Cardiac Radiography > Pathology > Cardiac Enlargement


Cardiac Enlargement

The chest radiograph is quite insensitive to enlargement of the cardiac silhouette in general, and to cardiac chamber enlargement specifically. On an upright PA chest radiograph the ratio of the transverse width of the heart shadow to the diameter of the rib cage at the same level should not exceed 0.5 in normal individuals. As mentioned above, however, there are a number of factors that may cause the cardiac silhouette to appear enlarged. Furthermore, a normal sized cardiac silhouette does not indicate a lack of cardiac pathology. Enlargement of the cardiac silhouette is best thought of as an indicator that a chronic cardiac condition is present.

With regard to enlargement of specific chambers, left atrial enlargement is the most reliably identified and should be suspected by the presence of a "double density" behind the right heart border (figure), abnormal elevation of the left main bronchus, or posterior displacement of the barium filled esophagus:

Left atrial enlargement in a patient with chronic mitral regurgitation. There is a double density behind the right side of the heart (arrows).

 

Right heart enlargement (the right atrium and ventricle cannot be separately identified on a radiograph) causes filling-in of the retrosternal clear space and prominence of the right heart border:

Right atrial enlargement in a patient with mild Ebstein's anomaly (normal pulmonary vascularity). The right heart border is prominent (arrows, left) and the retrosternal clear space is filled in by the right heart (arrows, right) 

 

Left ventricular enlargement should be suspected when there is posterior displacement of the posterior border of the heart relative to the shadow of the IVC in individuals without evidence of right heart enlargement:

Left ventricular enlargement in a patient with chronic aortic regurgitation. The posterior border of the heart (arrow) is displaced further posterior than usual. 

 

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