Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Moderate cardiomegaly and postoperative mediastinal contour with aortic valve replacement is unchanged . A left dual - lead pacer is unchanged in position . The hilar contours are unremarkable . There is mild bibasilar atelectasis . Lungs are otherwise clear . Pleural surfaces are clear without effusion or pneumothorax . There are multiple old right - sided rib fractures . There is a large hiatal hernia .
    OUTPUT:
    
Mild bibasilar atelectasis . No definite acute cardiopulmonary process .