Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Left - sided dual - chamber pacemaker device is noted with leads terminating in unchanged positions , within the right atrium and right ventricle . Moderate enlargement of cardiac silhouette persists . The mediastinal and hilar contours are stable . There is no pulmonary edema noted . Minimal retrocardiac opacity likely reflects atelectasis . No pleural effusion or pneumothorax is identified . No acute osseous abnormality seen .
    OUTPUT:
    
Minimal retrocardiac opacity likely reflecting atelectasis .