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.
Ventricular septal defect is a hole in the wall between the right and left ventricles of the heart. This abnormality usually develops before birth and is found most often in infants.1  The ventricles are the 2 lower chambers of the heart.entricular Septal Defect Causes. No one knows what causes ventricular septal defects, but they probably come from a malformation of the heart that occurs while the infant is developing in the womb. 1  There may be just one hole or several holes in the septum.