Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is enlarged , not significantly changed from prior examination . Sternotomy wires and mitral valve replacement is noted . Persistent retrocardiac opacity likely relates to a moderate pleural effusion with overlying atelectasis . However , an underlying infectious process can not be excluded . The right lung is essentially clear . No large pleural effusion on the right or pneumothorax identified .
    OUTPUT:
    
Persistent retrocardiac opacity , likely relates to moderate pleural effusion and overlying atelectasis , however an underlying infectious process can not be excluded .