Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are slightly low although the lungs are clear . Heart size is top normal . The mediastinal contours are normal . There are no pleural abnormalities . The patient is status post midline sternotomy and CABG . Degenerative changes of the thoracic spine are noted .
    OUTPUT:
    
No acute cardiac or pulmonary process .