Left Atrium
 - The upper posterior border of the heart is formed by the left atrium.
 - Enlargement will result in bulging of the upper posterior contour
Left Ventricle
 - Forms the lower posterior border.
 - Enlargement will displace the contour more posteriorly.
Right Ventricle
 - The lower retrosternal space is filled by the right ventricle.
 - Enlargement of the right ventricle will result in more superior filling of this retrosternal space. #Anatomy #Radiology #CXR #Lateral #Atrium #Ventricle #Cardiac #Chambers #RadiologyAssistant