Nocturnal insights in chronic heart failure.

Two main types of sleep-related breathing disorders occur in patients with congestive heart failure: obstructive sleep apnoea and Cheyne–Stokes respiration with central apnoeas. Obstructive sleep apnoea is characterized by recurring upper airway collapse with ongoing respiratory effort during sleep, causing repetitive surges of negative intrathoracic pressure, arousals, and oxygen desaturations. This gives rise to sympathetic activation and increases systemic blood pressure. Obstructive sleep apnoea is strongly related to increased body weight and is common in the general population. In epidemiological and animal studies, an association between systemic hypertension and obstructive sleep apnoea independent of obesity was found. There is also evidence linking obstructive sleep apnoea with endothelial dysfunction and increased cardiovascular mortality. In 1818 John Cheyne, and in 1854 William Stokes, were the first to describe a regularly waxing and waning breathing pattern with central apnoeas (i.e. absence of respiratory effort) now known as Cheyne–Stokes respiration. With the propagation of polysomnography in the last decade it appeared that Cheyne–Stokes respiration, with repetitive oxygen desaturations, occurred at night in many patients. The high prevalence of sleep disordered breathing in congestive heart failure is highlighted by the systematic investigation using polysomnography by Tremel et al. in this issue. The authors reported that about 80% of 34 consecutive patients with a left ventricular ejection fraction <45% investigated 1 month after an episode of pulmonary oedema had an apnoea+ hypopnoea index (AHI) >15 . h. Obstructive sleep apnoea was less common (25%) than Cheyne–Stokes respiration (75%) and was chiefly observed in the more overweight patients. Recently Javaheri et al. reported on 81 ambulatory male congestive heart failure patients with a left ventricular ejection fraction <45%. The authors noted that 51% of their patients had an apnoea+hypopnea index >15. Again most of