Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest were provided . Midline sternotomy wires and mediastinal clips are new from prior exam . There is left basilar atelectasis and small left pleural effusion noted , also new from prior exam . The heart appears top normal in size . No convincing signs of pneumonia , though given the retrocardiac atelectasis , a subtle pneumonia is difficult to exclude . Mediastinal contour appears normal . Bony structures are intact .
    OUTPUT:
    
Interval sternotomy with left basal opacity , likely atelectasis , thought can not exclude an early pneumonia . Tiny left pleural effusion also present .