Anatomy Of The Heart On A Chest X Ray

Therefore, to understand how a heart is viewed on a chest X-ray (CXR) it is useful to also refer to the 'heart borders", this can be used to identify important cardiac structures in a 2D plane.

The left heart border is formed primarily of the left ventricle and a tiny part of the left atrium depending on the individual. Superiorly to the left atrium you can normally see on a CXR the "aortic knuckle", this represents the arch of the aorta curving outwards as it emerges from the superior aspect of the left ventricle.

The right heart border is primarily formed by the right atrium

The inferior border of the heart is formed by the inferior aspects of the left and right ventricles as they sit on the left hemidiaphragm.

Finally, the superior border of the heart is formed by the superior aspect of the atria and the great vessels including, as mentioned earlier, the arch of the aorta.

You can appreciate these structures when evaluating a CXR