Left Pulmonary Artery Sling Associated with Patent Ductus Arteriosus and Atrial Septal Defect: Evaluation with Multidetector CT

doi:10.4236/act.2012.13004

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Advances in Computed Tomography, 2012, 1, 17-20

http://dx.doi.org/10.4236/act.2012.13004 Published Online December 2012 (http://www.SciRP.org/journal/act)

Left Pulmonary Artery Sling Associated with Patent

Ductus Arteriosus and Atrial Septal

Defect: Evaluation with Multidetector CT

Rukeshman Shakya, Jianhua Liu, Xiaolin Xu, Mohit Godar, Qinghai Yuan

Department of Radiology, The Second Hospital of Jilin University, Changchun, China

Email: [email protected]

Received October 16, 2012; revised November 18, 2012; accepted November 26, 2012

ABSTRACT

We report a case of left pulmonary artery sling associated with patent ductus arteriosus and atrial septal defect in a

21-month-old child. 256-slice MDCT provides valuable information, such as abnormal origin of the left pulmonary ar-

tery, the relationship between pulmonary artery and airway, the diameter of the patent ductus artery and atrial septal

defect. The information is helpful in d iagnosis, pre-operative evaluation and post-operative follow-up of LPS.

Keywords: Left Pulmonary Artery Sling; Patent Ductus Arteriosus; Atrial Septal Defect; Multidetector CT;

CT Angiography

1. Introduction

The left pulmonary artery sling (LPS) is a rare congenital

abnormality, and is defined as that the LPA arising from

the posterior aspect of RPA, crossing over the right

mainstem bronchus near its origin, and coursing leftward

between the trachea and esophagus to enter the left

hemithorax. Atrial Septal Defect (ASD) is a congenital

heart disease in which abnormal blood flows between left

atrium and right atrium through defect in interatrial sep-

tum. Patent Ductus Arteriosus (PDA) is heart problem

that occurs due to abnormal blood flow between aorta

and pulmonary artery caused by persistent ductus arteri-

osus (tube) which didn’t close soon after child birth or

after few days.

The clinical manifestations of left pulmonary artery

sling are mild or occasional stridor, breathless, inspira-

tory and expiratory rhonchi, productive cough, cyanosis,

difficulty in feeding. It is due to external compression of

trachea or severe compression from complete tracheal

rings. Hypoplasia of entire tracheobronchial tree or res-

piratory distress with pneumonia, atelectasis, intercostal

recession or air trapping may occur. When it is associ-

ated with ASD and PDA, patient can present with short-

ness of breath, swelling of limbs, systolic ejection mur-

mur, wide splitting of P2, accentuation of right precordial

thrust, hoarse cry, cough, lower respiratory tract infec-

tions, failure to thrive, tachypnea, atelectasis or pneumo-

nia. We report a rare case of LPS associated with patent

ductus arteriosus and atrial septal defect.

2. Case Report

A 21-month-old child presented to the pediatric depart-

ment with recurrent cough for half a year and aggrava-

tion of the symptoms with wheezing for 3 days. She was

admitted after being diagnosed with lobar pneumonia on

chest radiography and CT (Figures 1(a)-(c)). The medi-

cal history revealed recurrent episodes of productive cough

with fever, and on auscultation, continuous systolic mur-

mur was heard along the upper left sternal border. Echo-

cardiography showed a patent ductus artery (PDA) and

atrial septal defect (ASD) (Figures 1(d) and (e)).

Two weeks later, after recovery from pneumonia

(Figure 1(f)), the patient was transferred to the depart-

ment of cardiac surgery. CT angiography (CTA) was

done using a 256-slice MDCT scanner both for diagnos-

tic and pre-operative evaluation (Figures 2(a)-(e)). CTA

showed a left pulmonary artery sling (PAS) associated

with PDA and ASD. During surgery, the pulmonary ar-

tery and aorta were separated and the patent ductus arte-

riosus was doubly ligated and divided. The left pulmo-

nary artery was dissected circumferentially to the hilar

branches, and then anastomosed to the origin of PDA

(Figure 2(f)). The ASD was also repaired. Two weeks

later, the patient was discharged without complication.

The case report was approved by the patient’s parents.

3. Discussion

Aberrant left pulmonary artery (LPA) from the right

pulmonary artery (RPA) is arare congen ital abnormality.

R. SHAKYA ET AL.

Figure 1. (a) Chest radiograph posteroanterior view shows prominent plumonary arterial segment (curved black arrow),

patchy density in the le ft lower field (white arrow ) and right upper field (c urved white arrow); (b) CT axial view shows high

density of the right upper lobe (arrow); (c) CT axial view shows irregular high density of the left lower lobe (w hite arr ow ); (d)

The color ultrasound shows PDA (curved white arrow), enlarged pulmonary trunk (white arrow) and normal aorta (white

star); (e) The color ultrasound shows a obvious left-to-right shunt (white arrow) from left atrium (white star) to right atrium

(curved white arrow); (f) CT axial view shows normal left lowe r lo be aft er treatmen t.

