Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post median sternotomy and mitral valve replacement . The cardiac silhouette is moderate to severely enlarged but unchanged . The mediastinal contours are stable with continued dilatation of the azygos vein . There is mild pulmonary edema , slightly improved compared to the previous exam . No pleural effusion or pneumothorax is clearly identified . There are no acute osseous abnormalities .
    OUTPUT:
    
Mild congestive heart failure .