Common causes of mild left atrial enlargement can be divided into both congenital causes, like ventricular septal defect, or VSD, and patent ductus arteriosus, or PDA, and acquired causes, like mitral stenosis, mitral regurgitation, left ventricular failure and left atrial myxoma, as reported by Radiopaedia. Left atrial enlargement generally happens when there is an increase in atrial wall tension due to an increase in filling pressures. Left atrial enlargement has also been commonly associated with atrial fibrillations, mortality after myocardial infractions and strokes.
To determine whether a patient has a mild left atrial enlargement, a chest X-ray will normally be performed. The radiologists will look for visual signs like:
- a double density sign. This is when the right side of the atrium pushes into the lung.
- oblique measurements greater than 2 3/4 inches. The measurement is made from the middle of the left main bronchus to the right border of the right atrium.
- a convex left atria appendage because the edge just below the pulmonary outflow track should be either flat or concave.
There are also some indirect signs to look for like:
- a posterior displacement of the left side of the main stem bronchus.
- splaying of the carina, which has caused the tracheal bifurcation angle to be more than 90 degrees.