Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A single lead pacemaker is seen projected over the left chest wall and extending to the right ventricle . The hilar and mediastinal contours are unchanged . Streaky opacities at the lung bases , are compatible with atelectatic changes . Again seen is an opacity in the retrocardiac region . There is no pleural effusion or pneumothorax . The visualized osseous structures , aside from multilevel degenerative changes in the thoracic spine , are unremarkable .
    OUTPUT:
    
Subtle opacity in the retrocardiac region , potentially atelectasis noting infection is possible .