Double density sign (left atrium)

Last revised by Francis Deng on 25 Nov 2023

The double-density sign, also known as the double right heart border, is seen on frontal chest radiographs in the presence of left atrial enlargement, and occurs when the right side of the left atrium extends behind the right cardiac shadow, indenting the adjacent lung and forming its own distinct silhouette 1-3

If large enough, the left atrium can actually reach beyond the border of the right atrium; this is known as atrial escape 3. The right superior pulmonary vein can lead to a similar appearance 1


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