Patent foramen ovale


  • A patent foramen ovale (PFO) is present in all babies prior to birth (to allow blood to by-pass the lungs which are not used in utero) – in 80% of people it closes after birth
  • It occurs in about 1 in 5 (20%) healthy individuals.
  • It is associated with about a 3 fold (relative risk = 3) risk of stroke in younger adults.
  • It may provide a route for so called “paradoxical emboli” to move from clots in the veins to the brain by by-passing the lungs which usually filter out clots. The illustration below shows a large clot going through the PFO.
  • It can be detected by a transthoracic or trans-oesophageal echocardiogram with bubble contrast (see video of bubbles crossing septum) or transcranial Doppler.

Duration: 10 seconds

A large clot going through patent foramen ovale