open
arrow). No abnormal contralateral bronchi or pulmonary arterial branches were detected.
A nonstenotic bicuspid aortic valve and coarctation of aorta with hypoplasia of the
distal aortic arch were identified. Subsequent echocardiography studies demonstrated
increased pulmonary pressure, a large patent ductus arteriosus (PDA) and a small anterior
muscular ventricular septal defect (VSD). In our case, the PAPVR anomaly included
one of the pulmonary veins draining into the right atrium that was detected antenatally,
and another pulmonary vein draining to the IVC at the level of the atrial–caval junction,
as per the chest CT angiogram findings.
He had surgical repair of the aortic coarctation by subclavian arterial flap repair
on day 16 of age. Pulmonary hypertension improved on sildenafil following successful
postoperative extubation.
Discussion
Scimitar syndrome was first described in 1836 by George Cooper during the autopsy
of a 10-month-old infant. The incidence of scimitar syndrome is estimated at 1 to
3/100,000 live births.[1]
[2] However, its true incidence may be much higher as some of those affected may be
asymptomatic.
The diagnosis is made by echocardiography, characteristic chest X-ray findings, and
confirmatory CT chest findings. CT chest angiography provides excellent visualization
of the vascular anatomy of this complex congenital defect noninvasively.[3]
Scimitar syndrome is a rare association of congenital cardiopulmonary anomalies characterized
by anomalous pulmonary veins (scimitar vein) that drains into the IVC, a hypoplastic
right lung, and dextroposition of the heart. It has been reported in 3 to 6% of patients
with partial anomalous pulmonary venous connection. Patients are either diagnosed
early with severe symptoms (infantile type) or late with minimal symptoms (childhood/adult
type).[4]
[5]
Schramel et al recognized two different types of scimitar veins: type 1 is simple
classic vein that runs from the middle of the right lung to the cardiophrenic angle
and type 2 is double arched vein in the upper and lower lung zones, with drainage
into the left atrium and inferior caval vein.[4]
[5]
The presentation of the syndrome could be as early as immediately after birth, and
the diagnosis should be suspected when the signs of respiratory distress and/or heart
failure are present in association with radiological findings of cardiac dextroposition
and haziness or suspicion of atelectasis of the right lung.[6]
Scimitar syndrome often presents as an isolated finding with a benign outcome; however,
when associated with other cardiac defects and pulmonary arterial hypertension, there
is an increased risk of congestive heart failure and mortality. The etiology of pulmonary
hypertension in infants with scimitar syndrome is variable and may be related to a
decreased right-sided pulmonary vascular bed, scimitar vein stenosis, and unappreciated
systemic collateral blood flow along with intracardiac shunts, or additional comorbidities,
such as developmental lung disease. Horseshoe lung is a rare pulmonary malformation
associated with scimitar syndrome. Eighty percent of reported cases occur in patients
with congenital pulmonary venolobar (scimitar) syndrome.[7] Typical features of horseshoe lung include an isthmus of the pulmonary parenchymal
tissue arising from the right lung base, bridging the right and left lungs, which
resides posterior to the inferior aspect of the middle mediastinum. Pulmonary arterial
and bronchial supply extend from the right lower lobe pulmonary artery and bronchus.
It has been suggested that when the isthmus is completely encased in a pleural membrane,
as it was in our patient, this be termed pseudohorseshoe lung.[8]
Pulmonary hypertension is a problem seen in infants and older children with scimitar
syndrome.[9] The age of presentation and the presence of associated anomalies are important in
predicting the outcome. In general, presentation in infancy and presence of heart
failure are poor prognostic factors.
The combination of scimitar syndrome with aortic coarctation is rare, with only few
cases reported.[10]
[11]
[12] The literature describes the correction of associated cardiac defects with the therapeutic
occlusion of anomalous arterial supply to the affected lung can led to benign outcomes
comparable to that in primarily isolated forms.[13]
We did a review of literature of published cases with scimitar syndrome that associated
with aortic arch abnormalities ([Table 1]).
Table 1
Review of literature of published cases with scimitar syndrome that associated with
aortic arch abnormalities
|
Author
|
Year
|
Number of cases
|
Cardiac anomaly
|
Outcome
|
|
Gikonyo et al[14]
|
1986
|
2
|
Case #1: Bicuspid aortic valve, tubular hypoplasia of aortic arch, ASD, VSD, PDA.
Persistent left superior vena cava to coronary sinus
|
Died at the age of 7 d in a state of congestive failure following right
ventricular angiography
|
|
Case # 2:
Tubular hypoplasia of aortic arch, VSD, PDA, anomalous venous drainage
|
Experienced intraoperative cardiac arrest, and resuscitation was unsuccessful
|
|
Oshima et al[12]
|
2003
|
1
|
Coarctation of aorta, extremely hypoplastic right pulmonary artery and right lung,
pulmonary sequestration, and ASD
|
At 35 d of life, patient underwent successful repair of coarctation and PAPVR
|
|
Marcondes et al[15]
|
2014
|
1
|
Mild aortic arch hypoplasia, no coarctation, PAPVR; hypoplastic right pulmonary artery.
Aortopulmonary collaterals arising from the descending aorta
|
At 7 wk of life patient underwent successful surgical repair
|
|
Rezaei et al[16]
|
2016
|
1
|
Coarctation of aorta, right pulmonary artery stenosis, and right to left ductus arteriosus
flow
|
Discharged on day 22nd of life postcoarctation correction
|
Abbreviations: ASD, atrial septal defect; PAPVR, partial anomalous pulmonary venous
return; PDA, patent ductus arteriosus; VSD, ventricular septal defect.
Conclusion
Although scimitar syndrome has been described in the literature, it is rare and variable
in its presentation, especially in the neonatal period. This diagnosis should be considered
when right-sided “atelectasis” does not improve or when dextroposition of the heart
is associated with right lung hypoplasia. Scimitar syndrome can be associated with
cardiac anomalies but only few cases are reported with aortic coarctation. Our case
report highlights this rare combination.
