Bronchial Compression due to Dilated Branch Pulmonary Artery in Tetralogy of Fallot with Absent Pulmonary Valve

INTRODUCTION

Tetralogy of Fallot (TOF) is one of the most common cyanotic congenital heart diseases. However, the association of TOF with additional anomalies such as atrial septal defect, absent pulmonary valve (APV), pulmonary hypoplasia, coronary anomalies, and persistent left-sided superior vena cava remains relatively rare but clinically significant.

TOF with APV (TOF-APV) is an uncommon form of TOF, accounting for approximately 3–6% of all TOF cases.^[1] It is characterized by absent or rudimentary pulmonary valve cusps or leaflets, severe pulmonary valve incompetence, annular pulmonary stenosis, and dilatation of the pulmonary arteries (PAs), leading to a varying degree of airway compression.^[2,3]

This case highlights a late-presenting child with TOF-APV and severe unilateral bronchial compression. The report is intended to emphasize the role of pre-operative airway assessment, intraoperative bronchoscopy, and post-operative respiratory follow-up in selected patients with complex airway compromise.

CASE REPORT

A 9-year-3-month-old female child was admitted with failure to thrive and recurrent respiratory tract infections. The intracardiac defect had been detected at 2 months of age during evaluation for recurrent infections, and echocardiography at 9 months of age confirmed TOF with APVS. Surgical repair had been advised at that time, but the child continued to have recurrent chest infections throughout childhood and was brought for operative correction later in life. There was no history of prior bronchial intervention, endobronchial stenting, or surgical airway procedure.

She was born at term by normal vaginal delivery with a birth weight of 2.5 kg. At the time of admission, she weighed 14.7 kg and appeared severely malnourished. On clinical examination, she was noted to have signs of chronic cardiopulmonary disease with a to-and-fro murmur and a prominent systolic murmur best heard along the upper and mid-left sternal borders. The respiratory examination was notable for reduced air entry over the left hemithorax. The overall evaluation suggested a congenital heart defect with significant pulmonary involvement and possible chronic left lung volume loss. A pre-operative chest radiograph showed perihilar infiltrates and prominent bronchovascular markings on the right side and left middle and lower lobar atelectasis. The patient is in a post-surgical state with multiple drains and devices present, indicating therapeutic success [Figure 1].

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Figure 1: (a) Baseline chest radiograph showing right perihilar infiltrates (yellow arrows), prominent broncho-vascular markings (yellow arrowheads), and total left middle and lower lobar atelectasis (red double-headed arrow). (b) POD 0: Initial post-op film showing partial re-inflation of the left lung (blue arrow). (c) Post-operative chest radiograph showing right-sided pulmonary infiltrates (green arrow), left-sided pulmonary opacities/infiltrates (green star), focal atelectatic change (light green arrow), and ECMO cannulae/ lines (green arrowheads (d) POD 2: Stable near-normal lungs (white arrows). POD: Post operative days, ECMO: Extracorporeal membrane oxygenation.

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Transthoracic echocardiography showed situs solitus, levocardia, atrioventricular and ventriculo-arterial concordance, normal systemic and pulmonary venous drainage, a large subaortic ventricular septal defect, aortic override of 50%, APV with severe pulmonary stenosis (peak systolic gradient = 85 mmHg), and moderate pulmonary regurgitation. The PAs were confluent, with aneurysmal dilatation of the main pulmonary artery. Biventricular systolic function was preserved.

Computed tomographic (CT) angiography confirmed the diagnosis of TOF-APVS and demonstrated gross dilatation of the main, right, and left PAs [Figure 2]. The main pulmonary artery measured 55 mm, the right pulmonary artery 33.5 mm, and the left pulmonary artery 30 mm. The left pulmonary artery showed abrupt tapering, likely reflecting long-standing left lung collapse. Marked compression of the left main bronchus by the dilated PAs was seen, with non-visualization of the distal bronchial tree beyond the compressed segment. There was complete collapse and consolidation of the left lung with ipsilateral mediastinal shift and rib crowding [Figure 3]. Mild anteroposterior indentation of the left main coronary artery was also noted from the surrounding mediastinal structures. The imaging findings raised concern for chronic bronchial compression with possible irreversible airway narrowing.

