[Autonomic function and circulatory failure]

To define fundamental mechanisms for sympathoexcitation could provide a therapeutic opportunity to interrupt the specific site linking sympathetic activation with heart failure. Central sleep apnea is characterized by apnea, hypoxia, sleep fragmentation, and increased sympathetic nerve activity. Since this sympathoexcitation is directly related to the frequency of arousals from sleep and the degree of apnea-related hypoxia, but not to left ventricular ejection fraction, it is therefore not simply a compensatory response to hemodynamic derangement but is excessive and pathologic sympathoexcitation with aftereffects that persist into wakefulness. Thus, central sleep apnea could participate in a vicious pathophysiologic cycle involving the cardiovascular, respiratory, and autonomic nervous system.