Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Left - sided dual - chamber pacemaker device is noted with leads terminating in right atrium and right ventricle . The patient is status post median sternotomy and aortic valve replacement . Heart size remains mildly enlarged . The aorta is diffusely tortuous and calcified . The pulmonary vascularity is normal . The mediastinal and hilar contours are stable . Increased interstitial markings are noted along the periphery of the lung bases , likely reflecting NSIP , and better assessed on the recent chest CT . Overall , these opacities may be slightly progressed , which suggest perhaps that there is superimposed atelectasis or infection . No focal consolidation or pleural effusion is visualized . Lung volumes are reduced . There is no pneumothorax . Mild degenerative changes are seen within the thoracic spine .
    OUTPUT:
    
Bibasilar airspace opacities likely reflecting atelectasis , though infection is not excluded , superimposed on a background of chronic interstitial lung disease previously characterized as NSIP .