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Figure 2: Cinematic volume rendered images as seen from (a) front and (b) back show aneurysmal dilatation of the main pulmonary artery (MPA) and the right pulmonary artery (RPA) in a patient with tetralogy of Fallot - absent pulmonary valve syndrome. The right panel shows abrupt tapering of the left pulmonary artery (LPA) (black arrow) and normal arborization of RPA is also seen.

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Figure 3: Multiplanar reconstructed (a) oblique axial view and (b) minimum intensity airway view show abrupt tapering and compression of the left main bronchus due to a grossly dilated pulmonary artery, white arrow in (a), and completely collapsed left lung and hyperinflated right lung.

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The patient underwent complete repair of TOF with pulmonary valve reconstruction. Following median sternotomy and cardiopulmonary bypass, the subaortic ventricular septal defect was closed with a Dacron patch, infundibular muscle bundles were resected, and pulmonary valve reconstruction was performed using the planned Nunn’s bi-leaflet technique. The dilated pulmonary artery segments were addressed with reduction arterioplasty to reduce the vascular cause of airway compression.

After anesthesia induction and endotracheal intubation (with 5.5 mm ID cuffed endotracheal tube), the patient was evaluated with a flexible intubation videoscope (Karl Storz Flexible intubation video endoscope 4 mm × 65 cm, 11302 BDXK) [Karl Storz Endoskope] which showed significant narrowing of the entire left main stem bronchus. Intraoperative bronchoscopy confirmed that the airway narrowing was predominantly extrinsic and chronic in nature. The decision was made not to attempt bronchial stenting because the lesion was not considered amenable to immediate endobronchial intervention in the operative setting, and adequate oxygenation was maintained through the right lung.

Following completion of the cardiac repair and separation from cardiopulmonary bypass, the patient was hemodynamically stable. A repeat bronchoscopy revealed persistent narrowing of the left main bronchus. On gentle advancement of the bronchoscope, the left upper lobe bronchus was partially patent, but the lower lobe bronchus was completely obstructed by a tenacious whitish mucus plug. Suctioning was not attempted because the plug was likely to be densely adherent, and the working channel of the bronchoscope was inadequate for effective evacuation. The right lung provided satisfactory ventilation and oxygenation with standard ventilatory settings.

The child was transferred to the intensive care unit on pressure-regulated volume control ventilation, followed by synchronized intermittent mandatory ventilation. Ventilatory support was provided with a tidal volume of 8–10 mL/kg and positive end-expiratory pressure of 5 cm H₂O. Intermittent lung recruitment maneuvers were used. Serial post-operative chest radiographs showed progressive re-expansion of the left lung. She was extubated successfully on the 2^nd postoperative day. Chest physiotherapy and incentive spirometry were continued during recovery, and gradual improvement in left lung expansion was documented. Post-operative transthoracic echocardiography demonstrated no residual pulmonary stenosis, mild pulmonary regurgitation, a right ventricular outflow tract gradient of 20 mmHg, and preserved biventricular systolic function. Post-operative follow-up echocardiography was advised to assess residual right ventricular outflow tract gradient, pulmonary valve function, and right ventricular pressure after repair.

DISCUSSION

TOF-APVS is a rare variant of TOF in which the pulmonary valve is absent or rudimentary, resulting in severe pulmonary regurgitation and progressive dilatation of the main and branch PAs.^[4,5] The main clinical burden in this condition is not limited to the intracardiac defect; airway compression and bronchomalacia are major contributors to morbidity and mortality.^[5,6] The left main bronchus is particularly vulnerable because of its anatomic course and proximity to the enlarged PAs.^[6,7]

