Symptoms of clinically significant enlarged left atriums include the abnormal heart rhythms that are medically referred to as atrial fibrillations, explains the Ochsner Journal on the U.S. National Library of Medicine website. Every 5-millimeter increase in the size of the left atrium elevates the risk of triggering these pathological cardiac rhythms by 39 percent. Other conditions that may accompany left atrial enlargement include ischemic strokes and congestive heart failures.
A variety of hereditary and acquired conditions can precipitate left atrial enlargement, notes Radiopaedia. These include ventricular septal defects, a congenital condition in which interventricular septum deformities allow communication between the left and right ventricles, and patent ductus arteriosus, a congenital abnormality in which the ductus arteriosus, the connection between the pulmonary arterial system and the aorta that develops in-utero, fails to close.
Acquired causes include left atrial myxoma, a type of primary heart tumor; mitral stenosis, a condition in which an attenuated mitral passage restricts blood flow from the left atrium to the left ventricle; mitral valve regurgitation, which refers to anatomical or functional abnormalities of the mitral valve; and failure of the left ventricle, reports Radiopaedia. Hypertension can also cause the left atrium to pathologically enlarge, warns the American Heart Association. Whether acquired or hereditary, these conditions trigger an increase in the atrial filling pressure, elevating tension on the walls of the heart chamber, and eventually precipitating its enlargement.