Atrial Septal Defect. Buy backpacks, exercise machines, athletic shoes, and more at Fogdog Sports. Normally, this opening closes before birth, but if it does not, the child is born with a hole between the left and right atria. This abnormal opening is called an atrial septal defect and causes blood from the left atrium to flow into the right atrium. Different types of atrial septal defects can occur, and they are classified according to where in the separating wall they are found.
Abnormal openings can form in the upper and lower parts of the atrial septum as well.
These abnormalities can go unnoticed if the opening is small, producing no abnormal symptoms. If the defect is big, large amounts of blood flowing from the left to the right atrium will cause the right atrium to swell to hold the extra blood. Diagnosis Atrial septal defects can be identified by various methods. Abnormal changes in the sound of the heart beats can be heard when a doctor listens to the heart with a stethoscope. An atrial septal defect can also be diagnosed by using a test called cardiac catheterization .