ASD is a birth defect with a gap in the heart's upper wall. This gap happens when the wall does not form right before birth.Generally an ASD hole is larger than a PFO. The larger the hole, the more likely symptoms are. Patent foramen ovale (PFO) refers to the nonclosure of the potential space between septum primum and secundum (analogous to a flap valve) Percutaneous PFO closure techniques have been derived from established atrial septal defect (ASD) closure techniques. There are two types of holes which can be present between the upper chambers of the heart: an Atrial septal defect (ASD) and a patent foramen ovale (PFO). While an Atrial Septal Defect is always considered a structural abnormality in the heart, everyone at birth has a PFO. Several studies have previously compared the performance of PFO occluders based on markedly different fabric7-10. Patent foramen ovale (PFO) and atrial septal defects (ASDs) represent the most common and second most common congenital heart abnormalities.