patent foramen ovale
The blood in a child in the womb is bypassed by a connection between the two atria of the heart. This connection is called the foramen ovale. After birth, the child starts to breathe independently and the connection between the atria closes. In as many as 1 out of 4 people the atria does not close properly, and a trap-door-like opening a few millimeters wide is left open, known as a Patent Foramen Ovale (PFO).
As the PFO is constructed like a trap-door, the opening is normally closed, since the pressure in the left atrium is higher than in the right atrium and this pressure closes the lid of the door.
As many as 20% of all people have a PFO. Usually there are no problems. Adults or older people may suffer more frequently from clotting disorders based on risk factors typical for older age (i.e. smoking, obesity, hormonal contraception (the pill), high blood pressure, arteriosclerosis, etc.). Therefore adults with a PFO may have a higher risk of getting certain types of strokes, namely a stroke via a paradoxical embolism. In these circumstances, medication to prevent blood clots can be advantageous.
Once a person has had a stroke caused by a clot in the brain, and a PFO is diagnosed with the likelihood of a paradoxical embolism, a closure of the PFO is recommended to avoid future strokes.