An opening exists between the two upper chambers of the heart. This allows some blood from the left atrium (blood that's already been to the lungs) to return via the hole to the right atrium instead of flowing through the left ventricle, out the aorta and to the body. Many children with ASD have few, if any, symptoms. Closing the atrial defect by open-heart surgery in childhood can prevent serious problems later in life. Recently a new technique has allowed cardiologists to close some ASDs at cardiac catheterization using a specially designed detachable plug, avoiding the need for open heart surgery. This new procedure is still being evaluated.