Posted by on April 26, 2005 at 10:38:18:
Apr 26 (Reuters Health) - Before birth a connection called the foramen ovale exists between the right and the left side of the heart that allows blood to bypass the lungs. Usually this connection closes after birth, but new research indicates that an open or "patent" foramen ovale (PFO) may be common in one group of adults -- scuba divers.
In divers, a PFO can allow tiny gas bubbles to pass from the vein side of the body to the artery side, leading to certain types of "the bends," also called decompression sickness, according to the report in The American Journal of Cardiology.
The observation that some people have uneventful dives for many years and then suddenly become more susceptible to the bends, led Dr. Peter Germonpre, from the Military Hospital Brussels in Belgium, and colleagues to hypothesize that the foramen ovale was not closing as expected.
To test this theory, the researchers used cardiac ultrasound to look for PFO in 40 divers on two occasions 7 years apart. The group included 16 subjects who had experienced the bends and 24 who had not.
PFO was diagnosed and graded according to the number of test bubbles that passed through the opening during ultrasound -- the more bubbles that passed, the bigger the opening. With a normal foramen ovale, no bubbles should pass, meaning that the opening had closed.
On initial evaluation, 20 subjects were diagnosed with PFO and 20 had a closed opening. At follow-up, 21 subjects were diagnosed with the condition and 19 had a closed opening.
Although the increase in subjects with PFO was slight, there was a pronounced shift to more severe PFO. For example, the number of subjects with the largest PFOs, known as grade 2, increased by six between the two assessment periods.
"To our knowledge, this is the first (forward-looking) study to actually document the increase in PFO size in humans, using a standardized and reliable...technique," the authors point out. Further research is needed to determine exactly why a PFO does not follow its typical course in some divers, they add.