BIATRIAL ENLARGEMENT is an increase in size of the upper two chambers (left and right atria). Size is based on volumes of ventricular (lower chamber) and atrial chambers, estimated on the basis of segmented images, demonstrate the increased size of the atria and the abnormal proportion between atrial and ventricular volumes The dimensions are an estimate and whether or not it is problematic is another issue....the condition if pathological can be caused by intra-chamber pressures as a result of valve stenosis (narrrowing of the orifice), regurgitation, etc. right side can be due to pulmonary pressure, etc.
Ejection fraction is normally at 55 to 75%. That is the amount of blood pumped into circulation with each heartbeat.