Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Low lung volumes persist . Left sided dual - chamber pacemaker is re - demonstrated with leads terminating in unchanged positions . Widening of the superior mediastinum is due to low lung volumes and technique . The heart size again is likely top normal , but is accentuated due to poor inspiratory effort . There is crowding of the bronchovascular structures . No overt pulmonary edema is seen . There is likely mild bibasilar atelectasis though assessment for pneumonia is limited on this low lung volume study . No pleural effusion or pneumothorax is present .
    OUTPUT:
    
Suboptimal study due to low lung volumes . Mild bibasilar atelectasis with crowding of the bronchovascular structures .