ScienceDaily (Nov. 17, 2006) — People with sleep apnea could also be at risk for a particular kind of deadly heart arrhythmia, finds Saint Louis University researchers. They presented the findings this week at the American Heart Association Scientific Sessions meeting in Chicago.

Researchers looked at 134 patients with coronary heart disease who hadn't been diagnosed with a sleep disorder. In the patients who had a type of an irregular heartbeat called ventricular premature contraction, more than 40 percent also had severe sleep apnea -- and didn't realize it.

"The real worry is that benign arrhythmia can be a harbinger of a much more serious -- and lethal -- heart rhythm disorder," says principal investigator Raj Bhalodia, M.D., of Saint Louis University School of Medicine. "While most people with the mild version of arrhythmia will be just fine, in some people, it's possible it can worsen during the night and lead to sudden death."

The researchers found that sleep apnea -- which is the collapse of the upper windpipe during sleep, leading to decreased levels of oxygen in the blood -- seemed to exacerbate ventricular premature contraction, especially during the dream stage, or REM, of sleep.

"There's less oxygen being pumped through the body in REM than in other stages of sleep, and this can bring on arrhythmia," Bhalodia says. "The brain is less alert, which is why people don't simply wake up to solve the problem."

Bhalodia says he was interested in studying the link between the two disorders because previous research showed that people with sleep apnea who died suddenly from arrhythmia tended to die more during sleep -- unlike other heart disease patients whose sudden death tends to happen the most often in the few hours after waking up.

Sleep apnea is significantly underdiagnosed, says Bhalodia. Symptoms include feeling sleepy during the day and snoring during sleep. Overweight and obese people also are more likely to suffer from sleep apnea.

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