Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is new retrocardiac opacity silhouetting the descending thoracic aorta . Elsewhere , lungs are clear . Cardiac silhouette is moderately enlarged as on prior . Left chest wall dual lead pacing device is well as epicardial leads are again noted . Median sternotomy hardware again noted .
    OUTPUT:
    
New left lower lobe opacity which could be due to pneumonia in the proper clinical setting .