Answer

[Figure 2]

Figure 2: (chest X-ray) Answer Click here to view

D. Absent pericardium

Description

Posterior-anterior (AP) chest X-ray showed levoposition of the heart without tracheal deviation, no rotation of the film (equidistance of medial end of the clavicle from spinous process), right heart border superimposed on the spine (straight arrow), an imprint of the main pulmonary artery (curved arrow), and the interposition of lung parenchyma between the aortic arch and left pulmonary artery (star).

Discussion

The normal cardiac position is approximately one-third to the right of the mediastinum and two-third to the left. If no heart projects to the right of the mediastinum, the appearance is abnormal. In the absence of left lower lung volume loss or right chest displacing pathology, the first consideration should be patient rotation. If the patient is well-centered, the next point of call is the thoracic shape. If the lateral chest X-ray demonstrates reduction of the AP dimension (straight spine) or Pectus excavatum, this may displace the cardiac silhouette to the left. If the chest morphology is generally normal, the heart is significantly displaced to the left and there is left cardiac border straightening consider congenital absence of the pericardium. Additionally noted features may be a deep or very well-defined aortopulmonary window caused by the absence of pleura allowing lung to invaginate into this space.

Absent Pericardium-Quick Facts

• Absence of the pericardium is almost invariably on the left
• Caused by incomplete formation of the pleuropericardial membrane due to premature atrophy of the left common cardinal vein (duct of Cuvier)
• The abnormality may be complete or incomplete
• Incomplete type is less frequent but is more problematic as the PA or left atrial appendage may herniate and become incarcerated or torsed in the defect
• The abnormality is more frequent in males and may be associated with atrial septal defect, patent ductus arteriosus, Fallot's tetralogy, bronchogenic cyst, or pectus in one-third of the cases.^[1],[2]