The heart is divided into four separate chambers. The upper chambers, or atria, are divided by a wall called the atrial septum.
The foramen ovale is a flap or tunnel shaped hole in the atrial septum during fetal development that allows blood to travel through the heart without going to the lungs. When in the womb, a baby does not use his or her own lungs, receiving oxygen rich blood from the the mother through the umbilical cord. Therefore, blood can travel from the right side of the baby’s heart to the left side of the heart through the foramen ovale, skipping the trip to the baby’s lungs.
This small flap-like opening normally closes shortly after birth as the pressure from the baby’s heart pushes the flap to the septal wall. If this opening does not close shortly after birth, a Patent Foramen Ovale (PFO) results. For people with PFO, some blood from the right atrium can leak into the left atrium. PFO is the most common heart defect. In fact, one in four people may have a PFO to some degree, but in many cases the PFO is not large enough to create symptoms or require any immediate treatment in childhood.
Patent Foramen Ovale is categorized as an atrial septal defect, but with a different origin and symptoms than single-hole or multi-fenestrated atrial septal defects. ( learn more about atrial septal defects )
Many people grow up and lead normal lives without even knowing that they have a PFO. PFO is frequently not diagnosed until adulthood. However, there are a number of life-affecting and potentially harmful conditions that may be caused by PFO.
Patent Foramen Ovale is suspected to be a cause of embolic cryptogenic stroke. This type of stroke has no clearly known origin, but blood clotting at or near the PFO is one possible cause. Research is underway to verify this connection between embolic cryptogenic stroke and PFO. Learn more about PFO and stroke research.