Table 1 : Demographics, clinical presentation, and operative
procedure (LAA/ RAA: Left/Right aortic arch, CAVCD: Complete
atrioventricular canal defect, PAPVR: Partial anomalous venous return,
PDA: Patent ductus arteriosus, TEF: Tracheo-esophageal fistula, CPB:
Cardiopulmonary bypass).
Discussion : AA for IAS was first described by Gross in
1948[1]. The patient was a 4 month-old female infant who had
recurrent episodes of severe respiratory distress and respiratory tract
infections. The AA was performed through a left anterior thoracotomy
approach. After a partial thymectomy, an abnormal leftward arising
innominate artery was fixed to the retrosterum. The operation was
successful with complete relief of the symptoms. Since then, various
approaches to AA have been described such a left or right thoracotomy, a
thoracoscopic approach, a full median sternotomy and a partial upper
median sternotomy [4, 6]. Our preferred technique is the partial
upper median sternotomy.
IAS is thought to be due to an abnormal innominate artery arising
distally along the aortic arch and hence crossing the trachea anteriorly
from a left to right direction. This leads to a potential for a
compressive effect and is further facilitated by overcrowding of the
upper mediastinum due to the presence of a large thymus especially in
the younger children [5, 7].
Common symptoms include stridor, reflex apnea (a sudden respiratory
arrest cause by an irritation of the area of compression), and recurrent
respiratory tract infections. It can also present as failure to wean
from mechanical ventilation. Stridor by itself is not an indication.
Strong indication for surgery are reflex apnea, two or more episodes of
infection, severe compression (> 70% luminal reduction),
and dependence on mechanical ventilation. Of these, reflex apnea is the
strongest indication for an intervention as it can lead to mortality
[2, 3].
IAS is diagnosed by flexible bronchoscopy, which shows an anterior
pulsatile compression in the distal trachea. Besides this, a flexible
bronchoscopy facilitates the conduct of the AA operation. It helps
determine the number and position of the anchoring sutures and helps
evaluate the result of the AA by assessing the degree of resolution of
IAS (Figure 1 ). Cross-sectional imaging such as a CT angiogram
or an MRI is obtained to further evaluate the anatomy (Figure
2 ).
A partial upper median sternotomy approach to an AA for tracheomalcia
from various causes has been previously described by Elliot
[6]. In this paper, we describe our technique for AAselectively for IAS. This has become our preferred approach for
the following reasons. Firstly, it facilitates the performance of a
complete thymectomy. The bilateral phrenic nerves are better visualized
and thus at a lesser risk for injury. A complete thymectomy is central
to the success of the operation as it increases the available
anteroposterior dimension in the upper mediastinum as often these
children have a large thymus gland. Without a thymectomy, the degree to
which the innominate artery moves towards the sternum is limited and
thus the distracting force on the trachea. Secondly, the goal is to get
a good anatomic result by accepting only a ≤20 % residual stenosis
after an AA. This was evident in our study as the patients who did not
achieve a technical success needed an alternative procedure. If this not
achieved, one needs to look for alternative factors such as an intrinsic
tracheal pathology. A partial sternotomy approach facilitates this as it
is easy to convert to a full sternotomy and explore the anterior surface
of the trachea between the SVC and the aorta as compared to a
thoracotomy approach. In one case, the patient had an intrinsic tracheal
stenosis due to isolated tracheal cartilage deficiency which was not
diagnosed preoperatively and required a tracheal resection and has been
previously published by us [8]. Thirdly, the anatomy of the
innominate artery is better appreciated by this approach. Alternative to
an AA to treat IAS is an innominate artery reimplantation procedure. As
previously described, the innominate artery in IAS arises further
leftward along the aortic arch. Hence, it crosses anterior to the
trachea from a left to right direction compressing it anteriorly. The
innominate artery can be reimplanted in an off- pump manner by
re-implanting the artery 1 cm proximal on the greater curvature of the
aorta rightward of the trachea [5, 7].Such an reimplantation has an
immediate effect of relieving the compression with no long-term
consequence [5]. Only one patient needed this approach in this
series after a test AA failed to produce an optimal result. Again, a
midline approach as compared to the thoracotomy approach greatly
facilitated this operation as this approach requires a median
sternotomy. Fourthly, a full sternotomy is unnecessary as the operative
procedure is limited to the upper mediastinum and an upper partial
sternotomy actually facilitates when a future re-sternotomy is needed
arises as described next.
AA by an upper partial median sternotomy does not preclude a repeat
sternotomy if certain precautions are taken. In an infant with Down
syndrome, prune belly syndrome, complete atrioventricular canal defect
and recurrent failure to wean from mechanical ventilation, an AA was
performed at age 2 months and a complete repair of the canal defect was
performed at age 8 months. The patient did well after the aortopexy and
was liberated from mechanical ventilation. At redo sternotomy, because
the lower pericardium and the sternum were intact after the initial
surgery, an easy retrosternal plane could be established and the
posterior sternal table in the region of the aortopexy was divided under
direct vision by deviating rightwards of it. The repair was intact and
did not interfere with the canal repair. As previously described, if the
aortic arch is left sided, then the innominate artery is fixed to the
left half of the sternal table, distracting it away from the trachea in
an anterior and leftward fashion and if the aortic arch is right sided,
the aortopexy is done to the right half of the sternotomy. This also
helps with a future redosterntomy as the innominate artery is not fixed
across the sternotomy incision.
It is critical not to develop a pretacheal plane and we believe is
another key step for a successful AA. By dissecting the innominate
artery circumferentially away from the trachea, the compressive effect
will be relieved. However, if severe tracheomalcia is present, it will
lead to collapse of the anterior wall of the trachea. Pulling the
innominate artery anteriorly, besides producing a distracting
compression relieving effect on the trachea, has an additional
suspensory effect. This was evident in the original description by Gross
[1] where a residual tracheal stenosis was seen due to underlying
tracheomalacia due to such as circumferential dissection of the artery.
The composite suture technique simplifies the operation. While fine
sutures are used on the artery, heavy sutures are used for the AA. If
the suspension sutures were to snap, they can be easily replaced before
the sternum is closed.
The strengths of the study are the description of the technical pearls
and pitfalls for a successful AA via an upper partial sternotomy as
evidenced by the good operative outcomes. The limitations are the small
sample size, absence of a comparator such as another technique for an AA
and lack of long-term follow up.
Conclusion : An upper partial sternotomy approach provides a
very versatile approach to an AA for IAS. Besides facilitating an
adequate AA, it provides options for direct tracheal surgery or an
innominate artery reimplantation in case an optimal result is not
obtained by an AA.
Funding Source : None
Conflict of Interest : None
Ethics Statement : The study is a retrospective review of a
prospectively maintained de-identified database. No further chart-review
or any form of patient contact was attempted for this study and hence is
IRB exempt. The study was not part of any research protocol and written
informed consent was obtained for the operative procedures. No portions
of the manuscript and the submitted pictures have any information that
can lead to identification of the patient as per the Healthcare
Insurance Portability and Accountability ACT of (HIPAA) 1996.