Sleep apnea in congestive heart failure.

Obstructive sleep apnea (OSA) is a form of sleep disordered breathing in which pharyngeal muscle relaxation leads to recurrent nighttime apneas and hypopneas that, through increased afterload, intermittent hypoxia, and excess sympathetic activity, weaken the already failing heart. This review presents the current evidence regarding the complex relationship between OSA and heart failure (HF), including support for OSA as both a cause and consequence of HF. The impact of OSA on other cardiovascular diseases, such as hypertension, ischemic heart disease and arrhythmias, as they relate to HF development or exacerbation, also are reviewed.