Patent foramen ovale (PFO) is a hole between your heart's upper chambers. The foramen ovale is a hole in the wall between the left and right atria of every human fetus.This hole allows blood to bypass the fetal lungs. The healthcare provider inserts the catheter through a blood vessel in the groin and guides it to the PFO. A patent foramen ovale (PFO) is a hole in the heart that didn't close the way it should after birth. Patent foramen ovale (PFO) is a hole between the left and right atria (upper chambers) of the heart. This hole exists in everyone before birth. A PFO closure uses a medical device to close an opening between your heart's two upper chambers. You only need this opening as a fetus. The foramen ovale (feh-RAY-men oh-VAL-ee) is a normal opening between the upper two chambers (the right atrium and left atrium) of an unborn baby's heart.