Sleep apnoea triggers irregular heartbeat

New research provides the first hard evidence that the characteristic snorting and gasping of sleep apnoea can spur potentially fatal heartbeat abnormalities.

Previous studies have suggested an association between sleep apnoea and cardiac arrhythmias but they had not established a cause-and-effect relationship, said study senior author Dr. Susan Redline, a professor of medicine at Case Western Reserve University in Cleveland.

But in this research, "we studied the specific risk of cardiac arrhythmias and sleep apnoea do these events act as a trigger for cardiac abnormalities?" she said. "And we established that there is a close temporal relationship."

The study will be published in the Nov. 3 issue of the Journal of the American College of Cardiology.

How the study was done
Redline and colleagues at sleep research centers across the country studied nearly 2,900 polysomnograms detailed sleep-time recordings of biophysical activities of the brain, muscles and heart of more than 2,500 people participating in the nationwide Sleep Heart Health Study. Specifically, the researchers compared heartbeat patterns seen during normal breathing against those occurring within 90 seconds of a sleep apnoea episode.

They detected 62 arrhythmias occurring in 57 people with a wide range of sleep apnoea disorders. Overall, the study found that the odds of experiencing a heartbeat abnormality were 18 times higher immediately after an episode of sleep apnoea than during periods of normal breathing of sleep.

The researchers focused on two dangerous heartbeat abnormalities: atrial fibrillation, a disordered fluttering of the two upper chambers of the heart (a major risk factor for stroke); and ventricular tachycardia, a too-fast beating of the lower blood-pumping chambers that can cause sudden death.

Abnormal heartbeat not linked to severity of sleep apnoea
One important finding of the study was that these abnormal heart rhythms were not linked to the severity of a person's sleep apnoea, Redline said. "The study did look to see whether more intense sleep apnoea increased the risk of arrhythmias," she said. "In fact, most of the arrhythmias occurred in people with mild-to-moderate sleep apnoea."

The researchers stressed that abnormal heartbeats were relatively rare, with sleep apnoea increasing their incidence by one for every 40,000 breathing disturbances. But the potentially serious effect of those heartbeat errors requires alertness in detecting sleep apnoea, Redline said.

Conversely, the study suggests that doctors should be alert for the possibility of sleep apnoea in people who have heart rhythm abnormalities, Redline said. "Those who present with arrhythmias should be screened for apnoea," she advised.

For now, the study is more of scientific interest than immediate medical application, added study author Dr. Ken Monahan, an assistant professor of medicine. "It adds additional evidence to what was already suggested in the literature," he said.

It is important to note that the relationship established in the new study, "was built on the work of others," he said. "It raises a lot of very interesting questions about what the ultimate clinical applications of other findings may be." – (Ed Edelson/HealthDay News, October 2009

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