There are different parameters that we used to make decisions regarding valvular surgery, however, the development of symptoms, for either the mitral or the aortic valve, is an indications that surgery should be done soon. It is, however, sometimes difficult to be certain that the symptoms are related to the valve. Stress echocardiography or TEE can be helpful in making these distinctions. The fact that you left atrium is severely enlarged makes me concerned about the mitral valve, namely its severity. It is possible that the regular echocardiography, or the exam aren't accurate in your case. I would recommend stress testing or a TEE to further quantify the degree of mitral insufficiency in your case. Mitral valves can generally be repaired. The bicuspid valve usually is very difficult to repair and generally needs a replacement.