In this patient, the presentation was dominated by recurrent respiratory infections, poor weight gain, and chronic left lung collapse. These findings are consistent with long-standing extrinsic bronchial compression in TOFAPVS.^[5,6] Chronic compression may lead not only to fixed narrowing of the affected airway but also to distal atelectasis, retained secretions, bronchiectatic change, and recurrent infection.^[5,6] In severe cases, even after successful intracardiac repair, the airway may remain narrowed because structural bronchomalacia and long-standing luminal deformation do not always reverse immediately.^[6,8]

Pre-operative airway imaging was essential in this case. Chest radiography suggested unilateral lung volume loss, while CT angiography clearly demonstrated the relationship between the dilated PAs and the compressed left main bronchus. CT is particularly useful in TOF-APVS because it simultaneously defines cardiovascular anatomy, airway compromise, and the extent of lung collapse.^[7,9] In our patient, the abrupt tapering of the left pulmonary artery and non-visualization of distal bronchial divisions supported the impression of chronic left-sided pulmonary compromise. The possibility of a hypoplastic or non-functional left lung was therefore considered, although the post-operative radiographic improvement suggested that at least part of the collapse was potentially reversible.^[10]

Bronchoscopy added important functional information beyond cross-sectional imaging. Intraoperative flexible bronchoscopy confirmed severe narrowing of the left main bronchus and helped determine the nature of the obstruction.

The persistence of bronchial narrowing after cardiac repair indicated that airway compromise was not purely hemodynamic and that chronic extrinsic compression had likely caused fixed deformity or bronchomalacia. This finding is clinically important because repair of the cardiac lesion alone may not fully restore airway patency in late-presenting patients. In selected reports, bronchial stenting has been used to relieve severe airway obstruction in TOF-APVS, but such an approach is generally reserved for carefully selected infants or patients with persistent critical obstruction. In the present case, stenting was not attempted because the child maintained adequate gas exchange through the contralateral lung, and the airway narrowing was considered chronic and not suitable for immediate endobronchial intervention.

The surgical strategy in TOF-APVS must address both the intracardiac defect and the dilated PAs.^[5,7] Repair typically includes closure of the ventricular septal defect, relief of right ventricular outflow tract obstruction, and pulmonary valve reconstruction. In the presence of grossly enlarged PAs, reduction arterioplasty or related procedures may be considered to decrease airway compression.

The post-operative course in this patient is instructive. Although the left bronchus remained narrowed immediately after repair, the left lung showed progressive re-expansion on serial radiographs, suggesting that a component of the atelectasis was reversible. This observation supports the view that even in late-presenting TOF-APVS, some improvement in lung aeration can occur after relief of vascular compression and aggressive post-operative pulmonary care.^[5,7] However, persistent airway narrowing after repair underscores the need for long-term follow-up, particularly in children with recurrent infections or residual unilateral lung hypoventilation.

The prognosis in TOF-APVS depends on several factors, including the severity of pulmonary artery dilatation, the degree and chronicity of airway compression, associated bronchomalacia, the timing of surgical intervention, and the quality of post-operative airway recovery. Early recognition and timely repair are associated with better respiratory outcomes, whereas delayed intervention may leave residual airway compromise and incomplete lung recovery. In this regard, the present case emphasizes the importance of a multidisciplinary approach involving pediatric cardiology, cardiothoracic surgery, anesthesiology, radiology, and respiratory care.

This case also has educational value because it illustrates that TOF-APVS can present predominantly as a respiratory problem in later childhood, with recurrent infections and unilateral lung collapse rather than overt cyanotic spells. The case further demonstrates the complementary role of CT angiography and bronchoscopy in defining both the anatomical and functional aspects of airway compromise. Persistent post-operative bronchial narrowing should not be dismissed; rather, it should prompt ongoing respiratory surveillance and follow-up imaging.

CONCLUSION

TOF-APVS is a rare congenital cardiac defect in which airway compression may become the dominant clinical issue. In late-presenting patients, chronic bronchial compression may produce fixed airway narrowing and prolonged lung collapse even after successful cardiac repair. Careful pre-operative imaging, intraoperative bronchoscopy, appropriate surgical correction, and structured post-operative follow-up are essential to optimize outcomes in such patients.