THURSDAY, Jan. 9, 2003 (HealthDayNews) -- Researchers say they have identified a genetic mutation that causes the irregular, potentially fatal heartbeat called atrial fibrillation.
However, the researchers, from France and China, say the discovery will not have any immediate medical application for the condition that affects an estimated 2 million Americans. In fact, still unidentified genes could also play a role in the disorder.
Reached at his laboratory at the Institute for Biological Sciences-Chinese Academy of Sciences in Shanghai, Shi-Jie Xu, a leader of the research team, says the finding could lead to better treatments "by identifying important pathways involved in atrial fibrillation."
In atrial fibrillation, the two upper chambers of the heart tend to flutter, rather than contract forcefully. It can lead to heart failure; formation of clots that can block a major artery, causing a heart attack; or other problems. Treatments include drugs, pacemakers and surgery.
While genetics can cause the disorder, it is more often triggered by environmental factors such as high blood pressure, coronary artery disease and chronic lung disease.
"Our results may suggest new therapeutic strategies for both the inherited and the more common acquired forms of atrial fibrillation," the researchers say in tomorrow's issue of Science.
The scientists studied one family living in China's Shandong province with a history of inherited atrial fibrillation; 16 of the 44 living members have the condition.
Previous studies led the researchers to examine one section of chromosome 11 (of the 23 pairs that make up the human genome) that had been linked to atrial fibrillation. They zeroed in on a gene called KCNQ1, and found all the family members with atrial fibrillation had the same mutation of that gene. The mutation was not found in family members without the disorder.
The KCNQ1 gene governs a channel through which potassium ions, electrically charged particles, flow through the membrane of cells called myocytes, a type of heart cell. This KCNQ1 channel has been linked to other heart conditions. The mutation found in the family members keeps the channel open for an abnormally long time. Another mutation, which keeps the channel closed, has been found in persons with an abnormal heartbeat called "long QT syndrome."
In the case of atrial fibrillation, the researchers write, "the mutation in KCNQ1 causes a marked enhancement of its [the ion channel's] function, tips the normal balance of the process, and renders the cardiac myocyte more susceptible to atrial fibrillation."
Research on the genetics of atrial fibrillation is just beginning, Xu says. "Most people with the condition will not have any mutation," he says. "They are most likely to have some kind of polymorphism," a subtly different gene.
And the fact that this mutation was not found in other families with hereditary atrial fibrillation indicates that other genes are likely to be involved, he says.
What To Do
You can learn more about atrial fibrillation from the Cleveland Clinic or the American Heart Association.
