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). A review of atrial septal closure, including the surgical evolution and the subsequent progression of transcatheter device closure.Generally an ASD hole is larger than a PFO. The larger the hole, the more likely symptoms are. Why do these birth defects occur? ASD is a development issue, leaving a lasting hole. In this case, elevation of pressure in the pulmonary circulation (e.g. You may also need a cardiac closure device for a patent foramen ovale (PFO). They can range from a small opening, a series of holes, or the complete absence of the atrial septum. A pfo is a type of an asd.