Heart rate variability analysis in the assessment of autonomic function in heart failure.

Heart rate is not static, but rather changes continuously in response to physical and mental demands. In fact, an invariant heart rate is associated with disease processes such as heart failure. Heart rate variability analysis is a noninvasive technique used to quantify fluctuations in heart rate. In this article, the authors review neural control of heart rate, briefly describe heart rate variability, and summarize research data demonstrating that heart failure is associated with altered heart rate variability. In addition, the authors present evidence that heart failure patients with decreased heart rate variability are at risk for future cardiac events, heart transplantations, and death.