Sleep apnea and congestive heart failure

Sleep apnea encompasses 2 forms of sleep disordered breathing, namely obstructive and central sleep apnea. Both these conditions are prevalent in patients with congestive heart failure (CHF) despite quite different etiology and pathogenesis. The last 15 years have seen the development of a large database of mechanistic data implicating both these conditions in the progression of cardiac dysfunction in patients with heart failure. Epidemiological data have also revealed that obstructive sleep apnea may be an independent risk factor for the development of cardiac diseases. Central sleep apnea, conversely, is more likely to emerge as a consequence of severe cardiac dysfunction, but through an elaborate vicious cycle could potentially lead to augmentation of sympathetic activity and contribute to further cardiac decline. In recent years a number of randomized controlled trials suggests secondary endpoints such as symptoms, sympatho-excitation and left ventricular function can be improved with the effective therapies available for both central and obstructive sleep apnea in patients in which these conditions co-exist. Mortality data is emerging also, and the first of a large scale mortality trial assessing the effect of attenuating central sleep apnea with continuous positive airway pressure in patients with moderate to severe CHF, is well underway. This review summarizes the important mechanistic, epidemiological and interventional studies in relation to sleep apnea and congestive heart failure with some commentary on the future direction of this rapidly growing field.