Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral radiograph of the chest show no major interval changes since prior chest x-ray with low lung volumes and bibasilar atelectasis and minimal left pleural effusion . Left upper lung atelectasis has disappeared . There is no pneumothorax . Heart is still enlarged , with normal postoperative appearance of the mediastinum related to CABG procedure .
    OUTPUT:
    
Persistent left small pleural effusion and improved left upper lung ventilation .