Earliest sign of left atrial enlargement is -
Left atrial enlargement presents radiologically with elevation of left main bronchus which is the earlier feature ,splaying or widening of carina ,indentation and displacement of oesophagus posteriorly , double contour / shadow / density or double right hea border and prominent left atrial appendage.
Posterior displacement of esophagus
Widening of carinal angle
Elevation of left bronchus
Double shadow of right border
Cardiovascular system