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Sleep Apnea Tied to Abnormal Heartbeat

Screening for nighttime disorder urged in atrial fibrillation patients

MONDAY, July 12, 2004 (HealthDayNews) -- Ever feel like your heart is racing or beating erratically? The culprit could be an underlying sleep problem.

A new study adds to increasing evidence linking atrial fibrillation with sleep apnea. People diagnosed with the abnormal heart rhythm were twice as likely to have the sleeping disorder as general heart patients, researchers report in the July 13 online issue of the journal Circulation.

While the study doesn't prove a cause-and-effect relationship, it does suggest that obstructive sleep apnea -- when breathing stops repeatedly during sleep -- predisposes people to the heart rhythm abnormality.

"The bottom line is that if you have atrial fibrillation, at least consider the possibility that there may be underlying sleep apnea," said Dr. Virend K. Somers, professor of medicine at the Mayo Clinic's Division of Cardiovascular Diseases and a senior author of the study.

The study is believed to be the first to examine the prevalence of atrial fibrillation in people with sleep apnea. That information could have significant implications for screening and treating patients with atrial fibrillation.

Dr. Meir Kryger, a Canadian sleep disorders specialist and member of the board of directors of the National Sleep Foundation, said the findings suggest that cardiologists need to begin asking their patients about symptoms of sleep apnea. In addition, the study points to the need for greater collaboration between cardiologists and sleep specialists.

"There are very, very few cardiologists around who are actually involved in sleep research," he said. "Hopefully this trend is going to change."

Cardiac arrhythmia, the term used to describe an abnormal heart rhythm, is the result of a change in the normal sequence of electrical impulses that stimulate the heart. In the case of atrial fibrillation, the most common type of arrhythmia, the upper chambers of the heart quiver instead of contracting. Since blood isn't pumped out completely, it can pool, leaving the risk of clotting.

The condition affects about 2 million Americans, according to the American Heart Association, but research suggests that the number will exceed 5 million by 2050.

Obstructive sleep apnea occurs when the soft tissue at the back of the throat collapses and closes during sleep. People with this condition literally stop breathing, sometimes hundreds of times during the night for periods ranging from 10 seconds to more than one minute.

An estimated 18 million Americans may have sleep apnea, according to the National Sleep Foundation.

Both atrial fibrillation and obstructive sleep apnea share certain links with cardiovascular diseases, including hypertension, congestive heart failure, and coronary heart disease. Being male or obese also are risk factors for each condition, experts say.

"What's interesting about [the study] is something that's been evolving in the last two to three years -- the notion that there's a huge link between cardiovascular disease and sleep apnea," said Kryger, director of the Sleep Disorders Center at St. Boniface Hospital in Winnipeg and a professor of medicine at the University of Manitoba.

The Mayo study involved 151 patients with atrial fibrillation or flutter and 312 general cardiology patients. People in each group completed questionnaires about their snoring, daytime sleepiness, body mass index, and hypertension to identify risk for sleep apnea.

Almost half of the atrial fibrillation patients were deemed to be at high risk for sleep apnea, compared with a third of general cardiology patients, or 49 percent vs. 32 percent.

The association of sleep apnea with heart arrhythmia was greater than the association of sleep apnea with its traditional risk factors, such as body mass index, neck circumference, and hypertension, the authors noted.

Overall, patients with atrial fibrillation were more than twice as likely as general heart patients to have sleep apnea.

Why the strong connection? When sleep apnea interrupts breathing, oxygen in the blood drops and carbon dioxide increases. The body's "fight-or-flight" response is activated. And the struggle to breathe may result in dramatic shifts in pressure across the heart chambers. These reactions, if left untreated over time, may predispose someone to atrial fibrillation, the authors suggest.

A Mayo Clinic study reported last year showed that the risk of recurrent atrial fibrillation is doubled in people with untreated sleep apnea. The new study shows just how widespread sleep apnea is among patients with that heart arrhythmia.

"I think the evidence that's coming out slowly from our lab and from other laboratories is beginning to sensitize people to this link," Somers said.

More information

The American Heart Association has more on diagnosing and treating atrial fibrillation.

SOURCES: Virend K. Somers, M.D., Ph.D., professor of medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minn.; Meir Kryger, M.D., member, National Sleep Foundation board of directors, and director, Sleep Disorders Center, St. Boniface Hospital, Winnipeg, Canada, and professor of medicine, University of Manitoba, Canada; American Heart Association; National Sleep Foundation; July 13, 2004, Circulation online
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