Back to Medical Articles List  Patent Foramen Ovale - Is It
Important to Divers?  Bookmark and Share  By Dr. Alfred A. Bové
and Dr. Richard E. Moon  What is a PFO?  The upper chambers of
the heart (the atria) are separated into a right chamber that
conveys blood from the veins to the right ventricle, then to the
lungs, and a left atrium that conveys blood from the lungs to
the left ventricle and then to the whole body.  In the unborn
fetus, the lungs are not functioning, and to provide oxygen to
the fetal circulation, an opening is present (the foramen ovale)
in the wall between the two atria (the atrial septum). The
foramen ovale allows blood coming from the placenta to flow
through the right atrium directly into the left atrium and then
into the body, providing the oxygen needed for growth and
development.  At birth, when the baby begins to breathe, a flap
valve closes over the opening in the atrial septum and
eventually becomes part of the atrial septum from growth of
tissue sealing the opening. However, i