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In severe cases, this curvilinear density of the left atrium may even project beyond the right atrium border which is called the atrial escape.
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23-year-old female with difficulty in breathing and diagnosed with mitral valve disease. PA chest radiograph shows double density behind the right heart with two separate borders due to right atrium (white arrowhead) and left atrium (white arrow) producing the radiologic sign, double density sign.
Kumaresh A, Kumar M, Dev B, Gorantla R, Sai PV, Thanasekaraan V. Back to Basics - 'Must Know' Classical Signs in Thoracic Radiology. J Clin Imaging Sci. 2015;5:43. Published 2015 Jul 31. doi:10.4103/2156-7514.161977
![Chest radiography -posteroanterior view. Enlarged heart. Next to the mitral valve, there is an ovulated hyperdense lesion (red arrows) measuring about 3,5cm x 2,0cm. The double density sign (blue arrow) and elevation of the left bronchus (yellow arrow) indicate left atrial enlargement. The left costodiaphragmatic recess is obliterated (black arrow), and a calcified line is noted at the left hemithorax seemingly along the pleura (white arrow).
Caseous Calcification of the Mitral Annulus: A Post-Heart Transplant Diagnosis - Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/Chest-radiography-posteroanterior-view-Enlarged-heart-Next-to-the-mitral-valve-there_fig1_366529209 [accessed 11 Jul 2025]](attachment:b4677b94-aac7-490f-ae98-4b02746eca20:Chest-radiography-posteroanterior-view-Enlarged-heart-Next-to-the-mitral-valve-there.png)
Chest radiography -posteroanterior view. Enlarged heart. Next to the mitral valve, there is an ovulated hyperdense lesion (red arrows) measuring about 3,5cm x 2,0cm. The double density sign (blue arrow) and elevation of the left bronchus (yellow arrow) indicate left atrial enlargement. The left costodiaphragmatic recess is obliterated (black arrow), and a calcified line is noted at the left hemithorax seemingly along the pleura (white arrow).
Caseous Calcification of the Mitral Annulus: A Post-Heart Transplant Diagnosis - Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/Chest-radiography-posteroanterior-view-Enlarged-heart-Next-to-the-mitral-valve-there_fig1_366529209 [accessed 11 Jul 2025]