CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 5, September/October 2011
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AFRICA
vessels which supplied all three lung segments on the right side
were slightly elevated, with a systolic pressure of 35 mmHg and
the mean pressure 19 mmHg. The patient was not offered any
further treatment.
Case 2
The second case was a six and a half-year-old female patient who
presented with anomalous origin of the left pulmonary artery
from the ascending aorta, pulmonary atresia with a ventricular
septal defect (VSD), associated again with MAPCAs as the only
supply to the right lung. She was diagnosed with this problem
as a newborn baby. Unfortunately, she was lost to follow up and
presented at six and a half years with worsening cyanosis and
decreased effort tolerance.
Clinically, she had no dysmorphism. She was cyanosed with
pulse oximetry saturations of 85% at room air. There was associ-
ated digital clubbing. The precordium was bulging with a later-
ally displaced apex. The second heart sound was loud and single,
and there was a three-sixth ejection systolic murmur over the left
upper parasternal border. There was no evidence of congestive
cardiac failure.
On chest X-ray, the cardiothoracic ratio was slightly increased
at 62%, there was a left arch of the aorta, and the pulmonary
artery segment was absent. Of note in this patient as well,
there was differential perfusion with plethoric left lung fields
compared to the right. The electrocardiogram revealed features
of left atrial and left ventricular hypertrophy.
On echocardiographic assessment, there was a large sub-
aortic mal-aligned VSD with 50% aortic override and bidirec-
tional shunting across the VSD. The ventricles were balanced
in size and the left atrium was dilated, with a left atrium:aortic
index of 2.6. There was associated pulmonary atresia. The left
pulmonary artery was noted to be arising from the ascending
aorta just above the sino-tubular junction and both the main
and the right pulmonary arteries were not seen. At cardiac cath-
eterisation, the systemic arterial saturations were low at 67%, in
keeping with a mixing situation. There were balanced ventricular
pressures with a systolic pressure of 82 mmHg. As expected, the
AOLPA pressures were systemic at 82 mmHg as well.
Angiography confirmed the echocardiographic findings of
pulmonary atresia with a VSD, associated with an anomalous
origin of the left pulmonary artery from the ascending aorta.
There were no native pulmonary arteries supplying the right
lung that were seen, and the only source of blood supply to the
right lung was the partially stenosed MAPCAs arising from the
descending thoracic aorta. This patient was managed conserva-
tively as well.
Discussion
The presentation of a single pulmonary artery arising directly
from the ascending aorta is very rare, and even less common is
the entity of AOLPA. Besides the well-known association with
tetralogy of Fallot, AOLPA is usually associated with right-sided
aortic arch and an absent patent ductus arteriosus (PDA).
1
By
contrast, the case study patients presented with a left arching
aorta.
1,6,8
A frequent association of AORPA is the CATCH 22
syndrome,
7,9-14
which was not found in one of our cases, based
on the absence of the 22q11 deletion anomaly following a
fluorescent immuno-sorbent hybridisation (FISH) chromosomal
analysis. The other patient was not tested for this chromosomal
aberration.
Only one case has been reported in the literature where
AOLPA and tetralogy of Fallot with membranous pulmonary
atresia was diagnosed.
7
In this patient, there were well-developed
central pulmonary arteries and the patient underwent successful
complete surgical repair. The aetiology of AOPA is unclear, but
one case of AORPA has been reported to be associated with
foetal valproate syndrome.
15
The pathogenesis of anomalous pulmonary artery origin from
the aorta is said to be related to an abnormality in the develop-
ment of the aortic or branchial arches.
1,6
The failure of resorp-
tion of the fifth branchial arch and the presence of the sixth
brachial arch usually lead to the anomalous origin of the right
pulmonary artery from the aorta.
1,6
By contrast, the anomalous
origin of the left pulmonary artery from the aorta is reported to
be due to developmental absence of the fifth and sixth branchial
arches. Abnormalities of the branchial or aortic arches are asso-
ciated with neural crest cell aberrations and therefore may be
associated with the CATCH 22 syndrome.
7,9-14
Precursors of the
trunco-aortic sac are mainly of mesodermal origin,
16
therefore
AOPA is unlikely to be associated with the trunco-aortic sac
abnormalities.
1
The origin of AOPA, anatomically is usually very proximal,
arising from ascending aorta just distal to the aortic sinus.
1,2,7,17
Other origins of the pulmonary arteries such as at the base of the
innominate artery or from a patent ductus arteriosus, or from the
thoracic aorta distal to the subclavian artery have been described
and can be labelled as ‘distal types of AOPA’ and are not the
same entity that is described in this case report.
18
The clinical presentation is that of a significant left-to-right
shunt with early and rapidly progressive pulmonary hypertension
with or without right-sided heart failure.
3,14,19,20
The pulmonary
vascular disease affects both lungs, and may be seen as early as
three months of age.
20
The mechanism by which both lungs are
affected involves neurogenic crossover from the involved lung to
affect the protected lung, thereby producing reflex vasoconstric-
tion in the protected lung.
3,7,20
Diastolic run-off due to shunting
of blood away from the aorta in to the aberrant pulmonary artery
may affect coronary perfusion and result in left ventricular
dysfunction.
14
The diagnosis of AOPA can easily be achieved by careful
echocardiography.
7,10,21-24
Other imaging modalities such as cine-
angiography
21,22,25
or magnetic resonance angiography have also
been used.
26
Due to the rapid development of irreversible pulmo-
nary vascular disease in infancy and associated high mortality
in the patients presenting with AOPA, re-implantation of the
pulmonary artery is an operation that needs to be performed
within the first year of life.
2,3,8,10,27
Conclusion
Anomalous origin of the pulmonary arteries from the ascending
aorta, and more specifically, the left pulmonary artery is a rare
entity, which can be diagnosed with readily available imaging
modalities. The management is surgical re-implantation of the
anomalous vessel, but it may provide a management challenge
if complicated by pulmonary hypertension or other associations
such as pulmonary atresia with collateral vessels.
