The atrial septal defect (ASD) is the most common congenital heart defect encountered in adults, accounting for up to 15% of all adult CHD, It results from the failure of proper embryologic development of the atrial septum. There are many different types of ASD , the most common of which is the secundum ASD, in which the defect occurs in the middle of the atrial septum.
The flow of blood across the defect (shunt) is determined by the size of the defect and the compliance of the atria. ASD should be suspected whenever right heart enlargement is present without an alternative explanation. Occasionally, patients present late in life with ASD-related symptoms when the left atrial pressure increases because of a stiff left ventricle and diastolic dysfunction, usually the result of long-standing hypertension or coronary artery disease, resulting in increased shunt.
The larger the left-to-right shunt is in patients with ASD, the greater is the risk for long-term complications, such as atrial fibrillation and pulmonary hypertension. The latter condition affects up to 15% of adults with ASD and, if it remains uncorrected, it can result in Eisenmenger’s syndrome (see later). Another condition associated with ASD is stroke, which presumably results from paradoxical embolization—blood clots forming in the extremities and reaching the cerebral circulation by passing through the ASD.
Other, less-common variations of ASD include the sinus venosus ASD, in which there is abnormal fusion of the vena cava (superior or inferior) to the left atrium. This defect is almost always associated with partial anomalous return of the pulmonary veins (right superior or both right pulmonary veins drain into the right atrium). The primum ASD involves the lower portion of the atrial septum and typically affects the ventricular septum as well (the atrioventricular [AV] canal defect). Both AV valves are structurally abnormal, and the mitral valve is typically cleft. The least common form of ASD involves unroofing of the coronary sinus, which results in shunting into the left atrium. At this time, only the secundum ASD has been successfully occluded through percutaneous means.
What happens during the closure procedure?
When your child is asleep, we will do a test called a transesophageal echocardiogram. "Echocardiogram" ,"Transesophageal" means we do the ultrasound with a small probe that is placed in your child's esophagus, the tube that connects the mouth to the stomach. This test will measure the size of the hole and help place the closure device.
- If the test shows that the hole is too big to close with the device, we will wake up your child and send him or her to the recovery room. Your child's cardiologist will discuss the next steps with you and your child.
- If the hole is small enough and in the right position, we will go on with the catheterization.
During the catheterization, the doctor puts a catheter with a small deflated balloon on the tip through the blood vessel to the hole. The balloon is inflated to measure the size of the hole again. If the hole can be closed with the device, the doctor puts the closure device inside the catheter and places the device into the hole.
Once the device is in place, the doctor takes out the catheter and covers the cut on your child's leg with a bandage.