Heart rate variability and nonlinear dynamics

Abstract

In this review the importance of nonlinear analysis of heart rate variability is discussed. In the introduction the complexity of the heart rate signal is highlighted which reflects an abundance of external and internal control mechanisms. It is shown that one way to improve analysis of heart rate variability in terms of risk prediction is “perturbation” analysis. In this system analysis approach, the response of heart rate to a specific perturbation rather than the global dynamics of a 24 hour recording are analyzed. Prominent examples of this approach are “heart rate turbulence” and “heart rate recovery”. After mentioning 1/f-fluctuations as the dominant but still linear phenomenon in spectral analysis of heart rate variability, the remainder of the review is focused on the return map. Fundamental properties of the return map of heart rate are delineated which clearly demonstrate nonlinear properties of the heart rate signal. In addition, practical aspects of return map analysis are reviewed which prove to be very fruitful in the handling of heart rate data.