Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Pacer defibrillator leads are unchanged , terminating in the right atrium and right ventricle . There is a left retrocardiac opacity , which most likely represents atelectasis . No other focal consolidation , pleural effusion or pneumothorax . No evidence of pulmonary edema . Heart size is mildly enlarged .
    OUTPUT:
    
No acute cardiopulmonary process .