Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP upright and lateral chest radiographs demonstrate interval placement of a left chest wall pacer device with leads projecting over the right atrium and ventricle . Sternal wires and a valve prosthesis are also new compared to ___ . Cardiomediastinal silhouette appears grossly normal . A small to moderate left pleural effusion is noted with associated lower lobe atelectasis , difficult to exclude pneumonia . There is no pneumothorax . No free air below the right hemidiaphragm . Clips project over the right upper chest .
    OUTPUT:
    
Left effusion with associated lower lobe atelectasis versus pneumonia .