Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There has been interval placement of a left - sided pacemaker with 2 leads seen in appropriate position . Heart size is normal . The mediastinal and hilar contours are normal . The pulmonary vasculature is normal . There is mildly increased retrocardiac opacity from the prior study which likely represents atelectasis . No pleural effusion or pneumothorax is seen . There are no acute osseous abnormalities .
    OUTPUT:
    
Left - sided dual lead pacemaker seen in appropriate position . Increased retrocardiac opacity most likely representative of atelectasis .