The left and right sides of the heart are separated by a wall called the septum. Some people are born with a hole in either the upper septum (atrial septal defect) or the lower septum (ventricular septal defect). When these defects are present, oxygen-rich blood from the lungs may mix with oxygen-poor blood returning from the body.
Common symptoms of a septal defect may include shortness of breath, hard or fast breathing, and frequent respiratory infections.
