"Double density sign" of left atrial enlargement

Answer: 

 

69-year-old female with rheumatic mitral valve stenosis and regurgitation, who had undergone mitral valve repair two years ago. Currently, a TAVR was performed for aortic valve stenosis. The radiograph, along with other findings, demonstrates left atrial enlargement.

 

The left atrium, as it enlarges, can be directly visualized, or can displace adjacent structures.

 

Double density sign: The right border of the left atrium bulges into the adjacent lung, and becomes apparent projecting over or beyond the normal right heart border.

Although the double density sign may be present in patients without left atrial enlargement, it allows for measurement of the left atrium to assess for the presence of enlargement. The measurement of the oblique angle between the left atrium and midpoint of the left mainstem bronchus should be <7cm, in this patient the measurement is 11 cm and represents left atrial enlargement.

 

Third mogul sign: On a normal chest radiograph, the left cardiac border, caudal to the main pulmonary artery contour should be plane or concave.   Convexity of the left atrial appendage contour is a direct sign of enlargement.

 

Splaying of the carina: Widening of the carinal angle to over 90 degrees is an indirect sign of LA enlargement. The subcarinal angle on this radiograph is 126 degrees.

 

References:

 

Higgins CB, Reinke RT, Jones NE, Broderick T. Left atrial dimension on the frontal thoracic radiograph: a method for assessing left atrial enlargement. AJR Am J Roentgenol. 1978; 130:251-255.

Taskin V, Bate MC, Chillag SA. Tracheal carinal angle and left atrial size. Arch Intern Med 1991; 151:307-308.

 

Murray JG, Brown AL, Anagnostou EA et-al. Widening of the tracheal bifurcation on chest radiographs: value as a sign of left atrial enlargement. AJR Am J Roentgenol. 1995;164 (5): 1089-92.