Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a dual - lead pacer with tips projecting over the right atrium and right ventricle . The lungs and pleural spaces are essentially clear without pneumothorax or pleural effusions . There is mild retrocardiac opacity that likely reflects atelectasis , although infection is not definitively excluded . The heart is normal in size . The thoracic aorta is slightly tortuous . There is no evidence of pneumoperitoneum and there is mild degenerative change within the thoracolumbar spine .
    OUTPUT:
    
Retrocardiac opacity reflects atelectasis , although infection is not entirely excluded .