Keating does not believe that routine testing is warranted. The test is fairly simple and inexpensive, so many people may elect to have it, he said. Those most likely to seek testing are people whose medical condition or medications might make them vulnerable to arrhythmias.
"It is worth knowing if you have the variant because there are simple things you can do to prevent arrhythmias," he said. According to Keating, these steps include avoiding any of a broad range of drugs, including antibiotics such as erythromycin and antihistamines such as Seldane, which affect heart rhythm. People with a risk of arrhythmia should monitor their potassium levels to ensure that they remain in the normal range and take beta-blockers to stabilize the heartbeat.
In beginning their search for polymorphisms (gene variants) that might contribute to arrhythmia, Keating and his colleagues started with the gene SCN5A because mutations in that gene were known to play a role in rare inherited arrhythmia disorder, called long QT syndrome, that can cause sudden death.
"Almost nothing was known about the effects of polymorphisms on cardiac arrhythmias, but we were among those predicting that variants would be discovered that were reasonably common and would have a subtle effect on arrhythmia risk," said Keating. He pointed out that the effort to understand the genetic and environmental origins of arrhythmias is spurred by the seriousness of the disorder, which kills about 450,000 people in the United States each year.
In their initial studies, the scientists found the same polymorphism, which they named Y1102, in several patients with arrhythmias that did not appear to run in their families. Their studies showed that changing one nucleotide in the SCN5A gene resulted in a sodium channel that carried an alteration in a single amino acid.
A broader survey of several population groups revealed that the Y1102 polymorphism occurred in
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
22-Aug-2002