Middle back pain: Back pain in the middle back area. See detailed information below for a list of 31 causes of Middle back pain, Symptom Checker, Assessment Questionnaire, including diseases and drug side effect causes. Â» Review Causes of Middle back pain: Causes | Symptom Checker Â» | Assessment Questionnaire Â» Causes of Middle back pain:
Valvular Heart Disease. Disorders of certain heart valves can also lead to left atrial enlargement. The mitral valve separates the left atrium from the left ventricle. If the mitral valve becomes narrow -- a condition known as mitral stenosis -- blood accumulates in the left atrium and causes enlargement.
Atrial fibrillation and a corresponding enlargement of the left atrium may cause an increase in size of the mitral valve annulus. With a sinus rhythm, the mitral annulus undergoes dynamic changes during the cardiac cycle.