>i hate to blantently display my ignorance, but what the hell does PFO
>stand for?  reading all these posts w/out that knowledge is really 
>annoying.  thanks

What ignorance? It takes us years of medical school and residency 
training to learn to confuse folks with this stuff!   ;-)


PFO stands for "Patent Foramen Ovale" which is doc-speak for a 
developmental anomaly where there is a hole between the two "receiving" 
chambers of the heart, the atria.

Normally, the atrial septum, the wall between these two chambers is 
formed when you are just a twinkle in your mother's eye from two nubins 
of tissue, the endocardial cushions. After some dividing into such 
obtusely named components as the septum primum and septum secundum, they 
normally all fuse together to form a wall (the atrial septum).

There is a normally ocurring thinner portion, the foramen ovale. If these 
fusing portions don't quite line up and fuse, there is a hole left...a 
"patent" foramen ovale.

The problem is that higher pressure, oxygenated blood from the pulmonary 
vein (coming from lungs) instead of going from the left atrium into the 
left ventricle (then out to the body where you need it) instead goes 
through this hole into the right ventricle only to be resent to the 
lungs. This also exposes the lungs and the right side of the heart to 
higher pressures than nature intended which causes various forms of 
damage. However, people with such big defects are detected and repaired 
as children so would not be diving.

As far as divers are concerned (assuming those with with very small 
defects), there is the possibility that gas bubbles on the venous side of 
the house, instead of getting trapped in the lungs, could get across this 
open hole to the left side and get sent to the brain and other organs 
(not a good thing) if the pressure on the right is raised, say by trying 
to clear your ears doing a Valsalva maneuver.

Hope I haven't muddied the waters further.

Robb Wolov

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