Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Patient is status post median sternotomy and mitral valve repair . The heart remains moderately enlarged , unchanged , with aortic knob calcifications again demonstrated . The pulmonary vascularity is not engorged . There is minimal streaky opacity in the retrocardiac region likely reflecting atelectasis . No pleural effusion or pneumothorax is identified . There are no acute osseous abnormalities .
    OUTPUT:
    
Probable mild retrocardiac atelectasis . Unchanged moderate cardiomegaly without evidence of congestive heart failure .