Since the availability of atrial septal defect closure (ASD) devices in the 1990s in Europe, and in the early 2000s in the US, percutaneous closure of secundum ASDs has become the procedure of choice over surgical repair. This is due to the lower morbidity associated with percutaneous repair compared with surgery and similar, low mortality . However, there are some groups that may behave differently when specifically examined. These include the differences between pediatric and adult populations and the closure of less anatomically favorable ASD compared with simpler ASDs. One of the obvious characteristics of a more challenging ASD is that of a very large defect. These can be more challenging for a variety of reasons. 1) the hole may simply be too large for a device, 2) there may be less optimal rim of tissue in larger holes, 3) sizing the defects may be more challenging, as balloon sizing may be difficult, and 4) more advanced techniques may be needed to position the device properly. These may include the use of specialty delivery catheters (e.g., Hausdorf-Lock sheath) or techniques such as balloon stabilization during device deployment or partial deployment in a pulmonary vein. For all these reasons, one might anticipate higher risks of failure or complications, such as embolization, “erosion” (or the development of a pericardial effusion), and atrial fibrillation.