Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Right - sided pacer is noted with leads terminating in the right atrium and right ventricle , unchanged . Left - sided central venous catheter tip terminates in the proximal right atrium . Mild enlargement of the cardiac silhouette is present . Aortic knob calcifications are noted . The mediastinal and hilar contours are unremarkable . A small left pleural effusion is substantially decreased in size compared to the previous study . Subsegmental atelectasis or scarring accounts for the linear opacity within the left mid lung field . There is minimal left basilar atelectasis . Right lung is clear . No pulmonary edema or pneumothorax is present .
    OUTPUT:
    
Small left pleural effusion with minimal left basilar atelectasis and subsegmental atelectasis or scarring in the left mid lung field .