What causes Double density sign in heart on frontal chest radiograph?
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Answer:
Enlargement of the left atrium creates a second density superimposed on the right heart border on frontal chest x-ray (CXR), most commonly due to mitral valve disease such as mitral stenosis or regurgitation, leading to left atrial dilatation.
Why is it called so?:
It is named for the appearance of two overlapping densities on the right heart border: the usual right atrial shadow and a second distinct shadow from the enlarged left atrium extending posteriorly.
Pathophysiology
Chronic pressure or volume overload of the left atrium, typically from mitral stenosis or insufficiency, causes left atrial enlargement; the posteromedial portion of the enlarged left atrium projects behind the right atrium, creating a discrete second silhouette against the adjacent lung on the frontal projection while remaining hidden on lateral view.
Alternative names: Double density sign — Double right heart border sign
Other associated named signs: None
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