Keywords
absent pulmonary valve syndrome - CPAM - CT angiography - tetralogy of Fallot
Case History
A 9-year-old acyanotic boy visited the pediatric outpatient clinic due to recurring lower respiratory tract infections. Clinical evaluation revealed cardiomegaly and a low-pitched early diastolic murmur in the pulmonary area. A chest radiograph showed cardiomegaly and plethoric lung fields. Further, transthoracic echocardiography revealed dilated right-sided heart chambers, dilated tricuspid valve annulus, hypoplastic pulmonary annulus, and absent pulmonary valve leaflets with free pulmonary regurgitation. Large subaortic ventricular septal defect (VSD) and dilated confluent pulmonary arteries were also noted. Subsequently, the patient underwent a computed tomography angiography (CTA) to delineate the intracardiac anatomy and to rule out any other structural abnormality. CTA confirmed the presence of a subaortic VSD, absent pulmonary valve with dilated right atrium, and right ventricle with hypoplastic pulmonary annulus. The main and right pulmonary arteries were dilated ([Fig. 1], [Supplementary Video S1]). No other cardiovascular anomalies were detected, thus leading to a diagnosis of tetralogy of Fallot (ToF) with absent pulmonary valve. In addition, mosaic attenuation was noted in both lungs with multiple variable sized cystic lesions (0.5–2 cm) seen in the right lower lobe. A similar small cluster of cysts was seen in the left upper lobe, right middle lobe, and right lower lobe ([Fig. 2], [Supplementary Video S2]). No communication with tracheobronchial tree was identified. Hence, a diagnosis of ToF with absent pulmonary valve syndrome (APVS) with type 2 congenital pulmonary airway malformation (CPAM) was made.
Fig. 1 Three-dimensional (3D) reconstructed volume rendered image shows hypoplastic pulmonary annulus (yellow arrow) with dilated main and right pulmonary artery (black asterisk). RVOT, right ventricular outflow tract.
Supplementary Video S1 Axial computed tomography angiography video loop showing subaortic ventricular septal defect, hypoplastic pulmonary arteries, and dilated pulmonary arteries.
Fig. 2 Computed tomography angiography images (A, B) showing subaortic ventricular septal defect (VSD) (black asterisk), hypoplastic pulmonary annulus (yellow arrow in B) with dilated main and right pulmonary artery. Minimum intensity projection (MinIP) images in coronal (C) and sagittal (D) plane shows mosaic attenuation in both lungs with hypoattenuating area involving the right lower lobe with multiple variable-sized cystic lesions (white asterisk). Small cluster of microcysts seen in the left upper lobe (C). Ao, aorta; LV, left ventricle; RV, right ventricle; RVOT, right ventricular outflow tract; RPA, right pulmonary artery.
Supplementary Video S2 Axial computed tomography lung window video loop showing mosaic attenuation in both lungs with hypoattenuating area involving the right lower lobe with multiple variable-sized cystic lesions. And small cluster of microcysts seen in the left upper lobe, right middle, and lower lobe.
Discussion
APVS was initially described by Cheevers et al in 1847.[1] Typically, APVS is associated with atrial septal defect or VDS, patent ductus arteriosus, or ToF. CPAM are hamartomatous lesions with cystic and adenomatoid components arising from the tracheobronchial tree. Five types of CPAM have been described by Stocker et al, wherein type 2 CPAM arises from terminal bronchioles and accounts for approximately 15 to 30% of the cases and is associated with cardiovascular anomalies.[2]
Pulmonary abnormalities in cases of ToF with APVS are usually attributed to extrinsic compression of airways by dilated pulmonary arteries. In addition, pulmonary findings can also be because of abnormal pulmonary arterial branching at the segmental level leading to compression at the level of intrapulmonary bronchi.[3] Generally, mosaic attenuation involves both lung fields secondary to areas of hyperperfusion mediated by dilated pulmonary arteries and geographical hypoattenuating areas due to air trapping. Segmental or subsegmental atelectasis can be seen as a consequence of extrinsic airway compression. In a retrospective review of 47 cases of ToF with APVS by Verma et al,[4] air trapping was seen in 35 (74.5%) patients whereas atelectasis was observed in 15 (31.9%) patients. None of the patients had any abnormal pulmonary malformation. Presence of a bronchopulmonary malinosculation like CPAM may further exacerbate symptoms of respiratory distress seen in patients with ToF-APVS and may complicate the postoperative course necessitating prolonged intubation depending upon their size. To the best of our knowledge, the present case represents a rare instance of ToF-APVS in association with type 2 CPAM in a young child, which is previously undescribed. This case underscores the importance of CTA in defining intricate anatomy and identifying potential associated pulmonary anomalies in patients suspected of having ToF with APVS and also highlighting the need to actively look for such associated lesions while reporting these scans.
