Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral chest radiographs again demonstrate a left chest wall pacer device with leads overlying the right atrium and ventricle . Moderate cardiomegaly is unchanged . The mediastinal silhouette is within normal limits . Faint retrocardiac opacity likely represents atelectasis , though pneumonia can not be excluded in the right clinical setting . There is no appreciable pleural effusion or pneumothorax . The visualized upper abdomen is unremarkable .
    OUTPUT:
    
Faint retrocardiac opacity likely represents atelectasis , although early pneumonia can not be excluded in the right clinical setting .