Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Patient is status post median sternotomy and mitral valve replacement . Stable cardiomegaly . Improving aeration in both lower lobes with minor residual atelectasis remaining . Additional linear focus of atelectasis in the lingula . Residual small left pleural effusion but no evidence of pneumothorax .
    OUTPUT:
    
Marked improvement in bibasilar atelectasis . Small residual left pleural effusion .