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Aortic Dissection

Aortic wall motion can produce curvilinear artifacts in the proximal ascending aorta near the aortic root, which mimic a dissection. These artifacts are typically at the left anterior (12 to 1 o’clock) and right posterior (6 to 7 o’clock) locations.1

True versus False Lumen

The true and false lumens are usually easily distinguished. However, the distinction can occasionally be difficult. The false lumen typically has a larger cross-sectional area. The presence of an acute angle between the flap and the outer wall (the “beak” sign) is seen only in the false lumen. Slender lines of low attenuation can be seen in the false lumen (the “cobweb” sign), which represent residual strands of the media. If one lumen wraps around another in the aortic arch, the inner lumen is the true lumen. Outer wall calcification always indicates the true lumen in an acute dissection. However, the outer wall of the false lumen can calcify in a chronic dissection if the false lumen lining endothelializes.^2,3

Features of the False Lumen in an Aortic Dissection

• Larger cross-sectional area
  
• Beak sign
  
• Cobweb sign
  
• Outer lumen

A Thrombosed False Lumen versus a Mural Thrombus

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