Right ventricular enlargement is seen as a decrease in the retrosternal space on the lateral image. Right atrial enlargement may be present if significant tricuspid regurgitation is present. This finding may be recognized by the widened right heart border in the frontal projection and enlargement of the right atrial appendage in the lateral projection, which is seen as increased retrosternal opacity above the expected location of the right ventricle.
Enlarged central pulmonary arteries that taper distally may be found.
Peripheral vessel opacity-oligemic lung fields may be observed. This oligemia may be asymmetrical. This is also a useful finding suggestive of chronic pulmonary embolism (PE).
An increase in the transverse diameter of the right interlobar artery is indicative of pulmonary hypertension. The upper limit of the transverse diameter of the right interlobar artery from its lateral aspect to the intermediate bronchus is 15 mm in women and 16 mm in men.
The transverse diameter of the left interlobar artery is difficult to appreciate on the posteroanterior (PA) view. Using a lateral view, one can measure from the circular lucency of the left upper lobe bronchus to the posterior margin of the vessel; the upper limit is 18 mm.
Evidence of right atrial dilatation and right ventricular dilatation may be noted.
Kerley B lines may be present. These indicate the presence of pulmonary venous hypertension.