Patent foramen ovale (PFO) is defined as a communication at the fossa ovalis between the primum and secundum atrial septa that persists after the first year of life.
In utero the PFO functions as a physiological conduit for right to left shunting and it functionally closes at birth once the pulmonary circulation is established and there is a rise in left atrial pressure. This is followed by anatomical closure of the septum primum and septum secundum by one year of age.
