Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post recent median sternotomy , aortic valve replacement , and apparent bypass surgery . Cardiomediastinal contours are stable in the postoperative period . Improving retrocardiac atelectasis with residual linear atelectasis remaining . Small left pleural effusion is best visualized on the lateral view and may be slightly decreased since the recent study of ___ .
    OUTPUT:
    
Improving left retrocardiac atelectasis and slightly decreased small left pleural effusion .