Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is moderately enlarged . The patient status post median sternotomy with wires intact . A prosthetic mitral valve projects over the heart . A persistent opacity at the right lung base is moderately improved in comparison the prior examination . Mild pulmonary edema is a chronic finding .
    OUTPUT:
    
A persistent opacity at the right lung base is moderately improved . This may represent improving aspiration or pneumonia . Mild pulmonary edema is chronic .