Figure 2. (a) CTA axial view shows left pulmonary artery from the right pulmonary artery (white arrow) and slightly stenosis

of the trachea, the diameter of plumonary trunk is 23.6 mm; (b) Multiplanar reconstruction (MPR) CTA image shows the

patent ductus arte ry (white arrow ) and enlarged plumonar y trunk (curve d white arrow); (c ) CTA axial view shows the atrial

septal defect (arrow ); (d) Volume rendering image shows the LPS (white star), enlarged plumonary trunk (cur ved white ar-

row), the patent ductus artery (white arrow); (e) Volume rendering image shows the slightly stenosis of the trachea (curved

hite arrow); (f) Volume rendering image shows left pulmonary artery from the pulmonar y trunk (white star). w

R. SHAKYA ET AL. 19

The concept of vascular sling was first introduced for

differe nt iation fr om vascular ri ng.

According to the location of the LPS, it is classified

into two types [1]. The type 1 is defined by the location

of the LPS (levels of T4-T5), then regarding the course

of the tracheal bronchus (TB), the type 1 is divided into

subtype 1A (the course of TB is normal) and subtype 1B

(with additional upper TB). Type 2 is defined by a more

caudal location of LPS (level of T6) and then according

to the existence of the right upper lobe bronchus. Type 2

is further classified into subtype 2A (with normal upper

lobe bronchus) and subtype 2B (without existence of

upper lobe bronchus). Because of the lower location of

the LPS, one to three pulmonary lobes are supplied by a

single bronchus arising fr om the left bron chus, and this is

known as “bridging bronchus”. Our case belongs to the

subtype 1B .

Multidetector CT is recent technical advance in helical

CT imaging. It is performed by moving the patient table

through the CT gantry at a constant speed during con-

tinuous scanning with x-ray tube rotating around the pa-

tient and includes multiple rows of detector rings. It al-

lows acquisition of thin multiple slices creating isotropic

voxels from which reconstruction of image can be done

in different anatomic planes without loss of resolution.

CT Angiography is a diagnostic test that uses CT scanner

and contrast materials which is administered as rapid

bolus through a small catheter placed in a vein of the arm.

CT scan is then performed during contrast material flows

through the blood vessels to various organs which will

increase CT numbers of blood vessels and can be isolated

from low density structures producing 3-dimensional

images of the blood vessels and su rrounding tissues after

reconstructed in different planes by usin g c omputer.

Radiologic examinations play an important role in dia-

gnosis of LPS. Usually a multi-modality approach, such

as chest radiograph y, echocardiography, esophagogr aphy,

computed tomography angiography (CTA), and magnetic

resonance angiography (MRA) are used for diagnostic

work-up [2]. CTA and MRA have almost replaced con-

ventional ang iography for diagnosis, and the sens itivities

of these techniques are nearly 100% [3]. Although MRA

has advantage of non-ionizing radiation exposure, MRA

usually needs long scan time requiring deep conscious

sedation or anesthesia in uncooperative children. MRA

also has a limited role in visualization of the airway and

lung parenchyma. However, CTA can reduce the scan

time significantly to nearly 2.0 sec with conventional

helical protocol and 3.95 sec with prospective ECG-gat-

ing protocol as in our case. CTA also has advantage of

evaluating the trachea. CTA shows detailed information

of the relationship between pulmonary artery and airway

with post processing techniques as in this case. CTA is

also helpful in pre-operative evaluation and post-opera-

tive follow-u p [4]. Although CTA bears th e burden of ra-

diation exposure, a variety of techniques had been used

to reduce the radiatio n dose [5].

There are no adverse effects which could be seen in

this patient. But there maybe adverse effect, one is about

the radiation dose, because the children are more sensi-

tive to the radiation dose in comparison to the adult.

However, the benefit from CTA is more than the adverse

effect as mentioned to pre-operation evaluation.

Management of LPS is based on anatomical classifica-

tion and symptoms. Asymptomatic Type 1 patients can

be followed clinically, and those with respiratory symp-

toms are appropriate for surgery [6]. Because of the

lower mortality and morbidity than other techniques,

slide tracheoplasty is currently regarded as the choice of

surgical repair [7].

The prognosis of PAS is variable according to clinical

presentation. Asymptomatic patients have an excellent

prognosis compared with symptomatic patients [8]. Fiore

et al. [9] reported a 79% survival rate in patients with

surgery.

4. Conclusion

CTA with its multi reconstruction techniques is a valu-

able tool for diagnostic, pre-operative evaluation and

post-operative follow-up of LPS.

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