Atrial fibrillation (AF) is a heart rhythm abnormality in which the heart's two upper chambers (the atria) quiver instead of beating effectively, which can cause blood to pool and clot. A blood clot that leaves the heart and lodges in a brain artery can cause a stroke. Obstructive sleep apnea contributes to heart attack and stroke risks. It is characterized by repeated interruption of breathing during sleep. The prevalence of sleep apnea is directly related to body mass index. As obesity increases, so does the incidence of sleep apnea. AF and obstructive sleep apnea share associations with other common diseases and risk factors such as male gender, hypertension, congestive heart failure and coronary artery disease, but the prevalence of sleep apnea among AF patients is unknown, said senior author Virend K. Somers, M.D., Ph.D., professor of medicine in the Division of Cardiovascular Diseases at the Mayo Clinic, Rochester, MN. "Because sleep apnea is significantly underdiagnosed and treatment may lower the risk of recurrent AF, determining its prevalence in patients with AF can be very important," he said.
A group of 151 AF patients and 312 general cardiology patients answered a questionnaire regarding snoring, daytime sleepiness, body mass index, and hypertension to identify risk of sleep apnea. Almost half (49 percent) of the AF patients were identified as high risk for sleep apnea compared with about a third (32 percent) of general cardiology patients.
Patients with AF were twice as likely to have sleep apnea (2.19 odds ratio).
"Atrial fibrillation is predicted to affect more than 5 million people by the year 2050. The coinciding epidemics of obesity and AF underscore the clinical importance of these results," said Apoor S. Gami, M.D., instructor in medicine in the Division of Cardiovascular Diseases at the Mayo Clinic, and lead author of the study.
Another novel observation was that the association of obstructive sleep apnea with AF was greater than the association of sleep apnea with its traditional risk factors such as body mass index, neck circumference and hypertension, Gami said.
The study also suggests that it is not only the common diseases associated with both conditions that may lead to AF, but there may be a unique interaction between the pathophysiologies of sleep apnea and AF.
When sleep apnea interrupts breathing, oxygen in the blood drops while carbon dioxide increases. The sympathetic nervous system (the flight-or-fight response) is activated. Also, the forceful breathing efforts through the obstructed airway may result in dramatic pressure shifts across the cardiac chambers. These reactions, if untreated over time, may predispose to AF.
While sleep apnea is ideally diagnosed by being observed overnight in a sleep lab, researchers say the questionnaire was able to very reliably predict who did or did not have sleep apnea.
Researchers suggest that the presence of obstructive sleep apnea be considered in all AF patients and screening might be warranted in AF patients who are also obese or have hypertension.
Co-authors are Gregg S. Pressman, M.D.; Sean M. Caples, M.D.; Ravi Kanagala, M.D.; Joseph J. Gard; Diane E. Davison, R.N., M.A.; Joseph F. Malouf, M.D.; Naser M. Ammash, M.D.; and Paul A. Friedman, M.D.
The study was partly funded by the National Institutes of Health.
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