Central sleep apnea and chronic heart failure.

Central sleep apnea with Cheyne-Stokes respiration (CSR) during sleep affects about 40 % of patients with chronic heart failure (CHF). During CSR simultaneous periodic fluctuations in wakefulness and respiration with accompanying changes in blood pressure and heart rate are observed. CSR can be described as an oscillation of the ventilatory feedback loop controlling respiration. The major synergistically acting mechanisms causing this oscillation include reduced body stores of oxygen and carbon dioxide, hyperventilation with concomitant hypocapnia, prolonged circulation time, and a relatively high hypercapnic ventilatory response. The repetitive desaturations and arousals following CSR cause daytime symptoms and an increase in sympathetic activity. In CHF chronically increased sympathetic activity has negative effects on left ventricular function and is associated with reduced exercise tolerance and poor prognosis. Therefore CSR is expected to have an unfavorable influence on the course of CHF. Whether successful treatment of nocturnal CSR has any impact on the high mortality of CHF needs to be resolved in controlled studies with sufficient sample size.