A PFO is a type of hole in the heart that occurs in infancy. A device is used to close the opening so that blood and blood clots don't flow through the opening anymore.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. Your doctor used a thin, flexible tube called a catheter to place a small device that closes the PFO. What is the PFO closure procedure? Learn about patent foramen ovale (PFO), risk of PFO-associated stroke, and treatment options for PFO closure. If you have a PFO and low blood oxygen levels or an unexplained stroke, you may need a procedure to close the hole. Patent foramen ovale (PFO) is part of a group of entities known as atrial septal defects (ASDs), and it is a remnant of normal fetal anatomy. Clinical Study investigators and partici- pating organizations is provided in the.