Chest X-Ray (CXR) PA view showing cardiomegaly due to biatrial enlargement. Right atrial enlargement is evidenced by shift of the right cardiac border grossly to the right side. Left atrial enlargement is seen as a double contour within the right atrial shadow. Main pulmonary artery shadow is prominent on the left upper cardiac border. Right hilum is prominent due to enlargement of right pulmonary artery. Upper lobe vessels are prominent (inverted mustache sign, antler sign, cephalization). It is called cephalization because in normal pulmonary vasculature, lower lobe vessels are more prominent than upper lobe vessels. In pulmonary venous hypertension, there is redistribution of pulmonary blood flow towards the upper lobes, making upper lobe vessels more prominent.
Another manifestation of left atrial enlargement is elevation of left bronchus seen as the air bronchogram on CXR.