Heart is the most hard working organ it never stops beating since it started pumping by the time of our birth. The muscles are very strong too , its very tolerant that s why by the time there s a problem, it sends a signal. Left atrial enlargement has a lot of causes. Like too much blood in the atrium, heart pressures,narrowing of the valves, hardening or stiffness of the heart.Treatment depends on the cause and signs and symptoms. This is a long topic. Don t worry to much. But if you are worried follow your conscience and seek 2nd opinion with the cardiologist. I was a cardiac ICU nurse. When i was in my country i felt palpitation and the Dr. advised an echo cardiogram, because it was free procedure because i work there i did not hesitated. It showed mild mitral regurgitation but did not need treatment. that was 5 years ago. Last year when i was pregnant and since i m 34 years old i was worried. i was seen by cardiac consultant. But after the echo again,. She said it was nothing. 90% of all patients being having EKG will have that result. I had a very active life but because of that mitral regurgitation, i tried to mellow down. I collapsed twice after exercise before and i always say may be because of my regurgitation but i just worried too much, for the things i should not be worrying. i was worried for 5 years for nothing. That diagnosis ruin my life.