May 15, 2007 Researchers from the Veterans Affairs Medical Center and the University of Cincinnati College of Medicine, Cincinnati, OH, evaluated the potentially deadly effects of sleep apnea in patients with heart failure. Sleep apnea is a disorder in which the brain fails to send messages to the respiratory muscles, causing breathing to stop for short periods throughout the night.
The largest of its kind, the study recruited 88 patients with heart failure to spend 2 nights being evaluated in a sleep laboratory. Researchers documented the number of times breathing completely stopped during sleep (apnea) or became shallow for at least 10 seconds (hypopnea). Patients who experienced 5 or more instances of apnea or hypopnea per hour were diagnosed with clinically important sleep apnea.
Over a follow-up that averaged 51 months, patients with central sleep apnea were far more likely to die than those who breathed normally during sleep. The median survival was 45 months in patients with central sleep apnea, as compared to 90 months in those without a sleep disorder. When multiple patient characteristics were taken into account, only 3 were independently linked to an increased risk of death: central sleep apnea, a poorly functioning right ventricle, and a low blood pressure during relaxation of the heart.
"The results of this study are particularly important because previous studies of survival in patients with heart failure, including those considering the role of angiotensin-converting enzyme inhibitors or beta blockers, have not routinely included sleep studies; therefore, the impact of sleep apnea on survival was not known," the authors noted.
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