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SCUBA DIVERS WITH COMMON HEART CONDITION MAY BE AT INCREASED RISK FOR NEUROLOGICAL PROBLEMS
CHICAGO -- People with a common heart condition that affects a quarter of the population may be at increased risk for several problems, including skin rashes, the accumulation of brain lesions and serious neurological problems, if they scuba dive, according to information being presented here today at the 85th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).
"We feel testing for this heart condition with a special ultrasound examination should be included in the fitness-to-dive exam that people take before being certified to scuba dive," said Michael Knauth, M.D., a neuroradiologist at the University of Heidelberg Medical School, Germany, where the study was conducted. "That way, divers will know if they have the condition and can take precautions to reduce their risk."
Using magnetic resonance imaging (MRI), the study found that scuba divers with a patent foramen ovale (PFO) -- a common and usually harmless condition found in 1 in 4 people -- are more likely to have small lesions in the brain that are likely scars, or areas of dead tissue. They also are more likely to get decompression sickness and suffer from problems ranging from relatively harmless skin rashes to serious neurological problems such as vertigo and transient or even permanent paralysis.
"It is unclear whether the brain lesions can cause long-term problems, but common sense would tell you if you have enough of them and they're in the right places, they could cause problems, such as memory disturbances or difficulty concentrating," said Dr. Knauth.
PFO is a usually harmless opening in the connection between the right and left sides of the heart. In most people, it closes after birth. During dives, inert gas bubbles that form in venous blood and that typically are pumped by the heart to the lung, may bypass the filter in people with PFOs and travel throughout the body, including to the brain. There, they may cause small lesions, which Dr. Knauth believes are most likely small infarctions that lead to dead tissue or scarring. The bubbles traveling through the body also might cause blockages in small arteries, leading to decompression sickness.
During training, scuba divers learn to follow the rules of decompression, meaning they descend and ascend at a specific rate, and follow guidelines regarding the depth of the dive, to avoid ending up with decompression sickness. The problems with PFOs may occur even when all the rules of decompression are followed, leading Dr. Knauth to suggest these divers take further precautions.
The study consisted of two parts. In the first, cranial MRI was performed on 88 scuba divers, and brain lesions were detected in 12 divers (14 percent). One lesion each was found in 7 divers who did not have a PFO, whereas 37 lesions total were found in 5 divers with a PFO. One of those divers had 1 lesion, and the remaining 4 divers had up to 16 lesions.
The second aspect of the study compared 24 divers who had an unexplained diving incident although the rules of decompression were followed, to 14 divers who accompanied them on the same dive and did not suffer from decompression symptoms. Nineteen of the 24 divers (79 percent) with an unexplained diving incident had a large PFO, detected by echo-contrast transcranial Doppler ultrasound, whereas only 3 of the 14 (21 percent) accompanying divers had a large PFO. Six of the 22 divers (27 percent) with a large PFO also had a number of brain lesions. None of the divers without a large PFO had brain lesions.
"Divers with PFOs should reduce the depth they are decending to, not stay deep too long, ascend slowly, increase the time they spend above water between dives and avoid several descents during one dive," said Dr. Knauth. "These recommendations are not fool-proof, but they should lower the risk."
Co-authors of a paper on the topic being presented by Dr. Knauth are: Stefan Ries, M.D.; Christoph Klingmann, M.D.; Rolf Kern, M.D.; and Klaus Sartor, M.D.
The RSNA is an association of 31,000 radiologists and physicists in medicine dedicated to education and research in the science of radiology. The Society's headquarters are located at 820 Jorie Blvd., Oak Brook, Illinois 60523-2251.
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Note: Copies of 1999 RSNA news releases are available online at http://www.pcipr.com/rsna beginning Monday, Nov. 29.
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