If someone has a hole in their heart, it falls into one of two most common categories: patent foramen ovale (PFO) or an atrial septal defect (ASD). PFO (Patent Foramen Ovale) and ASD (Atrial Septal Defect) are congenital heart conditions that affect the structure of the heart.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) PFO is an opening that does not seal after you are born. Even though many adults have PFO, they often do not know it. A patent foramen ovale occurs when a hole that is always present in a newborn's heart fails to close as it should once the lungs begin to function after birth. ASD is a defect in the septum between the heart's two upper chambers. The septum is a wall that separates the heart's left and right sides.