Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable AP upright chest radiograph was obtained . Midline sternotomy wires and prosthetic cardiac valve are again noted . The heart is enlarged with a LV configuration . Mild atelectasis is noted at the lung bases , not significantly changed from prior . There is no definite sign of pneumonia or overt CHF . The overall cardiomediastinal contour appears stable . Bony structures are intact . No free air below the right hemidiaphragm is seen .
    OUTPUT:
    
Cardiomegaly again noted without overt signs of CHF or pneumonia . Bibasilar opacities likely reflect atelectasis .