Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post median sternotomy and prosthetic valve replacement . Lung volumes are low which accentuates the size of the cardiac and mediastinal silhouette . The heart size is at ___ mildly enlarged . Crowding of the bronchovascular structures is noted , with possible mild pulmonary vascular congestion . Bibasilar airspace opacities could reflect atelectasis but infection or aspiration can not be completely excluded . The right costophrenic angle is excluded from the field of view though no large pleural effusion is demonstrated , and there is no pneumothorax .
    OUTPUT:
    
1 . Low lung volumes . Bibasilar airspace opacities could reflect atelectasis but infection or aspiration are not excluded . Consider repeat PA and lateral radiographs with improved inspiratory effort . 2 . Possible mild pulmonary vascular congestion .