Discussion
The association between congenital heart defects and CLE is well known,
and large left-to-right shunts are commonly associated with CHD. Cough,
tachypnea, and respiratory distress in early infancy are the usual
clinical presentations in both conditions. As CHD is more prevalent, it
is often suspected and diagnosed first. In cases where the entire
clinical constellation is attributed to CHD, the presence of CLE is only
detected after correction of the CHD. Similar cases have been reported
in the past6,7.
The etiology of CLE remains unknown in almost half of the cases. Absent
or dysplastic bronchial cartilage is evident in one-fourth of the cases.
Internal obstruction or external compression of the lobar bronchus due
to various causes is postulated in the remaining cases. These defects
cause a ball valve effect and air trapping during expiration with
progressive hyperinflation of the affected lung lobe. The hyperinflated
lobe may compress the surrounding normal lobes. In patients with severe
disease, the hyperinflated lung lobe can herniate to the surrounding
lobes as well as to the opposite thoracic cavity with tracheal and
mediastinal shifts. This reduces the respiratory reserve and causes a
ventilation/perfusion mismatch with resultant
hypoxia1,3.
In the embryo, the development of the bronchial cartilage occurs during
the 4th to 6th intrauterine weeks.
This time coincides with the developmental stage of cardiac chamber
septation. Thus, a defect during this stage can affect both the heart
and lungs1. CLE is usually secondary to bronchial
compression due to aberrant or dilated pulmonary vessels owing to
pulmonary hypertension in the presence of a large left-to-right shunt.
In this case, CLE may get resolved with the correction of the underlying
CHD5,6.
CLE continues to pose a diagnostic dilemma. The initial diagnostic
modality is usually a chest X-ray. The affected lung lobe is hyperlucent
with atelectasis of the adjacent lung lobes due to compression, and a
mediastinal shift can be seen. Though all the features are not evident
at an early age, X-ray findings are often misreported as pneumonia owing
to the crowding of the surrounding lobes, and the hyperlucency of the
affected lobe may get reported as a pneumothorax. A CTscan of the lung
is confirmatory and delineates anatomical details. Bronchoscopy may aid
the diagnosis when an internal bronchial obstruction is
suspected1-4.
Treatment of CLE involves the surgical resection of the affected lobe.
Conservative management is proposed for older children with no or
minimal symptoms. Infants with persistent distress are ideal candidates
for surgery. The surgery is generally well tolerated, with low mortality
and favorable outcomes2,8. In the case of concomitant
CLE and CHD, there are diverging views regarding the defect to be
repaired first, or whether a combined lung and cardiac repair is the
ideal approach. An individualized approach has been suggested. CLE often
gets corrected with the relaxation of the vascular compression, the
repair of the large left-to-right shunt, and the reduction of pulmonary
hypertension5,9.
In the present case, the child presented with respiratory distress.
During the assessment, clinical suspicion led us to perform 2D
echocardiography, which revealed a large VSD with moderate PDA and PAH.
The presence of a congenital lung defect was overshadowed by the
presence of a large cardiac defect. The symptoms were obviously
contributed to the heart defect.The X-ray findings were initially
interpreted as being due to pneumonia. As seen in Figure 1 (2 months of
age), there is no obvious hyperlucency of the right middle lobe; rather,
haziness is evident in the right upper lobe. In contrast, a later X-ray( Figure 2), performed at 7 months of age, clearly demonstrated
a large hyperlucent area in the right middle lobe with surrounding lobe
crowding and mediastinal shift.In retrospect, we could discern the faint
hyperlucency in Figure 1, which was initially missed. We believe that
the X-ray chest, being a basic investigation, is often given less
attention, particularly when another advanced diagnostic modality has
suggested an alternate diagnosis.
CLE is a diagnostic challenge, and the confusion can be further
augmented in the presence of an obvious large congenital heart defect.
Regular follow-up and a high index of suspicion are necessary for early
diagnosis. Lobectomy can lead to dramatic improvement and is generally
well tolerated.