Nonlinear Analysis of Heart Rate Variability: A Comprehensive Review

The traditional techniques for Heart Rate Variability (HRV) analysis in time and frequency domains are often not sufficient to characterize the complex dynamics of the heartbeat, since the mechanisms involved in cardiovascular regulation probably interact with each other in a nonlinear manner. There are already dozens of techniques for non-linear evaluation of HRV. However, until now, systematic studies of large groups of patients using this approach have not been conducted. We present the current state of knowledge in this area based on nonlinear variables more prevalent in existing publications. It can be concluded that the analysis of HRV in the nonlinear domain provides very useful information to characterize the appropriate autonomic balance and is a more reliable marker of complications and mortality in patients with cardiovascular disease.