The septum is the muscular wall separating the heart into the left and right sides. The atrial septum is the wall separating the atria (the two upper chambers). The ventricular septum is the wall separating the ventricles (the two lower chambers).
What is Foramen Ovale?
The foramen ovale is a small hole located in the septum (wall) between the two upper (atrial) chambers of the heart.
The foramen ovale is used during fetal circulation to speed up the travel of blood through the heart. When in the womb, a baby does not use its own lungs for oxygen-rich blood; it relies on the mother to provide oxygen rich blood from the placenta through the umbilical cord to the fetus. Therefore, blood can travel from the veins to the right side of the baby's heart and cross to the left side of the heart through the foramen ovale and skip the trip to the baby's lungs.
What is a Patent Foramen Ovale (PFO)?
Normally the foramen ovale closes at birth when increased blood pressure on the left side of the heart forces the opening to close.
If the atrial septum does not close properly, it is called a patent foramen ovale. This type of defect generally works like a flap valve, only opening during certain conditions when there is more pressure inside the chest. This increased pressure occurs when people strain while having a bowel movement, cough, or sneeze.
If the pressure is great enough, blood may travel from the right atrium to the left atrium. If there is a clot or particles in the blood traveling in the right side of the heart, it can cross the PFO, enter the left atrium, and travel out of the heart and to the brain (causing a stroke) or into a coronary artery (causing a heart attack).
How Common is Patent Foramen Ovale?
PFO is present is up to 25 percent in the general population. Young adults (less than age 55) who have stroke of unknown cause (cryptogenic stroke), are more likely to have a PFO. In fact young adults who have had a cryptogenic stroke are more likely to have both a PFO and a deep vein thrombosis (DVT).
A PFO can be associated with atrial septal aneurysm, which is characterized by excessive mobility of the atrial septum.