Here is basic info on Lylas procedure that will be done tomorrow. This info comes from wikipedia.
Until the early 1990s, surgery was the usual method for closing all ASDs. Now, thanks to medical advances, doctors can use catheter procedures to close secundum ASDs, the most common type of ASD. For this procedure, the patient is given medicine so he or she will sleep through it and not feel any pain. During the procedure, the doctor inserts a catheter (a thin, flexible tube) into a vein in the groin (upper thigh) and threads it to the heart’s septum. The catheter has a tiny umbrella-like device folded up inside it. When the catheter reaches the septum, the device is pushed out of the catheter and positioned so that it plugs the hole between the atria. The device is secured in place and the catheter is withdrawn from the body. Within 6 months, normal tissue grows in and over the device. There is no need to replace the closure device throughout the patient’s life. Doctors often use echocardiography (echo) or transesophageal echo (TEE) as well as angiography to guide them in threading the catheter to the heart and closing the defect. TEE is a special type of echo that takes pictures of the heart through the esophagus (the passage leading from the mouth to the stomach). Catheter procedures are much easier on patients than surgery because they involve only a needle puncture in the skin where the catheter is inserted. This means that recovery is faster and easier. The outlook for patients having this procedure is excellent. Closures are successful in more than 9 out of 10 patients, with no significant leakage. Rarely, a defect is too large for catheter closure and surgery is needed.