Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single portable frontal AP chest radiograph demonstrate intact median sternotomy wires , mediastinal clips , pacemaker device projecting over the left upper thoracic cavity with intact leads within the right atrium and right ventricle . Persistently low lung volumes with bibasilar atelectasis with slightly increased patchy opacity within the retrocardiac region . No additional focal opacity . No pleural effusion or pneumothorax . Persistent moderate cardiomegaly . Limited assessment of the osseous structures are unremarkable and upper abdomen is within normal limits .
    OUTPUT:
    
1 . Markedly limited exam . Assessment for subtle abnormalities is limited . 2 . Increased opacity within the retrocardiac region , likely representing atelectasis however can not exclude superimposed pneumonia in the appropriate clinical setting . 3 . Persistent low lung volumes with bibasilar atelectasis and moderate cardiomegaly .