Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is markedly enlarged and probably even larger than on the earlier comparison study , protruding more posterior , suggesting marked left atrial enlargement . Opacification in the left lower hemithorax suggests a pleural effusion with associated parenchymal opacity , but decreased . A trace pleural effusion is suspected on the right . The lungs appear otherwise clear .
    OUTPUT:
    
Marked cardiomegaly . Small to moderate left - sided pleural effusion with associated opacity , likely atelectasis ; overall decreased , although an infectious process is hard to entirely exclude .