Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post sternotomy and coronary artery bypass graft surgery . The cardiac , mediastinal and hilar contours are unchanged . There are severe emphysematous changes with marked attenuation of lung markings in the upper lungs . Surgical staple material projects over the right mid lung . However , there has been no significant change .
    OUTPUT:
    
No evidence of acute disease . Severe emphysema . Status post coronary artery bypass graft surgery .