NEW YORK, NY (13 July 2004) -- Scuba divers with a relatively common heart defect appear to be at higher risk than normal for decompression sickness, a new report shows. The defect is known as a patent foramen ovale (PFO), in which a tiny opening between the heart's two upper chambers that normally closes during fetal development remains open. It is believed to affect up to 30 percent of the population. Researchers found that divers with PFO were around five times more likely to experience a major bout of decompression sickness -- caused by gas bubbles forming in the bloodstream -- than people without the heart defect, and the risk increased with the size of the defect. However, the researchers stress that the risk of suffering decompression sickness among divers with PFO remains quite low -- indeed, they report a rate of only 5 incidents of major decompression illness for every 10,000 dives. Nevertheless, the team from the University Hospital in Bern, Switzerland, recommends that people with relatively large opening between the left and right atria of the heart should refrain from diving. And for people with smaller defects who have experienced decompression sickness, precautions such as avoiding dives deeper than 30 meters, and refraining from repetitive dives during a single day, are also wise, they add. Decompression sickness, also known as "the bends," occurs when a diver stays too deep for too long or comes up too quickly. The sudden lowering of outside pressure can cause bubbles to form in the blood that can result in pain, paralysis or death. Previous research has also shown that divers with a patent foramen ovale are at higher risk of developing the bends, and have double the risk of bubbles traveling to the brain, where they can do damage. That's because the opening creates a connection between the venous circulation, where bubbles form, and the arterial circulation supplying oxygenated blood to the body. | | To investigate further, researchers led by Dr. Sandra Rea Torti used ultrasound to examine the hearts of 230 divers, then asked them about how many dives they had performed and what had gone wrong. Every participant had logged at least 200 dives. Reporting in the European Heart Journal, the investigators found that 63 divers, or 27 percent, had a PFO. None of the divers knew they had the defect. Approximately 29 percent of the divers with PFO had experienced at least one major episode of decompression sickness, compared with only 6 percent of divers without the heart defect. An episode of decompression sickness was considered major if divers experienced symptoms such as impaired bowel or bladder control, or lost consciousness after the dive. The researchers also found that the risk of major decompression illness increased as PFO size increased. However, people with the smallest PFO -- classified as grade 1 -- had the same risk of illness as people without PFO. SOURCE - Reuters, European Heart Journal |
